getting-started-with-lotus-suspension-analysis

GETTING STARTED WITH
LOTUS SUSPENSION
ANALYSIS
VERSION 4.03

GETTING STARTED
WITH LOTUS SUSPENSION ANALYSIS
VERSION 4.03

The information in this document is furnished for informational use only, may be
revised from time to time, and should not be construed as a commitment by Lotus
Cars Ltd or any associated or subsidiary company. Lotus Cars Ltd assumes no
responsibility or liability for any errors or inaccuracies that may appear in this
document.
This document contains proprietary and copyrighted information. Lotus Cars Ltd
permits licensees of Lotus Cars Ltd software products to print out or copy this
document or portions thereof solely for internal use in connection with the licensed
software. No part of this document may be copied for any other purpose or
distributed or translated into any other language without the prior written permission
of Lotus Cars Ltd.
©2005 by Lotus Cars Ltd. All rights reserved.

Getting Started with Lotus Suspension Analysis
Contents
i
CONTENTS
1 INTRODUCING LOTUS SUSPENSION ANALYSIS...............................................1
1.1 Overview..........................................................................................................1
1.2 What is Lotus Suspension Analysis? ...............................................................2
1.3 Normal Uses of Lotus Suspension Analysis.....................................................2
1.4 Overall Concepts .............................................................................................2
1.5 Co-ordinate system..........................................................................................3
1.6 Sign convention. ..............................................................................................3
1.7 About the Tutorials...........................................................................................4
2 TUTORIAL 1 - GETTING STARTED.......................................................................5
2.1 Overview..........................................................................................................5
2.2 Starting the Application ....................................................................................6
2.3 Creating a New Model .....................................................................................8
2.4 Manipulating the Graphical View....................................................................11
2.5 Displaying Graphical Results .........................................................................14
2.6 Displaying Text Results .................................................................................15
2.7 Bump, Steer and Roll Kinematics ..................................................................16
2.8 Animation Suspension Kinematics.................................................................19
2.9 Saving Data Files...........................................................................................20
2.10 Closing the Application.................................................................................20
3 TUTORIAL 2 - FULL SUSPENSION MODEL.......................................................21
3.1 Overview........................................................................................................21
3.2 Target suspension design..............................................................................22
3.3 Tutorial 2.a.....................................................................................................23
3.4 Tutorial 2.b.....................................................................................................27
4 TUTORIAL 3 - USER TEMPLATES (1) ................................................................31
4.1 Overview........................................................................................................31
4.2 Description of User Templates.......................................................................32
4.3 The ‘Parts’ Data Set.......................................................................................33
4.4 The ‘Points’ Data Set .....................................................................................34
4.5 The ‘Settings’ Data Set ..................................................................................36
4.6 ‘Settings’ - Parts.............................................................................................36
4.7 ‘Settings’ - General Types..............................................................................37
4.8 ‘Settings’ - Bushes .........................................................................................42
4.9 ‘Settings’ – Point Solution Type .....................................................................44
4.10 Template Validation .....................................................................................54
4.11 Exercise 1 – Modifying an Existing Template...............................................56
4.12 Exercise 1 – Solution ...................................................................................57
5 TUTORIAL 4 - USER TEMPLATES (2) ................................................................59
5.1 Overview........................................................................................................59
5.2 Template Sources..........................................................................................60
5.3 Storing and Saving Templates.......................................................................63
5.4 Saving to the User Templates File.................................................................63

Contents
ii
5.5 Saving Custom template Files .......................................................................64
5.6 Creating New Templates................................................................................64
5.7 Exercise 2 – Creating a New Template..........................................................65
5.8 Template Graphics.........................................................................................70
5.9 Exercise 3 – Adding Graphics to a Template.................................................76
5.10 Using the New Template..............................................................................78
6 TUTORIAL 5 - COMPLIANT ANALYSIS ..............................................................79
6.1 Overview........................................................................................................79
6.2 Enabling compliance calculation....................................................................80
6.3 Editing compliant bush properties..................................................................82
6.4 Adding external forces ...................................................................................84
6.5 Displaying compliance results........................................................................88
7 TUTORIAL 6 - INTERNAL OPTIMIZER................................................................91
7.1 Overview........................................................................................................91
7.2 Introduction ....................................................................................................92
7.3 Setting Kinematic Targets via User Lines ......................................................93
7.4 Weighting Settings for Kinematics .................................................................94
7.5 Identifying Positional Optimiser Parameters ..................................................96
7.6 Running a Kinematic Optimisation.................................................................97
7.7 Kinematic Tutorial ..........................................................................................99
7.8 Setting Compliant Targets via Compliance Coefficients ..............................101
7.9 Weighting Settings for Compliant Coefficients .............................................102
7.10 Specifying Compliant Optimiser Parameters and Limits .............................103
7.11 Running a Compliant Optimisation..............................................................105
8 COMMAND REFERENCE CARD .......................................................................107

About This Guide
iii
About This Guide
Welcome to Lotus Engineering Suspension Analysis. This product will allow you to
design and analyse the vehicle suspension hard points to achieve the required
suspension characteristics. The optional addition of compliant bushes and operating
forces allow compliant characteristics to be calculated and bushes tuned to obtain
the desired behaviour.
What You Need to Know
This guide assumes the following:
Lotus Suspension Analysis is installed on your computer or network and you
have permission to execute the relevant Lotus modules.
The necessary password file is installed to allow you to run the necessary
modules.
You have a basic understanding of vehicle suspension mechanisms, their loading
regimes and functional operating requirements.

1 Introducing Lotus Suspension Analysis
1.1 Overview
This chapter introduces you to the Lotus Suspension Analysis Tool and
explains the normal uses for it. It also introduces the tutorials that we’ve
included in this guide to get you started working with Lotus Suspension
Analysis (LSA).
This chapter contains the following sections:
• 1.1 Overview, 1
• 1.2 What is Lotus Suspension Analysis?, 2
• 1.3 Normal Uses of Lotus Suspension Analysis, 2
• 1.4 Overall Concepts, 2
• 1.5 Co-ordinate system, 3
• 1.6 Sign conventions, 3
• 1.7 About the Tutorials, 4
1

Introducing Lotus Suspension Analysis
2
1.2 What is Lotus Suspension Analysis?
LSA is a design and analysis tool that can be used for both the initial layout of a
vehicle suspensions hard points, and also the design and orientation of suspension
bushes for the tuning of the complaint behaviour.
Models are created and modified through a 3d-viewing environment. This allows
hard points and bushes to be ‘dragged’ on screen and graphical/numerical results
updated in ‘real time’. A template-based approach to the modelling allows users to
create their own suspension models, supplementing the ‘standard’ suspension
templates provided.
1.3 Normal Uses of Lotus Suspension Analysis
LSA is used by both designers and analysts alike for the layout of the suspension
hard point positions, in order that the required kinematic behaviour is achieved. Any
number of results can be displayed graphically, (e.g. Camber angle, Toe angle),
against bump motion, roll motion or steering motion. These results are updated in
‘real time’ as the suspension hard points are moved. The inclusion of compliant
bushes to the kinematic model allows the tuning of bush properties to be carried out,
to achieve required compliant response for items such as lateral force steer.
1.4 Overall Concepts
LSA has two main display and analysis modes, 2D and 3D, and it is possible to
import a 2D model into 3D.
Suspensions can be articulated in bump/rebound, roll, steering and combined bump
and steering (3D only) modes.
LSA uses templates to identify specific 3D suspension types. These templates define
the number of parts, the number of points and connectivity of the parts. A large
number of ‘standard’ templates are include with the installation, whilst users can
create their own or modify existing ones to model kinematic suspension types not
catered for.
3D models can be built as corner, axle or full vehicle suspension models.
LSA can be used just in Kinematic mode, (i.e. rigid bodies with ball joints), or in
compliant mode where the deflection due to bushes is added to the kinematic results
on an incremental basis, (note that the compliant module is licensed additionally to
the kinematic module). The compliant mode includes modal analysis and forced
damped capability.

3
1.5 Co-ordinate system
The LSA co-ordinate system is a right-handed system the origin of which must be in
front of the car and coincide with the vehicle longitudinal centre line.
Y-axis is across the car track, and the +ve direction being towards the right side
when sitting in the car.
X-axis is along the vehicle wheel base and positive toward the rear of the car.
Z-axis is the vertical height and positive upwards.
When inputting suspension hard point data you must ensure that all co-ordinates are
constant with the origin you have selected and be aware that all suspension hard
point output generated by LSA will be relative to that origin. The only restrictions are
that the X-Z plane must pass through the centre of the car and the origin must be in
front of the car. The co-ordinate system origin need not be coincident with the
ground plane.
Figure 1.1 LSA co-ordinate System
1.6 Sign convention.
Camber - Inclination of the wheel plane to the vertical, negative when the wheel
leans in at the top
King Pin Angle - The front view angle between the steering axis and the vertical.
Positive when the steering axis leans inwards at the top.
Toe - Angle between the plane of the wheel and the forward direction, positive if the
front of the wheel is “toed in” toward the centre of the car.
Castor - The angle in side view between the steering axis and vertical. Positive
when the top of the steering axis is inclined toward the rear.
Steering Lock - Linear Y-axis displacement of the steering rack. Positive steering
lock can produce negative or positive toe depending if the steering rack is in front or
behind the steering axis.
Roll - Right hand rule applied to the vehicle positive x-axis. When sitting in the car
roll to the left is positive.

4
1.7 About the Tutorials
The remainder of this guide is structured around a series of tutorials that introduce
you to the features of Lotus Suspension Analysis. Each tutorial builds on what was
learnt in those before it and are thus linked such that the user should work through
them in the order presented. The essential steps required to complete the tutorial
have been bulleted as shown below.
Essential steps in the tutorial are bulleted and italic.
To save time you can skip through the text and only do the essential steps. The rest
of the text gives a more complete description.
• Tutorial 1 - Getting Started - Describes the layout and gives you an overview of
the application, teaches you how to load existing files and introduces basic
editing, viewing and saving concepts.
• Tutorial 2 - Full Vehicle Suspension – A double wishbone front and rear
suspension model is setup in LSA. Target characteristics are defined and the
tutorial gives step by step instructions to modify the suspension geometry so that
a compromise suspension solution is achieved.

2 Tutorial 1 - Getting Started
2.1 Overview
This tutorial introduces the main features of the product and gives a
summary of its base functionality.
• 2.1 Overview, 5
• 2.2 Starting the Application, 6
• 2.3 Creating a New Model, 8
• 2.4 Manipulating the Graphical View, 11
• 2.5 Displaying Graphical Results, 14
• 2.6 Displaying Text Results, 15
• 2.7 Bump, Steer and Roll Kinematics, 16
• 2.8 Animation Suspension Kinematics, 19
• 2.9 Saving Data File, 20
• 2.10 Closing the Application, 20
2

Tutorial 1 - Getting Started
6
2.2 Starting the Application
To start Lotus Suspension Analysis from the main Start menu point to Programs
and then Lotus Engineering Software and then Lotus Suspension Analysis. If
the program fails to start or the menu item is missing from your start menu, firstly
confirm that the software has been installed correctly. You can browse for the
application directly, the executable file name is Shark.exe. As the program starts the
start up ‘splash’ screen will be displayed, before the main application window is
opened.
Start LSA from windows start menu
Start -> Programs -> Lotus Engineering Software -> Lotus Suspension
Analysis
Figure 2.1 Start-up Splash Screen
On start-up the application will open with an empty 3D display window. A number of
the menus and icons are disabled until either a new model has been started or an
existing model has been loaded.
The settings of both the display and analysis modes is initially set either by the
defaults, (if not previously run), or by the settings saved to the ‘ini’ file from the
previous run.

7
Figure 2.2 Layout of application
Additional context specific menu items are used throughout the application and can
be accessed by clicking the right mouse on the window/graph of interest

8
2.3 Creating a New Model
To create a new model select the File / New menu option from the main menu bar,
(note that we are in 3D module and will thus be creating a new 3D model creating a
new model in the 2D module works in exactly the same way). The ‘new model’
dialogue box is then displayed.
File -> New
Figure 2.3 New Model Dialogue Box
The dialogue box allows you to pick the required suspension type for the front or rear
or both. For our example we will consider a model with only the front. Suspensions
are modelled in LSA based on specific template types. Depending whether the
template has been built with provision for a steering attachment point will dictate if it
appears in the list of available front suspension types, (all defined templates are
listed in the rear suspension list).
Check ‘Front Suspension- PickType’
From the front suspension drop down box select ‘Type 1: Double
Wishbone, damper to lower wishbone’
From steering type drop down box select ‘steering rack’

9
Once you have selected the front suspension type the ‘View/Edit Front Co-ordinates’
icon becomes enabled, allowing you to change the default hard point co-ordinate
values.
Click ‘View/Edit Front Co-ordinates’ to inspect the front suspension
co-ordinate. Once done click OK to accept defaults
Figure 2.4 Type 1 Default hard points display
For a front suspension you can choose between a conventional steering rack or a
steering box, (a steering box requires additional hard point data to be defined). We
will stick with the more normal steering rack.
From the ‘new’ dialogue box we can also view/change the ‘Parameter’ data
associated with the model, (such as wheelbase, c of g height, bump travel, brake
split etc and geometric data associated with the tyre). All of the model properties can
also be modified at a later stage as required.
Figure 2.5 Parameter Data Lisiting

10
To complete the creation of a new front suspension model, select ‘Done’. This will
now enable all the previously ‘greyed-out’ menus and icons. The created model is
now displayed in the ‘3d display’ window.
Click ‘Done’ to open the model.
Now that we have a model we will set up the 3D display. The first time LSA is
opened the default view settings will be applied. Subsequently each time that LSA is
closed, the current view setting are saved and will be used the next time LSA is
opened (the default settings can only be restored by deleting the LSA initiation file
’SHARK.INI’ from the ‘WINNT directory).
‘Graphics -> Screen Display -> Static Only’
‘Graphics -> Point Limits’, ensure neither ‘visible’ nor ‘use’ have a tick mark
next to them.
Display both sides of the suspension by left clicking on the ‘Display Both
Sides’ tool .
Auto scale the view with ‘Autoscale Display .
Figure 2.6 Screen shot of new front suspension model.

11
2.4 Manipulating the Graphical View
Use the Setup menu from the menu bar to display only the ‘View’ toolbar.
From the ‘SetUp’ menu setup the toolbars so that only ‘View Toolbar
Visibilities’ is displayed, as shown in the Figure 2.7.
Figure 2.7 Selecting View Toolbar Visibilities from SetUp menu
The suspension 3D display interface has two modes, ‘Dynamic viewing’ for
manipulating the view and ‘Edit’ mode for modifying the suspension geometry. The
left mouse button is clicked on the dynamic view icon to toggle between ‘Viewing’
and ‘editing’ mode. In viewing mode markers are displayed in each corner of the 3D
suspension display window
Toggle the ‘dynamic view icon’ so that viewing mode is selected, ie
markers displayed in each corner of the suspension 3D display window.
The graphical display is manipulated through the mouse cursor and buttons. It allows
you to rotate, translate and zoom in/out by the combination of holding the left mouse
button down whilst moving the mouse. Specific menu options exist for ‘autoscale’,
pick centre and setting the view to orthogonal projections.
If you are in the ‘edit’ mode selecting any one of the dynamic viewing options will
change the mode to dynamic viewing. Alternatively selecting the dynamic view icon
will cycle between edit and view modes.

12
Change to ‘Translate view’ . Select a point on the 3D-suspension
window with the left mouse button, hold down and drag.
Change to ‘Scale view’. Select with left mouse button, hold down and
move down to zoom in, up to zoom out.
Change to ‘Rotate view’ . Select with left mouse button, hold down and
move to rotate view. Picking towards the centre rotates the eye point
around the object, picking towards the edge rotates around the object axis.
(when in dynamic view mode, the Right Mouse button will cycle through the three
dynamic view types, zoom, translate, rotate)
In some situations it is desirable to make frequent use of a particular user defined
view. To achieve this LSA can save user define views for latter use.
Use the rotate view tool to set a non-orthogonal view similar to figure
2.8.
Figure 2.8 ‘Pictorial’ view of front suspension.

13
Select the ‘Save Current View Settings’ tool and enter a name for the
view, click ok
Restore the front view by selecting the front view icon , then the
‘Autoscale display’ icon ‘ ’
The saved view can be used via the ‘View’ main menu . ‘View - > Saved
Views -> Recall Saved’ and select the saved view from the list
To proceed re-set the suspension display to front view and ensure the view
is fitted to the display window.

14
2.5 Displaying Graphical Results
Graphs are used to display analysis results for any of the calculated results. To open
a graph select Graphs / New/Open. The created window will show the current model
results for a particular parameter, e.g. camber angle. To change the displayed
parameter for a particular graph select the graph with the right mouse button and
pick the required parameter from the displayed list. The right mouse menu also
contains options for setting axis scales and general viewing options such as zoom
and autoscale.
Any number of graphs can be open at the same time, the positions and sizes of
which can be modified and saved by the user for future use, (see SetUp / Save
Window Settings To…).
Figure 2.9 Graph showing right mouse menu
From the menu bar select ‘Graphs -> New/Open’
Set the graph to display camber angle by placing the cursor over the new
graph then ‘Right Click -> Y-Variable -> camber Angle’.
Open two more graphs for Toe Angle and Castor Angle and arrange the
windows so you can view the suspension 3d display and each graph
simultaneously.

15
2.6 Displaying Text Results
The text results for the currently defined suspension model can be displayed in a
scrollable text window, Results / List Formatted SDF File… This lists an echo of the
input data and tabulated/headed suspension derivatives. This provides a convenient
reporting medium for numerically summarising the suspension properties.
From the main menu select ‘Results -> List SDF File’. When done
inspecting results close the text results window
Figure 2.10 Sample Formatted SDF Display
The text results can also be listed as a series of spline fits rather than tabulated data.
The user having control of which splines to list and the power of the spline fits. This
provides a method of exporting suspension properties to external spline based full
vehicle handling applications.
Figure 2.11 Sample Spline Results Display

16
2.7 Bump, Steer and Roll Kinematics
Display the File Toolbar from the SetUp menu by selecting ‘SetUp -> File
Toolbar Visibility’
Figure 2.12 Displaying the File Toolbar
The suspension articulation type can be bump/rebound, roll or steering. Steering
articulation is applicable to 3D front suspension models only. The articulation type
can be changed via the relevant toolbar icons or the Module / Shark pull down menu
options.
Figure 2.13 3D articulation type icons ringed
Changing the articulation type will change any displayed result graphs to show the
same variables but over the new articulation motion range (roll, bump, steer). Graph
axis scales may need to be re-set to show the new results.
In turn select each of the ‘3D bump’ ‘3D Roll, and ‘3D Steer’ articulation
Icons on the File Toolbar and note how the results displayed on each graph
change for each motion type.
An additional combined bump and steering mode is available. Users define each
point separately through an interactive display.
Each articulation type range is controlled by user defined limits. These can be
changed via the ‘Data -> Parameters’ main menu. The bump/rebound travel can also
be set for specific positions.

17
Figure 2.14 Parameters Data Display
Now we can move the suspension hard points and see the effect on the suspension
kinematics.
Suspension hard points can be modified by one of three ways, using input edit
boxes, using the keyboard arrow keys or by dragging hard points with the mouse
Select the ‘Change to 3D bump Module’ icon from the file toolbar.
Click the ‘Set to Joggle Mode’ icon on the File Toolbar and left click on
one of the left inboard suspension ball joints.
Left Click on the ‘Toggle Tracking Setting’ icon on the ‘View’ toolbar
until both up/down and left/right arrows are displayed over the suspension
point you have selected.
Manipulate the suspension hard point by holding down the ‘Ctrl’ key then
pressing the arrows on the keyboard.

18
As the suspension point is moved the suspension geometry graphs will be
continuously updated and the position of the suspension roll centre will move on the
3D display. The roll centre is displayed as a blue circular dot on the display.
Toggling between 3D bump, steer and roll using the ‘File’ Toolbar icons will update
the graphs for each of the kinematic motion types.
Select the ‘Set To Drag Mode’ icon
From the main menu select ‘Tracking -> Length’ and set the ‘3D Drag Line
Length’ to 50 mm.
Now left click and hold a suspension hard point. This can now be dragged
around the screen and the results will be continuously updated on the
graphs as you move the suspension.
The suspension hard point can each be moved in the front, plan and side views.
The suspension is modelled symmetrically, any change to one side is mirrored on
the opposite hard point.
Select the ‘Set to Edit’ icon on the File toolbar and left click on a lower
inboard suspension point.
In the edit box add 5 mm to the ‘y’ co-ordinate and click ‘OK’. The
suspension will now have moved to the new location.
When in edit mode ‘tracking lines’ are drawn to indicate the current ‘tracking’
direction(s). This is not relevant to the hard point-editing mode as tracking only
applies to the dragging and joggle edit modes. To change the current tracking
direction the right mouse button will cycle through the available tracking direction
options. A similar action is achieved by selecting the mouse icon from the ‘view’
toolbar.
Hard point joggling operates in a similar way to dragging with regard to available
directions. The drawn joggle symbol indicates the number of joggle directions
available. To use joggle select either Ctrl + Arrow Key for coarse joggle or Shift +
Arrow Key for fine joggle. The joggle fine size is a tenth of the coarse size, the
coarse size can be set via SetUp / Gen Defaults…
For a full description of the suspension hard point editing options refer to the help
file, ‘Overview – Hard Point Editing’ and ‘Overview – Hard Point Dragging’.
LSA can also be set up to retain the length of suspension parts when modifying the
suspension. In this mode the whole suspension moves to satisfy the new hard point
location without changing any suspension part lengths.
From the menu bar select ‘Edit -> Change mode -> Retain Part Length’.
Now try dragging suspension hard points with the mouse.
Return ‘Change mode’ to ‘Change part lengths’

19
2.8 Animation Suspension Kinematics
The suspension can now be animated to give a movie of the suspension movement
in bump, roll and steer. The movement of the roll centre is also displayed in the
animation and the suspension hard points can be edited during the animation.
Display the graphics tool bar by using the SetUp menu ‘SetUp -> Graphics
Toolbar Visibility’
Left click the ‘Animate mechanism’ icon on the graphics toolbar.
Whilst the animation is displayed switch between bump, roll and steer
modes.
As the suspension is animating try dragging suspension hard points and
see the effect on the roll centre location in roll, bump and steer.

20
2.9 Saving Data Files
Models can be saved in the conventional way using File / Save or File / SaveAs
menu items. You will always be warned about overwriting existing model files. Data
files will include all suspension hard point data, compliant bush properties and model
parameters. What it does not necessarily include is the template definition. A data
file can in refer to the template via an entry number if the 'include User Templates in
Data File' option is not checked. For further information on the definition and storing
of suspension templates see the template sections in this document.
Figure 2.15 Okay to Overwrite dialogue
2.10 Closing the Application
To close the program select ‘File -> Exit’ from the main menu, and then confirm the
‘okay to exit’ prompt. Alternative methods to close the application include the
conventional ‘X’ from the windows top right corner, Alt+F4 or close from the main
windows top left menu. In addition the ‘esc’ key will close the application, (subject to
accepting the prompt).
Figure 2.16 Okay to Exit Prompt

3 Tutorial 2 - Full Suspension Model
3.1 Overview
In this tutorial we will develop separate front and rear suspensions in
two separate files then combine the two to create a full vehicle
suspension kinematic model.
A target hypothetical suspension characteristics has been set in Section
3.2 and we will attempt to achieve a design that gives the best
compromise solution. The target does not necessary represent
desirable kinematics nor have other limitations such as packaging been
considered. The suspension specification shown in Table 3.1 is a
subset of all the dimensions / specifications required. All other data has
been left as LSA default values.
• 3.1 Overview, 21
• 3.2 Target Suspension Design, 22
• 3.3 Tutorial 2.a, 23
• 3.4 Tutorial 2.b, 27
3

Tutorial 2- Full Vehicle Suspension
22
3.2 Target suspension design
Front suspension: Type 1: double wish bone
Steering: Steering rack
Rear suspension: Type 1: double wish bone
Table 3.1 Suspension specifications.
Settings
Front Rear
Toe 0 0
Camber -1.5 -1.5
Castor 3 0
KPI 5 5
Anti-dive 40 -
Anti-squat - 44
Ackerman 80% -
% braking 60% 40%
Roll centre height 75 100
Suspension travel
Front Rear
Bump 40 40
Rebound 40 40
Roll 2.5 2.5
Steering 30 -
Tire
Front Rear
Rolling radius 225 225
Width 150 150
Goals:
• Minimise roll and bump steer.
• Minimise movement of roll centre.
• Keep roll centre above ground at maximum bump.
• Camber less than zero at maximum body roll angle.
• Minimise tire scrub with bump

23
3.3 Tutorial 2.a
Open new front suspension model
From the file main menu select ‘File -> New’ to bring up the new model
dialog box.
Select front suspension only with Type 1: double wishbone suspension and
steering rack.
On the ‘New Model’ dialog left click on the ‘View/Edit parameter data’ icon
.
Go through the list of parameters and modify: Bump travel, Rebound travel,
Roll angle and Steer travel to match the data in table 3.1
Left click ‘Ok’ to close parameter dialog box then ‘Done’ to generate the
new model.
To set the static toe and camber angles from the main menu select ‘Data ->
Set Static Angles…’ and input 0.0 for toe and –1.5 for camber, then click
‘ok’.
Check that all of the 4 toolbars are displayed. If any are missing they can
be displayed from ‘setup’ on the main menu.
The model parameter and static settings have now been set up. We will now
proceed to set up graphs to display the results as we manipulate the suspension
geometry. Our goal is to manipulate the hard points to give kinematic motion in
bump/rebound, steer and roll that gives the best compromise compared with our
design goals. The static toe angle has been set to zero for now to avoid confusion
when analysing the steering Ackerman geometry. If the toe angle is non-zero then
the % Ackerman steering is ill-defined and the LSA Ackerman output cannot be
used.
Open Graphs
Left click on the ‘open new results graph’ icon on the graphics+data
toolbar to open a new results graph.
Right click on the new graph and select ‘Y-Variable -> Camber angle’
Open another 5 graphs for toe angle(deg) {SAE}, castor angle (deg), King
Pin Angle (deg), Roll Centre Height {To Grnd} (mm) and Half Track change.
Once all the graphs are open arrange the 3d display window and the graphs
so they can all be viewed simultaneously.

24
Select 3D Bump mode by left clicking the icon .
Right click on each graph in turn and select ‘AutoScale to Y increment’ to
auto scale each graph. (The axis scale and y increment size can be set to
your own custom values by right clicking on the graph and selecting ‘Axes
Scales’).
The castor angle and KPI will be modified first to achieve the specified values. For
this tutorial we will modify the upper ball joint on the suspension upright.
Turn off display of the wheels by clicking on the ‘Toggle Enhanced Wheel
Vis’ icon .
Select joggle mode and left click on the top upright ball joint. You can now
move the ball joint in the y direction. As you move the hardpoint (keyboard
keys ‘ctrl’ + ‘->’) the KPI graph will be updated. Move the ball joint to give 5
degrees KPI at zero bump as shown on the KPI graph.
With the ball joint selected the mouse right click will toggle through the available
joggle directions in that view
Right click on the KPI graph and select ’List data line(s)’ to verify angle.
Close the dialog when done.
Change the view to z-x
Move the top upright ball joint in the x-direction to give 3 degrees castor
angle.
The castor and KPI are now set and you can manipulate the views to visually verify
that the top of the king pin axis is inclined inwards towards the centre line of the car
and backwards toward the rear. The castor and KPI are also listed in the SDF
output file available in the ‘results menu’. Return to front view and 3d roll mode
when done.
• Next we will manipulate the inboard suspension hard points to achieve desired
suspension kinematics in bump and roll.
To achieve these characteristics we will move the inboard suspension hard points on
the upper and lower suspension wishbones and the inner and outer steering ball
joints. Before proceeding experiment with moving these 6 suspension hard points
and see if you can achieve a compromise between the target suspension kinematic
characteristics. As movement of any one hard point can effect all of the
characteristics we are interested in you will need to iteratively move and adjust each
hard point in front and side view until you have reached a best compromise. Figures
3.1 and 3.2 give an indication of one hard point configuration that satisfies this

25
condition. Once you have finished experimenting continue with the tutorial to input
the suspension hard points manually.
Figure 3.1
Figure 3.2
Set viewing mode to front view y-z
Turn hard point numbering on by toggling the ‘Point Nos Visibility’
tool.

26
Select the ‘Set to Edit Mode’ icon and select the lower front inboard
pivot: ‘Point 1’ and type in the hard point location shown in Figure 3.3
Figure 3.3
Now go through each of the hard points listed in table 3.2 and use the same
method to set the hard point locations listed in the table.
Table 3.2 Suspension hard points that require modification.
Point Name X (mm) Y(mm) Z(mm)
1 Lower wishbone front pivot 3819 91 181
2 Lower wishbone rear pivot 4179 92 197
5 Upper wishbone front pivot 4092 308 385
6 Upper wishbone rear pivot 4332 308 369
11 Outer track rod ball joint 4214 668 233
12 Inner track rod ball joint 4245 197 230
With the suspension now located toggle between 3D bump roll and steer modes and
verify that the design criteria are satisfied. Note that the calculation for Ackerman is
based on having zero static toe. If the static toe is non-zero the output for %
Ackerman is not properly defined and cannot be used.
You can now verify yourself from the graphs and animating the suspension
in steering, bump and roll that a compromise solution to the targets set out
in section 3.2 has been achieved.
From the main menu select ‘File -> Save As’ and save the model as ‘Tutorial
2a’.

27
Now we have setup the graphs we can also save window setting which will save
which output graphs are displayed. The next time you use the model you can load
the windows setting file to reset the graphs.
From the main menu select ‘SetUp -> Save Window settings To…’. Enter
‘Tutorial 2a’ as the file name and save the widows settings file.
This completes tutorial one. The solution obtained is a compromise between all the
desired and sometimes conflicting requirements of the suspension. You may want to
experiment to see if you can improve the design. Also notice that the camber and
castor angles achieved are not an exact match to the targets.
3.4 Tutorial 2.b
Open New Rear Suspension Model
From LSA menu select ‘File -> New’.
Check the rear suspension tick box and select Type 1 Double wishbone,
damper to lower wishbone (we will add the front suspension later).
Check that the parameter data and tyre data are correct (you may need to
modify Bump travel, Rebound travel, Roll angle and Steer travel to match
the data in table 3.1) then click done on the ‘New Model’ dialog to open the
new rear suspension model.
Now we have a new rear suspension model open we will setup a new graph to
display % anti-squat for the rear suspension.
From the main menu select ‘Setup -> Load Windows settings From….’.
Select the settings file ‘Tutorial 2a’ that we saved earlier and open.
Add another graph by clicking on the ‘Open New Results Graph’ tool
and position the graph so it does not obstruct any of the other graphs.
Right click on the new graph and select ‘Y-Variable -> Anti-Squat (%)’.
Auto scale the Y-axis. Right click on graph and select ‘Autoscale To Y
Increment’.
The new graph settings can be now saved to the windows settings file.
From the main menu select ‘SetUp -> Save Window settings To…’. Enter
‘Tutorial 2b’ as the file name and save the widows settings file.
Setup of the rear suspension follows the same procedure as the front therefore we
will omit manipulating the suspension hard points and edit the rear suspension co-
ordinates table directly. At this point you can experiment for yourself to see if you

28
can meet the suspension characteristic targets then continue from this point once
you are done (you may want to save your own model before you proceed).
Click on the ‘View/Edit rear co-ordinates’ icon to bring up the rear
suspension co-ordinates table.
Now you can manually edit each of the suspension hard point locations by
directly editing the (X,Y,Z) co-ordinates of each hard point. Use table 3.3 for
input data. Click ‘OK’ when finished.
Table 3.3 Rear suspenion hardpoints co-ordinate table.
You can check for yourself that the new rear suspension co-ordinates give a ‘good’
compromise solution compared to the targets set out in Section 3.2. To complete
the full suspension model we will now proceed to add the front suspension from
tutorial 2.a.

29
From the main menu select ‘File -> Add End From File’ and select the front
suspension model developed in tutorial 2a.
You now have a full vehicle suspension kinematic model with satisfies the target
kinematic characteristics.
When working with full suspensions, displaying both the front and rear suspensions
can be visually confusing. LSA allows you to display only the front or rear
suspension and also only one side of the suspension.
Displays only the front suspension.
Displays only the rear suspension.
Displays both front and rear suspension.
Toggles between displaying one side and both sides.
In this tutorial you have learnt all the basic operations for setting up, manipulating
and analysing suspension kinematics. To complete this tutorial save your file and
quit LSA.
Save model as ’Tutorial 2b’ and close Lotus Suspension Analysis to end
tutorial 2.

4 Tutorial 3 - User Templates (1)
4.1 Overview
This chapter describes the structure of the model Templates used by
Lotus Suspension Analysis to define and solve each suspension type.
This then details how users can create their own templates and make
them available as extra ‘default’ templates or share them with other
users.
• 4.2 Description of User Templates, 32
• 4.3 The ‘Parts’ Data Set, 33
• 4.4 The ‘Points’ Data Set, 34
• 4.5 The ‘Settings’ Data Set, 36
• 4.6 Settings - ‘Parts’, 36
• 4.7 Settings - ‘General Types’, 37
• 4.8 Settings – ‘Bushes’, 44
• 4.9 Settings – ‘Point Solution Type’, 44
• 4.10 Template Validation, 54
• 4.11 Exercise1 – ‘Modifying an Existing Template’, 56
• 4.12 Exercise 1 – ‘Solution’, 57
4

User Template (1)
32
4.2 Description of User Templates
All suspension types used in LSA (Shark) are defined using a template structure.
This structure uses a combination of data sets separated up into ‘Parts’, ‘Points’,
‘Settings’ and ‘Graphics’. A significant number of the most common suspension
types are ‘hard coded’ into the application as defaults, but the user can modify these
‘defaults’ or add their own through the template editing tool, (File / Edit Templates).
Figure 4.1 Opening the template editor
Each template is given a location number in the templates’ database, (for example
the default double wishbone suspension is stored in location number 1). The
template is also given a descriptive string to make recognition of each type easier.
Data values in the various data sets within the template editor are grouped into four
further categories. These are ‘compulsory’, level 1, level 2 and level 3. Each
category is identified by a colour. These are used to illustrate which values must be
defined by the user and which can be filled via the ‘auto-fill’ routines. The auto-fills
can be used to assist in identify missing template values through a series of menu
options.

User Template (1)
33
4.3 The ‘Parts’ Data Set
The Parts data set defines how many parts are in the suspension corner (or axle)
model. Parts include wishbones, tie rods, uprights and rockers. There is no need to
add a part for the vehicle body, (this is taken as part number –1), spring/dampers or
the tyre. Each of these are implicitly included later by ‘Point’ definition.
By convention the upright must be the last part in the list. The only data fields for a
part is an identifying label. This label is used in the other data sets to ease part
recognition/selection.
Figure 4.2 ’Parts’ Data Set editing – Default template 1 shown
Part Numbers and Part Labels for the defined model can be displayed on the model
using the visibility switches, Graphics / Part Nos and Graphics / Part Labels.
All data values in the ‘Parts’ data set are in the ‘Compulsory’ category.

User Template (1)
34
4.4 The ‘Points’ Data Set
The Points data set defines how many ‘hard points’ are include in the suspension
corner/axle model. The data fields for each point is a descriptive label, (again used to
aid identification/selection) and the default x, y and z co-ordinate values. The default
co-ordinate values are those that are applied to a ‘new’ model using the particular
template. The ‘SHARK’ co-ordinate system is a right handed system with the Y-axis
across the car track, the origin of which is assumed to be on the vehicle centre line
and the +ve direction being towards the offside suspension (Right hand Corner
sitting in car). The X-axis is along the vehicle wheelbase, normally with the origin in
front of the vehicle with the +ve direction towards the rear. The Z-axis is the vertical
height, which for the 3D mode can be at any height position. The +ve direction is
taken as upwards.
Figure 4.3 ‘Shark’ Co-ordinate System
Connections between Parts are made at points, (i.e. wishbone ball joint). These
connection points should only be entered once in the list of points, (the association to
two parts is made later). Remember to add points for springs and damper connection
points. You need to include points for both the suspension attachment point of the
spring (or damper) and the attachment to the body.
If you have a combined spring/damper unit that employs common attachment points,
you need not define the spring and damper points separately. We can associate both
the spring and damper to the same connection point later.
For strut type suspensions the strut is defined by three points, the strut top mount
point and two further points on the slider axis. These later two points would normally
be placed at the upper and lower bearing centres to ensure the correct
moments/forces. These three points will always be forced to lie along a single 3D
line and thus get updated/corrected by the application.
Two points are always used to define the wheel spindle axis. The first is the wheel
centre and the second is a point on the wheels rotational axis. This second spindle
point can be either inboard or outboard of the wheel centre, although it is usually
placed inboard of the wheel centre since its is the normal convention to draw
between these two, a graphical element representing the spindle shaft.

User Template (1)
35
Figure 4.4 ’Points’ Data Set editing – Default template 3 shown
Although we have given each point a descriptive label, they can also be referenced
by a simple number. This number is defined in the ‘settings’ data set when the
templates is not in ‘full list’ mode. This number need not be the same as its
numerical position in the list. The use of this number is somewhat historical relating
back to earlier version of the program when points were only referenced by number
rather than by label. The visibility of both ‘number’ and ‘label’ on the model is set
using the visibility switches, Graphics / Point Nos. and Graphics / Point Labels.
You do not define a point for the tyre contact point. This is calculated automatically
from the tyre properties and the wheel spindle points. It is given the internal point No.
of 99.
All data values in the ‘Points’ data set are in the ‘Compulsory’ category.
The 'Points' data set does have some optional identification labels that are used for
the import/export options to some specific file formats. These can be seen in the
right hand columns of the spread sheet.

User Template (1)
36
4.5 The ‘Settings’ Data Set
The ‘Settings’ data set has a row entered for each point defined in the ‘Points’ data
set. It is through the Settings data set that we identify the association of points to a
part, (or Parts), the solution method to solve for each point, a bush No. and any
special function that the point has. Some of these data fields are compulsory others
may be filled through the ‘auto-fill’ options. It should be noted that the ‘auto-fill’
routines are not foolproof and thus should be applied with care. Auto-fill routines
should only be used once all the compulsory data fields have been filled.
Figure 4.5 ’Settings’ Data Set editing – Default template 1 shown
4.6 ‘Settings’ - Parts
Columns 3 (‘part 1’) and 4 (‘part 2’) define the parts that a
point is associated with. These are compulsory data fields.
A point can at most be associated with two parts, (this
would be a connection between parts and requires a bush)
and a minimum of one. In the case of a point associated to
one part, always fill column 3 in preference to column 4.
Note that additional part options, ‘Ground’ and ‘None’ are
added to the available parts list.

User Template (1)
37
4.7 ‘Settings’ - General Types
Column 12 (‘Gen Type 1’) which, whilst it is a compulsory data field, it can be left
blank, (the equivalent of ‘none’ from the menu options). This column defines whether
a point performs one of the ‘General Types’ functions. These functions identify to the
solver and the template builder that a point has specific properties. Column 13 (‘Gen
Type 2’) is a repeat of column 12 and is used if a point has more than one General
Type classification. There are currently 27 different ‘General Types’. Each is
discussed below.
Figure 4.6 General Types Menu
0 = None: Identifies that the point has no specific type. This could include points
such as wishbone attachment points to ground.
1 = Wheel Centre: One point must always be identified as ‘wheel centre’. Identifies
that the point is the wheel centre.

User Template (1)
38
2 = Stub Axle: One point must always be identified as ‘stub axle’. Identifies that the
point is the second point on the wheel spindle which together with the ‘wheel centre’
define the stub axle and hence all wheel related parameters.
3 = Steering Attachment Point to Rack: This optional point identifies that the
template has a point at which steering input can be applied, (either rack or steering
box). It is also used to determine whether the template will appear in the list of
available ‘Front’ suspensions on the File/New option, (all templates appear in the list
of ‘Rear; suspensions irrespective of this general type).
4 = Damper 1 to Suspension: This optional point identifies that the specified point
is the position in the template at which the damper is attached to the moving
suspension. This is used to determine damper travel, damper ratio etc. To work
correctly it will need general type 5 to also be defined. This would also be used to
identify the point at the upper bearing position on the slider of a McPherson-strut
suspension. The reference to ‘Damper 1’ in the description is a recognition for
potential future expansion to include multiple damper templates.
5 = Damper 1 to Body (also Strut Top): This optional point identifies that the
specified point is the position in the template at which the damper is attached to the
body. It is used in conjunction with general type 4 above. This would also be used to
identify the point at the top of the slider for a McPherson-strut suspension.
Figure 4.7 Example Rear Suspension – Showing General Types 1,2,4,5,6 and 7
6 = Spring 1 to Suspension: This compulsory point identifies that the specified
point is the position in the template at which the spring is attached to the moving
suspension. This is used to apply suspension spring forces to the template and
determine spring travel, spring ratio etc. To work correctly it will need general type 7
to also be defined. The reference to ‘Spring 1’ in the description is a recognition for
potential future expansion to include multiple spring templates.

User Template (1)
39
7 = Spring 1 to Body: This optional point identifies that the specified point is the
position in the template at which the spring is attached to the body. It is used in
conjunction with general type 6 above.
8 = Upper Ball Joint: This optional point identifies that the specified point is the
upper ball joint on the steering axis. Whilst this is optional if it exists and can be
identified this will improve the calculation speed/accuracy. Together with general
type 9 it defines the steering axis. If a steering axis can not be defined but a steering
attachment point has been identified, (see default template No. 20), then additional
calculations are used involving a small steering perturbation to identify the ‘effective’
steering axis. This normally involves suspension types that have twin outer ball joints
rather than a single one.
Figure 4.8 Example Front Suspension – Showing General Types 3,8 and 9
9 = Lower Ball Joint: This optional point identifies that the specified point is the
lower ball joint on the steering axis, (see comments for type 8 above).
10 = Strut Slider Point: This optional point identifies that the template is a strut type
suspension and the specified point is the strut body upper bearing position. This
should not be confused with the strut top mount, (which is identified via general type
5). This point moves with the strut body and is used as the sliding connection
between the slider and the strut body, (see also type 11 below).

User Template (1)
40
11 = Strut End Point: This optional point identifies that the template is a strut type
suspension and the specified point is the strut slider end bearing. This point moves
with the strut slider and is used as the sliding connection between the slider and the
strut body.
Figure 4.9 Example McPherson Strut – Showing General Types 5,6,7,10 and 11
14 = Roll Bar – Link attachment: This optional point identifies the point where the
roll bar drop link is attached to the anti-roll bar. This is used to identify the amount of
twist in the bar and hence the force applied to the suspension.

User Template (1)
41
Figure 4.10 Example Front Suspension – General Types 14 and 34
15 = Rack Lateral Mount point: This optional point identifies the point as being a
the rack attachment point that also takes the axial reaction load. User defined bush
properties should be defined accordingly.
16 = Rack Mount Point: This optional point identifies the point as being the second
rack attachment point. No axial load is carried by this point when using the default
bush settings.

User Template (1)
42
Figure 4.11 Example Front suspension – General Types 3, 15 and 16
17 = Wheel Centre(2): This optional point identifies the point as being the second
wheel centre for rigid axle and full axle templates.
18 = Damper 2 to suspension: This optional point identifies the point as being the
second dampers’ attachment point to the suspension. It may be a second damper on
a single corner model or the opposite side on a full axle model.
19 = Damper 2 to body: This optional point identifies the point as being the second
dampers’ attachment point to the body. As for point 18 above it may be one of two
cases.
20 = Spring 2 to suspension: This optional point identifies the point as being the
second springs’ attachment point to the suspension. It may be a second spring on a
single corner model or the opposite side on a full axle model.
21 = Spring 2 to body: This optional point identifies the point as being the second
springs’ attachment point to the body. As for point 20 above it may be one of two
cases.
22 = Rigid axle revolute: This optional point identifies the point as being a revolute
joint at the centre of a rigid axle. It is required for rigid axle templates to enable them
to pre-solve in kinematic mode when in roll mode.
23 = Stub Axle(2): This optional point identifies the point as being the second wheel
stub axle point. This is needed for full axle models.

User Template (1)
43
24 = Shear Point: Used just for twist beam suspensions to identify the different pivot
point position used in bump and roll. (Optional).
25 = Part C of G Point: Used to identify a point as being the C of G point for its
primary part. It is normal for this point to not be used except as the C of G point, i.e.
no involved in any joints. (Optional).
26 = Upper Ball Joint(2): Identifies a point as being the upper ball joint for the
steering axis on full axle templates only. This must be a connection between two
parts to conform with the concept of a steering axis. It is an optional setting in that if
it (and the lower ball joint) are not defined the steering axis is determined via a small
perturbation of the steering input mechanism. If it can be defined it will lead to faster
solution times than the small perturbation method. (Optional).
27 = Lower Ball Joint (2): Identifies a point as being the lower ball joint for the
steering axis on full axle templates only. This must be a connection between two
parts to conform with the concept of a steering axis. It is an optional setting in that if
it (and the upper ball joint) are not defined the steering axis is determined via a small
perturbation of the steering input mechanism. If it can be defined it will lead to faster
solution times than the small perturbation method. (Optional).
28 = Strut Slider Point(2): Sets the point for a Macpherson strut suspension type
that is considered to be the location of the top bush for the strut for full axle
templates only, (attached to the strut body). (Required for Struts).
29 = Strut End Point(2): Sets the point for a Macpherson strut suspension type that
is considered to be the location of the strut lower bush for full axle templates only,
(attached to the strut slider). (Required for Struts).
32 = Roll Bar – Link Attachment(2): Identifies the point as being the second
connection between the roll bar drop link and the suspension. (Optional). Roll bars
can only be added to full axle templates so a template must have both this and point
14 defined.
33 = Steering Attachment Point(2) to Rack: T Identifies which suspension link end
point should be used for the steering input from the rack or steering box for the
second end in a full axle model only. See also point 3 above. This point should be
the inboard end of the track rod, i.e. link point connected to body or rack. (Optional).
For a compliant rack to be added to the model this point must be defined together
with point 3 above.
34 = Roll Bar, Revolute Joint: Identifies the point as being the centre point of a two
part roll bar. In kinematic mode this is treated as a simple revolute allowing roll
motion. In compliant mode the roll bar stiffness is applied to this point to simulate the
effect of the roll bar stiffness. (Optional). Roll bars can only be added to full axle
templates so a template must have this point and points 14 and 32 defined.

User Template (1)
44
4.8 ‘Settings’ - Bushes
The settings data set is where we define the number of bushes in the model and
assign a bush number to each connection, (column 5). A bush is added at any point
that is a connection between two parts and at a point that is the connection of a part
to ground. Bush Nos. are primarily used for internal identification and need not be
sequential.
4.9 ‘Settings’ – Point Solution Type
Column 2, (‘Point Type’) defines for each point the solution type used to solve its
incremental position. This controls the number of equations and the values used in
solving the set of simultaneous equations. Some solution definitions can be post
solved. That is determined after the set of simultaneous equations are solved. Ten
different point solution types are available although by far the most common is the
use of the ‘sphere’ equation. A description of each solution type is given below.
Depending on the solution type selected the values required in columns 6 to 11 alter.
These level 3 data fields identify the relevant points for the selected solution type.
Figure 4.12 Point ‘Type’ options list
-1 = Dummy Axis Point: This option would not normally be used. It was added to
deal with a specific issue identified for backward compatibility with default template
type 12. It had in its original formulation an additional undefined point used to
restrain the upright and enable the use of a steering knuckle. It is not envisaged that
users would need to use this special option, as it is perfectly feasible to build this
suspension template without recourse to this point solution type.
0 = To Body/Ground: This sets the point solution type as being pre-filled, (by bump,
rebound or roll articulation) and hence no equations are added to the solver for this
point. No arguments are required in columns 6 to 11 for this solution type. Points that
use this type are usually those that are attached directly to the body.

User Template (1)
45
Figure 4.13 Typical Point Type 0’s, To Body/Ground
1 = Solve Direct (sphere): This sets the point solution type to be based on the
equation of a sphere. A spherical equation is added to the list of simultaneous
equations for each point referenced in columns 6 to 11. The sphere equation
controls the 3D distance between two points. The two points being the current rows
point and the column 6 to 11 data field values.
Figure 4.14 Typical Double Wishbone Type 1‘s, Solve direct (Sphere)
Data entry in columns 6 to 11 can be completed using the ‘auto-fill’ routines. The
auto fill routines tend to add duplication but these are checked for and ignored by the
solver.

User Template (1)
46
Figure 4.15 Screen Shot for settings on solution type 1, Adds 4 Equations

User Template (1)
47
2 = Solve Post (Vector Pos): This sets the point solution type to be based on a
fixed position relative to three other points on the same body. It is a ‘post’
simultaneous equation solution calculation and as such has no control on the
suspension articulation. Typical cases where this solution type is applied would be
the case of a simple damper attachment to a wishbone. By definition it requires a
minimum of four points to be associated with the relevant part. It is used where
possible in preference to type 1 above, to increase the overall calculation speed by
not adding three more sphere equations to the list. This solution type should not be
used on push-rod or pull-rods since additional mechanism positions rely on it.
Figure 4.16 Example Solver Point Type 2.
Define in columns 6,7 and 8 the three point No’s of points on the same part as this
point. No numbers are required for columns 9 to 11.
Figure 4.17 Screen Shot for settings on solution type 2

User Template (1)
48
3 = Define Z Pos (Wheel Centre): This point solution type is specific to wheel centre
points. A point that has already been identified as the wheel centre would be given
this point solution type by the ‘auto-fill’ routines. It requires in columns 6,7 and 8
three other reference points to be identified on the same part. One of these points
should not be the wheel spindle point since that point is always post calculated and
therefore not available to use in defining the wheel centre. This point solution type
adds one equation to the simultaneous equation list. No values are required in
columns 9,10 and11.
Figure 4.18 Example Solver Point Type 3, Typical point dependency
Figure 4.19 Screen Shot for settings on solution type 3, Adds 1 Equation

User Template (1)
49
4 = Solve Direct (Slider Conn): This point solution type is specific to Strut slider
points. A point that has already been identified as the ‘Strut slider point’, (general
type 10), would be given this point solution type by the ‘auto-fill’ routines. It requires
in columns 6 and 7 the two other strut slider points to be identified, (general types 5
and 11). This adds two equations to the simultaneous equations list.
Figure 4.20 Example Solver Point Type 4, Shows both part definitions.
No value is required for column 8. In columns 9,10 and 11 point No’s are required for
up to three other points on the Strut Upright part, that define the location of it on that
part. Each point number adds a sphere constraint equation between it and the strut
slider point. The auto-fill routine will always add three points, any subsequent
duplication in spherical constraints is ignored.
Figure 4.21 Screen Shot for settings on solution type 4, Adds 5 Equations

User Template (1)
50
5 = Solve Post (Stub axle): This point solution type is specific to the point general
type 2 ‘Stub Axle’. A point that has already been identified as the ‘Stub axle point’,
(general type 2), would be given this point solution type by the ‘auto-fill’ routines. It
requires three points to be defined through columns 6,7 and 8 that are also on the
upright part. This is a post simultaneous solution method and so does not add any
equations to the list.
Figure 4.22 Example Solver Point Type 5, Shows typical three point definition.
The normal point selection would include the wheel centre point. Because this is a
Post simultaneous equation solver type it can use any three points on the body that
have already been solved in the main simultaneous equation solution, this is typically
major defining points such as all ball joints. It can not use points that are also post
solved since depending on the solver order sequence they may not yet have been
evaluated.
Figure 4.23 Screen Shot for settings on solution type 5.

User Template (1)
51
6 = Solve Direct (Slider Bottom): This point solution type is specific to Strut End
Points. A point that has already been identified as the ‘Strut End Point’, (general type
10), would be given this point solution type by the ‘auto-fill’ routines. It requires in
column 6 the strut top point to be identified, (general types 5). This adds one
equation to the simultaneous equations list.
Figure 4.24 Example Solver Point Type 6, Shows single point identification.
No values are required for columns 7 and 8 or columns 9,10 and 11.
Figure 4.25 Screen Shot for settings on solution type 6, Adds 1 Equation

User Template (1)
52
7 = Solve via Hookes Joint: This point solution type is a post calculation solution
type that was added to handle the specific case of an under constrained kinematic
model. The normal use for this solution type is when a spring or damper is attached
to a tie rod. Kinematically a tie rod having just two attachment points provides a
single spherical constraint to the model but in itself it has a degree of freedom left,
rotation about the axis joining the two ends. When a damper is attached to this link,
unless it is placed exactly on the tie rod axis, this degree of freedom means that the
new position of the damper attachment cannot be solved. By placing a Hookes joint
at one end of the tie rod this rotational degree of freedom is removed and a
kinematic solution can be identified.
Figure 4.26 Example Solver Point Type 7, Two points identified.
The use of a Hookes joint in the kinematic model does not effect the fully bushed
compliant solution. The rotational degree of freedom in the complaint case is taken
out via suitable bush properties. An example of the Hookes joint point solver can be
found in default template 19.
Figure 4.27 Screen Shot for settings on solution type 7, Example template 19.

User Template (1)
53
8 = Solve Post (sphere): This point solution type is a post calculation solution type
and as such adds no equations to the simultaneous equation list. It is used as an
alternative to point solution type 2 in special cases. It is always preferable to use
point solution type 2 rather than this one. Since the sphere equation always has
more than one solution which can lead to errors when two solutions are similar.
Default template 23 uses this solution type for the anti roll bar drop link attachment.
As with the conventional ‘Solve Direct (sphere)’ solution type up to three points are
listed in columns 6,7 and 8 a spherical constraint equation added for each point
number. All points entered must be on the same part as the point being solved. No
data points need be defined in columns 9,10 and 11.
Figure 4.28 Screen Shot for Settings on solution type 8.
9 = Pre-Solve (Kine Fix): A pre main solver option calculation. Requires no defining
points since the point is assumed to be inactive in kinematic mode. It remains fixed
to the part it is defined on (normally ground or a ground fixed part). It is used to add
additional compliance effects for parts such as rack mounts and sub frames that are
assumed to have no kinematic effect but are included in the compliance matrix.

User Template (1)
54
4.10 Template Validation
The definition of a template is used to identify unknown point positions, (x, y and z),
and the number of equations. For a successful template definition the number of
equations must equal the number of unknowns. A utility is provided to test the
unknown to equations count. From the template window select Data / Run Validation
Test… The produced display lists the number of unknowns and the number of
equations. Each equation is listed by type and with the associated point numbers.
Figure 4.29 Example Template validation for default template type 1
This list can be compared with expected equations to debug new template problems.
Remember that it will not list ‘post’ calculation unknowns or equations only those that
are solved as the list of simultaneous equations. If we compare the validation list with
the template ‘settings’ we can identify the source of each equation. The validation of
template 1, shows 12 unknowns. Looking at the conventional double wishbone
suspension we can identify these, (we will ignore additional points that are post
calculated);
Lower Wishbone Outer Ball Joint, X, Y and Z co-ordinates, (x3, y3, z3)
Upper Wishbone Outer Ball Joint, X, Y and Z co-ordinates, (x6, y6, z6)
Steering Arm Outer Ball Joint, X, Y and Z co-ordinates, (x9, y9, z9)
Wheel Centre Point, X, Y and Z co-ordinates, (x14, y14, z14)
These 12 unknowns are illustrated on the image below.

User Template (1)
55
Figure 4.30 Default Template Type 1, 12 unknowns indicated
If we now look at the data in the ‘Settings’ display we can identify the origin of the 12
equations used to solve for the 12 unknowns.
Figure 4.31 Screen shot of settings for default template type 1
Compare the paired numbers with those given in the validation list, they will match.
Minimum Z equation added automatically for wheel centre point. Three duplicate
spherical constraints ignored by the solver.

User Template (1)
56
4.11 Exercise 1 – Modifying an Existing Template
As a simple exercise in modifying a template we will take default template 1 and
change the component that the spring/damper is attached too. To validate that we
have changed the connection point of the spring we will use the compliant analysis
force display.
Open a new front-end only model and use default template type 1. Turn the
compliance ‘on’ and note the calculated force display, (see front view screen shot
below).
Figure 4.32 Standard templates calculated forces.
Now modify the points ‘Damper wishbone end’ and ‘lower spring pivot point’ such
that they are attached to the upright rather than the lower wishbone.
Remember to set any required changes to the new points in columns 6 to 11. For the
purpose of this exercise do not use the ‘auto-fill’ routines we will cover these later.
Make the require template changes and confirm the difference by checking for a
change in the calculated forces.
Hint: Use the ‘apply’ button to apply the changes to the current model. Otherwise you
will need to use the File / New option to pick up the changes to the template.

User Template (1)
57
4.12 Exercise 1 – Solution
You should have made changes to the ‘Part 1’ settings for points 7 and 12. You will
also have needed to change columns 6, 7 and 8 for both of them to reference three
points, (other than themselves), on the upright. Could pick any three from points 3, 6,
9 or 14.
Figure 4.33 Modified template 1, Changes ringed.
Figure 4.34 Revised model illustrating the change in calculated forces.
If this was required to be a permanent change we would probably change the default
x,y,z co-ordinates for points 7 and 12 to make them more realistic and change some
of the point descriptions to be inline with our new template.
Unless we save this modified template, our changes will be lost when we close the
application. In this instance we do not want to retain the changes to this default
template. In the next section we will look at creating and saving new templates such
that they are available for future use.

5 Tutorial 4 - User Templates (2)
5.1 Overview
This chapter we extend the previous chapters description of the data
structure for templates, by creating a new template and making this
available for subsequent analysis runs.
• 5.2 Template Sources, 60
• 5.3 Storing and Saving Templates, 63
• 5.4 Saving to the User Templates File, 63
• 5.5 Saving Custom Template Files, 64
• 5.6 Creating New Templates, 64
• 5.7 Exercise 2, ‘Creating a New Template’, 65
Step 1, 65
Step2, 66
Step 3, 67
• 5.8 Template Graphics, 70
‘Line’ Graphic, 73
‘Pivot’ Graphics, 74
‘Tube’ Graphics, 74
‘Triangular Facet’ Graphic, 75
• 5.9 Exercise 3, ‘Adding Graphics to a Template’, 76
• 5.10 Using the New Template, 78
5

User Template (2)
60
5.2 Template Sources
Each template is stored in a particular template ‘slot’, (normally referred to as
template type). So the conventional double wishbone suspension with damper
attached to the lower wishbone is stored in slot 1 by the hard coded default
templates.
Each saved model data file references the appropriate template slot via this number.
The data file itself does not necessarily have a copy of the template structure only
the slot number, (you can optionally save the template(s) with the data file SetUp /
Include User Templates in Data Files). Thus it is important to remember that if you
make a change to a template the safest approach is to save it to a new ‘free’ slot
number.
Templates are stored at four levels. Each subsequent level can overwrite the current
slot template with a new template, if it defines a template slot number that is already
defined by a previous level.
The first template source level is the ‘hard-coded defaults’. These are built into the
program at compile time and thus whilst they can be modified or over-written by
subsequent levels, (as identified above), they cannot be directly changed by the
user. The ‘hard-coded defaults’ at release version 4.03c are:-
Slot 1 Double Wishbone, damper to lower wishbone
Slot 2 Lower H frame, single upper link
Slot 3 Steerable Macpherson Strut
Slot 4 Non-Steerable Macph Strut, two lower ball joints, tie to ground
Slot 5 5-Link Rigid Axle (Panhard Rod)
Slot 6 Double Wishbone, damper to upper wishbone
Slot 7 Non/Steerable Macpherson Strut, steering arm to lower wishbone
Slot 8 4-Link Rigid Axle (Panhard Rod)
Slot 9 4-Link Rigid Axle (Twin Upper)
Slot 10 Trailing Arm with Two Cross Car Links
Slot 11 Semi/Trailing Arm
Slot 12 Steerable Twin Parallel Wishbones with Steering Knuckle
Slot 14 Double Wishbone with Push Rod Suspension
Slot 15 Double Wishbone, Rocker Arm Damper
Slot 16 Non/Steerable Lower ‘A’ Arm with Toe Link
Slot 17 Double Wishbone, Push Rod, Mono-shock
Slot 18 Double Wishbone, Upper Toe Link, Drop ‘S’ Link
Slot 19 Hinged Trailing Arm, Twin lower Link
Slot 20 Double Wishbone, Twin Outer Ball Joints
Slot 21 5-Link Rigid Axle (Watts Linkage)

User Template (2)
61
Slot 22 Double Wishbone, Twin Outer Ball Joints, Spring Front
Slot 23 Double Wishbone, Anti-Roll Bar
Slot 24 Steerable Macpherson Stut, Twin Outer Ball Joints
Slot 25 Double Wishbone, Twin Lower Outer Ball Joints
Slot 26 Double Wishbone, Damper to Lower Wishbone, Compliant Rack
Slot 27 Steerable Macpherson Strut, Twin Lower Link
Slot 28 4-Link Rear, Transverse Control Link
Slot 29 Twist Beam – Twin Wheel
The second template source level is the ‘User defined Templates’. The user defined
templates are stored in a specific file, (_user_templates.dat), in the same folder as
the software is installed in. On program start-up this file is checked for and if found
any user defined template information stored in it is loaded into the application. As
discussed above if the same slot number as one of the ‘hard coded defaults’ is used
the user template will overwrite the hard coded default. This file will only exist if the
user has previously selected to save a template from within the template editor.
The third template source level is the ‘Custom Templates’. These are stored by the
user into a user defined file, (disc location, folder location and name). They are only
loaded from the file into the relevant template slots when the users scans for and
reads the required file. Thus custom templates can be stored in any number of
separate files, these files can be passed between users or stored on a central
repository. As identified previously slot numbers referenced by the custom templates
will overwrite any existing default or user template definition. If you use custom
templates the template properties must be loaded before you load a data file that
references this custom template.
The fourth template source is from within a loaded data file. If the template has been
saved with the data file, this will be loaded into its respective slot when the data file is
opened. Note that these changes to the template will continue to reside in the loaded
slot until it in turn is overwritten, the program is restarted or one of the File / Re-Read
menu options is run.

User Template (2)
62
Slot No. 1 - Hard-coded defaults 2 - User Defined
Templates
3 – Custom
Templates
4-Data Files
1 Double Wishbone, damper to lower wishbone.
2 H-frame Lower, single upper link.
3 Steerable Macpherson Strut.
4 Non-Steerable Macpherson Strut, twin lower link.
5 5-Link Rigid Axle (Panhard Rod)
6 Double Wishbone, damper to upper wishbone.
7 Non-Steerable Macph strut, toe link to wishbone. Would overwrite
hard coded
Would overwrite
defined
8 4-Link Rigid Axle (Panhard Rod)
9 4-link Rigid Axle (Twin Upper) Would overwrite
hard coded
10 Trailing Arm, upper and lower rear links.
11 Semi Trailing Arm.
12 Steerable Twin Parallel Wishbones and knuckle.
13 Free slot to use
14 Double Wishbone, Push Rod to damper.
15 Double Wishbone, Rocker arm damper.
16 Non Steerable lower A with toe link.
17 Double Wishbone, pushrod mono-shock.
18 Double Wishbone, Upper toe link + S link.
19 Hinged Trailing Arm, Twin Lower Link.
20 Double Wishbone, twin outer ball joints.
21 5-Link Rigid Axle (Watts Linkage)
22 Double Wishbone, twin outer ball joints Spring front.
23 Double Wishbone, twin outer ball anti roll bar.
24 Steerable Macpherson Strut, twin outer ball joints.
25 Double Wishbone, twin lower outer ball joints.
26 Double Wishbone, damper to lower, comp rack.
27 Steerable Macpherson Strut, Twin lower Link
28 4-Link Rear, Transverse Control Link
29 Twist Beam - Twin Wheel
30…. Free slot to use
…. Free slot to use
…50 Free slot to use
Figure 5.1 Schematic of Template Levels and Slot Nos.
The schematic above illustrates the templates levels. ‘Cyan’ shows the ‘free’ slots
where new ‘user’ or ‘custom’ templates could be stored. The ‘Red’ boxes indicate
example slots for ‘user’ and ‘custom’ templates that would overwrite the ‘Hard-coded’
defaults. The ‘mauve’ box indicates an example ‘custom’ template slot that would
have overwritten the ‘Red’ box ‘user’ template.

User Template (2)
63
5.3 Storing and Saving Templates
As identified previously the user can save templates either as ‘User’ templates,
‘Custom’ templates or within the data file. Saving templates involves writing the
specified template slot number to a file.
The ‘user’ templates file is a predefined file name and location, whilst the ‘custom’
templates are saved to user specified files. ‘Custom’ templates can be saved either
singularly or as a complete capture of all currently defined templates including
unaltered ‘default’ templates.
5.4 Saving to the User Templates File
A templates is saved to the user templates file from the template editor. Open the
template editor, File / Edit Templates. You would then display the required template
by selecting the ‘+’ and ‘-‘ icons. Once displayed select the menu Data / Save
Template to User File. You will be warned about the data change and overwrite
existing users file, (if found).
Figure 5.2 Saving current template to user template file
The user templates file, (_User_Templates.dat), will only exist if a previous template
has been saved to the user templates file. If the user templates file already contains
an entry for the slot number selected, this will be replaced with the current settings. If
no entry exists in the User templates file for the selected slot number then this
template definition will be added to the User templates file.
When adding/over writing the contents of the User templates file the existing file is
renamed to _User_Templates.dat.old.
If you choose to delete the user templates file all templates revert back to the hard
coded settings.
At any time during a program run you can revert back to the hard coded defaults +
saved user templates by selecting the main menu item, File / Re-Read Default +User
Templates. If the user templates has been deleted this will effectively set all template
settings back to the hard-coded defaults.

User Template (2)
64
5.5 Saving Custom template Files
A modified template data settings can be saved to a separate file as a ‘Custom’
template. On subsequent analysis runs this file would need to be re-read before this
custom template can be used. From within the template editor the currently
displayed template can be saved to a custom file by selecting Data / Custom
Template Save… Confirm the information message and use the file browser to
identify the required file location and name, (this could be on a remote/central
server).
Figure 5.3 Save Custom Template file message
Templates loaded from custom files will overwrite any existing data in the specified
slot number.
It is also possible to take a ‘snap-shot’ copy of all defined template data settings and
save them to a single ‘custom’ templates file. From the main menu select File / Save
Custom Templates (All), then use the displayed file browser to locate the required
file location and name.
If you require to on subsequent runs use a Custom template, these must be re-
loaded as unlike ‘user’ templates they are not automatically loaded when starting the
application. To load a ‘custom’ template from the main menu select File / Add
Custom Templates… Use the displayed file browser to locate the required custom
templates file.
5.6 Creating New Templates
If you need to create a new template you would normally pick a currently free ‘slot’ to
avoid overwriting an existing template. In the template editor step through until you
find a Slot identified as ‘Not Defined’.
To assist in building a template that is only a slight change from an existing one you
can pre-fill your new template from an existing one by using the File / Fill current
Template From /… menu option.
We will create a new template completely from scratch via the following exercise.

User Template (2)
65
5.7 Exercise 2 – Creating a New Template
As an exercise in understanding the structure of user defined templates we will
create from scratch a new template for the generic five link rear suspension
illustrated below.
Figure 5.4 Example five link rear suspension
To create the new template, open the template editor, (File / Edit Templates). Find a
convenient empty slot, (the screen shots shown with this examples use slot number
8). But you may wish to select a free slot such as number 30.
Step 1: Starting at the ‘Parts’ tab we need to;
1) Give the template a label
2) Identify the number of parts
3) Give each part a descriptive label.
Remember to make the upright the last part. No need to define a part for ‘Ground’.
See overleaf for example ‘Parts’ data values.

User Template (2)
66
Figure 5.5 Identification of Parts, Six in Model
Figure 5.6 Screen shot with ‘Parts’ data values entered
Step 2: Change to the ‘Points’ tab. Now we need to;
1) Identify the number of points
2) Give each point a descriptive label
3) Supply the default x, y and z values for each point.
Remember you don’t need to define a point for the tyre contact point and we can
make the spring-damper attachment points as coincident.
See overleaf for example ‘Points’ data values.

User Template (2)
67
Figure 5.7 Identification of Points, 14 in Model
Figure 5.8 Screen shot with ‘Points’ data values entered
Step 3: Change to the ‘Settings’ tab. Now we need to;
1) Identify the ‘Part 1’ and ‘Part 2’ settings for each point.
2) Define any General types for each point.
Remember any point that is a connection between two parts, or a connection
between a part and ground, requires two parts to be defined.
See overleaf for example point ‘Settings’.

User Template (2)
68
Figure 5.9 Initial Settings for Part 1, Part 2 and Gen Type values.
We can now use the auto-fill routines to complete the other required data values.
Alternatively you may want to try completing them by hand and then check them with
the auto-fill settings. To use the auto-fill select Data / Test Auto Fill and if you then
select Level 1 you can note the changes level by level.
Using the Test auto-fill routines allows you to visual review the differences and
accept or reject the changes.
Repeat the Test Auto-fills for Levels 2 and 3 such that you have a fully defined
template, (check with results on following page).

User Template (2)
69
Figure 5.10 Data Fill Complete to Level 3 using auto-fill routines.
We could now use this template to create a new model using the File / New option in
the normal way, (remember that because we have not identified a input steering
point it will only appear in the Rear suspension list).
If we did use this template in its current form, because we haven’t associated any
graphics with this template, we would only see the hard points, tyre graphic and
spring/damper graphic. We need to define template graphics.
Before we cover template graphics, save the currently defined values for our new
template to a user file. From the template editor select, Data / Custom Template
Save. Confirm the ‘save’ event and locate the required file folder and name using the
standard browser
Figure 5.11 Save custom template message.

User Template (2)
70
5.8 Template Graphics
When a template is used within a model, each has its own associated 3D graphics.
Apart from the generic graphics items such as the wheel/tyre, spring and damper the
remainder such as links and wishbones are specified by the fourth data set of the
template specification ‘Graphics’.
Currently nine basic graphics primitives are available, Line, Cylinder, Circle, Sphere,
Facet, Plane, Distance, Component and Angle. Each of these graphical types is
drawn based on hard point co-ordinates. Each primitive type has its own set of
property values and some may be defined in a number of ways. A full list of the
current options is given below, with further details of some specific examples
following this list.
Line Graphic Classes:
Pnt-Pnt Line: Adds a new Line graphical element to the selected ends’ template. Two hard point
picks are required, points need not be on the same part.
Pnt-Vector Line: Adds a new Line graphical element to the selected ends’ template. Three hard
point picks are required, a line is drawn through the first point who’s direction is set by the vector
defined by the second and third picks, points need not be on the same part. The first and second
picks can be the same point. The line is drawn to a global clipped length.
Pnt-Xvector Line: Adds a new Line graphical element to the selected ends’ template. One hard
point pick is required, a line is drawn through the picked point in the global X axis direction. The line is
drawn to a global clipped length.
Pnt-Yvector Line: Adds a new Line graphical element to the selected ends’ template. One hard
point pick is required, a line is drawn through the picked point in the global Y axis direction. The line is
Pnt-Zvector Line: Adds a new Line graphical element to the selected ends’ template. One hard
point pick is required, a line is drawn through the picked point in the global Z axis direction. The line is
Pnt-Plane-Norm: Adds a new Line graphical element to the selected ends’ template. A line is
drawn through the selected point in a direction normal to the selected plane. The plane is identified by
three point picks. The line is drawn to a global clipped length.
Pnt-UserVector: Adds a new Line graphical element to the selected ends’ template. A line is drawn
through the selected point in a direction defined by a user vector. The line is drawn to a global clipped
length.
Cylinder Graphic Classes:
Pivot: Adds a new Pivot graphical element to the selected ends’ template. Two hard point picks are
required, both points need not be on the same part.
Tube: Adds a new Tube graphical element to the selected ends’ template. Two hard point picks are
required, both points need not be on the same part.
Vector-Radius-Length: Adds a new cylinder graphical element to the selected ends’

User Template (2)
71
template. Drawn through the selected point in a direction defined by the second and third point picks.
The radius and length of the cylinder are defined directly.
Circle Graphic Class:
Pnt-Pnt-Pnt: Adds a new Circle graphical element to the selected ends’ template. Three hard point
picks are required through which is drawn a circle, both the circle centre and radius are calculated and
displayed as part of the graphical display.
Cntr-Rad-Norm: Adds a new Circle graphical element to the selected ends’ template. Three hard
point picks are required. The circle is drawn centered at the first point of a defined radius and who’s
normal is defined by the second and third picks. The first and second picks can be the same point.
Cntr-Pnt-Plane: Adds a new Circle graphical element to the selected ends’ template. Three hard
point picks are required. The circle is drawn centered at the first point and is drawn through the
second point, (i.e. defines the radius), in a plane that contains the third picked point. All picked points
must be different.
Pnt-Normal: Adds a new Circle graphical element to the selected ends’ template. Three hard point
picks are required. The circle is drawn through the first point about the defined normal vector. All
picked points must be different. The derived circle centre and radius is drawn as part of the graphical
element display.
Sphere Graphic Class:
Pnt-Pnt Radius: Adds a new Sphere graphical element to the selected ends’ template. Two unique
hard point picks are required. The sphere is centered at the first pick and the radius is set by the
second pick.
Pnt Radius: Adds a new Sphere graphical element to the selected ends’ template. One hard point
pick is required. The sphere is centered at the pick and given the radius specified by the user.
Pnt-Pnt Dia: Adds a new Sphere graphical element to the selected ends’ template. Two unique
hard point picks are required. The sphere is centered at the mid point of the two picks, the radius
being half the distance between them.
Pnt-Pnt-Pnt-Pnt: Adds a new Sphere graphical element to the selected ends’ template. Four
unique hard point picks are required. The sphere is drawn through the selected four points. Four
points will define a unique sphere who’s calculated radius and centre position is identified as part of
the drawn graphical element.
Facet Graphic Class:
Pnt-Pnt-Pnt Facet: Adds a new Triangular Facet graphical element to the selected ends’ template.
Three hard point picks are required, points need not be on the same part.
Pnt-Pnt-Pnt-Pnt Facet: Adds a new Four noded Facet graphical element to the selected ends’
template. Four unique hard point picks are required, points need not be on the same part. Whilst
points need not be in a plane, any facet drawn of non-planar nodes is not fully define

User Template (2)
72
Plane Graphic Class:
Pnt-Pnt-Pnt Plane: Adds a plane graphical element to the selected ends’ template. Three unique
hard point picks are required, points need not be on the same part. All plane elements are drawn
clipped to a global value, (which the user can edit).
Pnt-X-Y Plane: Adds an X-Y plane graphical element to the selected ends’ template drawn through
the selected pick. All plane elements are drawn clipped to a global value, (which the user can edit).
Pnt-X-Z Plane: Adds an X-Z plane graphical element to the selected ends’ template drawn through
Pnt-Y-Z Plane: Adds an Y-Z plane graphical element to the selected ends’ template drawn through
Pnt-UserVector Plane: Adds an plane graphical element to the selected ends’ template drawn
through the selected pick. The orientation of the plane is controlled by two user defined vectors. All
plane elements are drawn clipped to a global value, (which the user can edit).
Distance Graphic Class:
Pnt-Pnt Dist: Adds a point to point distance graphical element to the selected ends’ template. Any
two hard point picks are required, both points must be on the same suspension corner. The display
shows the total distance between the two points.
Pnt-Line Dist: Adds a point to line distance graphical element to the selected ends’ template. Any
three hard point picks are required, all points must be on the same suspension corner. The last two
picks define the required line. The display shows the total perpendicular distance between the point
and the line.
Line-Line Dist: Adds a minimum distance between two lines graphical element to the selected
ends’ template. Any four hard point picks are required, all points must be on the same suspension
corner. The first two picks define one line whilst the last two picks define the other required line. The
display shows the minimum normal distance between the two lines as a total distance.
Pnt-Plane Dist: Adds a points’ distance from a plane as a graphical element to the selected ends’
template. Any four hard point picks are required, all points must be on the same suspension corner.
The first point is the required point whilst the last three picks define the required plane. The display
shows the normal distance between the point and the plane as a total distance.
Component Graphic Class:
Pnt-Pnt Comps: Adds a point to point distance graphical element to the selected ends’ template.
Any two hard point picks are required, both points must be on the same suspension corner. The
display shows the distance between the two points in its x, y and z components.
Pnt-Line Comps: Adds a point to line distance graphical element to the selected ends’ template.
Any three hard point picks are required, all points must be on the same suspension corner. The last
two picks define the required line. The display shows the perpendicular distance between the point
and the line in its x, y and z components.
Line-Line Comps: Adds a minimum distance between two lines graphical element to the selected
corner. The first two picks define one line whilst the last two picks define the other required line. The
display shows the minimum normal distance between the two lines in its x, y and z components.

User Template (2)
73
Pnt-Plane Comps: Adds a points’ distance from a plane as a graphical element to the selected
corner. The first point is the required point whilst the last three picks define the required plane. The
display shows the normal distance between the point and the plane in its x, y and z components.
Angle Graphic Class:
Pnt-Pnt-Pnt Angle: Adds an angle between three points graphical element to the selected ends’
template. Any three hard point picks are required, all points must be on the same suspension corner.
The middle picks is the point for which the angle is given. The display shows the angle created by the
three point picks in degrees.
‘Line’ Graphic:
This is a simple line joining two hard points. It could be representing a simple link or
be part of a wishbone, the graphics of which are built up using a number of ‘lines’.
The properties of a ‘Line’ are;
Point 1 Hard point at start of line, (pick from list).
Point 2 Hard point at end of line, (pick from list).
Position 1 Sets association with either first or second part, (if applicable).
Property 1 Offset in Global ‘x’ from Point 1 x-value
Property 2 Offset in Global ‘y’ from Point 1 y-value
Property 3 Offset in Global ‘z’ from Point 1 z-value
Colour Optional colour setting, (numerical 1-n).
The ‘position’ settings are used to show compliance deflections. A hard point that is
associated with two parts, (by virtue of being the connection between them), can
have in compliance solution mode two positions. The ability to pick either the first or
second parts allows a visual representation of deflection of a bush by the separation
of two graphics points.
Figure 5.12 Examples of ‘Line’ graphics

User Template (2)
74
‘Cylinder - Pivot’ Graphic:
This is a simple cylinder joining two hard points. Normally used to indicate a pivot
axis, (also added automatically joining the wheel centre and the spindle point). The
properties of a ‘Pivot’ are;
Figure 5.13 Examples of ‘Pivot’ Graphics
‘Cylinder - Tube’ Graphic:
This is a tube joining two hard points. Normally used to indicate a bar or tubular link.
The difference between this and the ‘Pivot’ graphic is that the properties of the tube
allow you to control the diameter and the axial offsets from the ends. The properties
of a ‘Tube’ are;
Property 1 Outer diameter of tube.
Property 2 Offset of tube start from point 1 position, along the tube axis.
Property 3 Offset of tube end from point 2 position, along the tube axis.

User Template (2)
75
Figure 5.14 Example of ‘Tube’ Graphics.
‘Facet - Triangular’ Graphic:
This is a triangular facet joining three hard points. Normally these would be on the
same body and used to indicate a face of a solid link. It will only appear as a ‘filled’
facet when the view fill style is set to something other than wire frame. In wire frame
mode only the boundary of the facet is drawn. The properties of a ‘Tri Facet’ are;
Point 1 Hard point at first corner of the facet, (pick from list).
Point 2 Hard point at second corner of the facet, (pick from list).
Point 3 Hard point at third corner of the facet, (pick from list).
Figure 5.15 Examples of ‘Tri Facets’ Graphics

User Template (2)
76
5.9 Exercise 3 – Adding Graphics to a Template
To complete the template we created earlier, we will know add some graphics to the
template. Open the template editor and select the correct template and change to
the ‘Graphics’ tab. Currently the number of graphical elements is set to zero.
For our template add a ‘Tube’ graphic for each of the five links, and fill the upright
with 6 triangular facets. Remember we do not need to add graphics for the spring,
damper, spindle axis or tyre as these are automatically drawn, using our point ‘gen
type’ settings.
Remember to identify the required properties for each element, and select the
relevant points.
Once complete compare to the solution overleaf and re-save the completed custom
template.

User Template (2)
77
Figure 5.16 Graphical Element Settings for Five Link Template
The screen shot above shows the settings used, values have been entered for the
tube diameters and end offsets, all other property values are left as zero.
Make any alterations as necessary and re-save you’re custom template.
We can now use our template to create a model.
Note: You can add extra points to your templates that are used purely for applying
graphical elements too. These ‘dummy’ points can be included to the template in the
same way as any other point. Remember, because these points do not have any
influence on the kinematic mechanism, they do not need to use one of the Pre-solve
options that adds to the simultaneous equations set. Since this would lead to a
increase in solution time. These dummy points would normally be solved using
‘Solve Post (Vector Pos)’, Solve Post (Sphere) or ‘Solve via Hookes joint’.
Whilst the method outlined above is perfectly valid, the addition of convenience
menus under sub-menu Graphics / Add it is far easier to add graphical elements to
templates by using the graphical interface to identify required graphics primitive and
then select points directly from the 3D view.

User Template (2)
78
5.10 Using the New Template
We can now use our new template. Open a new model in the normal way, (File /
New), and select our new template from the rear suspension list.
Figure 5.17 Selecting the new template.
Your new model should look like that shown below. This new template can be used
as a generic template for all 5-link rear suspensions. We could with a small change
to the template make it available for use as a steerable front suspension.
Figure 5.18 Screen Shot of Generic 5-link rear suspension template
Try modifying the template for use as a steerable front 5-link suspension.

6 Tutorial 5 - Compliant Analysis
6.1 Overview
Up to now we have only considered the pure kinematics of the
suspension system. The suspension members and joints have been
considered rigid and any deflection of the suspension due to force
compliance has been ignored. In this chapter the compliant bush
analysis features of Lotus Suspension Analysis are introduced. The
suspension arms are still modelled as rigid members but the bushes
joining the suspension arms are compliant.
Lotus Suspension Analysis solves for compliant bushes by superposition
of kinematic and compliant bush solutions. First the kinematic solution
for any particular suspension displacement is calculated then a linearised
bush compliance calculation is performed at that kinematic position. The
two results are then superimposed to give the final result.
For any particular suspension displacement the effect of bush
compliance is assumed to give a small perturbation of the position of the
suspension members from the pure kinematic position. The system
equations defining the bush compliance can then be linearised by
assuming that the change in angle between suspension members due to
compliance is very small and can be taken as being negligible. Doing
this makes the compliance equations linear and gives direct solution that
executes very quickly allowing suspension compliance results to be
updated onscreen as the suspension design is manipulated with mouse
and keyboard input.
• 6.2 Enabling compliance calculation, 80
• 6.3 Editing compliant bush properties, 82
• 6.4 Adding external forces, 84
• 6.5 Displaying compliance results, 88
6

Compliant Analysis
80
6.2 Enabling compliance calculation
For this tutorial we will work with a front suspension model to illustrate compliant
bush analysis.
Use the ‘File’ menu and select ‘New’. Create a new default ‘type 1’ double
wishbone front suspension model.
Turn on compliance calculation by clicking on ‘Toggle 3D Compliance
Solver’
Figure 6.1 Screen shot of front suspension with compliant joints.
The ball joints are now represented by red wire frame spheres denoting that the
compliant solver module is active. You will also note that the tyre stiffness has also
been included in the solver and it is graphically represented by a spring connecting
the stub axle to the contact patch. Although the suspension forces are calculated
the joints remain rigid until their individual compliance is activated. It is now possible
to load external forces onto the model and view the resulting loads on each of the
points within the model. To start we will add the force due to spring compression.
Load the model with the spring force by selecting ‘Solve -> Suspension
Spring Force’. Ensure all other forces are removed from the model by un-
checking; ‘External Forces’, ‘Suspension Roll Bar Force’ and ‘Rack Cross-
link Forces’ in the ‘Solve’ menu.
If not already displayed, the force vectors can be added to the graphical
display from the menu by selecting ‘Graphics -> Compliance visibility ->
Calculated Forces’.

Compliant Analysis
81
Fig 6.2 Calculated compliance forces due to spring force
Arrows now appear on the model representing the load vector exerted by the
suspension members on each ball joint/bush in the model. To compare the results
of the kinematic solution to the combined kinematic and compliant model the
deflection due to force/load can be magnified by selecting ‘View -> Deformed
Geometry Scale’ and increasing the magnification factor.
Toggling between the kinematic and compliant model using the ‘Toggle 3D
compliance tool’ now shows a clear difference between the two
models due to deflection of the tire.
To animate the deflection due to compliance select ‘Graphics -> Screen
Display -> Animate (deformed Geom)’ from the main menu bar.

Compliant Analysis
82
6.3 Editing compliant bush properties
The LSA 3D compliance solver treats rigid and compliant bushes the same. The
only difference between ‘rigid’ and ‘compliant’ bushes is the value of stiffness used
for each degree of freedom of the joint. A rigid ball joint is defined as a compliant
bush that has a zero stiffness in rotation about the x, y and z axes but a very high
stiffness in translation along the x, y and z axes (can be thought of as approaching
infinity) i.e. the joint is free to rotate in all directions but has a fixed x, y, z position.
The only change that occurs when the rigid ball joint is switched to a compliant bush
is the stiffness in each degree of freedom changes to represent a real bush.
Set the view to the ‘x-y view’ then select ‘Set to Edit mode’ and click
on the front lower wishbone pivot.
A bush data table will be brought up displaying the current ball joint/ bush setting and
the stiffness of the bush in all directions.

Compliant Analysis
83
Select ‘Bush (compliant)’. The greyed out boxes are now active and the
bush axis are set relative to the centre of the bush.
To define bush compliance the local co-ordinate system of the bush first needs to be
specified. This is achieved by specifying a point that lies on the local z axis and a
second point that lies within the local x-z plane of the local co-ordinate system.
These two points and the location of the bush uniquely define a local co-ordinate
system. These two points can be defined in a number of ways.
1) Absolute (Abs). Defines a point in the absolute global co-ordinate system.
2) Relative (Rel). Defines a point along the axes of the global co-ordinate system
but relative to the location of the bush.
3) Point (Pnt). Uses another suspension point.
From the ‘point’ drop down select ‘Point 1: Lower Wishbone Front Pivot’
and set the bush to ‘Bush (compliant)’.
Set the ‘Point on Bush Local Z-axis’ to Pnt and select ‘point 2: Lower
Wishbone Rear Pivot’.
Set the ‘Point on Bush Local x-z Plane’ to relative and select x = 0, y = 100,
z = 0
Accept default bush stiffness and click ‘Apply’
From the ‘point’ drop down select ‘Point 2: Lower Wishbone Rear Pivot’
and set the bush to ‘Bush (compliant)’.
Set the ‘Point on Bush Local Z-axis’ to Pnt and select ‘Point 1: Lower
Wishbone Front Pivot’.
Set the ‘Point on Bush Local x-z Plane’ to relative and select x = 0, y = 100,
z = 0
Accept default bush stiffness and click ‘OK’
A slight deflection of the lower wishbone rear bush has occurred due to the effect of
compliance. Also note that this slight bush movement has caused toe out of the
wheel, illustrating the effect of the small deflection caused by this compliance and
the resultant effect on the suspension system as a whole.

Compliant Analysis
84
Fig 6.3 Deflection of compliant bush due to spring force
6.4 Adding external forces
In addition to the spring force LSA allows application of force vectors to any
suspension member. Combination of force vectors can be used to simulate any
arbitrary road load condition. LSA contains a number of force sets that can be
applied to the system and also allows user defined forces. Each force set is applied
separately to the suspension. To investigate the effect of multiple forces on a
suspension all the forces must be combined within the one force set. LSA does not
simultaneously apply more than one force set at a time however more than one force
set can be turned on and LSA will then calculate results for each force set applied
separately. The suspension graphic display window always displays the compliant
results for the default force set that is set by the user.
From the main menu select ‘Data -> Compliance Data -> External Forces’.
Now both ‘Spring force’ and ‘External forces’ should be active.

Compliant Analysis
85
Fig 6.4 External Force Data edit screen
Set up a 1000N inward acting lateral load applied to the upright acting at the centre
of the front contact patch.
Select ‘Set 0’, ‘User Definable Default Set’
Click the ‘Add’ button next to the force selector to add a force to the force
set.
Check that front right is selected for ‘end’ and select ‘upright’ in the ‘Apply
to Part’ drop down box.
Give the force a magnitude of 1000 N.
The force can be turned on and off using the ‘On‘ button in the second box. Multiple
forces can be added to each component in turn by adding additional forces in the
same Force Set.
Define the point where the force is acting by setting up the ‘Force Head’ so
that it acts at the ‘Tyre Contact Patch x, y, z (mm)’ by selecting it from the
‘Pnt’ drop down box.
Define the ‘Force Tail’ relative, Rel, to the Force Head at y = 100.
Click ‘OK’ to close the external force dialog box when done.

Compliant Analysis
86
Fig 6.4 External force applied to upright at Contact Patch.
As with the bushes axes each of the force vectors can be defined using two
reference points. The force head can be defined as acting at a pre-defined point
selected from the drop down menu or by giving it an absolute value expressed as a
global Cartesian co-ordinate.
The force tail, can also be set using several reference points. It can be defined as
an absolute point defined in 3D space, as a point relative to another selected point or
can be given a co-ordinate relative to the force head .
We will now add more forces to force set 0 using table 6.1 for input data. Once each
of the external forces have been included in the model the effect of these forces both
individually and combined can be calculated.

Compliant Analysis
87
Use table 6.1 to setup 4 forces in force ‘Set 0’.
Force End Apply to part
Magnitude
(N)
Force Head
Force Tail
(Rel.To Head)
1 Front Right Upright 1000 Tyre Contact Patch Y = 100
2 Front Right Upright 1000 Tyre Contact Patch X = -100
3 Front Left Upright 1000 Tyre Contact Patch Y = 100
4 Front Left Upright 1000 Tyre Contact Patch X = -100
Table 6.1
Turn both halves of the model on using the button.
The model now reflects the systems reaction to a series of forces that would typically
be exerted as the vehicle enters a right hand corner under slight braking. Similar
forces acting on the system due to other conditions can be added in other force sets
to represent say, braking or accelerating.

Compliant Analysis
88
6.5 Displaying compliance results
Select ‘Results -> Display Compliance Values’ from the main menu bar.
Fig 6.5 Compliance Values
The Compliance Values (figure 6.5) show the change in the displayed values due to
application of the force Set. By default the two displayed variables are Camber
angle and Toe Angle but other variables can be added by left clicking on the force
set background then right clicking, selecting ‘Add Extra Variable’. The variable
displayed on any particular graph can also be changed by left clicking on the
particular graph then right clicking to select the variable from the ‘Y-Variable’ menu.
Each force set can be turned off as required or all force sets can be turned on by
right clicking and selecting Turn Force Set ‘Off’ and Turn All Force Sets ‘On’
respectively. Similarly the spring force set, can also be added or removed. Note
that the Graphic suspension display will only display the deformed suspension
geometry for the user selected default force set.
Add the ‘Castor Trail’ variable to the Force Set 0 results by first left clicking
on the background of the force set 0 display then right clicking, select ‘Add
Extra Variable’.
Left click on the new graph then Right click and select ‘Y-Variable -> Castor
Trail (mm)’.
Fig 6.6 Compliance Variables relevant to External Forces
Compliance data can also be displayed numerically in the form of ‘Bush Forces’ and
‘Bush Deflections’ by selecting Results > List Bush Forces… and Results > List Bush
Deflections… from the main menu bar. The list of values display deflection and
forces for all three modes i.e. Bump, Steer and Roll. In addition, they are displayed
over a range for each of these three modes.

Compliant Analysis
89
Fig 6.7 Compliance Data expressed as numeric values
Tutorial Done.

Compliant Analysis
90

7 Using the Optimiser
7.1 Overview
This chapter describes the use of the internal optimiser to provide a
numerical method of identifying an 'optimum' solution. The requirements
for this optimum solution are defined as a series of kinematic and/or
compliant targets. The solution can be achieved by moving identified
points within a defined limited space, and/or varying bush properties,
again within a limited variation.
• 7.2 Introduction, 92
• 7.3 Setting Kinematic Targets via User Lines, 93
• 7.4 Weighting Settings for Kinematics, 94
• 7.5 Identifying Positional Optimiser Parameters, 96
• 7.6 Running a Kinematic Optimisation, 97
• 7.7 Kinematic Tutorial, 99
• 7.8 Setting Compliant Targets via Compliance Coefficients, 101
• 7.9 Weighting Settings for Compliance Targets, 102
• 7.10 Specifying Compliant Optimiser Parameters and Limits, 103
• 7.11 Running a Compliant Optimisation, 105
7

Compliant Analysis
92
• Introduction
The optimiser is a fully integrated solution technique for quickly and efficiently
identifying 'optimum' solutions. The approach used is not based on a design of
experiment or Taguchi type techniques. It instead uses a combination of scoring,
sensitivity and trends to identify the optimum.
The scoring technique is used to convert the deviation of the current solution from all
desired characteristics and values to a single number (or score). The objective of the
optimisation process is to reduce this score to zero.
The score is determined by summing the deviation of each point on the calculated
curve (e.g. camber angle against bump travel) or value when compared to a defined
target curve. Any number of characteristics can be included in this way, the
summation of each made with reference to a weighting factor. It does rely on the
user knowing what target responses they require for each included characteristic.
Increasing the number of characteristics does not significantly alter the analysis time
of the optimisation process.
The variables for the optimisation are identified as point positions and/or bush
properties. Whilst the optimisation can include both kinematic and compliant
variables they are more normally performed in isolation of each other. Each included
variable has a user-defined range to contain the solution within sensible bounds.
Also within these bounds a minimum resolution is specified to limit the number of
solution steps. The number of variables included directly affects the run time for the
optimisation so it should be kept to the minimum possible.
The optimiser assess each variable to identify a sensitivity value. This is the amount
the score changes over the defined range at the specified step size. This then sets
the order that each variable is adjusted to produce its minimum value before moving
on to the next variable in the sensitivity order list. The user can run the optimisation
either from the most to the least sensitive or more successfully from the least
sensitive to the most sensitive.
Thresholds can be set to ignore variables whose sensitivity is significantly less than
the most sensitive, as well as an solution acceptance tolerance on getting the
deviation score down to zero.
At the end of the optimisation process the user is presented with the original score
and the best position score. The user can then optionally accept the new 'optimised'
solution or return to the original models data.

Compliant Analysis
93
7.2 Setting Kinematic Targets via User Lines
The kinematic targets for the optimiser, such as camber, toe and roll centre height
are defined via user lines, defined for each of the required suspension derivatives
graphs. (Note that although graphs can display graphical element properties, they
cannot be used for the optimisation, as you cannot define user lines for them). User
lines can be defined directly or extracted from user line data sets. These data sets
are managed through a series of menu options that allow the user to add too, edit or
remove user line data from data sets. Each dataset can have any number of
complete sets of user lines stored in them, and any number of datasets can be
referenced by the application at any one time. These data set files are stored by their
full pathname in the users ini file such that they a searched for at program start up
and added to the relevant menu tree. In a similar manner to 'add' datasets can be
removed from the available list. These dataset files can thus be shared between
users, either through a central server type location or by local copies of the same file.
Example Graph showing User Line and deviation 'score'
A convenience menu function is provided, Graphs / Copy Front-2D data to User for
copying the current result line values to the user line. This menu function performs a
copy not just for the currently visible graph parameters but all available results,
(some 45 different parameters). Thus for a given target model this function provides
a complete set of user line curves, that could be stored/added to a dataset for use as
a future target for an alternative model.
Individual graphs user lines can be edited directly through the right mouse menu
option on the chosen graph. Note that user lines are stored and edited by corner.
This is to support asymmetric model options.

Compliant Analysis
94
Example user line edit
7.3 Weighting Settings for Kinematics
Each graph/curve used in summing the total deviation from its respective user line is
included via its own weighting factor. This allows the user to balance the numerical
differences between say an angle such as camber and a distance such as roll centre
height. A number of convenience functions are available to automatically set these
but before we can look at these we need to review how we specify which graphs we
wish to include in the optimisation process. It doesn't necessarily follow that because
a particular graph is visible it will be included in the optimisation score.
Optimiser Display Screen

Compliant Analysis
95
All optimiser settings are accessed through the Results / Display Kinematic
Sum/Optimizer display. This display can be with or without 'details'. The screen shot
on the previous page illustrates the 'with details' display.
Through this display you can specify which graphs to include into the sum. The top
left corner shows the 'sum using' options. We can choose to include, No Graph lines,
All defined (i.e. any with a user line specified visible or not), All visible defined graph
lines, (i.e. as per the previous option but must also be visible), or a user defined list.
The user defined list is set graph by graph in the lower right hand corner. Note that
the top left hand box also has the compliance sum options that we will cover later.
Once we have identified which Graph selection to include we can then set the
appropriate weightings. The 'Graph weightings' panel shows the current value for
each graph. We can either edit them directly or use one of the menu options (lower
left). This will either set them all to zero, all to unity or to a weighted value based on
the individual graphs y-range. The latter option attempts to provide a convenience
weighting regime without recourse to lengthy editing of each graphs value. These
weighting numbers will directly influence the optimisation process, in both the order
and final achieved model. When using this auto-weight option it is import to have the
graph y-axes correctly set. This may be nothing more than using the graph autoscale
option or may involve more specific axis setting.
Graph weightings ringed - Set by Auto-weight routine

Compliant Analysis
96
7.4 Identifying Positional Optimiser Parameters
Having specified how we are to determine the targets and summation we need to
identify which hard point positions we intend to move. We can set positional
parameter limits by individual corner. In the simplest single corner symmetrical
model we would only be interested in one corners points set.
Accessing the positional parameters settings
Within each corner set we identify which points are to be included with a simple
on/off selection. On the same line we also define the limits of motion in each axis for
the selected point. Menu options are available to set the limits as the current
position, or the current points tolerance limits. As a display option we can either view
the parameter limits as absolute or deltas.
Example Parameter setting - Point 1 selected viewed as deltas
The above screen shot shows just point 1 as having been selected, and only the x-
axis will be considered since the limits for y and z are set to 0. This display has been
switched to show delta's and thus the zero's imply no change from the current actual
value.

Compliant Analysis
97
Once we have set all our required parameters we can list them through the 'List
parameters' button. Our simple case of a single parameter is shown below.
Parameter listing - single point position single axis
In a similar display we can list the parameters in sensitivity order. This can be useful
in identifying parameters that have a small impact on the solution and they can thus
either be removed from the list, or used to identify a value for the 'sensitivity ignore
ratio'. The objective being to reduce the number of parameters to produce a quicker
solution time.
Sensitivity listing - three parameters shown, Y insensitive.
7.5 Running a Kinematic Optimisation
With the targets defined and the parameters specified we can run the optimiser. As
stated previously the solver will run through each parameter in a sensitivity based
order selecting the setting for each parameter that gives the lowest deviation, this
positional setting for minimum score is retained as the solver moves to the next
parameter. During this process the user can view the intermediate steps in the
graphical window as well as the animated score. Two optimisation options are
available, one of which is a simple full matrix solution. This full matrix option is
impractical for all but the most simple cases, (simple in terms of few variables). The
normal solution method is the 'Sensitivity Based Optimization'.
When you first select the optimisation button a summary display is shown listing the
step size resolutions, number of parameters, total number of steps and an estimate
of the run time.

Compliant Analysis
98
Optimisation summary
Selecting Ok will start the optimisation and display the progress display shown
below. The display shows the progress and three scores. The scores are the value
at the start, the minimum value found so far and the score for the last iteration.
Progress display

Compliant Analysis
99
7.6 Kinematic Tutorial
To illustrate the previous discussion we will run a simple example involving three
graph curves and three parameters.
Create a new single corner front model based on default type 1.
Open three graphs, Camber Angle, Kingpin Angle and Castor Angle, Graphs / New.
Ensure you are set to 3d bump module and that bump/rebound is set to +-60mm with
a 20mm increment, Data / Parameters.
Use the graph convenience menu item to pre-fill the user lines with the current data
values, Graphs / Copy Front-2D data to User.
Edit point 3, the outer lower ball joint to a new position, X=4072, Y=733.5, Z=177.0
Before opening the optimiser display autoscale the graphs. They should now appear
as below. Note deviation scores visible.
Graph screen shot for tutorial
Open the Optimiser display, Results / Display Kinematic Sum/Optimiser, and set the
display to show details. For this simple example we will use a fine positional
increment, so set 'Position Mesh Size' to 1.0 mm.
We are going to have point 3's X,Y and Z position as variables so open the relevant
'Position Limits' display and set them 'on' and range to the current tolerances. Check
by comparing your parameter list with that shown below.
Parameter Listing

Compliant Analysis
100
Before we can run the analysis we need to define what weightings we will apply.
Initially try the 'Auto-Set weightings based on display' option. This should give 1.0
(camber), 0.2724 (castor) and 0.4543 (kingpin) for our three graphs.
Try running the optimiser with these weightings…
Auto-Weightings Result - Score = 0.4654
The auto-weightings do not produce a very effective solution. In particular the
Camber curve is not very close. Try re-running but this time double the camber
weighting, i.e. 2.0, 0.2724, 0.4543. No need to reload the original values can re-run
from this new position.
Revised Weighting Graphs
In this case we get a much-improved match and a score of zero. Are the co-
ordinates for point 3 the same as originally? Would we have got here in one step had
we set the weightings to 2.0 etc. from the start?

Compliant Analysis
101
7.7 Setting Compliant Targets via Compliance Coefficients.
To extend the use of the optimiser into the use of tuning compliant properties such
as bush stiffness and orientation we need to have a additional compliant results
scoring method similar to that used with our derivative graphs. We can of course use
the graph curves user lines as targets for compliant bush optimisation, but it is more
normal to use the 'Compliance Values' bar chart display, (Results / Display
Compliance Values) as this allows us to use compliant specific results under a range
of different load cases.
Example Screen Shot - Compliance Values
Each bar on the display has an associated target or limit setting. These are drawn as
horizontal lines across each bar display. We can use the sum of differences from
these 'limit' settings to control our optimisation process in a similar way to the x-y
graph user lines. To set the limit values for a particular bar select it with the right
mouse button and then edit as required. Alternatively to edit them all through a single
display select from the right mouse menu on the compliance values graph the menu
option Edit All Line Limits/Scale/Weights…

Compliant Analysis
102
Limit Setting for Individual Bar
In a similar manner to user line setting a convenience menu option is available, Set
All Limit Values to Current, from the right mouse menu to take the current values as
required limits.
No database system exists for these limit settings but they are saved into the users
ini file.
7.8 Weighting Settings for Compliance Targets
As with the kinematic user lines we need to apply a weighting factor to each
compliant bar graph. We can either edit them individually using the right mouse
menu item Edit Weighting Setting… or use the Edit All option.
Setting Weighting Values via the edit all display

Compliant Analysis
103
Individual weighting values are applied to each separate bar in each load set,
although the same value is used for each corner within a single bar variable, though
each corner can have a separate target/limit.
The optimiser display has two convenience options for auto-setting the bar weighting
values. The lower left panel has Auto-Set Compliance Weights Based on Display
and Set All Compliance Weightings to Unity. They function as implied to provide one-
click settings for the weightings.
Compliance Weighting Settings
7.9 Specifying Compliant Optimiser Parameters and Limits.
The compliant properties available as parameters for the optimiser are the bush X, Y
and Z axial stiffness, the bush X-X, Y-Y and Z-Z rotational rates and the bush
orientation. The bush orientation is controlled by the optimiser through an Euler
sequence of local axis rotations about the X, Y and Z axes.
Obviously compliant optimisation can only be applied to model points that are either
a connection to ground or a connection between parts. They must also have been
identified as 'compliant' rather than 'rigid'.
Because of the often symmetric nature of bushes special options are provided to
couple the X and Y stiffness, (i.e. no need to set both the X and Y axial stiffness as a
parametric variable just change one and the other will be automatically made the
same). A similar option is available for the x-x and y-y rotation rates.

Compliant Analysis
104
Coupling the X and Y Stiffness parameters
To select the required bushes to optimise select the 'Bush Stiffness Limits' icon.
Within this display toggle on the required bushes, and set the x, y and z limits in a
similar manner to that performed previously for point position.
You can pre-fill all the stiffness values using the two convenience menu items, Pre-
Fill Min/Max Using Defined Values and Pre-Fill Using Actual Values. The first of
these two options requires the user to specify what the min and max limits should be.
Single Bush enabled, limits set for x, y and z
Once all the required parametric bush properties are defined they can be viewed via
the list parameters option. The axis will be identified as 'Xstiff', 'Ystiff' and 'Zstiff' as
applicable.
Parameter listing, stiffness variables indicated.
We can similarly review sensitivities of the defined parameters. The step size used
between minimum and maximum stiffness is defined in the top right panel entries.
Here you define both the step sizes for both the axial and rotational stiffness.
The same process can be applied to set up bush rotations as parametric variables.
Identify the points, set the limits and step the step size.

Compliant Analysis
105
Sensitivity listing - note min and max sums given
7.10 Running a Compliant Optimisation.
With the variables, limits and parameters defined we can no run the optimisation in
exactly the same way as for the previous kinematic only example.
Because this is a compliant solve the solution run times will be longer than
previously. Check the total number of steps and run time for sensible values before
submitting the optimisation run. You may need to revise the step size to reduce the
run time.
check run time before submitting
You can stop a optimiser run before it finishes and still have the option to take the
lowest score solution already found. This can be useful when in a long run a suitable
solution has already been found. Alternatively you could set the 'Auto-Stop' value to
be higher.
Stop button identified

Compliant Analysis
106

8 Command Reference Card
Change between dynamic Viewing mode and
dynamic Point Picking. Shortcut Alt+Z
Change to Translate view. Select with left mouse
button, hold down and drag.
Change to Scale view. Select with left mouse button,
hold down and move down to zoom in, up to zoom
out.
Change to Rotate view. Select with left mouse button,
hold down and move to rotate view. Picking towards
the centre rotates the eye point around the object,
picking towards the edge rotates around the eye to
object axis.
(when in dynamic view mode, the Right Mouse
button will cycle through the three dynamic view
types)
Point-pick mode set to Edit. Selecting a point with the
left mouse button brings up a dialogue box to edit the
points values.
Point pick mode set to Joggle. Selecting a point
draws the ‘joggle’ symbol on the selected point.
Ctrl+Arrow keys joggles the points position in coarse
steps, Shift+Arrow keys joggles the point in fine
steps. Joggle is affected by current tracking direction.
Point pick mode set to Drag. Select a point with the
left mouse button hold down and drag along current
tracking axis direction(s).
(when in dynamic point pick mode, the Right-Mouse
button will cycle through the Tracking directions)
Cycles through the available tracking directions. The
current Tracking direction(s) is indicated on screen
by visible lines drawn through each hard point, along
the relevant axis.
Autoscales the 3D graphical display. Shortcut Ctrl+A.
Opens a new Graph. The displayed variable can be
changed by selecting the graph with the Right-Mouse
button, and picking the required parameter.
Animates the suspension over the currently selected
articulation type, Bump, Roll or Steer.
Displays the Suspension Derivatives listing (SDF’s) in
a pop-up dialogue box.
Displays the suspension Co-ordinates for a specified
bump and steer position in a pop-up dialogue box.
Enables the Tolerance analysis. In the first instance
the point to run the tolerance analysis on must be
defined.
8

Command Reference Card
108
Display for editing the current front/rear suspension
hard points.
Change solver to 2D Bump module.
Change solver to 2D Roll module.
Change solver to 3D Bump module.
Change solver to 3D Roll module.
Change solver to 3D Steer module.
Set view mode to Wire Frame.
Set view mode to Solid Fill.
Set view mode to Hidden Line. This view mode only works
correctly with the graphics frame type set to OpenGl, (see
View/Graphics Frame Type).
Set view mode to Depth Buffered solid fill. This view mode
only works correctly with the graphics frame type set to
OpenGl, (see View/Graphics Frame Type).
Toggles the visibility of the hard Point Reference
No’s.
Toggles the use of the Limit Bboxes for the hard points.
Limits can also be either visible or invisible. Turning limit
boxes on will always make them visible.
Toggles the visibility of the hard point (x,y,z) Co-
ordinates.
Toggles the visibility of the Spring enhanced graphics
display. When off spring is drawn as a simple line.
Toggles the visibility of the Damper enhanced graphics
display. When off damper is drawn as a simple line.
Toggles the visibility of the Wheel enhanced graphics
display. When off wheel is drawn as a simple line.
Toggles the visibility of the Pivot Axes enhanced
graphics display. When off is drawn as simple line.
Toggles the visibility of the any Body graphics
currently selected, (see Data / Body Type).
Displays both Front and Rear suspensions, (if in
current model).
Displays Front suspension only.
Display Rear suspension only.

Command Reference Card
109
Toggle 3D compliance solver. Toggles between
compliant joints with resultant forces and pure
kinematic joints.
Toggles between Display both sides of the
suspension and right-hand side only.
Toggle 3D Compliance Forces. Toggles the model
to display compliance forces such as Spring Forces,
External Forces, Compliance Forces ETC.

GROUP
HEADQUARTERS
Group Lotus Plc
Potash Lane, Hethel
Norwich
Norfolk, NR14 8EZ
United Kingdom
Phone: 01953 608000
Fax: 01953 608000
Email Cars: carsales@lotuscars.co.uk
Email Eng: engsales@lotuscars.co.uk
Email Group: group@lotuscars.co.uk
INTERNATIONAL
OFFICES
Lotus Engineering Inc.
PO Box7209
1254 N.Main St.
Ann Arbor MI 48104
USA
Phone: 734-995-2544
Fax: 734-995-9301
Lotus Engineering Malysia Sdn. Bhd.
Lot G-5 Enterprise 3
Technology Park Malaysia
Lebuhraya Puchong-Sungia Besi
Bukit Jalil
57000 Kuala Lumpur, Malaysia
Phone: 00 603 8994 3621
Fax: 00 603 8994 1172

getting-started-with-lotus-suspension-analysis

More Related Content

What's hot (20)

Viewers also liked (9)

Recently uploaded (20)

getting-started-with-lotus-suspension-analysis