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Introduction to Intelligent Robots. The Reactive Paradigm. Embedded System Lab Kim Jong Hwi. Chapter Objectives Define what the reactive paradigm List the characteristics of a reactive robotic system - PowerPoint PPT Presentation
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The Reactive Par-adigm
Embedded System Lab Kim Jong Hwi
Chonbuk National University
Introduction to Intelligent Robots
Chonbuk National University
Chapter Objectives
• Define what the reactive paradigm • List the characteristics of a reactive robotic
system• Describe the two dominant methods for com-
bining behaviors in a reactive architecture: subsumption and potential field summation
• Be able to program a behavior using a poten-tial field methodology
• Be able to construct a new potential field form primitive potential fields, and sum potential fields to generate an emergent behavior
Contents
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Reactive Paradigm - Overview Subsumption Architecture Potential Field Methodologies Pros and cons Summary
Reactive Paradigm
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The Reactive Paradigm• emerged in the late 1980’s• grew out of dissatisfaction with the hier-
archical paradigm -summarized by Roney Brooks
Reactive Paradigm
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The Reactive Paradigm• layered in a vertical decomposition• access to sensors and actuators indepen-
dently
Reactive Paradigm
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Attributes of Reactive Paradigm• all actions are accomplished through
behaviors
• motor schema : algorithm for generating the pattern of action in physical actuator
• perceptual schema : algorithm for ex-tracting the percept and its strength
Reactive Paradigm
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S-A organization
Reactive Paradigm
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Behavior-specific sensing orga-nization in the Reactive Para-digm
Reactive Paradigm
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Connotations of reactive behav-iors
• executes rapidly• have no memory
Reactive Paradigm
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5 Characteristics of reactive be-haviors• Robots are situated agents operating in an
ecological niche• Behaviors serve as the basic building
blocks for robotic actions, and the overall behavior of the robot is emergent
• Only local, behavior-specific sensing is permitted
• These systems inherently follow good software design principle
• Animal models of behavior are often cited as a basis for these systems or a particu-lar behavior
Reactive Paradigm
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Representative architectures
• Subsumption – how behaviors are com-bined
• Potential Field Methodologies – require behaviors to be implemented as potential fields and the behaviors are combined by summation of the fields
• Rule encoding, fuzzy methods, winner-take-all voting …
Subsumption Architecture
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Subsumption architecture Rodney Brooks’s architecture the most influential of the purely Reactive Paradigm
systems
Subsumption Architecture
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Subsumption architecture
• Modules are grouped into layers of com-petence
(low layer ~ high layer)• Modules in a higher layer can override, or
subsume, the output from behaviors in the next lower layer
• The use of internal state is avoided• A task is accomplished by activating the
appropriate layer
Subsumption Architecture
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Example
Subsumption Architecture
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Level 0 recast as primitive behav-iors
Subsumption Architecture
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Level 1 : wander
Subsumption Architecture
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Level 1 recast as primitive behav-iors
Subsumption Architecture
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Level 2 : follow corridors
Potential Fields Methodologies
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Potential Field• force field on the surrounding space
exerted from perceivable objects Vector
– Magnitude; real number between 0.0 and 1– Direction
Potential Fields Methodologies
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Potential Field
Potential Fields Methodologies
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Potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Potential Fields Methodologies
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Programming a single potential Field
Pros and cons
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Advantages and disadvantages• Advantages
– easy to visualize over a large region of space– easier for the designer to visualize the robot’s overall
behavior– easy to combine fields, and languages such as C++– well works behaviors developed for 2D in 3D inviro-
ment• Disadvantages
– Local minima (vector with 0 magnitude)» producing vectors with a small magnitude
from random noise» NaTs (navigation templates)
Summary
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Summary• subsumption and potential fields
appear to be largely equivalent in practice
• The ease of portability to other domains is relative to the complexity of the changes in the task and enviroment
• Neither style of architecture explicitly addresses robustness
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Thank you for listening!