ROBOTICS PPT.pdf

INDUSTRIAL ROBOTICS
INDUSTRIAL ROBOTICS
UNIT V
UNIT V

ROBOT ANATOMY AND RELATED ATTRIBUTES
ROBOT ANATOMY AND RELATED ATTRIBUTES
•
• The
The anatomy
anatomy of
of industrial
industrial robots
robots deals
deals with
with the
the assembling
assembling of
of outer
outer
components of a robot such as wrist, arm and body
components of a robot such as wrist, arm and body.
.
•
• Before
Before jumping
jumping into
into robot
robot configurations,
configurations, here
here are
are some
some of
of the
the key
key facts
facts about
about
robot anatomy
robot anatomy.
.
(a) Joints
(a) Joints and
and Links
Links
(b) Common
(b) Common Robot Configurations
Robot Configurations
2

JOINTS AND LINKS
JOINTS AND LINKS
•
• The manipulator of an industrial robot consists of a series of joints and links
The manipulator of an industrial robot consists of a series of joints and links.
.
•
• Robot
Robot anatomy
anatomy deals
deals with
with the
the study
study of
of different
different joints
joints and
and links
links and
and other
other
aspects of the manipulator's physical construction
aspects of the manipulator's physical construction.
.
•
• A robotic joint provides relative motion between two links of the robot
A robotic joint provides relative motion between two links of the robot.
.
•
• Each joint, or axis, provides a certain degree-of-freedom (dof) of motion
Each joint, or axis, provides a certain degree-of-freedom (dof) of motion.
.
•
• In most of the cases, only one degree-of-freedom is associated with each joint
In most of the cases, only one degree-of-freedom is associated with each joint.
.
•
• Robot's
Robot's complexity
complexity can
can be
be classified
classified according
according to
to the
the total
total number
number of
of degrees
degrees
-of-freedom they possess.
-of-freedom they possess.
•
• Each
Each joint is connected to two links, an input link and an output link.
joint is connected to two links, an input link and an output link.
3

JOINTS AND LINKS
JOINTS AND LINKS
•
• A
A Joint
Joint provides
provides controlled
controlled relative
relative movement
movement between
between the
the input
input link
link and
and
output link. A robotic link is the rigid component of the robot manipulator
output link. A robotic link is the rigid component of the robot manipulator.
.
•
• Most
Most of
of the
the robots
robots are
are mounted
mounted upon
upon a
a stationary
stationary base,
base, such
such as
as the
the floor.
floor.
From
From this
this base,
base, a
a joint-link
joint-link numbering
numbering scheme
scheme may
may be
be recognized
recognized as
as shown
shown in
in
Figure.
Figure.
4

JOINTS AND LINKS
JOINTS AND LINKS
•
• The
The robotic
robotic base
base and
and its
its connection
connection to
to the
the
first joint are termed as link-0.
first joint are termed as link-0.
•
• The
The first joint in the sequence is joint-1
first joint in the sequence is joint-1.
.
•
• Link-0
Link-0 is
is the
the input
input link
link for
for joint-1,
joint-1, while
while the
the
output
output link
link from
from joint-1
joint-1 is
is link-1
link-1 which
which
leads to joint-2
leads to joint-2.
.
•
• Link
Link 1
1 is
is the
the output
output link
link for
for joint-1
joint-1 and
and the
the
input link for joint-2.
input link for joint-2.
•
• This
This joint-link-numbering
joint-link-numbering scheme
scheme is
is further
further
followed
followed for
for all
all joints
joints and
and links
links in
in the
the
robotic systems.
robotic systems. 5

JOINTS AND LINKS
JOINTS AND LINKS
•
• Nearly
Nearly all
all industrial
industrial robots
robots have
have mechanical
mechanical joints
joints that
that can
can be
be classified
classified into
into
following five types as shown in Figure below
following five types as shown in Figure below.
.
6

JOINTS AND LINKS
JOINTS AND LINKS
a) Linear joint (type L joint)
•
• The
The relative
relative movement
movement between
between the
the input
input link
link and
and the
the output
output link
link is
is a
a translational
translational
sliding motion, with the axes of the two links being parallel.
sliding motion, with the axes of the two links being parallel.
b) Orthogonal joint (type U joint
b) Orthogonal joint (type U joint)
)
•
• This
This also
also has
has a
a translational
translational sliding
sliding motion,
motion, but
but the
the input
input and
and output
output links
links are
are
perpendicular to each other during the move.
perpendicular to each other during the move.
c) Rotational joint (type R joint
c) Rotational joint (type R joint)
)
•
• This
This type
type provides
provides rotational
rotational relative
relative motion,
motion, with
with the
the axis
axis of
of rotation
rotation perpendicular
perpendicular
to the axes of the input and output links.
to the axes of the input and output links. 7

JOINTS AND LINKS
JOINTS AND LINKS
d) Twisting joint (type T joint)
• This joint also involves rotary motion, but the axis or rotation is parallel to the
axes of the two links.
e) Revolving joint (type V-joint, V from the “v” in revolving)
• In this type, axis of input link is parallel to the axis of rotation of the joint. Axis
of the output link is perpendicular to the axis of rotation.
8

COMMON ROBOT CONFIGURATIONS
•
• Basically
Basically the robot manipulator has two parts viz.
the robot manipulator has two parts viz.
•
• A
A body-and-arm
body-and-arm assembly
assembly with
with three
three degrees-of-freedom
degrees-of-freedom and
and A
A wrist
wrist
assembly with two or three degrees-of-freedom.
assembly with two or three degrees-of-freedom.
•
• For
For body-and-arm
body-and-arm configurations,
configurations, different
different combinations
combinations of
of joint
joint types
types are
are
possible for a three-degree-of-freedom robot manipulator
possible for a three-degree-of-freedom robot manipulator.
.
9

•
• Five common body-and-arm configurations are outlined below.
Five common body-and-arm configurations are outlined below.
10

(i
(i) Polar configuration
) Polar configuration
•
• It
It consists
consists of
of a
a sliding
sliding arm
arm L-joint,
L-joint, actuated
actuated relative
relative to
to the
the body,
body, which
which rotates
rotates
around both a vertical axis (T-joint)and horizontal axis (R-joint
around both a vertical axis (T-joint)and horizontal axis (R-joint).
).
11

(
(ii
ii) Cylindrical configuration
) Cylindrical configuration
•
• It
It consists
consists of
of a
a vertical
vertical column.
column. An
An arm
arm assembly
assembly is
is moved
moved up
up or
or down
down relative
relative to
to the
the
vertical column
vertical column.
.
•
• Arm
Arm can
can be
be moved
moved in
in and
and out
out relative
relative to
to the
the axis
axis of
of the
the column.
column. Common
Common
configuration is to use a T-joint to rotate the column about its axis
configuration is to use a T-joint to rotate the column about its axis .
.
•
• An
An L-joint
L-joint is
is used
used to
to move
move the
the arm
arm assembly
assembly vertically
vertically along
along the
the column,
column, while
while an
an O-
O-
joint is used to achieve radial movement of the arm.
joint is used to achieve radial movement of the arm.
12

(iii
(iii) Cartesian
) Cartesian co-ordinate
co-ordinate robot
robot
•
• It
It is
is also
also known
known as
as rectilinear
rectilinear robot
robot and
and x-y-z
x-y-z robot.
robot. It
It consists
consists of
of three
three sliding
sliding
joints, two of which are orthogonal O-joints.
joints, two of which are orthogonal O-joints.
13

(iv
(iv) Jointed-arm robot
) Jointed-arm robot
•
• It is similar to the configuration of a human arm
It is similar to the configuration of a human arm.
.
•
• It
It consists
consists of
of a
a vertical
vertical column
column that
that swivels
swivels about
about the
the base
base using
using a
a T-joint.
T-joint.
Shoulder joint (R-joint) is located at the top of the column.
Shoulder joint (R-joint) is located at the top of the column.
•
• The
The output link is an elbow joint (another R joint).
output link is an elbow joint (another R joint).
14

(
(v) SCARA
v) SCARA
•
• Its full form is ‘Selective Compliance Assembly Robot Arm
Its full form is ‘Selective Compliance Assembly Robot Arm'.
'.
•
• It
It is
is similar
similar in
in construction
construction to
to the
the jointer-arm
jointer-arm robot,
robot, except
except the
the shoulder
shoulder and
and
elbow rotational axes are vertical
elbow rotational axes are vertical.
.
•
• The
The arm
arm is
is very
very rigid
rigid in
in the
the vertical
vertical direction,
direction, but
but compliant
compliant in
in the
the horizontal
horizontal
direction.
direction. Robot
Robot wrist
wrist assemblies
assemblies consist
consist of
of either
either two
two or
or three
three degrees-of-
degrees-of-
freedom
freedom.
.
15

(
(v) SCARA
v) SCARA
•
• A
A typical three-degree-of-freedom wrist joint is depicted in Figure
typical three-degree-of-freedom wrist joint is depicted in Figure.
.
•
• Roll joint is accomplished by use of a T-joint.
Roll joint is accomplished by use of a T-joint.
•
• Pitch
Pitch joint
joint is
is achieved
achieved by
by recourse
recourse to
to an
an R-joint.
R-joint. Yaw
Yaw joint,
joint, a
a right-and-left
right-and-left
motion, is gained by deploying a second R-joint.
motion, is gained by deploying a second R-joint.
16

(
(v) SCARA
v) SCARA
•
• SCARA body and arm configuration does not use a separate wrist assembly
SCARA body and arm configuration does not use a separate wrist assembly.
.
•
• Its
Its usual
usual operative
operative environment
environment is
is for
for insertion-type
insertion-type assembly
assembly operations
operations
where wrist joints are unnecessary
where wrist joints are unnecessary.
.
•
• The
The other
other four
four body
body and
and arm
arm configurations
configurations more
more or
or less
less follow
follow the
the wrist-joint
wrist-joint
configuration by deploying various combinations of rotary joints.
configuration by deploying various combinations of rotary joints.
17

CLASSIFICATION OF ROBOTS
•
• The
The three
three types
types of
of drive
drive systems
systems that
that are
are generally
generally used
used for
for industrial
industrial robots
robots
are:
are:
(
(i)Hydraulic
i)Hydraulic drive
drive
(
(ii)Electric
ii)Electric drive
drive
(
(iii)Pneumatic drive
iii)Pneumatic drive
18

i
i) Hydraulic
) Hydraulic drive
drive
•
• It
It gives
gives a
a robot
robot great
great speed
speed and
and strength.
strength. They
They provide
provide high
high speed
speed and
and strength,
strength,
hence they are adopted for large industrial robots
hence they are adopted for large industrial robots.
.
•
• This
This type
type of
of drives
drives are
are preferred
preferred in
in environments
environments in
in which
which the
the use
use of
of electric
electric drive
drive
robots may cause fire
robots may cause fire hazards
hazards
•
• Example: In spray painting
Example: In spray painting.
.
Disadvantages of a hydraulic robot
Disadvantages of a hydraulic robot:
:
•
• Occupy
Occupy more
more floor
floor space
space for
for ancillary
ancillary equipment
equipment in
in addition
addition to
to that
that required
required by
by the
the
robot
robot.
.
•
• There are housekeeping problems such as leaks.
There are housekeeping problems such as leaks. 19

ii) Electric
ii) Electric drive
drive
•
• This
This provides
provides a
a robot
robot with
with less
less speed
speed and
and strength.
strength. Electric
Electric drive
drive systems
systems are
are
adopted for smaller robots.
adopted for smaller robots.
•
• Robots
Robots supported
supported by
by electric
electric drive
drive systems
systems are
are more
more accurate,
accurate, exhibit
exhibit better
better
repeatability and are cleaner to use.
repeatability and are cleaner to use.
•
• Electrically driven robots are the most commonly available .
Electrically driven robots are the most commonly available .
20

ii) Electric
ii) Electric drive
drive
•
• Electrically driven robots can be classified into two broad categories
Electrically driven robots can be classified into two broad categories.
.
(
(i)Stepper motor driven
i)Stepper motor driven.
.
(
(ii)Direct Current (DC) servo-motor driven.
ii)Direct Current (DC) servo-motor driven.
•
• Most stepper motor-driven robots are of the open loop type
Most stepper motor-driven robots are of the open loop type.
.
•
• Feedback
Feedback loops can be incorporated in stepper-driven robots
loops can be incorporated in stepper-driven robots.
.
•
• Servo-driven
Servo-driven robots
robots have
have feedback
feedback loops
loops from
from the
the driven
driven components
components back
back to
to the
the
driver.
driver. 21

iii) Pneumatic
iii) Pneumatic drive
drive
•
• Generally used for smaller robots.
Generally used for smaller robots.
•
• Have
Have fewer axes of movement
fewer axes of movement.
.
•
• Carry
Carry out
out simple
simple pick-and-place
pick-and-place material-handling
material-handling operations,
operations, such
such as
as picking
picking
up an object at one location and placing it at another location
up an object at one location and placing it at another location.
.
•
• These operations are generally simple and have short cycle times
These operations are generally simple and have short cycle times.
.
•
• Here
Here pneumatic power can be used for sliding or rotational joints
pneumatic power can be used for sliding or rotational joints.
.
•
• Pneumatic
Pneumatic robots are less expensive than electric or hydraulic robots.
robots are less expensive than electric or hydraulic robots.
22

ROBOT CONTROL SYSTEMS
•
• The
The Joint movements must be controlled if the robot is to perform as desired
Joint movements must be controlled if the robot is to perform as desired.
.
•
• Micro-processor-based
Micro-processor-based controllers
controllers are
are regularly
regularly used
used to
to perform
perform this
this control
control
action
action.
.
•
• Controller is organised in a hierarchical fashion, as illustrated in
Controller is organised in a hierarchical fashion, as illustrated in Figure.
Figure.
•
• Each
Each joint
joint can
can feed
feed back
back control
control data
data individually,
individually, with
with an
an overarching
overarching
supervisory
supervisory controller
controller co-ordinating
co-ordinating the
the combined
combined actuations
actuations of
of the
the joints
joints
according to the sequence of the robot programme.
according to the sequence of the robot programme.
23

•
• Controller
Controller is organised in a hierarchical fashion, as illustrated in
is organised in a hierarchical fashion, as illustrated in Figure.
Figure.
24

Hierarchical control
Hierarchical control structure
structure
(a) Limited
(a) Limited Sequence
Sequence Control
Control
•
• Elementary
Elementary control
control type,
type, it
it is
is used
used for
for simple
simple motion
motion cycles,
cycles, such
such as
as pick
pick and
and
place operations.
place operations.
•
• It
It is
is implemented
implemented by
by fixing
fixing limits
limits or
or mechanical
mechanical stops
stops for
for each
each joint
joint and
and
sequencing the movement of joints to accomplish operation
sequencing the movement of joints to accomplish operation.
.
•
• Feedback
Feedback loops
loops may
may be
be used
used to
to inform
inform the
the controller
controller that
that the
the action
action has
has been
been
performed, so that the programme can move to the next step
performed, so that the programme can move to the next step.
.
•
• No
No servo-control
servo-control exists
exists for
for precise
precise positioning
positioning of
of joint.
joint. Many
Many pneumatically
pneumatically
driven robots are this type.
driven robots are this type. 25

structure
(b) Playback
(b) Playback with Point to Point
with Point to Point Control
Control
•
• Playback
Playback control
control uses
uses a
a controller
controller with
with memory
memory to
to record
record motion
motion sequences
sequences in
in
a
a work
work cycle,
cycle, as
as well
well as
as associated
associated locations
locations and
and other
other parameters
parameters and
and then
then
plays back the work cycle during programme execution
plays back the work cycle during programme execution.
.
•
• Point
Point to
to point
point control
control means
means individual
individual robot
robot positions
positions are
are recorded
recorded in
in the
the
memory
memory.
.
•
• These
These positions
positions include
include both
both mechanical
mechanical stops
stops for
for each
each joint
joint and
and the
the set
set of
of
values that represent locations in the range of each joint
values that represent locations in the range of each joint.
.
•
• Feedback
Feedback control
control is
is used
used to
to confirm
confirm that
that the
the individual
individual joints
joints achieve
achieve the
the
specified locations in the programme.
specified locations in the programme.
26

structure
(c) Playback
(c) Playback with Continuous Path
with Continuous Path Control
Control
•
• Playback is as described above.
Playback is as described above.
•
• Continuous
Continuous path
path control
control refers
refers to
to a
a control
control system
system capable
capable of
of continuous
continuous
simultaneous control of two or more axes.
simultaneous control of two or more axes.
•
• Greater
Greater storage
storage capacity—the
capacity—the number
number of
of locations
locations that
that can
can be
be stored
stored is
is
greater
greater than
than in
in point
point to
to point
point and
and interpolation
interpolation calculations
calculations may
may be
be used,
used,
especially linear and circular interpolations.
especially linear and circular interpolations. 27

structure
(d) Intelligent Control
(d) Intelligent Control
•
• An
An intelligent robot is one that exhibits behaviour that makes it seem intelligent
intelligent robot is one that exhibits behaviour that makes it seem intelligent .
.
•
• For
For example,
example, capacities
capacities to
to interact
interact with
with its
its ambient
ambient surroundings,
surroundings, decision-making
decision-making
capabilities,
capabilities, communication
communication with
with humans;
humans; computational
computational analysis
analysis during
during the
the work
work
cycle and responsiveness to advanced sensor inputs
cycle and responsiveness to advanced sensor inputs.
.
•
• They may also possess the playback facilities of the above two instances.
They may also possess the playback facilities of the above two instances.
•
• Requires
Requires a
a high
high level
level of
of computer
computer control
control and
and an
an advanced
advanced programming
programming language
language
to input the decision-making logic and other ‘intelligence’ into the
to input the decision-making logic and other ‘intelligence’ into the memory.
memory.
28

END EFFECTORS
END EFFECTORS
•
• It is commonly known as robot hand
It is commonly known as robot hand.
.
•
• It
It is mounted on the wrist, enables the robot to perform specified tasks
is mounted on the wrist, enables the robot to perform specified tasks.
.
•
• Various
Various types
types of
of end-effectors
end-effectors are
are designed
designed for
for the
the same
same robot
robot to
to make
make it
it
more flexible and versatile
more flexible and versatile.
.
•
• End-effectors are categorised into two major types
End-effectors are categorised into two major types:
:
1
1.
. Grippers
Grippers
2
2. Tools
. Tools
29

END
END EFFECTORS - GRIPPERS
EFFECTORS - GRIPPERS
•
• Grippers grasp and manipulate objects during the work cycle.
Grippers grasp and manipulate objects during the work cycle.
•
• Typically
Typically the
the objects
objects grasped
grasped are
are work
work parts
parts that
that need
need to
to be
be loaded
loaded or
or
unloaded from one station to another
unloaded from one station to another.
.
•
• It
It may
may be
be custom-designed
custom-designed to
to suit
suit the
the physical
physical specifications
specifications of
of the
the work
work parts
parts
they have to grasp.
they have to grasp.
30

END
•
• End effectors, grippers are described in detail in table below
End effectors, grippers are described in detail in table below.
.
31
Type comment
Mechanical gripper
Two or more fingers that can be actuated by
robot controller to open and close on a work
part.
Vacuum gripper Suction cups are used to hold flat objects.
Magnetised devices
Making use of the principles of magnetism,
these are used for holding ferrous work parts.
Adhesive devices
Deploying adhesive substances these hold
flexible materials, such as fabric.
Simple mechanical devices For example, hooks and scoops.

END
•
.
32
Type comment
Dual grippers
Mechanical gripper with two gripping
devices in one end effector for machine
loading and unloading.
Reduces cycle time per part by gripping two
work parts at the same time.
Interchangeable fingers
Mechanical gripper whereby, to
accommodate different work part sizes,
different fingers may be attached.
Sensory feedback fingers
Mechanical gripper with sensory feedback
capabilities in the fingers to aid locating the
work part and to determine correct grip
force to apply (for fragile work parts).

END
•
.
33
Type comment
Multiple fingered grippers
Mechanical gripper with the general anatomy of
the human hand.
Standard grippers
Mechanical grippers that are commercially
available, thus reducing the need to custom-
design a gripper for each separate robot
application.

END
END EFFECTORS - TOOLS
EFFECTORS - TOOLS
•
• The robot end effecter may also use tools
The robot end effecter may also use tools.
.
•
• Tools
Tools are used to perform processing operations on the work part.
are used to perform processing operations on the work part.
•
• Typically
Typically the
the robot
robot uses
uses the
the tool
tool relative
relative to
to a
a stationary
stationary or
or slowly
slowly moving
moving
object
object.
.
•
• In
In this way the process is carried out.
this way the process is carried out.
34

END
END EFFECTORS - TOOLS
EFFECTORS - TOOLS
•
• Examples
Examples of
of the
the tools
tools used
used as
as end
end effectors
effectors by
by roots
roots to
to perform
perform processing
processing
applications include
applications include:
:
•
• Spot welding
Spot welding gun
gun
•
• Arc welding
Arc welding tool
tool
•
• Spray painting
Spray painting gun
gun
•
• Rotating spindle for drilling, routing, grinding, etc
Rotating spindle for drilling, routing, grinding, etc.
.
•
• Assembly tool (e.g. automatic screwdriver
Assembly tool (e.g. automatic screwdriver)
)
•
• Heating
Heating torch
torch
•
• Water-jet cutting tool
Water-jet cutting tool 35

END
END EFFECTORS
EFFECTORS
•
• For
For each
each instance,
instance, the
the robot
robot controls
controls both
both the
the position
position of
of the
the work
work part
part and
and the
the
position of the tool relative to the work part
position of the tool relative to the work part.
.
•
• For
For this
this purpose,
purpose, the
the robot
robot must
must be
be able
able to
to transmit
transmit control
control signals
signals to
to the
the tool
tool
for starting, stopping and otherwise regulating the tools actions
for starting, stopping and otherwise regulating the tools actions.
.
•
• Figure illustrates a sample gripper and tool.
Figure illustrates a sample gripper and tool.
36

SENSORS IN ROBOTICS
SENSORS IN ROBOTICS
•
• Two basic categories of sensors used in industrial robots:
Two basic categories of sensors used in industrial robots:
(
(i)Internal sensors
i)Internal sensors
(
(ii)External sensors
ii)External sensors
37

SENSORS IN ROBOTICS
SENSORS IN ROBOTICS
(
(i
i) Internal sensors
) Internal sensors
•
• Internal sensors are used to monitor and control the various joints of the robot
Internal sensors are used to monitor and control the various joints of the robot.
.
•
• They
They form a feedback control loop with the robot controller
form a feedback control loop with the robot controller.
.
•
• Examples
Examples of
of internal
internal sensors
sensors include
include potentiometers
potentiometers and
and optical
optical encoders,
encoders,
while
while tachometers
tachometers of
of various
various types
types can
can be
be deployed
deployed to
to control
control the
the speed
speed of
of
the robot arm
the robot arm.
.
38

SENSORS IN ROBOTICS
SENSORS IN ROBOTICS
(ii) External sensors
(ii) External sensors
•
• These are external to the robot
These are external to the robot itself.
itself.
•
• They
They are
are used
used when
when we
we wish
wish to
to control
control the
the operations
operations of
of the
the robot
robot with
with other
other
pieces of equipment in the robotic work cell
pieces of equipment in the robotic work cell.
.
•
• External
External sensors
sensors can
can be
be relatively
relatively simple
simple devices,
devices, such
such as
as limit
limit switches
switches that
that
determine
determine whether
whether a
a part
part has
has been
been positioned
positioned properly
properly or
or whether
whether a
a part
part is
is
ready to be picked up from an unloading bay.
ready to be picked up from an unloading bay. 39

SENSORS IN ROBOTICS
SENSORS IN ROBOTICS
40
•
• Micro Sensor board
Micro Sensor board

SENSORS IN ROBOTICS
SENSORS IN ROBOTICS
41
•
• Advanced sensor model technologies for robotics
Advanced sensor model technologies for robotics

END
•
• A
A number
number of
of advanced
advanced sensor
sensor technologies
technologies may
may also
also be
be used;
used; these
these are
are
outlined in Table.
outlined in Table.
42
Sensor Type Description
Tactile sensors
Used to determine whether contact is made
between sensor and another object. Two
types: touch sensors which indicate when
contact is made and force sensors which
indicate the magnitude of the force with the
object.
Proximity sensors
Used to determine how close an object is to
the sensor. Also called a range sensor.
Optical sensors
Photocells and other photometric devices that
are used to detect the presence or absence of
objects. Often used in conjunction to proximity
sensors.

END
•
• A
A number
number of
of advanced
advanced sensor
sensor technologies
technologies may
may also
also be
be used;
used; these
these are
are
outlined in Table.
outlined in Table.
43
Sensor Type Description
Machine vision
Used in robotics for inspection, parts
identification, guidance and other uses.
Miscellaneous category
temperature, fluid pressure, fluid flow,
electrical voltage, current and other physical
properties.

ROBOT ACCURACY AND REPEATABILITY
•
• The
The capacity
capacity of
of the
the robot
robot to
to position
position and
and orient
orient the
the end
end of
of its
its wrist
wrist with
with
accuracy
accuracy and
and repeatability
repeatability is
is an
an important
important control
control attribute
attribute in
in nearly
nearly all
all
industrial applications.
industrial applications.
•
• Some
Some assembly
assembly applications
applications require
require that
that objects
objects be
be located
located with
with a
a precision
precision
of only 0.002 to 0.005 inches.
of only 0.002 to 0.005 inches.
•
• Other
Other applications,
applications, such
such as
as spot
spot welding,
welding, usually
usually require
require accuracies
accuracies of
of 0.020
0.020
to 0.040 inches.
to 0.040 inches.
44

•
• There are several terms that must defined in the context of this discussion:
There are several terms that must defined in the context of this discussion:
• Control resolution
• Control resolution
• Accuracy
• Accuracy
• Repeatability
• Repeatability
45

Resolution
Resolution
•
• Resolution
Resolution is
is based
based on
on a
a limited
limited number
number of
of points
points that
that the
the robot
robot can
can be
be
commanded to reach for, these are shown here as black dots
commanded to reach for, these are shown here as black dots.
.
•
• These
These points
points are
are typically
typically separated
separated by
by a
a millimetre
millimetre or
or less,
less, depending
depending on
on
the type of robot.
the type of robot.
•
• This
This is
is further
further complicated
complicated by
by the
the fact
fact that
that the
the user
user might
might ask
ask for
for a
a position
position
such
such as
as 456.4mm,
456.4mm, and
and the
the system
system can
can only
only move
move to
to the
the nearest
nearest millimetre,
millimetre,
456mm, this is the accuracy error of 0.4mm.
456mm, this is the accuracy error of 0.4mm.
46

Accuracy
Accuracy
•
• “
“How close does the robot get to the desired point
How close does the robot get to the desired point”.
”.
•
• This
This measures
measures the
the distance
distance between
between the
the specified
specified position,
position, and
and the
the actual
actual
position of the robot end effector.
position of the robot end effector.
•
• Accuracy
Accuracy is
is more
more important
important when
when performing
performing off-line
off-line programming,
programming, because
because
absolute coordinates are used.
absolute coordinates are used.
47

Repeatability
Repeatability
•
• How
How close
close will
will the
the robot
robot be
be to
to the
the same
same position
position as
as the
the same
same move
move made
made
before
before”.
”.
•
• A
A measure
measure of
of the
the error
error or
or variability
variability when
when repeatedly
repeatedly reaching
reaching for
for a
a single
single
position.
position.
•
• This
This is the result of random errors
is the result of random errors only.
only.
•
• R
Repeatability
epeatability is often smaller than accuracy.
is often smaller than accuracy.
48

INDUSTRIAL ROBOT APPLICATIONS
INDUSTRIAL ROBOT APPLICATIONS
•
• Industrial Robot Applications can be divided into:
Industrial Robot Applications can be divided into:
(
(i
i) Material-handling
) Material-handling applications
applications
(
(ii
ii) Processing
) Processing Operations
Operations
(
(iii
iii) Assembly
) Assembly Applications
Applications
49

MATERIAL-HANDLING APPLICATIONS
•
• The robot must have following features to facilitate material handling:
The robot must have following features to facilitate material handling:
1. The
1. The manipulator must be able to lift the parts safely
manipulator must be able to lift the parts safely.
.
2. The
2. The robot must have the reach needed
robot must have the reach needed.
.
3. The
3. The robot must have cylindrical coordinate type
robot must have cylindrical coordinate type.
.
4.
4. The
The robot’s
robot’s controller
controller must
must have
have a
a large
large enough
enough memory
memory to
to store
store all
all the
the
programmed points so that the robot can move from one location to another.
programmed points so that the robot can move from one location to another.
5.
5. The
The robot
robot must
must have
have the
the speed
speed necessary
necessary for
for meeting
meeting the
the transfer
transfer cycle
cycle of
of
the operation.
the operation. 50

•
• This category includes the following
This category includes the following:
:
(1) Part Placement
(1) Part Placement
(2) Palletizing
(2) Palletizing or
or depalletizing
depalletizing
(3) Machine
(3) Machine loading or
loading or unloading
unloading
(4) Stacking
(4) Stacking and insertion operations
and insertion operations
51

(1) Part
(1) Part Placement
Placement:
:
•
• The
The basic
basic operation
operation in
in this
this category
category is
is the
the relatively
relatively simple
simple pick-and-place
pick-and-place
operation
operation.
.
•
• This
This application
application needs
needs a
a low-technology
low-technology robot
robot of
of the
the cylindrical
cylindrical coordinate
coordinate
type
type.
.
•
• Only
Only two, three or four joints are required for most of the applications
two, three or four joints are required for most of the applications.
.
•
• Pneumatically
Pneumatically powered robots are often utilized.
powered robots are often utilized.
52

(2) Palletizing
(2) Palletizing and/or Depalletizing
and/or Depalletizing:
:
•
• The
The applications
applications require
require robot
robot to
to stack
stack parts
parts one
one on
on top
top of
of the
the other,
other, that
that is
is to
to
palletize
palletize them
them or
or to
to unstack
unstack parts
parts by
by removing
removing from
from the
the top
top one
one by
by one,
one, that
that is
is
depalletize them
depalletize them.
.
•
• Example:
Example: Process
Process of
of taking
taking parts
parts from
from the
the assembly
assembly line
line and
and stacking
stacking them
them on
on a
a
pallet or vice versa.
pallet or vice versa.
53

(3) Machine
(3) Machine loading and/or unloading:
loading and/or unloading:
•
• Robot transfers parts into and/or from a production machine.
Robot transfers parts into and/or from a production machine.
There are three possible cases:
There are three possible cases:
•
• Machine
Machine loading
loading in
in which
which the
the robot
robot loads
loads parts
parts into
into a
a production
production machine,
machine, but
but the
the
parts are unloaded by some other means.
parts are unloaded by some other means.
Example:
Example: A
A press
press working
working operation,
operation, where
where the
the robot
robot feeds
feeds sheet
sheet blanks
blanks into
into the
the press,
press,
but the finished parts drop out of the press by gravity.
but the finished parts drop out of the press by gravity. 54

•
• Machine
Machine loading
loading in
in which
which the
the raw
raw materials
materials are
are fed
fed into
into the
the machine
machine without
without robot
robot
assistance. The robot unloads the part from the machine assisted by vision or no vision.
assistance. The robot unloads the part from the machine assisted by vision or no vision.
Example:
Example: Bin picking, die casting and plastic moulding.
Bin picking, die casting and plastic moulding.
•
• Machine
Machine loading
loading and
and unloading
unloading that
that involves
involves both
both loading
loading and
and unloading
unloading of
of the
the work
work
parts
parts by
by the
the robot.
robot. The
The robot
robot loads
loads a
a raw
raw work
work part
part into
into the
the process
process and
and unloads
unloads a
a
finished part.
finished part.
Example:
Example: Machine operation
Machine operation
55

PROCESSING OPERATIONS
•
• In
In processing
processing operations,
operations, the
the robot
robot performs
performs some
some processing
processing actions
actions such
such as
as
grinding, milling, etc. on the work part
grinding, milling, etc. on the work part.
.
•
• The end effector is equipped with the specialised tool required for the process
The end effector is equipped with the specialised tool required for the process.
.
•
• The
The tool is moved relative to the surface of the work part
tool is moved relative to the surface of the work part.
.
•
• Robot
Robot performs a processing procedure on the part
performs a processing procedure on the part.
.
•
• The robot is equipped with some type of process tooling as its end effector
The robot is equipped with some type of process tooling as its end effector.
.
•
• Manipulates
Manipulates the tooling relative to the working part during the cycle.
the tooling relative to the working part during the cycle.
56

•
• Industrial robot applications in the processing operations include
Industrial robot applications in the processing operations include:
:
(1) Spot welding
(1) Spot welding
(2) Continuous
(2) Continuous arc
arc welding
welding
(3) Spray painting
(3) Spray painting
(4) Metal
(4) Metal cutting and deburring
cutting and deburring operations
operations
(5)
(5) Various
Various machining
machining operations
operations like
like drilling,
drilling, grinding,
grinding, laser
laser and
and
waterjet cutting and riveting
waterjet cutting and riveting.
.
(6) Rotating
(6) Rotating and spindle
and spindle operations
operations
(7) Adhesives
(7) Adhesives and sealant dispensing
and sealant dispensing 57

ASSEMBLY OPERATIONS
ASSEMBLY OPERATIONS
•
• The applications involve both material handling and the manipulation of a tool
The applications involve both material handling and the manipulation of a tool.
.
•
• They
They typically
typically include
include components
components to
to build
build the
the product
product and
and to
to perform
perform material
material
handling operations
handling operations.
.
These are classified as
These are classified as:
:
•
• Batch
Batch assembly:
assembly: As
As many
many as
as one
one million
million products
products might
might be
be assembled.
assembled. The
The
assembly operation has long production runs
assembly operation has long production runs.
.
•
• Low-volume:
Low-volume: In
In this
this a
a sample
sample run
run of
of ten
ten thousand
thousand or
or less
less products
products might
might be
be
made
made. The
. The assembly robot cell should be a modular cell
assembly robot cell should be a modular cell.
.
•
• One
One of
of the
the well
well suited
suited area
area for
for robotics
robotics assembly
assembly is
is the
the insertion
insertion of
of odd
odd
electronic components.
electronic components. 58

FUTURE APPLICATIONS
FUTURE APPLICATIONS
The medical applications of the
The medical applications of the robot
robot
• Routine examinations
• Routine examinations
• Surgical procedures
• Surgical procedures
Underwater
Underwater applications
applications
• Involves
• Involves prospecting for minerals on the floor of the ocean
prospecting for minerals on the floor of the ocean.
.
• Salvaging
• Salvaging of sunken vessels, repair the ship either at sea or in dry dock
of sunken vessels, repair the ship either at sea or in dry dock.
.
• Mobile
• Mobile firefighters to be used by air force and navy
firefighters to be used by air force and navy.
.
59

FUTURE APPLICATIONS
FUTURE APPLICATIONS
Surveillance and Guard
Surveillance and Guard duty
duty
•
• Used
Used in
in military
military
•
• Used
Used in
in power
power generating
generating plants,
plants, oil
oil refineries
refineries and
and other
other civilian
civilian facilities
facilities that
that
are potential targets of terrorist groups.
are potential targets of terrorist groups.
60

ROBOT PART PROGRAMMING
•
• It
It is
is a
a path
path in
in space
space to
to be
be followed
followed by
by the
the manipulator,
manipulator, combined
combined with
with
peripheral actions that support the work cycle.
peripheral actions that support the work cycle.
•
• To
To programme
programme a
a robot
robot ,
, specific
specific commands
commands are
are entered
entered into
into the
the robot’s
robot’s
controller memory and this action may be performed in a number of ways.
controller memory and this action may be performed in a number of ways.
•
• For
For limited
limited sequence
sequence robots
robots ,programming
,programming occurs
occurs when
when limit
limit switches
switches and
and
mechanical stops are set to control the endpoints of its motions.
mechanical stops are set to control the endpoints of its motions.
61

•
• A
A sequencing
sequencing device
device controls
controls the
the occurrence
occurrence of
of the
the motions,
motions, which
which in
in turn
turn controls
controls
the movement of the joints that completes the motion cycle
the movement of the joints that completes the motion cycle.
.
•
• For
For industrial
industrial robots
robots with
with digital
digital computers
computers as
as controllers
controllers three
three programming
programming
methods can be distinguished.
methods can be distinguished.
(a) Lead-through
(a) Lead-through programming
programming
(b) Computer-like
(b) Computer-like robot programming languages
robot programming languages
(c) Off-line
(c) Off-line programming.
programming.
•
• Lead-through
Lead-through methodologies
methodologies and
and associated
associated programming
programming methods,
methods, are
are
outlined in detail in table
outlined in detail in table
62

ROBOT PART PROGRAMMING - LEAD-THROUGH
ROBOT PART PROGRAMMING - LEAD-THROUGH
PROGRAMMING
PROGRAMMING
•
• Task
Task is
is ‘taught’
‘taught’ to
to the
the robot
robot by
by manually
manually moving
moving the
the manipulator
manipulator through
through the
the
required
required motion
motion cycle
cycle and
and simultaneously
simultaneously entering
entering the
the programme
programme into
into the
the
controller memory for playback.
controller memory for playback.
•
• Two
Two methods
methods are
are used
used for
for teaching:
teaching: powered
powered lead-through
lead-through and
and manual
manual lead-
lead-
through.
through.
63

ROBOT PART PROGRAMMING - MOTION
PROGRAMMING
PROGRAMMING
•
• To
To overcome
overcome difficulties
difficulties of
of co-ordinating
co-ordinating individual
individual joints
joints associated
associated with
with lead-
lead-
through programming, two mechanical methods can be used
through programming, two mechanical methods can be used:
:
•
• The
The world
world co-ordinate
co-ordinate system
system whereby
whereby the
the origin
origin and
and axes
axes are
are defined
defined relative
relative
to
to the
the robot
robot base
base and
and the
the tool
tool co-ordinate
co-ordinate system
system whereby
whereby the
the alignment
alignment of
of the
the
axis system is defined relative to the orientation of the wrist face plate.
axis system is defined relative to the orientation of the wrist face plate.
•
• These
These methods
methods are
are typically
typically used
used with
with Cartesian
Cartesian co-ordinate
co-ordinate robots
robots and
and not
not for
for
robots with rotational joints.
robots with rotational joints.
64

PROGRAMMING
PROGRAMMING
•
• The
The latter
latter robotic
robotic types
types must
must rely
rely on
on interpolation
interpolation processes
processes to
to gain
gain straight
straight line
line
motion.
motion.
•
• Straight
Straight line
line interpolation
interpolation where
where the
the control
control computer
computer calculates
calculates the
the necessary
necessary
points
points in
in space
space that
that the
the manipulator
manipulator must
must move
move through
through to
to connect
connect two
two points
points
and
and Joint
Joint interpolation
interpolation where
where joints
joints are
are moved
moved simultaneously
simultaneously at
at their
their own
own
constant speed such that all joints start/stop at the same time.
constant speed such that all joints start/stop at the same time.
65

MANUAL LEAD-THROUGH PROGRAMMING
•
• Manual
Manual lead
lead through
through programming
programming is
is convenient
convenient for
for programming
programming playback
playback
robots
robots with
with continuous
continuous path
path control
control where
where the
the continuous
continuous path
path is
is an
an irregular
irregular
motion pattern such as in spray painting.
motion pattern such as in spray painting.
•
• This
This programming
programming method
method requires
requires the
the operator
operator to
to physically
physically grasp
grasp the
the end
end of
of
arm
arm or
or the
the tool
tool that
that is
is attached
attached to
to the
the arm
arm and
and move
move it
it through
through the
the motion
motion
sequence, recording the path into memory.
sequence, recording the path into memory.
66

•
• Because
Because the
the robot
robot arm
arm itself
itself may
may have
have significant
significant mass
mass and
and would
would therefore
therefore be
be
difficult
difficult to
to move,
move, a
a special
special programming
programming device
device often
often replaces
replaces the
the actual
actual robot
robot for
for the
the
teaching procedure.
teaching procedure.
•
• The
The programming
programming device
device has
has the
the same
same joint
joint configuration
configuration as
as the
the robot
robot and
and is
is equipped
equipped
with
with a
a trigger
trigger handle
handle (or
(or other
other control
control switch)
switch) which
which the
the operator
operator activates
activates when
when
recording motions into memory.
recording motions into memory.
•
• The
The motions
motions are
are recorded
recorded as
as a
a series
series of
of closely
closely spaced
spaced points.
points. During
During playback
playback the
the
path
path is
is recreated
recreated by
by controlling
controlling the
the actual
actual robot
robot arm
arm through
through the
the same
same sequence
sequence of
of
points.
points. 67

ADVANTAGES AND DISADVANTAGES
ADVANTAGES AND DISADVANTAGES
Advantages
Advantages
• It
• It can readily be learned by shop personnel
can readily be learned by shop personnel.
.
• It
• It is a logical way to teach a robot
is a logical way to teach a robot.
.
• It
• It does not require knowledge of computer programming
does not require knowledge of computer programming.
.
Disadvantages
Disadvantages
• Downtime
• Downtime regular production must be interrupted to program the robot
regular production must be interrupted to program the robot.
.
• Limited
• Limited programming logic capability
programming logic capability.
.
• Not
• Not readily compatible with modern computer based technologies.
readily compatible with modern computer based technologies.
68

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