Introduction to Behavior-Based Robotics

1. Introduction to Behavior-Based Robotics Based on the book Behavior-Based Robotics by Ronald C. Arkin

2. What is a Robot? • A robot is a re-programmable, multi-functional, manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks. • Robotics is the intelligent connection of perception to action.

3. What is a Robot? (cont.) • An intelligent robot is a machine able to extract information from its environment and use knowledge about its world to move safely in a meaningful and purposive manner.

4. Related Areas • Cybernetics • Artificial intelligence • Robotics

5. Spectrum of Robot Control • Deliberative/Hierarchical control • Requires relatively complete knowledge about the world. • Requires strong assumptions about this world model. • Hierarchical in structure with a clear identifiable subdivision of functionality. • Communication and control occurs in a predictable and predetermined manner. • Higher levels in the hierarchy provide subgoals for lower subordinate levels. • Planning scope changes during descent in the hierarchy.

6. Spectrum of Robot Control (cont) • Reactive control • Reactive control is a technique for tightly coupling perception and action, typically in the context of motor behaviors, to produce timely robotic response in dynamic and unstructured worlds. • Behaviors serve as the basic building blocks for robotic actions. • Use of explicit abstract representational knowledge is avoided in the generation of a response. • Animal models of behavior often serve as a basis. • Reactive systems are inherently modular from a software design perspective.

7. Design Paradigms for Building Behavior-Based Systems • Ethologically guided/constrained design • Situated activity-based design • Experimentally driven design

8. Expressions of Behaviors • Stimulus-response (SR) diagrams • Functional notation b(s) = r • Finite state acceptor (FSA) diagrams Behavior Stimulus Response

9. Expressions of Behaviors (cont) • A Navigational Example Consider a student going from one classroom to another. The following kinds of things are involved. • Getting to the destination from current location • Not bumping into anything along the way • Skillfully negotiating the way around other students • Observing cultural customs • Coping with change and doing whatever else is necessary

10. Behavior Encoding • Mapping from the stimulus plane to the motor plane. • A behavior can be expressed as a triple (S, R, β) where S denotes the domain of all interpretable stimuli, R denotes the range of possible responses, and βdenotes the mappingβ:S->R. • Discrete encoding • Continuous functional encoding

11. Assembling Behaviors • Behavioral coordination • Competitive methods • Cooperative methods

12. Behavior-Based Architectures • Definition Robot architecture is the discipline devoted to the design of highly specific and individual robots from a collection of common software building blocks.

13. Behavior-Based Architectures (cont) • Evaluation Criteria • Supporting for parallelism • Hardware targetability • Niche targetability • Support for modularity • Robustness • Timeliness in development • Run time flexibility • Performance effectiveness

14. Behavior-Based Architectures (cont) • A foraging example The tasks consists of a robot’s moving away from a home base area looking for attractor objects. • Wander • Acquire • Retrieve

15. Behavior-Based Architectures (cont) • Subsumption architecture (Brooks) • AFSM model • It is a layered architecture that uses arbitration strategies and AFSM as its basis. • Coordination: Inhibition and suppression • Pros • Hardware retargetability • Support for parallelism • Niche targetability • Cons • Run time flexibility • Support for modularity

16. Behavior-Based Architectures (cont) • Motor schemas (Arkin) • A schema is the basic unit of behavior from which complex actions can be constructed; it consists of the knowledge of how to act or perceive as well as the computational process by which it is enacted. • Motor schemas are a software-oriented dynamic reactive architecture that is non-layered and cooperative.

17. Behavior-Based Architectures (cont) • Motor schemas (cont) • Coordination: vector summation • Pros • Support for parallelism • Run time flexibility • Timeliness for development and support for modularity • Cons • Niche targetability • Hardware retargetability

18. Behavior-Based Architectures (cont) • Other architectures • Circuit architecture • Colony architecture • Animate agent architecture • Distributed architecture for mobile navigation • Skill network architecture