PR 502 Robot Dynamics & Control
2/28/2007
PR 502: Robot Dynamics and
Control
Introduction
Asanga Ratnaweera
Department of Mechanical Engineering
Faculty of Engineering
University of Peradeniya
What is a Robot?
“Robot” derives from the Czech word
“robota”
forced labor; slavery (Karel Capek)
Robot Industry Association:
A re-programmable, multi-functional manipulator
designed to move material, parts, tools, or specialized
devices through variable programmable motions for the
performance of a variety of tasks
Working definition:
physical agent that has an “intelligent” connection
between sensors and actuators
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
The Three Laws of Robotics

A robot may not injure a human being, or,
through inaction, allow a human being to
come to harm.
A robot must obey the orders given it by
human beings except where such orders
would conflict with the First Law.
A robot must protect its own existence as
long as such protection does not conflict
with the First or Second Law.
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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A Brief History of Robotics

1940s - Master slave manipulators
{

First “remove manipulators” for hazardous
substances
1950s - Programmable robot manipulators
{
{
Industrial manipulators
Closed loop control (an electrical engineering
approach)
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
A Brief History of
Robotics…

1960s
{ Manufacturing robots
{ Automatic guided
vehicles
{ Precise, repeatable
movement
1970s
{ Planetary landers
{ Machine vision
expands
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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A Brief History of
Robotics…

1980
{

1985
{

First AI robot: Shakey
Reactive based robotics
emerge
1990s
{
Hybrid reactive/deliberative
Shakey
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Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
Two Major Types of Robots

Industrial Robots
{
{
{

Operates in a stable and known
environment
Fixed or limited mobility
Relatively simple control program
Mobile Robots
{
{
{
Operates in the “real” world
Mobile!
Requires a high degree of autonomy
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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Types of Robots

Robot Manipulators

Mobile Robots
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Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
Types of Robots

Walking Robots

Humanoid Robots
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Asanga Ratnaweera, Department of
Mechanical Engineering
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Primitive Robotic Functions

Sense
{
{

Plan
{
{

The function of acquiring information from
the environment
bump sensors, optical sensors
The function of determining high-level tasks
to accomplish
Various AI techniques
Act
{
The function of producing low-level
actuator commands
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
Basic Issues in Robotics
Environment
Sense
Sense
Plan
Plan
How to SENSE
How to PLAN
How to ACT

28 February 2007
Act
Act
Major focus of this section
Asanga Ratnaweera, Department of
Mechanical Engineering
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Robot’s Work Envelope

Work Envelope:
{

Restricted Envelope:
{

The volume of space encompassing the
maximum designed movements of all robot
parts including the end-effectors, workpiece,
and attachments.
That portion of the maximum envelope to which
a robot is restricted by limiting devices.
Operating Envelope:
{
That portion of the restricted envelope that is
actually used by the robot while performing its
programmed motions.
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
28 February 2007
2/28/2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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Robot Work Envelop

Ex: Draw the work envelop of the robot
shown below
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
Robot Classification

Drive Technology.
{
Which source of power drives the joints of the
robot.

Work-envelope geometries.
{

Non-servo Controlled
Servo Controlled
Points in space which can be reached by the
end-effector.
Motion control method.
{
Either point-to-point or continuous path
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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Robot Classification

Classification according to Topology:

Open Loop
Manipulator:
28 February 2007

Closed-Loop
Manipulator:
Asanga Ratnaweera, Department of
Mechanical Engineering
Hexapod
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PR 502 Robot Dynamics & Control
2/28/2007
Robot Classification

Classification according to Type of Joints:
{
{
{
{
Revolute Joint (Rotation Motion)
Prismatic Joint (Translation Motion)
Cylindrical Joint (Both Rotation and Translation)
Spherical Joint (Ball and Socket Joint)
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Asanga Ratnaweera, Department of
Mechanical Engineering
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Robot Classification

According to Japanese Industrial Robot association
(JIRA)
{
{
{
Class 1: Manual-Handling device
A device with multiple degrees of freedom that is
actuated by an operator
Class 2: Fixed-Sequencing Robots
A device that performs the successive stages of a
task according to a predetermined, unchanging
method and is hard to modify
Class 3: Variable-Sequence Robots
Same as class 2 but easy to modify
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Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
Robot Classification
{
{
{
Class 4: Playback Robots
A human operator performs the task manually
by leading the robot, which records the motions
and playback
Class 5: Numerical control Robots
The operator supplies the robot with a
movement programme.
Class 6: Intelligent Robots
A robot with the means to understand its
environment and the ability to successfully
complete a task despite changes in the
surrounding conditions
Note : The Robot Institute of America (RIA)
considers only class 3 to 6 as robots.
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
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Degree of Freedom (DOF)

2D Motion
{

3 DOF: 2 translation & 1 rotation (2 lengths & 1
angle)
3D Motion
{
6 DOF: 3 translation & 3 rotation (3 lengths & 3
angles)
Z
X
Y
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Asanga Ratnaweera, Department of
Mechanical Engineering
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PR 502 Robot Dynamics & Control
2/28/2007
Robot degree of freedom

Robot Arm ?
Elbow
Shoulder
Wrist
• Six again
• 1-base, 1-shoulder, 1-elbow, 3-wrist
28 February 2007
Asanga Ratnaweera, Department of
Mechanical Engineering
Base
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Robot degree of freedom

General purpose
robot: 6 degrees of
freedom
Redundant robot:
More than 6 degrees
of freedom
Deficient robot: less
than 6 degrees of
freedom
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Asanga Ratnaweera, Department of
Mechanical Engineering
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