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The Reactive Paradigm

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

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The Reactive Paradigm

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  1. Introduction to Intelligent Robots The Reactive Paradigm • Embedded System Lab • Kim JongHwi Chonbuk National University

  2. Chapter Objectives • Define what the reactive paradigm • List the characteristics of a reactive robotic system • Describe the two dominant methods for combining behaviors in a reactive architecture: subsumption and potential field summation • Be able to program a behavior using a potential field methodology • Be able to construct a new potential field form primitive potential fields, and sum potential fields to generate an emergent behavior Chonbuk National University

  3. Reactive Paradigm - Overview Subsumption Architecture Potential Field Methodologies Pros and cons Summary Chonbuk National University

  4. The Reactive Paradigm • emerged in the late 1980’s • grew out of dissatisfaction with the hierarchical paradigm • -summarized by Roney Brooks Chonbuk National University

  5. The Reactive Paradigm • layered in a vertical decomposition • access to sensors and actuators independently Chonbuk National University

  6. 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 extracting the percept and its strength Chonbuk National University

  7. S-A organization Chonbuk National University

  8. Behavior-specific sensing organization in the Reactive Paradigm Chonbuk National University

  9. Connotations of reactive behaviors • executes rapidly • have no memory Chonbuk National University

  10. 5 Characteristics of reactive behaviors • 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 particular behavior Chonbuk National University

  11. Representative architectures • Subsumption – how behaviors are combined • 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 … Chonbuk National University

  12. Subsumption architecture • Rodney Brooks’s architecture • the most influential of the purely Reactive Paradigm systems Chonbuk National University

  13. Subsumption architecture • Modules are grouped into layers of competence • (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 Chonbuk National University

  14. Example Chonbuk National University

  15. Level 0 recast as primitive behaviors Chonbuk National University

  16. Level 1 : wander Chonbuk National University

  17. Level 1 recast as primitive behaviors Chonbuk National University

  18. Level 2 : follow corridors Chonbuk National University

  19. Potential Field • force field on the surrounding space exerted from perceivable objects • Vector • Magnitude; real number between 0.0 and 1 • Direction Chonbuk National University

  20. Potential Field Chonbuk National University

  21. Potential Field Chonbuk National University

  22. Programming a single potential Field Chonbuk National University

  23. Programming a single potential Field Chonbuk National University

  24. Programming a single potential Field Chonbuk National University

  25. Programming a single potential Field Chonbuk National University

  26. Programming a single potential Field Chonbuk National University

  27. Programming a single potential Field Chonbuk National University

  28. Programming a single potential Field Chonbuk National University

  29. Programming a single potential Field Chonbuk National University

  30. Programming a single potential Field Chonbuk National University

  31. 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 inviroment • Disadvantages • Local minima (vector with 0 magnitude) • producing vectors with a small magnitude from random noise • NaTs (navigation templates) Chonbuk National University

  32. 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 Chonbuk National University

  33. Thank you for listening! Chonbuk National University

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