RoboticsChapter 1 - Introduction

Dr. Amit Goradia

Topics

• Introduction – 2 hrs• Coordinate transformations – 6 hrs• Forward Kinematics - 6 hrs• Inverse Kinematics - 6 hrs• Velocity Kinematics - 2 hrs• Trajectory Planning - 6 hrs• Robot Dynamics (Introduction) - 2 hrs• Force Control (Introduction) - 1 hrs• Task Planning - 6 hrs

Introduction

• Definition (Robot Institute of America):– A robot is a programmable

multifunction manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.

Puma 560 Robot used for inspection

Types of Robots

• Stationary

• Mobile – Ground– Wheeled– Tracks– Legs

• Mobile – Underwater

• Mobile – Aerial

• Microgravity (Space)Honda ASIMO

Robot Types - Stationary

Puma 560 Arm

ABB Arm

MSU Microbot

Mobile

MSUMobileManipulatorResearch Platform (R2-D2) Stanford’s Stanley

(First winner of DARPA Grand Challenge)

MSUMicro Crawler

Sony’sQRIO

Space

Canada ArmOn InternationalSpace Station

Sojourner-First Mars Rover (1998)

JPL’sPioneerSpace Probe

ISRO’sChandrayaan -1

Robot – Mechanical Structure

Brief History• 1921 – Word robot derived from a Czech play• 1940s – Teleoperator developed at Oak Ridge national

Labs• 1954 – George Devol, Programmed articular transfer

device• 1956 – Joe Engelberg, Unimation (first robotics

company)• 1961 – First robot installed on assembly line in GM• 1968 – Japan, Kawasaki makes robots• 1969 – GE makes first walking robot• 1974 – First Hydraulic drive robot, Cinciniti Milacron• 1978 – First Puma Robot (Programmable Universal

Machine for Assembly)

Accuracy, Repeatability and Resolution

• Accuracy:– A measure of how close a

manipulator can come to a given point within its workspace

• Repeatability: – A measure of how close a

manipulator can return to a previously taught point

• Resolution (Precision): – The smallest increment of

motion that can be sensed (executed). It is a function of distance traveled and the number of bits of encoder accuracy.

A B

Resolution

Actual DesiredPosition

Accuracy

Robot Specifications• Joint Variable (joint):

– Relative displacement between adjacent links. Can be revolute or prismatic.

• End effector:– Gripper or tool used to perform the robots tasks.

• Degree of freedom (DOF)– Number of joints (DOF > 6 implies redundant robot)

• Configuration:– Determines the location of every point on the manipulator (not just the

end effector).• Configuration Space

– The set of all possible configurations• Workspace (work envelope):

– Total volume spread out by the end effector as the manipulator executes all possible motions

• Accuracy, Repeatability and Resolution• Speed and Acceleration (min and max)• Payload Capacity

Typical Robot Specifications

• Hydraulic or Electric• Payload capacity

– 50 – 100 Kgs (Hydraulic)– 1 – 25 Kgs (Electric)

• Degrees of freedom: 4 to 7 based on application• Repeatablity

– ± 1 mm – 1.5mm (Hydraulic)– ± 0.05mm – 0.01mm (Electric)

• Cost– $80,000 - $200,000 (Hydraulic)– $40,000 – $100,000 (Electric)

Robotic System Architecture

• Components– Mechanical structure– Drives

• Electric• Hydraulic• Pneumatic

– Computing and Control– Sensors

• Encoders• Force• Vision• many more

– Communication• CAN, ethernet, Wireless,

Serial link (RS232), USB, analog link, PROFIBus, GPIB, and many more

Environment Sensors

Planner

Controller DrivesMechanicalStructure

ConfigurationSensor

World spaceOutput

Computer

Common Robot Configurations

• Joint types– Revolute– Prismatic

• Revolute joints (R)– Compact– Increased dexterity – easier to

maneuver around obstacles– Large kinematic and dynamic

coupling between links– Larger error accumulation – Difficult control problem

• Prismatic joints (P)– Increased accuracy– Higher payload– Difficult to integrate– Require more volume

Cartesian Configuration

• PPP– First three joints are

prismatic

• Features– High resolution– High accuracy– High payload capacity– More volume needed for

motion– Difficult to integrate with

other machines– Uniform resolution

Epson Cartesian Arm

Reachable Workspace

Cylindrical Configuration

• RPP– One revolute joint– Two linear joints

• Joint coordinates map to cylindrical coordinates– r, θ, z

• Non-uniform precision– Horizontal precision highest

along inside edge of work envelope

Reachable Workspace

Denso Cylindrical arm

Spherical Configuration

• RRP– Two revolute joints– One prismatic joint

• Joint variables directly correspond to spherical coordinates– φ – θ – r

Reachable Workspace

Articulated Configuration

• RRR– Three revolute joints

• Features– Light payload capacity– Lower accuracy– Easy to integrate with

other manipulators

SCARA Configuration

• Selective Compliant Articulated Robot for Assembly (SCARA)

• RRP– Two revolute– One prismatic

• Introduced in 1979• Revolutionized

manufacturing of small electronics

Reachable Workspace

Basic Research Issues

• Effectors and Mobility– Autonomous Flight– Fish Robots– Legged Motion– Artificial Muscles– Drives

• Sensors– Vision– Force / Haptic– Communication– Encoder

• Control Systems– Behaviour control– Networked control– Active vibration control– Hyper redundant

robotic systems

• Task Planning– Understanding the real

world– Failsafe planning to

work in the real world

Robot Programming

• Motion based– RCCL– RAPID– VAL++

• Task / Goal based– Behavior Language– PRS (Procedural Reasoning

System)

• Intermediate level– Combines aspects of low level

motion based and high level task based

– FRP (Functional Reactive Programming)

– FROB (Functional Robotics)