Ch 8 Industrial Robotics
Sections:
1. Robot Anatomy and
Related Attributes
1. Robot Control Systems
2. End Effectors
3. Sensors in Robotics
4. Industrial Robot Applications
5. Robot Programming
6. Robot Accuracy and Repeatability
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Industrial Robot Defined
A general-purpose, programmable
machine capable of possessing certain
anthropomorphic characteristics.
The most obvious anthropomorphic
characteristic of an industrial robot is
its mechanical arm, which is used to
perform various industrial tasks.
Other human-like characteristics are:
ƒ robot’s capabilities to respond to sensory inputs,
ƒ communicate with other machines, and
ƒ make decisions.
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1
Industrial Robot Defined
These capabilities permit robots to perform a variety of
useful task.
The development of robot technology followed the
development of numerical control, and the two
technologies are quite similar.
They both involve coordinated control of multiple axes
(the axes are called joints in robotics), and they both
use dedicated digital computers as controllers.
Typical production applications of industrial robots
include spot welding, material transfer, machine
loading, spray painting, and assembly.
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Industrial Robot Defined
• Robots can be substituted for humans in hazardous or
uncomfortable work environments.
• A robot performs its work cycle with a consistency and
repeatability that cannot be attained by humans.
• Robots can be reprogrammed. When the production
run of the current task is completed, a robot can be
reprogrammed and equipped with the necessary
tooling to perform an another different task.
• Robots are controlled by computers and can therefore
be connected to other computer systems to achieve
computer integrated manufacturing.
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2
Robot Anatomy
Robot manipulator - a series of joint-link combinations
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Robot Anatomy
ƒ Manipulator consists of joints and links
ƒ Joints provide relative motion
ƒ Links are rigid members between joints
ƒ Various joint types: linear and rotary
ƒ Each joint provides a “degree-of-freedom”
ƒ Most robots possess five or six degrees-of-freedom
ƒ Robot manipulator consists of two sections:
ƒ Body-and-arm – for positioning of objects in the
robot's work volume
ƒ Wrist assembly – for orientation of objects
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3
Types of Manipulator Joints
ƒ Translational motion
ƒ Linear joint (type L)
ƒ Orthogonal joint (type O)
ƒ Rotary motion
ƒ Rotational joint (type R)
ƒ Twisting joint (type T)
ƒ Revolving joint (type V)
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Translational Motion Joints
Linear joint
(type L)
Orthogonal joint
(type O)
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4
Rotary Motion Joints
Rotational joint
(type R)
Twisting joint
(type T)
Revolving joint
(type V)
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Joint Notation Scheme
ƒ Uses the joint symbols (L, O, R, T, V) to designate joint
types used to construct robot manipulator
ƒ Separates body-and-arm assembly from wrist assembly
using a colon (:)
ƒ Example: TLR : TR
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5
Robot Body-and-Arm Configurations
ƒ
ƒ
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.
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Polar Coordinate
Body-and-Arm Assembly
ƒ Notation TRL:
ƒ 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)
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6
Cylindrical Body-and-Arm Assembly
ƒ Notation TLO:
ƒ Consists of a vertical column,
relative to which an arm
assembly is moved up or down
ƒ The arm can be moved in or out
relative to the column
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Cartesian Coordinate
Body-and-Arm Assembly
ƒ Notation LOO:
ƒ Consists of three sliding joints,
two of which are orthogonal
ƒ Other names include rectilinear
robot and x-y-z robot
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7
Jointed-Arm Robot
ƒ Notation TRR:
ƒ General configuration
of a human arm
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SCARA Robot
ƒ Notation VRO
ƒ SCARA stands for Selectively
Compliant Assembly Robot Arm.
ƒ Similar to jointed-arm robot except
that vertical axes are used for
shoulder and elbow joints.
ƒ The arm is very rigid in the vertical direction, but
compliant in the horizontal direction.
ƒ This permits the robot to perform insertion tasks (for
assembly) in a vertical direction, where some side-toside alignment may be needed to mate the two parts
properly.
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8
Joint Notations
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Wrist Configurations
ƒ Wrist assembly is attached to end-of-arm
ƒ End effector is attached to wrist assembly
ƒ Function of wrist assembly is to orient end effector
ƒ Body-and-arm determines global position of end
effector
ƒ Two or three degrees of freedom:
ƒ Roll
ƒ Pitch
ƒ Yaw
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9
Wrist Configuration
ƒ Typical wrist assembly has two or three degrees-offreedom (shown is a three degree-of freedom wrist)
ƒ Notation :RRT
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SCARA Robot - No wrist
ƒ The SCARA robot configuration is
unique in that it typically does not
have a separate wrist assembly.
ƒ Since it is used for insertion type
assembly operations in which the
insertion is made from above, the
orientation requirements are
minimal, and the wrist is therefore
not needed.
ƒ Orientation of the object to be inserted is sometimes
required, and an additional rotary joint can be provided
for this purpose.
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10
Work Volume
ƒ The work volume (the term work envelope is also used) of
the manipulator is defined as the envelope or threedimensional space within which the robot can manipulate
the end of its wrist.
ƒ Work volume is determined by the number and types of
joints in the manipulator (body-and-arm and wrist), the
ranges of the various joints, and the physical sizes of the
links.
ƒ The shape of the work volume depends largely on the
robot’s configuration. A polar configuration robot tends to
have a partial sphere as its work volume, a cylindrical
robot has a cylindrical work envelope, and a Cartesian
coordinate robot has a rectangular work volume.
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Work Volume
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11
Joint Drive Systems
ƒ Electric
ƒ Uses electric motors to actuate individual joints
ƒ Preferred drive system in today's robots
ƒ Hydraulic
ƒ Uses hydraulic pistons and rotary vane actuators
ƒ Noted for their high power and lift capacity
ƒ Pneumatic
ƒ Typically limited to smaller robots and simple material
transfer applications
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Speed
ƒ The drive system, position sensors (and speed sensors if
used), and feedback control systems for the joints
determine the dynamic response characteristics of the
manipulator.
ƒ The speed with which the robot can achieve a
programmed position and the stability of its motion are
important characteristics of dynamic response in robotics.
ƒ Speed refers to the absolute velocity of the manipulator at
its end-of-arm.
ƒ The maximum speed of a large robot is around
2 m/s (6 ft/s).
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12
Speed
ƒ Speed can be programmed into the work cycle so that
different portions of the cycle are carried out at different
velocities.
ƒ What is sometimes more important than speed is the
robot’s capability to accelerate and decelerate in a
controlled manner.
ƒ In many work cycles, much of the robot’s movement is
performed in a confined region of the work volume, so the
robot never achieves its top-rated velocity.
ƒ In these cases, nearly all of the motion cycle is engaged in
acceleration and deceleration rather than in constant
speed.
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Speed
ƒ A term that takes all of these factors into consideration is
speed of response, which refers to the time required for
the manipulator to move from one point in space to the
next.
ƒ Speed of response is important because it influences the
robot’s cycle time, which in turn affects the production rate
in the application.
ƒ Stability refers to the amount of overshoot and oscillation
that occurs in the robot motion a the end-of-arm as it
attempts to move to the next programmed location.
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13
Load Carrying Capacity
ƒ Load carrying capacity depends on the robot’s physical
size and construction as well as the force and power that
can be transmitted to the end of the wrist
ƒ The weight carrying capacity of commercial robots ranges
from less than 1 kg up to approximately 900 kg (2000 Ib).
ƒ Medium sized robots designed for typical industrial
applications have capacities in the range of 10 to 45 kg
(25 to 100 Ib).
ƒ One factor that should be kept in mind when considering
load carrying capacity is that a robot usually works with a
tool or gripper attached to its wrist.
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Robot Control Systems
ƒ The actuations of the individual joints must be
controlled in a coordinated fashion for the
manipulator to perform a desired motion cycle.
ƒ Microprocessor-based controllers are commonly
used today in robotics as the control system
hardware.
ƒ The controller is organized in a hierarchical
structure, so that each joint has its own feedback
control system, and a supervisory controller
coordinates the combined actuations of the joints
according to the sequence of the robot program.
ƒ Different types of control are required for different
applications.
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14
Robot Control System
ƒ Hierarchical control structure of a robot microcomputer
controller
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Robot Control Systems
1. Limited sequence control – pick-and-place
operations using mechanical stops to set positions
2. Playback with point-to-point control – records
work cycle as a sequence of points, then plays back
the sequence during program execution
3. Playback with continuous path control – greater
memory capacity and/or interpolation capability to
execute paths (in addition to points)
4. Intelligent control – exhibits behavior that makes it
seem intelligent, e.g., responds to sensor inputs,
makes decisions, communicates with humans
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15
Robot Control Systems
1. Limited sequence control
The most elementary control type.
It can be utilized only for simple motion cycles, such
as pick-and-place operations (i.e.. picking an object
up at one location and placing it at another location).
It is usually implemented by setting limits or
mechanical stops for each joint and sequencing the
actuation of the joints to accomplish the cycle.
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Robot Control Systems
1. Limited sequence control
Feedback loops are sometimes used to indicate that
the particular joint actuation has been accomplished
so that the next step in the sequence can be
initiated.
However, there is no servo-control to accomplish
precise positioning of the joint.
Many pneumatically driven robots are limited
sequence robots.
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16
Robot Control Systems
2. Playback with point-to-point control
Playback robots represent a more sophisticated
form of control than limited sequence robots.
Playback control means that the controller has a
memory to record the sequence of motions in a
given work cycle as well as the locations and other
parameters (such as speed) associated with each
motion and then to subsequently play back the work
cycle during execution of the program.
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Robot Control Systems
2. Playback with point-to-point control
In point-to-point (PTP) control, individual positions of
the robot arm are recorded into memory.
These positions are not limited to mechanical stops
for each joint as in limited sequence robots; instead,
each position in the robot program consists of a set
of values representing locations in the range of each
joint of the manipulator.
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17
Robot Control Systems
2. Playback with point-to-point control
Thus, each “point” consists of five or six values
corresponding to the positions of each of the five or
six joints of the manipulator.
For each position defined in the program, the joints
are thus directed to actuate to their respective
specified locations.
Feedback control is used during the motion cycle to
confirm that the individual joints achieve the
specified locations in the program.
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Robot Control Systems
3. Playback with continuous path control
Continuous path robots have the same playback
capability as the previous type.
The difference between continuous path and
point-to-point is the same in robotics as it is in NC.
A playback robot with continuous path control is
capable of one or both of the following:
1. Greater storage capacity for location
Thus, the points constituting the motion cycle can be
spaced very closely together to permit the robot to
accomplish a smooth continuous motion.
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18
Robot Control Systems
3. Playback with continuous path control
2. Interpolation
In point-to-point systems, the x,y, and z axes are
controlled to achieve a specified point location within
the robot’s work volume.
In continuous path systems, not only are the x,y, and
z axes controlled, but the velocities are controlled
simultaneously to achieve the specified linear or
curvilinear path.
Servo-control is used to continuously regulate the
position and speed of the manipulator.
It should be mentioned that a playback robot with
continuous path control has the capacity for PTP
control.
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Robot Control Systems
4. Intelligent control
Industrial robots are becoming
increasingly intelligent.
An intelligent robot is one that exhibits behavior that
makes it seem intelligent.
Some of the characteristics that make a robot
appear intelligent include the capacities to interact
with its environment, make decisions when things go
wrong during the work cycle, communicate with
humans, make computations during the motion
cycle, and respond to advanced sensor inputs such
as machine vision.
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19
End Effectors
ƒ The special tooling for a robot that enables it to
perform a specific task.
ƒ Two types:
ƒ Grippers – to grasp and manipulate objects (e.g.,
parts) during work cycle
ƒ Tools – to perform a process, e.g., spot welding,
spray painting
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End Effectors - Grippers
ƒ Mechanical grippers, consisting of two or more
fingers that can be actuated by the robot controller to
open and close to grasp the workpart.
ƒ Vacuum grippers, in which suction cups are used to
hold flat objects.
ƒ Magnetized devices, for holding ferrous parts.
ƒ Adhesive devices, which use an adhesive
substance to hold a flexible material such as a fabri.
ƒ Simple mechanical devices, such as hooks and
scoops.
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20
End Effectors –
Mechanical Grippers
Mechanical grippers are the most common gripper
type.
Some of the innovations and advances in
mechanical gripper technology include:
1. Dual grippers consisting of two gripper devices in
one end effector for machine loading and unloading.
(With a single gripper, the robot must reach into the
production machine twice.)
2. Interchangeable fingers that can be used on one
gripper mechanism.
To accommodate different parts, different fingers are
attached to the gripper.
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End Effectors –
Mechanical Grippers
3. Sensory feedback in the fingers that provide the
gripper with capabilities such as:
(1) sensing the presence of the workpart or,
(2) applying a specified limited force to the workpart
during gripping (for fragile workparts).
4. Multiple fingered grippers that possess the general
anatomy of a human hand.
5. Standard gripper products that are commercially
available, thus reducing the need to custom-design
a gripper for each separate robot application.
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21
Robot Mechanical Gripper
ƒ A two-finger mechanical gripper for grasping rotational
parts.
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Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Tools
ƒ The robot uses tools to perform processing operations
on the workpart.
ƒ The robot manipulates the tool relative to a stationary or
slowly moving object (e.g., workpart or subassembly).
ƒ Examples of the tools used as end effectors by robots to
perform processing applications include spot welding
gun; arc welding tool; spray painting gun; rotating
spindles for drilling, routing, grinding, and similar
operations; assembly tool (e.g., automatic screwdriver);
heating torch; ladle (for metal casting); and water jet
cutting tool.
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22
Tools
ƒ In each case, the robot must not only control the relative
position of the tool with respect to the work as a function
of time, it must also control the operation of the tool.
ƒ For this purpose. the robot must be able to transmit
control signals to the tool for starting, stopping, and
otherwise regulating its actions.
ƒ In some applications, the robot may use multiple tools
during the work cycle.
For example, several sizes of routing or drilling bits must
be applied to the workpart.
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Tools
ƒ Thus the robot must have a means of rapidly changing
the tools.
ƒ The end effector in this case takes the form of a fastchange tool holder for quickly fastening and unfastening
the various tools used during the work cycle.
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23
Sensors in Robotics
Two basic categories of sensors used in industrial robots:
1. Internal - used to control position and velocity of the
manipulator joints.
These sensors form a feedback control loop with the
robot controller.
Typical sensors used to control the position of the robot
arm include potentiometers and optical encoders.
Tachometers of various types are used to control the
speed of the robot arm.
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Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Sensors in Robotics
2. External - used to coordinate the operation of the robot
with other equipment in the work cell.
In many cases, these external sensors are relatively
simple devices, such as limit switches that determine
whether a part has been positioned properly in a fixture
or that a part is ready to be picked up al a conveyor.
Other situations require more advanced sensor
technologies.
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24
Sensors in Robotics - External
ƒ
ƒ
ƒ
ƒ
ƒ
Tactile - touch sensors and force sensors
Proximity - when an object is close to the sensor
Optical (e.g. Photocell)
Machine vision
Machine vision is used in robotics for inspection.
parts identification, guidance, and other uses.
Other sensors - temperature, fluid pressure, fluid flow,
electrical voltage, current, and various other physical
properties.
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Robot Application Characteristics
General characteristics of industrial work situations that
promote the use of industrial robots
1. Hazardous work environment for humans,
2. Repetitive work cycle,
3. Difficult handling task for humans (e.g., heavy parts),
4. Multishift operations, where workers should be changed,
5. Infrequent changeovers of the physical workplace,
6. Part position and orientation are established in the work
cell, since most robots in today’s industrial applications
are without vision capability.
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25
Industrial Robot Applications
1. Material handling applications
ƒ Material transfer – pick-and-place, palletizing
(e.g., Transferring parts from one conveyor to another.)
ƒ Machine loading and/or unloading
(e.g., Die casting, plastic molding, machining, forging,
pressworking, heat treating, ...)
2. Processing operations
ƒ Spot welding and continuous arc welding
ƒ Spray coating
ƒ Other – waterjet cutting, laser cutting, grinding, drilling,
polishing, wire brushing, ...
3. Assembly and inspection
4. Changing tools, even the work holding devices in the
machines.
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Arrangement of Cartons on Pallet
ƒ The robot retrieves parts, cartons, or other objects from
one location and deposits them onto a pallet or other
container at multiple positions on the pallet.
ƒ Although the pickup point is the same for every cycle, the
deposit location on the pallet is different for each carton.
ƒ Either the robot must be taught each position on the pallet
using the powered leadthrough method, or it must
compute the location based on the dimensions of the
pallet and the center distances between the cartons (in
both x- and y-directions).
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26
Arrangement of Cartons on Pallet
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Depalletizing
ƒ Other applications similar to palletizing include
depalletizing, which consists of removing parts from an
ordered arrangement in a pallet and placing them at
another location (e.g., onto a moving conveyor), stacking
operations, which involve placing flat parts on top of each
other, such that the vertical location of the drop-off position
is continuously changing with each cycle, and inspection
operations, in which the robot inserts parts into the
compartments of a divided carton.
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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27
Robotic Arc-Welding Cell
ƒ Robot performs
flux-cored arc
welding (FCAW)
operation at one
workstation while
fitter changes
parts at the other
workstation
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Robot Programming
ƒ Leadthrough programming - work cycle is taught to
robot by moving the manipulator through the required
motion cycle and simultaneously entering the
program into controller memory for later playback
ƒ Robot programming languages - uses textual
programming language to enter commands into robot
controller
ƒ Simulation and off-line programming – program is
prepared at a remote computer terminal and
downloaded to robot controller for execution without
need for leadthrough methods
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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28
Leadthrough Programming
Leadthrough programming dates from the early 1960s
before computer control was prevalent.
The same basic methods are used today for many
computer controlled robots.
In leadthrough programming, the task is taught to the
robot by moving the manipulator through the required
motion cycle, simultaneously entering the program
into the controller memory for subsequent playback.
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Leadthrough Programming
Two types:
1. Powered leadthrough
ƒ Common for point-to-point robots
ƒ Uses teach pendant to move joints to desired position
and record that position into memory
2. Manual leadthrough
ƒ Convenient for continuous path control robots
ƒ Human programmer physical moves manipulator
through motion cycle and records cycle into memory
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29
Teach Pendants for Powered
Leadthrough Programming
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Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Manual Leadthrough Programming
Manual leadthrough programming is convenient for
programming playback robots with continuous path
control where the continuous path is an irregular motion
pattern such as in spray painting.
This programming method requires the operator to physically
grasp the end-of- arm or the tool that is attached to the
arm and move it through the motion sequence, recording
the path into memory.
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30
Manual Leadthrough Programming
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Manual Leadthrough Programming
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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31
Manual Leadthrough Programming
Because the robot arm itself may have significant mass and
would therefore he difficult to move, a special
programming device often replaces the actual robot for
the teach procedure.
The programming device has the same joint configuration as
the robot and is equipped with a trigger handle (or other
control switch), which the operator activates when
recording motions into memory.
The motions are recorded as a series of closely spaced
points.
During playback, the path is recreated by controlling the
actual robot arm through the same sequence of points.
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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Leadthrough Programming
Advantages
ƒ Advantages:
ƒ Can readily be learned by shop personnel
ƒ A logical way to teach a robot
ƒ Does not required knowledge of computer
programming
ƒ Disadvantages:
ƒ Downtime - Regular production must be interrupted to
program the robot
ƒ Limited programming logic capability
ƒ Not readily compatible with modern computer-based
technologies
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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32
World and Tool Coordinate Systems
Coordinating the individual joints with the teach pendant is
an awkward and tedious way to enter motion commands
to the robot.
For example, it is difficult to coordinate the individual joints of
a jointed-arm robot (TRR configuration) to drive the endof-arm in a straight-line motion.
Therefore, many of the robots using powered leadthrough
provide two alternative methods for controlling movement
of the entire manipulator during programming in addition to
controls for individual joints.
With these methods the programmer can move the robot’s
wrist end in straight line paths.
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Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
World and Tool Coordinate Systems
The names given to these alternatives are
(1) world-coordinate system and
(2) tool-coordinate system.
Both systems make use of a Cartesian coordinate system.
In a world-coordinate system, the origin and axes are defined
relative to the robot base.
In a tool-coordinate system, the alignment of the axis system
is defined relative to the orientation of the wrist faceplate
(to which the end effector is attached).
In this way, the programmer can orient the tool in a desired
way and then control the robot to make linear moves in
directions parallel or perpendicular to the tool.
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33
World Coordinate System
ƒ Origin and axes of robot manipulator are defined relative
to the robot base
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Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Tool Coordinate System
ƒ Alignment of the axis system is defined relative to the
orientation of the wrist faceplate (to which the end effector
is attached)
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34
Robot Programming Languages
Textural programming languages provide the opportunity to
perform the following functions that leadthrough
programming cannot readily accomplish:
ƒ Enhanced sensor capabilities
ƒ Improved output capabilities to control external equipment
ƒ Program logic not provided by leadthrough methods
ƒ Computations and data processing similar to computer
programming languages
ƒ Communications with other computer systems
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Motion Programming Commands
MOVE P1
HERE P1 - used during leadthrough of manipulator
MOVES P1
DMOVE(4, 125)
APPROACH P1, 40 MM
DEPART 40 MM
DEFINE PATH123 = PATH(P1, P2, P3)
MOVE PATH123
SPEED 75
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35
Interlock and Sensor Commands
ƒ Input interlock:
WAIT 20, ON
ƒ Output interlock:
SIGNAL 10, ON
SIGNAL 10, 6.0
ƒ Interlock for continuous monitoring:
REACT 25, SAFESTOP
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Gripper Commands
ƒ Basic commands
OPEN
CLOSE
ƒ Sensor and and servo-controlled hands
CLOSE 25 MM
CLOSE 2.0 N
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36
Simulation and Off-Line Programming
ƒ In conventional usage, robot programming languages still
require some production time to be lost in order to define
points in the workspace that are referenced in the
program
ƒ They therefore involve on-line/off-line programming
ƒ Advantage of true off-line programming is that the program
can be prepared beforehand and downloaded to the
controller with no lost production time
ƒ Graphical simulation is used to construct a 3-D model
of the robot cell in which locations of the equipment in
the cell have been defined previously
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Simulation and Off-Line Programming
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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37
Robot Accuracy and Repeatability
Three terms used to define precision in robotics, similar to
numerical control precision:
1. Control resolution - capability of robot's positioning
system to divide the motion range of each joint into
closely spaced points
2. Accuracy - capability to position the robot's wrist at a
desired location in the work space, given the limits of the
robot's control resolution
3. Repeatability - capability to position the wrist at a
previously taught point in the work space
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Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
Control Resolution, Accuracy, and
Repeatability (from NC Chapter)
Desired
position
Addressable
position
0 Î CR/2
Possible
region for the
actual position
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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38
Robot Accuracy and Repeatability
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39