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 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

 The Reactive Paradigm emerged in the late 1980’s grew out of dissatisfaction with the hierarchical paradigm -summarized by Roney Brooks

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

Chonbuk National University  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  S-A organization

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

Chonbuk National University  Connotations of reactive behaviors executes rapidly have no memory

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

Chonbuk National University  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  Example

Chonbuk National University  Level 0 recast as primitive behaviors

Chonbuk National University  Level 1 : wander

Chonbuk National University  Level 1 recast as primitive behaviors

Chonbuk National University  Level 2 : follow corridors

Chonbuk National University  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  Potential Field

Chonbuk National University  Potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  Programming a single potential Field

Chonbuk National University  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  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 University33 Thank you for listening!