Introduction to Behavior-Introduction to Behavior-Based RoboticsBased Robotics

Based on the bookBased on the book Behavior-Bas Behavior-Based Robotics ed Robotics by Ronald C. Arkinby Ronald C. Arkin

What is a Robot?What is a Robot?

A robot is a re-programmable, multi-A robot is a re-programmable, multi-functional, manipulator designed to functional, manipulator designed to move material, parts, tools, or move material, parts, tools, or specialized devices through variable specialized devices through variable programmed motions for the programmed motions for the performance of a variety of tasks.performance of a variety of tasks.

Robotics is the intelligent connection Robotics is the intelligent connection of perception to action.of perception to action.

What is a Robot? (cont.)What is a Robot? (cont.)

An intelligent robot is a machine able An intelligent robot is a machine able to extract information from its to extract information from its environment and use knowledge environment and use knowledge about its world to move safely in a about its world to move safely in a meaningful and purposive manner. meaningful and purposive manner.

Related AreasRelated Areas

CyberneticsCybernetics Artificial intelligenceArtificial intelligence RoboticsRobotics

Spectrum of Robot ControlSpectrum of Robot Control

Deliberative/Hierarchical controlDeliberative/Hierarchical control• Requires relatively complete knowledge about the wRequires relatively complete knowledge about the w

orld.orld.• Requires strong assumptions about this world model.Requires strong assumptions about this world model.• Hierarchical in structure with a clear identifiable subHierarchical in structure with a clear identifiable sub

division of functionality.division of functionality.• Communication and control occurs in a predictable aCommunication and control occurs in a predictable a

nd predetermined manner.nd predetermined manner.• Higher levels in the hierarchy provide subgoals for loHigher levels in the hierarchy provide subgoals for lo

wer subordinate levels.wer subordinate levels.• Planning scope changes during descent in the hierarcPlanning scope changes during descent in the hierarc

hy.hy.

Spectrum of Robot Control Spectrum of Robot Control (cont)(cont)

Reactive controlReactive control• Reactive control is a technique for tightly coupling Reactive control is a technique for tightly coupling

perception and action, typically in the context of perception and action, typically in the context of motor behaviors, to produce timely robotic motor behaviors, to produce timely robotic response in dynamic and unstructured worlds.response in dynamic and unstructured worlds.

• Behaviors serve as the basic building blocks for Behaviors serve as the basic building blocks for robotic actions.robotic actions.

• Use of explicit abstract representational knowledge Use of explicit abstract representational knowledge is avoided in the generation of a response.is avoided in the generation of a response.

• Animal models of behavior often serve as a basis.Animal models of behavior often serve as a basis.• Reactive systems are inherently modular from a Reactive systems are inherently modular from a

software design perspective.software design perspective.

Design Paradigms for Building Design Paradigms for Building Behavior-Based SystemsBehavior-Based Systems

Ethologically guided/constrained Ethologically guided/constrained designdesign

Situated activity-based designSituated activity-based design Experimentally driven designExperimentally driven design

Expressions of BehaviorsExpressions of Behaviors Stimulus-response (SR) diagramsStimulus-response (SR) diagrams

Functional notationFunctional notationb(s) = rb(s) = r

Finite state acceptor (FSA) diagramsFinite state acceptor (FSA) diagrams

Behavior ResponseStimulus

Expressions of Behaviors Expressions of Behaviors (cont)(cont)

A Navigational Example A Navigational Example

Consider a student going from one classroom Consider a student going from one classroom to another. The following kinds of things are to another. The following kinds of things are involved.involved.• Getting to the destination from current locationGetting to the destination from current location• Not bumping into anything along the wayNot bumping into anything along the way• Skillfully negotiating the way around other studentsSkillfully negotiating the way around other students• Observing cultural customsObserving cultural customs• Coping with change and doing whatever else is Coping with change and doing whatever else is

necessarynecessary

Behavior EncodingBehavior Encoding

Mapping from the stimulus plane to the mMapping from the stimulus plane to the motor plane.otor plane.

A behavior can be expressed as a triple (A behavior can be expressed as a triple (S,S, R, R, ββ) ) where where SS denotes the domain of all in denotes the domain of all interpretable stimuli, R denotes the range oterpretable stimuli, R denotes the range of possible responses, and f possible responses, and ββdenotes the mdenotes the mappingappingββ:S->R.:S->R.

Discrete encodingDiscrete encoding Continuous functional encodingContinuous functional encoding

Assembling BehaviorsAssembling Behaviors

Behavioral coordinationBehavioral coordination• Competitive methodsCompetitive methods• Cooperative methodsCooperative methods

Behavior-Based Behavior-Based ArchitecturesArchitectures

DefinitionDefinition

Robot architecture is the discipline Robot architecture is the discipline devoted to the design of highly devoted to the design of highly specific and individual robots from a specific and individual robots from a collection of common software collection of common software building blocks.building blocks.

Behavior-Based Architectures Behavior-Based Architectures (cont)(cont)

Evaluation CriteriaEvaluation Criteria• Supporting for parallelismSupporting for parallelism• Hardware targetabilityHardware targetability• Niche targetabilityNiche targetability• Support for modularitySupport for modularity• RobustnessRobustness• Timeliness in developmentTimeliness in development• Run time flexibilityRun time flexibility• Performance effectivenessPerformance effectiveness

Behavior-Based Architectures Behavior-Based Architectures (cont)(cont)

A foraging exampleA foraging example

The tasks consists of a robot’s The tasks consists of a robot’s moving away from a home base area moving away from a home base area looking for attractor objects.looking for attractor objects.• WanderWander• AcquireAcquire• RetrieveRetrieve

Behavior-Based Architectures Behavior-Based Architectures (cont)(cont)

Subsumption architecture (Brooks)Subsumption architecture (Brooks)• AFSM modelAFSM model• It is a layered architecture that uses arbitration strategiIt is a layered architecture that uses arbitration strategi

es and AFSM as its basis.es and AFSM as its basis.• Coordination: Inhibition and suppressionCoordination: Inhibition and suppression• ProsPros

Hardware retargetabilityHardware retargetability Support for parallelismSupport for parallelism Niche targetabilityNiche targetability

• ConsCons Run time flexibilityRun time flexibility Support for modularitySupport for modularity

Behavior-Based Architectures Behavior-Based Architectures (cont)(cont)

Motor schemas (Arkin)Motor schemas (Arkin)• A schema is the basic unit of behavior from A schema is the basic unit of behavior from

which complex actions can be constructed; iwhich complex actions can be constructed; it consists of the knowledge of how to act or t consists of the knowledge of how to act or perceive as well as the computational proceperceive as well as the computational process by which it is enacted.ss by which it is enacted.

• Motor schemas are a software-oriented dynMotor schemas are a software-oriented dynamic reactive architecture that is non-layereamic reactive architecture that is non-layered and cooperative.d and cooperative.

Behavior-Based Architectures Behavior-Based Architectures (cont)(cont)

Motor schemas (cont)Motor schemas (cont)• Coordination: vector summationCoordination: vector summation• ProsPros

Support for parallelismSupport for parallelism Run time flexibilityRun time flexibility Timeliness for development and support for modTimeliness for development and support for mod

ularityularity• ConsCons

Niche targetabilityNiche targetability Hardware retargetabilityHardware retargetability

Behavior-Based Architectures Behavior-Based Architectures (cont)(cont)

Other architecturesOther architectures• Circuit architectureCircuit architecture• Colony architectureColony architecture• Animate agent architectureAnimate agent architecture• Distributed architecture for mobile Distributed architecture for mobile

navigationnavigation• Skill network architectureSkill network architecture