Title: Behavior-Based Approaches
1 Behavior-Based Approaches
2 Finishing up robotic architecture
Reactive control Motor Schemas
Subsumption
3Overview
Robot architecture from the bottom up Getting
around
Perceiving the world
4Overview
Reasoning
representing space motion planning
5Overview
Handling uncertainty
sensor fusion building maps localization
6Overview
Vision -- just another sensor ?
7Overview
- 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
8 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
9Classical 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
10Situated 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
11Situated 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
12Rosenscheins 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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14 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.
15Robot 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
16Robot 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()
17One 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
18Another view of reactive control
Direct mapping from the environment to a control
signal
goal-seeking behavior
obstacle-avoiding behavior
19Robot 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
20Behavior Summer
path taken by a robot controlled by the resulting
field
vector sum of the avoid and goal motor schemas
21Additional primitives
Direct mapping from the environment to a control
signal
go! schema
corridor-centering schema
22A more complex task
Direct mapping from the environment to a control
signal
larger composite task
23Another primitive
Direct mapping from the environment to a control
signal
larger composite task
random motion schema
24Local minima
Noise allows a system to jump out of local
minima.
the problem
a solution
25Bigger deadends...
How to get out of larger wells ?
26Bigger deadends...
uses memory of where the robot has been
past-avoiding motor schema
27Another example
Keeping away from past locations...
28Inspiration
29Inspiration
Study of how animals react to different stimuli
Rodents (Hull 1934)
Toads (Arbib 87)
Vowels
30Beyond subsumption
Navlab ALVINN
Polly
...
...
1995
31Polly
Ian Horswill _at_ MIT