Chapter 25: Robotics

oregontrimmingAI and Robotics

Nov 2, 2013 (4 years and 8 months ago)


Chapter 25: Robotics

April 27, 2004

The Week Ahead …

Wednesday: Dmitrii Zagorodnov

Thursday: Jeff Elser’s presentation,
general discussion

Friday: Rafal Angryk

Monday: CS 536 final @ 2 p.m.

25.1 Introduction

Robot Components:




Robot Types:

Manipulators (> 1 million worldwide)

Mobile (ULV and planetary, UAV, AUV)


Other (prosthetic devices, multibody systems)

Typical Environments

Partially Observable




25.2 Robot Hardware


passive (e.g. camera)

active (e.g. sonar, laser, radar)

Record distances, Figure 25.2

Record images

Record properties of robot
(propriocaptive), e.g. inertial sensors


Degrees of Freedom (DOF), e.g. a wrist
has 3 DOF

A car has 2 controllable DOF but 3
effective DOF

A non
holonomic robot has a higher
effective DOF than controllable DOF


Most robot arms are holonomic (simpler)

Most mobile robots are non

Prismatic joints allow sliding motion

Revolute joints allow rotational motion

Dynamic stability vs. Static stability

Power Sources: electric motor, pneumatic
actuator, hydraulic actuator

25.7 Robotic Software Architecture

Subsumption Architecture, Rodney
Brooks, 1986

Application: wall following

a framework to assemble reactive (as
opposed to deliberative) controllers out of

Figure 25.22

Difficult to understand

Difficult to change behavior (wasp)

Three Layer Architecture

Very common today

Reactive Layer (sense
act loop)

Executive Layer

Deliberative Layer

Robotic Programming Languages

General Robot Language, GRL, 2000


uses FSMs as building blocks

provides communication and control

C++ Embedded Systems, CES, 2000

integrates probability and learning

Robotic Programming Languages

Reactive Action Plan System, RAPS, 1994

can specify goals, plans, conditions for likely
plan success

ALisp, 2002

can program non
deterministic choice points

learns via reinforcement learning

25.8 Application Domains



Transportation, Figure 25.23, the challenge is to
use natural cues to locate robot

Hazardous Environments

Exploration, Figure 25.24

Health Care, Figure 25.23

Personal Service

Entertainment, Figure 25.4b

Human Augmentation

25.4 Planning to Move


motions are deterministic

localization is exact

Point to point motion

Compliant motion

Configuration space includes location,
orientation, joint angles

Path Planning

Involves continuous spaces

Two common techniques that map the
continuous space onto a discrete space

cell decomposition


Configuration Space

A workspace representation is easier. For
example, in Figure 25.12(a) everything
can be specified by (x
, y
) and (x
, y

The problem is that not all points are

Configuration Space

Use (


), the angles of the joints

Kinematics: Maps a configuration space onto a
workspace (easy)

Inverse Kinematics: Maps a workspace onto a
configuration space

Obstacles, Figure 25.12b

Free Space vs. Occupied Space, Figure 25.13

Cell Decomposition

Figure 25.14

Each region can be solved simply


hard for high dimensions

mixed cells are challenging (don’t want unsound
solutions or incomplete problem solving ability)

Irregular Shapes

Potential Field, Figure 25.15


Reduce the robot’s free space to 1

Voronoi Graphs, Figure 25.16a

Map the initial point onto the Voronoi Graph

Follow Voronoi Graph

Map point on Voronoi Graph onto goal point

Probabilistic Roadmaps, Figure 25.16b

Offers more routes than Voronoi Graphs

Exercise 25.8

Humans are so adept at basic tasks such
as picking up cups or stacking blocks that
they often forget how complex these tasks
are. In this exercise, you will discover the
complexity and recapitulate the last 30
years of developments in robotics. First,
pick a task, such as building an arch out of
three blocks. Then, build a robot out of
four humans as follows:

Exercise 25.8

Brain. The job of the Brain is to come up with a
plan to achieve the goal and to direct the hands
in the execution of the plan. The Brain receives
input from the Eyes, but cannot see the scene
directly. The brain is the only one who knows
what the goals is.

Eyes. The Eyes’ job is to report a brief
description of the scene to the Brain. The Eyes
should stand a few feet away from the working
environment, and can provide qualitative
descriptions or quantitative descriptions. Eyes
can also answer questions from the Brain.

Exercise 25.8

Left Hand and Right Hand. One person plays each
Hand. The two Hands stand next to each other; the Left
Hand uses only his or her left hand, and the Right Hand
only his or her right hand. The Hands execute only
simple commands from the Brain

for example, “Left
Hand, move two inches forward.” They cannot execute
commands other than motions; for example, “Pick up the
box” is not something a Hand can do. The Hands must
be blindfolded. The only sensory capability they have is
the ability to tell when their path is blocked by an
immovable obstacle such as a table or the other Hand.
In such cases, they can beep to inform the Brain of the