Behavior-Based Approaches

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Behavior-Based Approaches
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Finishing up robotic architecture
Reactive control Motor Schemas
Subsumption
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Overview
Robot architecture from the bottom up Getting
around
Perceiving the world
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Overview
Reasoning
representing space motion planning
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Overview
Handling uncertainty
sensor fusion building maps localization
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Overview
Vision -- just another sensor ?
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Overview

• Sonar Sound Navigation and Ranging
• Sonar provides useful information about objects
  very close to the robot and is often used for
  fast emergency collision avoidance.
• Camera data
• machine vision
• structured light sensors
• cross beam sensors
• parallel-beam sensors

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ARCHITECTURES

• How the job of generating actions from percepts
  is organized
• Concerned to Autonomous mobile robot in dynamic
  environments
• The design of robot architectures is essentially
  the same agent design problem that was discussed

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Classical architecture

• Shakey 1969, demonstrated the importance of
  experimental research in bringing to light
  unsuspected difficulties
• difficulties of general problem solving
• integrating geometric and symbolic representation
  of the world
• low level actions
• macro-operators
• error detection
• recovery capabilities

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Situated automata

• Since the mid 1980s , a significant minority of
  AI and robotics researchers have begun to
  question the classical view of intelligent
  agent design based on representation and
  manipulation of explicit knowledge
• In robotics, the principal drawback of the
  classical view is that explicit reasoning about
  the effects of low-level actions is too expensive
  to generate real time behavior

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Situated automata

• Finite state machine whose inputs are provided
  by sensors connected to the environment and whose
  outputs are connected to effectors
• Situated automata provide a very efficient
  implementation of reflex agents with state

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Rosenscheins basic design

• Theorem
• Any finite-state machine can be implemented as a
  state register together with a feed-forward
  circuit that updates the state based on the
  sensor inputs and the current state, and another
  circuit that calculates the output given the
  state register
• Execution time for each decision cycle is small

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Behavior-based robotics,Brooks

• The idea is that the overall agent design can be
  decomposed, not into functional components, such
  as perception,learning and planning, but into
  behaviors such as obstacle avoidance,
  wall-following and exploration
• The each behavioral module accesses the sensor
  inputs independently to extract just the
  information it needs, and sends its own signals
  to the effectors
• Behaviors are arranged into prioritized hierarchy

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CONFIGURATION SPACES A FRAMEWORK FOR ANALYSIS

• Both the configuration of the robots body and
  the locations of the objects in physical space
  are defined by real-valued coordinates.
• It is therefore impossible to apply standard
  search algorithms in any straightforward way
  because the number of states and actions are
  infinite.
• The configuration space is mathematical tool for
  design and analyzing motion planning algorithms.

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Robot Architectures
how much / how do we represent the world
internally ?
None.
Absolute Control
Just the current world.
Purely Reactive Control
Subsumption paradigm
Just what we need.
Motor Schema
As much as possible.
SPA architecture
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Robot Architectures
how much / how do we represent the world
internally ?
Just the current world.
Purely Reactive Control

• Decision-making based only on the current sensor
  readings.

• For the survivor robot assignment (A, part 1)
• int computeRotationalVelocity()

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One view of reactive control
Control is a function of the sensed data.

• Look at the front nine sonar values -- which are
  closest ?

Case 1 If sonars 12, 13, or 14
Turn left at 20 deg./sec
Case 2 If sonars 15, 0, or 1
Turn left at 40 deg./sec
Case 3 If sonars 2, 3, or 4
Turn right at 20 deg./sec
0
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Another view of reactive control
Direct mapping from the environment to a control
signal
goal-seeking behavior
obstacle-avoiding behavior
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Robot Architecture
how much / how do we represent the world
internally ?
Motor Schema
Just what we need.
Subsumption paradigm

• Motor schemas compose simple reactions by adding
  the outputs that each would send to the robot.
• Individual schemas may contain state

Ron Arkin _at_ Georgia Tech
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Behavior Summer
path taken by a robot controlled by the resulting
field
vector sum of the avoid and goal motor schemas
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Additional primitives
Direct mapping from the environment to a control
signal
go! schema
corridor-centering schema
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A more complex task
Direct mapping from the environment to a control
signal
larger composite task
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Another primitive
Direct mapping from the environment to a control
signal
larger composite task
random motion schema
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Local minima
Noise allows a system to jump out of local
minima.
the problem
a solution
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Bigger deadends...
How to get out of larger wells ?
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Bigger deadends...
uses memory of where the robot has been
past-avoiding motor schema
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Another example
Keeping away from past locations...
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Inspiration
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Inspiration
Study of how animals react to different stimuli
Rodents (Hull 1934)
Toads (Arbib 87)
Vowels
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Beyond subsumption
Navlab ALVINN
Polly
...
...
1995
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Polly
Ian Horswill _at_ MIT