PR 502: Robot Dynamics and Control

1
PR 502 Robot Dynamics and Control
Introduction
2
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
3
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.

4
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)

5
A Brief History of Robotics

• 1960s
• Manufacturing robots
• Automatic guided vehicles
• Precise, repeatable movement
• 1970s
• Planetary landers
• Machine vision expands

6
A Brief History of Robotics

• 1980
• First AI robot Shakey
• 1985
• Reactive based robotics
• emerge
• 1990s
• Hybrid reactive/deliberative

Shakey
7
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

8
Types of Robots

• Robot Manipulators
• Mobile Robots

9
Types of Robots

• Walking Robots
• Humanoid Robots

10
Primitive Robotic Functions

• Sense
• The function of acquiring information from the
  environment
• bump sensors, optical sensors
• Plan
• The function of determining high-level tasks to
  accomplish
• Various AI techniques
• Act
• The function of producing low-level actuator
  commands

11
Basic Issues in Robotics

• How to SENSE
• How to PLAN
• How to ACT

12
Robots Work Envelope

• Work Envelope
• The volume of space encompassing the maximum
  designed movements of all robot parts including
  the end-effectors, workpiece, and attachments.
• Restricted Envelope
• 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.

13
(No Transcript)
14
Robot Work Envelop

• Ex Draw the work envelop of the robot shown below

15
Robot Classification

• Drive Technology.
• Which source of power drives the joints of the
  robot.
• Non-servo Controlled
• Servo Controlled
• Work-envelope geometries.
• Points in space which can be reached by the
  end-effector.
• Motion control method.
• Either point-to-point or continuous path

16
Robot Classification

• Classification according to Topology

• Open Loop Manipulator

17
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)

18
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

19
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.

20
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)

21
Robot degree of freedom

• Robot Arm ?

• Six again
• 1-base, 1-shoulder, 1-elbow, 3-wrist

22
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

23
Robot Structure
End Effector
24
End effectors

• Gripper
• Suction/Vacuum
• Hooks
• Rack and Pinion
• Screw and Fastener Devices

25
End Effectors Mechanisms
26
Robot Links and Joints
Universal joint
27
Robot Coordinates

• Cartesian/rectangular/gantry (3P or PPP)
• Three linear (prismatic) joints

28
Robot Coordinates

• Cylindrical (R2P or RPP)
• Two prismatic joints and a revolute joint

29
Robot Coordinates

• Spherical (2RP or RRP)
• One prismatic joint and two revolute joint

30
Robot Coordinates

• Articulated/anthropomorphic (3R or more)
• All revolute joints

31
Two Famous Industrial Manipulators

• PUMA. (Programmable Universal Machine for
  Assembly). 78.
• SCARA. (Selective Compliant Articulated Robot
  Assembly). 79.

SCARA
PUMA
32
Robot Configuration
Cylindrical RPP
Spherical RRP
Cartesian PPP
Hand coordinate n normal vector s sliding
vector a approach vector, normal to the tool
mounting plate
SCARA RRP
Articulated RRR
33
Robot reference frame

• World reference frame
• A universal coordinate frame as defined by x, y,
  z coordinates
• Used to define the motion path reference to other
  objects

34
Robot Reference Frame

• Joint reference frame
• Coordinate system defined at each joint
• Used to specify movements of each joint

35
Robot Reference Frame

• Tool reference frame
• Coordinate system defined at the end effector
• Used to define the movement of the end effector

36
Robot Characteristics

• Payload
• The maximum weight a robot can carry
• Reach
• Maximum distance a robot can reach within its
  work envelop
• Precision
• How accurately a specified point can be reached
• Repeatability
• How accurately the same position can be reached
  it the motion is to be repeated many times

37
Robot Selection Measures

• Payload
• Precision
• Resolution
• Accuracy
• Repeatability
• Speed
• Work Envelope and Configuration
• Control System

• Degrees of Freedom
• Memory Size
• Software Capability
• Installation Factors
• Cost
• Drive System
• Programming Method
• Interfacing Capabilities

38
Robot Specifications

• Number of Axes
• Major axes, (1-3) gt Position the wrist
• Minor axes, (4-6) gt Orient the tool
• Redundant, (7-n) gt reaching around obstacles,
  avoiding undesirable configuration
• Degree of Freedom (DOF)
• Workspace
• Payload (load capacity)
• Precision vs Repeatability

39
Robot Applications in Manufacturing

• Material Handling/Palletizing
• Machine Loading/Unloading
• Arc/Spot Welding
• Water jet/Laser cutting
• Spray Coating
• Gluing/Sealing
• Assembly
• Inspection/Testing
• Injection Molding
• Polishing
• Packaging

40
Advantages

• Robots are more accurate
• Robots can work without breaks
• Robots dont get sick
• or take vacations
• Robots can be used in
• dangerous conditions
• Robots are very clean

41
Disadvantages

• Cost increases
• Initial equipment
• Maintenance staff
• Preventative maintenance
• Utilities
• Service contracts

Cup Packer