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Picture of Terminator. Introduction to Robotics (ES159) Advanced Introduction to Robotics (ES259) S pring 2007 Robert Wood 149 Maxwell Dworkin rjwood@eecs.harvard.edu www.eecs.harvard.edu/~rjwood. Personnel . Instructor: Me TFs: Shelton Yuen Dr. Benjamin Pierce. Primary:

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Introduction to Robotics (ES159)Advanced Introduction to Robotics (ES259)Spring 2007Robert Wood149 Maxwell Dworkinrjwood@eecs.harvard.eduwww.eecs.harvard.edu/~rjwood

ES159/ES259

personnel
Personnel
  • Instructor:
    • Me
  • TFs:
    • Shelton Yuen
    • Dr. Benjamin Pierce

ES159/ES259

texts
Primary:

M. Spong, S. Hutchinson, and M. Vidyasagar, “Robot Modeling and Control”, Wiley

Texts

Secondary:

Li, Murray, Sastry, “A Mathematical Introduction to Robotic Manipulation”, CRC Press

ES159/ES259

slide5
Lab
  • Multiple experiments with a 6-axis industrial robotic arm (RRR)
    • Forward/inverse kinematics
    • Velocity kinematics
    • Control
    • Path planning
    • Manipulation
  • Equipment:
    • Open architecture industrial arm from CRS (Catalyst-5), retrofitted by Quanser with a Matlab interface
  • Will require extensive use of Matlab/Simulink

ES159/ES259

problem sets and exams
Problem sets and exams
  • Problem sets: approximately every other week, due two weeks afterwards
    • Will often include Matlab/Simulink problems
    • Matlab review session(s)?
  • No midterm, one comprehensive final exam

ES159/ES259

final projects
Final projects
  • Required for graduate students
    • Bonus for undergraduates
  • Can involve any field of robotics
    • I will be happy to suggest topics
  • I strongly encourage you to incorporate your research into the project (or the final project into your research!)
  • You will have access to the following facilities:
    • The 159 lab arm
    • Machine shop
    • All resources in the Harvard Microrobotics Lab

ES159/ES259

course outline
Course outline
  • First 2/3: traditional analysis of robotic manipulators
    • Homogeneous transforms
    • Forward/inverse kinematics
    • Velocity kinematics, dynamics
    • Motion planning
    • Control
  • Final 1/3: introduction to special topics
    • Sensors and actuators
    • Mobile agents, SLAM
    • Computer vision
    • MEMS, microrobotics
    • Surgical robotics, teleoperation
    • Biomimetic systems

Labs will follow along with these topics

Active research areas, potential subjects for final projects

ES159/ES259

introduction
Introduction
  • Historical perspective
    • The acclaimed Czech playwright Karel Capek (1890-1938) made the first use of the word ‘robot’, from the Czech word for forced labor or serf.
    • The use of the word Robot was introduced into his play R.U.R. (Rossum's Universal Robots) which opened in Prague in January 1921. In R.U.R., Capek poses a paradise, where the machines initially bring so many benefits but in the end bring an equal amount of blight in the form of unemployment and social unrest.
  • Science fiction
    • Asimov, among others glorified the term ‘robotics’, particularly in I, Robot, and early films such as Metropolis (1927) paired robots with a dystopic society
  • Formal definition (Robot Institute of America):
    • "A reprogrammable, multifunctional manipulator designed to move material, parts, tools, or specialized devices through various programmed motions for the performance of a variety of tasks".

ES159/ES259

01 02
100s of movies

Chances are, something you eat, wear, or was made by a robot

01_02

Robots in everyday use and popular culture

http://www.robotuprising.com/

Roomba: $142M in sales for 2005

ES159/ES259

common applications
Common applications

Picture of Roomba

  • Industrial
    • Robotic assembly
  • Commercial
    • Household chores
  • Military
  • Medical
    • Robot-assisted surgery

ES159/ES259

common applications1

JHUROV; Johns Hopkins

Common applications
  • Planetary Exploration
    • Fast, Cheap, and Out of Control
    • Mars rover
  • Undersea exploration

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01 01
01_01

Industrial robots

  • High precision and repetitive tasks
    • Pick and place, painting, etc
  • Hazardous environments

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01 03
01_03

Representations

  • For the majority of this class, we will consider robotic manipulators as open or closed chains of links and joints
    • Two types of joints: revolute (q) and prismatic (d)

ES159/ES259

definitions
Definitions
  • End-effector/Tool
    • Device that is in direct contact with the environment. Usually very task-specific
  • Configuration
    • Complete specification of every point on a manipulator
    • set of all possible configurations is the configuration space
    • For rigid links, it is sufficient to specify the configuration space by the joint angles
  • State space
    • Current configuration (joint positions q) and velocities
  • Work space
    • The reachable space the tool can achieve
      • Reachable workspace
      • Dextrous workspace

ES159/ES259

01 06
01_06

Common configurations: wrists

  • Many manipulators will be a sequential chain of links and joints forming the ‘arm’ with multiple DOFs concentrated at the ‘wrist’

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01 07

Utah MIT hand

01_07

Example end-effector: Grippers

  • Anthropomorphic or task-specific
    • Force control v. position control

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01 09
01_09

Common configurations: elbow manipulator

  • Anthropomorphic arm: ABB IRB1400
  • Very similar to the lab arm (RRR)

ES159/ES259

01 10
01_10

Workspace: elbow manipulator

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01 12
01_12

Common configurations: Stanford arm (RRP)

  • Spherical manipulator (workspace forms a set of concentric spheres)

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01 14

Adept Cobra Smart600 SCARA robot

01_14

Common configurations: SCARA (RRP)

ES159/ES259

01 15

Seiko RT3300 Robot

01_15

Common configurations: cylindrical robot (RPP)

  • workspace forms a cylinder

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01 16
01_16

Common configurations: Cartesian robot (PPP)

  • Increased structural rigidity, higher precision
    • Pick and place operations

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01 17
01_17

Workspace comparison

(a) spherical

(b) SCARA

(c) cylindrical

(d) Cartesian

ES159/ES259

01 18

ABB IRB940 Tricept

6DOF Stewart platform

ABB IRB6400

01_18

Parallel manipulators

  • some of the links will form a closed chain with ground
  • Advantages:
    • Motors can be proximal: less powerful, higher bandwidth, easier to control
  • Disadvantages:
    • Generally less motion, kinematics can be challenging

ES159/ES259

01 19

Simple example: control of a 2DOF planar manipulator

01_19
  • Move from ‘home’ position and follow the path AB with a constant contact force F all using visual feedback

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01 20

0

1

2

0

1

2

01_20

Coordinate frames & forward kinematics

  • Three coordinate frames:
  • Positions:
  • Orientation of the tool frame:

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01 21
01_21

Inverse kinematics

  • Find the joint angles for a desired tool position
  • Two solutions!: elbow up and elbow down

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01 23
State space includes velocity

Inverse of Jacobian gives the joint velocities:

This inverse does not exist when q2 = 0 or p, called singular configuration or singularity

01_23

Velocity kinematics: the Jacobian

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01 24
01_24

Path planning

  • In general, move tool from position A to position B while avoiding singularities and collisions
    • This generates a path in the work space which can be used to solve for joint angles as a function of time (usually polynomials)
    • Many methods: e.g. potential fields
  • Can apply to mobile agents or a manipulator configuration

ES159/ES259

01 241

desired trajectory

controller

error

system dynamics

measured trajectory (w/ sensor noise)

actual trajectory

01_24

Joint control

  • Once a path is generated, we can create a desired tool path/velocity
    • Use inverse kinematics and Jacobian to create desired joint trajectories

ES159/ES259

other control methods
Other control methods
  • Force control or impedance control (or a hybrid of both)
    • Requires force/torque sensor on the end-effector
  • Visual servoing
    • Using visual cues to attain local or global pose information
  • Common controller architectures:
    • PID
    • Adaptive
    • Repetitive
  • Challenges:
    • Underactuation
    • Nonholonomy (mobile agents)
    • nonlinearity

ES159/ES259

general multivariable control overview
General multivariable control overview

joint controllers

motor dynamics

manipulator dynamics

desired joint torques

state estimation sensors

estimated configuration

inverse kinematics,

Jacobian

desired trajectory

ES159/ES259

sensors and actuators
Sensors and actuators
  • sensors
    • Motor encoders (internal)
    • Inertial Measurement Units
    • Vision (external)
    • Contact and force sensors
  • motors/actuators
    • Electromagnetic
    • Pneumatic/hydraulic
    • electroactive
      • Electrostatic
      • Piezoelectric
  • Basic quantities for both:
  • Bandwidth
  • Dynamic range
  • sensitivity

ES159/ES259

mobile agents and slam

Whegs; CWRU

RHex; Michigan

Mobile Agents and SLAM
  • For untethered and autonomous applications, the performance of a robotic system (P), whether defined by capability or robustness, can be related to an agent’s intelligence (I), mobility (M), and multiplicity (N):

MicroBat; UCLA

ES159/ES259

mobile agents and slam1
Mobile Agents and SLAM
  • Monte Carlo localization
  • SLAM: ‘Simultaneous locomotion and Map-building’

ES159/ES259

computer vision
Computer Vision
  • Simplest form: estimating the position and orientation of yourself or object in your environment using visual cues
    • Usually a statistical process
    • Ex: finding lines using the Hough space
  • More complex: guessing what the object in your environment are
  • Biomimetic computer vision: how do animals accomplish these tasks:
    • Obstacle avoidance
      • Optical flow?
    • Object recognition
      • Template matching?

ES159/ES259

mems and microrobotics

Donald; Dartmouth

MEMS and Microrobotics
  • Difficult definition(s):
    • Robotic systems with feature sizes < 1mm
    • Robotic systems dominated by micro-scale physics
  • MEMS: Micro ElectroMechanical Systems
    • Modified IC processes to use ‘silicon as a mechanical material’

Fearing; Berkeley

Pister; Berkeley

ES159/ES259

surgical robotics
Surgical robotics
  • Minimally invasive surgery
    • Minimize trauma to the patient
    • Potentially increase surgeon’s capabilities
    • Force feedback necessary, tactile feedback desirable

ES159/ES259

biomimetic robots

BigDog; Boston Dynamics

MFI; Harvard & Berkeley

Ayers; Northeastern

Biomimetic Robots
  • Using biological principles to reduce design space

ES159/ES259

humanoid robots
Humanoid robots
  • For robots to efficiently interact with humans, should they be anthropomorphic?

QRIO Sony

Asimo; Honda

ES159/ES259

next class
Next class…
  • Homogeneous transforms as the basis for forward and inverse kinematics
  • Come talk to me if you have questions or concerns!

ES159/ES259