Unit I_dany (1).pptx

Unit 1
Basic concepts of robotics
8/30/2023 1

8/30/2023 2
Definition (RIA – Robot institute of
america)
“ A reprogrammable, multifunctional manipulator
designed to move material, parts, tools, or
specialized devices through various programmed
motions for the performance of a variety of tasks”

Definition – (International Organization
for Standardization -ISO):
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“An automatically controlled, reprogrammable,
multipurpose manipulator programmable in
three or more axes, which can be either fixed in
place or mobile for use in industrial automation
applications”

To qualify as a robot, a machine
must be able to:
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1) Sensing and perception: get information from its
surroundings
2) Carry out different tasks: Locomotion or manipulation, do
something physical–such as move or manipulate objects
3) Re-programmable: can do different things
4) Function autonomously and/or interact with human
beings

Three Laws of Robotics
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FIRST LAW: Do not harm human being
A robot must not harm a human being, or, through
inaction, allow a human being to come to harm.
SECOND LAW: Obey human being
A robot must always obey the orders given it by human
beings except where such orders would conflict with
the First Law.
THIRD LAW: Protects itself from harm
A robot must protect its own existence as long as such
protection does not conflict with the First or Second
Law.

Robot Classification
The following is the classification of Robots according to the
Robotics Institute of America
• Variable-Sequence Robot : A device that performs the
successive stages of a task according to a predetermined method
easy to modify
• Playback Robot :A human operator performs the task manually
by leading the Robot
• Numerical Control Robot : The operator supplies the movement
program rather than teaching it the task manually.
• Intelligent Robot : A robot with the means to understand its
environment and the ability to successfully complete a task
despite changes to the environment.

Advantages of Robots
 Robots increase productivity, safety, efficiency, quality, and
consistency of products.
 Robots can work in hazardous environments.
 Robots need no environmental comfort.
 Robots work continuously without experiencing fatigue of
problem.
 Robots have repeatable precision at all times.
 Robots can be much more accurate than human.
 Robots replace human workers creating economic problems.
 Robots can process multiple stimuli or tasks simultaneously.

Disadvantages of Robots
 Robots are costly, due to Initial cost of equipment, Installation
costs, Need for Peripherals, Need for training, Need for
programming.
 Robots, although superior in certain senses, have limited
capabilities in Degree of freedom, Dexterity, Sensors, Vision
system, real time response.
 Robots lack capability to respond in emergencies.

Robot Anatomy
 The physical construction of the body, arm and wrist of the
machine
 The wrist is oriented in a variety of positions
 Relative movements between various components of body,
arm and wrist are provided by a series of joints
 Joints provide either sliding or rotating motions
 The assembly of body, arm and wrist is called
“Manipulator”
 Attached to the robot’s wrist is a hand which is called “end
effector”
 The body and arm joints position the end effector and wrist
joints orient the end effector
30 August 2023 Cont.
9

Robot Anatomy - study of skeleton of Robot
Base
Manipulator
linkage
Controller
Sensors Actuators
User interface
Power conversion
unit

Components of robotic system
8/30/2023 Fundamentals of robotics by dk pratihar 11
Various Components : 1.Base 2.Links and Joints 3.End-effector
/ gripper 4.Wrist 5.Drive / Actuator 6.Controller 7.Sensors

Serial Manipulator
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Parallel Manipulator
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Robot Anatomy
• Manipulator consists of joints and links
– Joints provide relative motion
– Links are rigid members between joints
– Various joint types: linear and rotary
– Each joint provides a “degree-of-freedom”
– Most robots possess five or six degrees-of-freedom
• Robot manipulator consists of two sections:
– Body-and-arm – for positioning of objects in the robot's
work volume
– Wrist assembly – for orientation of objects

Degrees of freedom (DOF)
• DOF / Connectivity is defined as one of the
variable required to define the motion of the
body in space.
• Degree of freedom of a system depends on the
number of variable or coordinates that are
needed to describe its position.
• Each joint in a robotic system gives the robot
one degree of freedom.

Degrees of freedom
• It is defined as the
number of independent
relative motions
(translation & rotation)
a pair can have.
• In a space a rigid body
will have 6 DoF;
• 3-translations (x,y,z)
and 3-rotations (about
the 3 axes)
• It is called as SPATIAL
MECHANISM

Degrees of freedom
• In a plane, a rigid body will have 3 DoF, translations
in (x,y) and rotation about z-axis.
• It is called as PLANAR MECHANISM

The Robotic Joints
• A robot joint is a mechanism that permits relative
movement between parts of a robot arm.
• The joints of a robot are designed to enable the
robot to move its end - effector along a path from
one position to another as desired.

The Robotic Joints
• These degrees of freedom, independently or in
combination with others, define the complete motion of
the end-effector.
• These motions are accomplished by movements of
individual joints of the robot arm. The joint movements
are basically the same as relative motion of adjoining
links.
• Depending on the nature of this relative motion, the
joints are classified as prismatic or revolute.

The Robotic Joints
• Prismatic joints (L) are also known as sliding
as well as linear joints.
• They are called prismatic because the cross
section of the joint is considered as a
generalized prism. They permit links to move
in a linear relationship.

The Robotic Joints
Revolute joints permit only angular motion between
links. Their variations include:
– Rotational joint (R)
– Twisting joint (T)
– Revolving joint (V)

Mechanical Joints for Robots
• Translational motion - Prismatic joints
– Linear joint (type L)
– Orthogonal joint (type O)
• Rotary motion - Revolute joints
– Rotational joint (type R)
– Twisting joint (type T)
– Revolving joint (type V)

Translational Motion Joints
• Linear joint
Type L joint; the relative movement
between the input link and the output link
is a translational sliding motion, with the
axes of the two links parallel.

Translational Motion Joints
• Orthogonal joint
Type O joint; the relative movement between
the input link and the output link is a
translational sliding motion, but the output
link is perpendicular to the input link.

Rotary motion
• Rotational joint
Type R joint; this provides rotational
relative motion, with the axis of rotation
perpendicular to the axes of the input and
output links.

Rotary motion
• Twisting joint
Type T joint; this provides rotary
motion, but the axis of rotation is parallel
to the axes of the two links.

Rotary motion
• Revolving joint
Type V joint; the axis of the input link
is parallel to the axis of rotation of the
joint, and the axis of the output link is
perpendicular to the axis of rotation.

Joint Notation Scheme
• Uses the joint symbols (L, O, R, T, V) to
designate joint types used to construct robot
manipulator
• Separates body-and-arm assembly from wrist
assembly using a colon (:)
• Example: TLR : TR

DOF??
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1 DOF - Revolute 1 DOF - Prismatic

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2 DOF – Cylindrical joint
2 DOF – Hooke joint
3 DOF – Ball and Socket joint

DOF
• A point in 2-D:
• A point in 3-D space:
• A rigid body in 3-D:
• Spatial Manipulator:
• Planar Manipulator:
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2 DOF
3 DOF
6 DOF
6 DOF
3 DOF

Redundant Manipulator:
• Either a Spatial Manipulator with more than 6
dof or a Planar Manipulator with more than 3
dof
Under-actuated Manipulator
• Either a Spatial Manipulator with less than 6
dof or a Planar Manipulator with less than 3 dof
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Exercise
• Draw the following configurations
– LRL - ORO
– RRL - RRO
– TRL
– LVL - OVO

• Sketch following manipulator
configurations
• (a) TRT:R, (b) TVR:TR, (c) RR:T.
Solution:
T
R
T
V
(a) TRT:R
R
T
R
T R
T
R
R
(c) RR:T
(b) TVR:TR

Joint representations
Symbols of joints (arrows show direction of motion). (a)
Prismatic joint. (b) Revolute joint
1. (c) Revolute joint 2. (cl) Up-and-down rotation. (c2) Back-
and-forth rotation.
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Foundations of Robotics
Analysis and Control
Tsuneo Yoshikawa

Can you name the common
coordinate systems in robots????
• Cartesian coordinate system
• Cylindrical coordinate system
• Polar or Spherical coordinate
system
• Revolute coordinate system

Robot Body-and-Arm
Configurations
• Five common body-and-arm configurations for
industrial robots:
1. Polar coordinate body-and-arm assembly
2. Cylindrical body-and-arm assembly
3. Cartesian coordinate body-and-arm assembly
4. Jointed-arm body-and-arm assembly
5. Selective Compliance Assembly Robot Arm
(SCARA)
• Function of body-and-arm assembly is to position an
end effector (e.g., gripper, tool) in space

Work volume (Work envelope)
- Volume in which the robot is able to work.
• The work volume is determined by the following
physical characteristics of the robot:
– The robots physical configuration
– The size of the body, arm, and wrist components
– The limits of the robots joint movements.
Dextrous Workspace
It is the volume of space, which the robot’s end-effector
can reach with various orientations
Reachable Workspace
It is the volume of space that the end-effector can reach
with one orientation

ROBOT CLASSIFICATION
Cartesian Configuration:
• Robots with Cartesian configurations consists of links
connected by linear joints (L). Gantry robots are
Cartesian robots (LLL).
• Also known as rectilinear robot and x-y-z robot.
Consists of three sliding joints, two of which
orthogonal (O joint).

Cartesian Coordinate
Body-and-Arm Assembly
A robot with 3 prismatic joints –
the axes consistent with a
Cartesian coordinate system.
Commonly used for:
•pick and place work
•assembly operations
•handling machine tools
•arc welding

 Advantages
 Linear motion in three dimension
 Simple kinematic model
 Rigid structure
 Higher repeatability and accuracy
 High lift-carrying capacity as it doesn’t vary at different
locations in work volume
 Easily visualize
 Can increase work volume easily
 Inexpensive pneumatic drive can be used for P&P
operation

 Disadvantages
 requires a large volume to operate in
 work space is smaller than robot volume
 unable to reach areas under objects
 must be covered from dust
 Applications
 Assembly
 Palletizing and loading-unloading machine tools,
 Handling
 Welding

Cartesian Robot - Work Envelope

Can you draw Orthogonal-
coordinate type robot?
(Symbolic representation)
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Cylindrical coordinate
Consists of a vertical column,
relative to which an arm assembly
is moved up or down. The arm can
be moved in and out relative to the
axis of the column. Common
configuration is to use a T joint to
rotate the column about its axis. An
L joint is used to move the arm
assembly vertically along the
column, while an O joint is used to
achieve radial movement of the
arm.

 Advantages
 Simple kinematic model
 Rigid structure & high lift-carrying capacity
 Easily visualize
 Very powerful when hydraulic drives used
 Disadvantages
 Restricted work space
 Lower repeatability and accuracy
 Require more sophisticated control
 Applications
 Palletizing, Loading and unloading
 Material transfer, foundry and forging

Cylindrical Robot - Work Envelope

Can you draw Cylindrical-
coordinate type robot?
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Polar Coordinate
Body-and-Arm Assembly
• Notation TRL:
• Consists of a sliding arm (L joint)
actuated relative to the body,
which can rotate about both a
vertical axis (T joint) and
horizontal axis (R joint)
• Polar robots have a work space of
spherical shape. Generally, the
arm is connected to the base with
a twisting (T) joint and rotatory
(R) and linear (L) joints follow.

Spherical/Polar Robots
A robot with 1 prismatic joint
and 2 rotary joints – the axes
consistent with a polar
coordinate system.
Commonly used for:
•handling at die casting or
fettling machines
•handling machine tools
•arc/spot welding

 Advantages
 Covers a large volume
 Can bend down to pick objects up off the floor
 Higher reach ability
 Disadvantages
 Complex kinematic model
 Difficult to visualize
 Applications
 Palletizing
 Handling of heavy loads e.g. casting, forging

Spherical Robot - Work Envelope

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Can you draw Polar-coordinate
type robot?

ROBOT CLASSIFICATION
• The designation of the arm for this
configuration can be TRL or TRR.
• Robots with the designation TRL are also
called spherical robots. Those with the
designation TRR are also called articulated
robots. An articulated robot more closely
resembles the human arm.

Articulated Robots
A robot with at least 3 rotary
joints.
Commonly used for:
•welding
•weld sealing
•spray painting
•handling at die casting or
fettling machines

Advantages:
• all rotary joints allows for maximum flexibility
• any point in total volume can be reached.
• all joints can be sealed from the environment.
Disadvantages:
• extremely difficult to visualize, control, and program.
• restricted volume coverage.
• low accuracy
Articulated Robots

Joint-arm Configuration
• The jointed-arm is a combination of cylindrical and
articulated configurations. The arm of the robot is
connected to the base with a twisting joint. The links in
the arm are connected by rotatory joints. Many
commercially available robots have this configuration.
• General configuration of a human arm, this consists of
a vertical column that swivels about the base using a T
joint. At the top of the column is a shoulder joint (an R
joint), output to an elbow joint (another R joint).

 Advantages
 Maximum flexibility
 Cover large space relative to work
volume objects up off the floor
 Suits electric motors
 Higher reach ability
 Disadvantages
 Complex kinematic model
 Difficult to visualize
 Structure not rigid at full reach
 Applications
 Spot welding, Arc welding

Can you draw Jointed Arm type
robot?
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Selective Compliance
Assembly Robot Arm.
Similar in construction to the
jointer-arm robot, except that
the shoulder and elbow
rotational axes are vertical,
which means that the arm is
very rigid in the vertical
direction, but compliant in
the horizontal direction.
SCARA Robots
(Selective Compliance Articulated Robot Arm)

A robot with at least 2 parallel
rotary joints.
Commonly used for:
•pick and place work
SCARA Robots
(Selective Compliance Articulated Robot Arm)

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Can you draw SCARA type robot?

Configuration Advantages Disadvantages
Cartesian
coordinates
3 linear axes, easy to
visualize, rigid
structure, easy to
program
Can only reach front of itself,
requires large floor space, axes
hard to seal
Cylindrical
coordinates
2 linear axes +1
rotating, can reach all
around itself, reach and
height axes rigid,
rotational axis easy to
seal
Can’t reach above itself, base
rotation axis as less rigid, linear
axes is hard to seal, won’t reach
around obstacles
SCARA
coordinates
1 linear + 2 rotating
axes, height axis is rigid,
large work area for
floor space
2 ways to reach point, difficult to
program off-line, highly complex
arm
Spherical
coordinates
1 linear + 2 rotating
axes, long horizontal
reach
Can’t reach around obstacles,
short vertical reach
Revolute
coordinates
3 rotating axes can
reach above or below
obstacles, largest work
area for least floor
space
Difficult to program off-line, 2 or
4 ways to reach a point, most
complex manipulator

Wrist Configurations
• Wrist assembly is attached to end-of-arm
• End effector is attached to wrist assembly
• Function of wrist assembly is to orient end effector
– Body-and-arm determines global position of end effector
• Two or three degrees of freedom:
– Roll
– Pitch
– Yaw

Six basic robot motions are ???
1. Radial traverse: Involve the extension and retraction
(in or out movement) of the arm relative to the base
2. Vertical traverse: Provide up-and-down motion of
the arm
3. Rotational traverse: Rotation of the arm about
vertical axis such as left-and-right swivel of the
robot arm about a base
4. Wrist Pitch/Bend: Provide up-and-down rotation to
the wrist
5. Wrist Yaw: Involve right-and-left rotation of the
wrist
6. Wrist Roll/Swivel: Is the rotation of the wrist about
the arm axis

Spatial Resolution
o Defined as smallest increment of movement into which
the robot can divide its work volume
o Depends on two factors: system’s control resolution
and the robot’s mechanical inaccuracies
o Control resolution is determined by robot’s position
control system and its feedback measurement system
o Ability to divide total range of movement for the
particular joint into individual increments that can be
addressed in the controller
o The increments are sometimes referred to as “
addressable points”

o Joint range depends on the bit storage
capacity in the control memory
o Number of increments for a axis is given by
o Number of Increments = 2n
o n = the number of bits in the control memory
o Have a control resolution for each joint in
case of several DOF
o Total control resolution depend on the wrist
motions as well as the body and arm motions
SPATIAL RESOLUTION

o Mechanical inaccuracies come from elastic
deflection in the structure elements, gear
backlash, stretching of pulley cords, leakage
of hydraulic fluids and other imperfections in
the mechanical system
o Also affected by load being handled, the
speed of arm moving, condition of
maintenance of robot
SPATIAL RESOLUTION

Accuracy
 Ability to position its wrist end at a desired
target point within the work volume
 Depends on spatial resolution means how
closely the robot can define the control
increments
 One half of the control resolution by ignoring
the mechanical inaccuracies

Repeatability
 Ability to position its wrist at a point in space
that had been taught
 Accuracy relates to its capacity to be
programmed to achieve a given target point
 Programmed point and target point may be
different due to limitations of resolution
 Repeatability refers to ability to return to the
programmed point when commanded to do so

Robot drive systems
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The drive system used to power the robot. The drive system determines the speed of the arm
movement, the strength of the robot, dynamic performance, and to some extent the kinds of
applications.
Characteristics
•Accuracy,Repeatability
•DOF, Mobility
•Gravitational and acceleration force
•Backlash, friction and thermal effects
•Coordinate system
 Drive system can be Powered by three types
1. Hydraulic
2. Pneumatic
3. Electric
Drive System

2004 88
Power Sources for Robots
• An important element of a robot is the
drive system. The drive system supplies
the power, which enable the robot to
move.
• The dynamic performance of a robot
mainly depends on the type of power
source.

Actuators
• Actuator is the term used for the mechanism that drives the
robotic arm.
• A motor to gather with the transmission and other accessories if
any is referred to as actuator.
• There are 3 main types of Actuators
1. Electric motors
2. Hydraulic
3. Pneumatic cylinder
• Hydraulic and pneumatic actuators are generally suited to
driving prismatic joints since they produce linear motion
directly
• Hydraulic and pneumatic actuators are also known as linear
actuators.
• Electric motors are more suited to driving revolute joints as they
produce rotation

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Hydraulic Drive
1. Linear piston or rotary vane types.
2. High power-to-weight ratio suitable for high loads at
moderate speeds.
3. Easily controllable due to high stiffness of hydraulic system.
4. Require high energy storage systems such as pumps and
accumulators.
5. Susceptible to leakage, which may reduce efficiency.
6. Require filtration.
7. Air entrapment and cavitation may cause difficulties.
8. Servo valves controlling the fluid flow must be placed close
to the actuators to increase the stiffness of the control system.
9. Suitable for harsh environments caused by dust, dirt, and
moisture.

1. Hydraulic Drive
– Associated with large robot
– Provide greater speed & strength
– Add floor space
– Leakage of oil
– Provide either rotational or linear motions
– Applications such as:
• Spray coating robot
• Heavy part loading robot
• Material handling robot
• Translatory motions in cartesian robot
• Gripper mechanism

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1. Used in inexpensive manipulators with low load-carrying
capacity.
2. Usually require mechanical stops for accurate positioning
in non-servo control.
3. Single- and double-acting piston or rotary vane types are
commonly used.
4. Inherently lightweight at moderate operating pressures.
5. Limited by low efficiency at reduced loads and low
stiffness due to compressibility.
Pneumatic actuators

2. Pneumatic Drive
– Reserved for smaller robot
– Limited to “pick-and-place” operations with fast
cycles
– Drift under load as air is compressible
– Provide either rotational or linear motions
– Simple and low cost components
– Used to open and close gripper

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1. Provide a variety of power systems.
2. Easier to control.
3. May not be as responsive as hydraulic systems and
stiffer than pneumatic systems with low pressure.
4. Normally require speed reducers, which introduce
inefficiency and error in operation.
5. Variety of types such as permanent magnet DC
motors, printedcircuit motors , stepping motors, and
direct drives.
Electric motors

3. Electric Drive
– Rotor, stator, brush and commutator assembly
– Rotor has got windings of armature and stator has got
magnets
– The brush and the commutator assembly switch the
current in armature windings
– The most commonly used are DC servomotors, AC
servomotors and stepper motors

Various types of drives for Robot
operation
S.No Factor Electrical Pnumatic Hydraulic
1 Power supply (Input) 24 to 460 V 35 - 3500 Kpa 350 - 35000 Kpa
2
Working Fluid Electricity Air , nitrogen combustion
products
Oil base with additives, Water
bsed solution.
3
Basic system Logic, Power simplifier,
DC or AC motor gear
boxes, coolers
Compressor, inter stage
coolers, pressure cotrols
filter, dryers, mufflers,
valve actuatros.
Pump, sump, regulators(pressure,
temp,flow), filters. Heat
exchangers, servo valves, motor
actuators and accumulators.
4 Efficiency Over 90% Over 30% Over 60 %
5
Delivered weirht to
force ratio
Poor:Poorest weight to
force ratio
Fair : Light weight Excellent: Highest force to
weight ratio
6
Susceptibility to
contamination
Low - RIF noice Intermediate - Oil
particals, moisture and
corroton problem
High - Filter and servo valves
7
Safety of operation Shock hazard and
grounding must be
considered
Flying debries, Explosions
possible when voltatile
oils present.
Leakage of flammable fluid.Jet
pressure affects skin and eye.

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Robot Controls with Hydraulic,
Pneumatic, and Electric Systems

Speed of motion and Load carrying
capacity
8/30/2023 100
Speed depends on the following factors
• The accuracy with which the end effector must be positioned
• The weight of the object being manipulated
• The distance to be moved

Speed of motion and Load carrying
capacity
8/30/2023 101
Can you tell me how much load you can carry??
The load carrying capacity should be specified
under the condition that the robots arm is in its
weakest position.

Unit I_dany (1).pptx

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Unit I_dany (1).pptx