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Topological Path Planning

Introduction to AI Robots Chapter 9. Topological Path Planning. JBNU, Division of Computer Science and Engineering Parallel Computing Lab Jonghwi Kim. Chapter Objectives. Define the difference between a natural and artificial landmark and give one example of each

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Topological Path Planning

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  1. Introduction to AI Robots Chapter 9 Topological Path Planning JBNU, Division of Computer Science and Engineering Parallel Computing Lab Jonghwi Kim

  2. Chapter Objectives • Define the difference between a natural and artificial landmark and give one example of each • Given a description of an indoor office environment and a set of behaviors, build a relational graph representation labeling the distinctive places and local control strategies using gateways • Describe in one or two sentences : gateway, image signature, visual homing, viewframe, orientation region • Given a figure showing landmarks, create a topological map showing landmarks, landmark pair boundaries, and orientation regions

  3. Contents • Overview • Landmarks and Gateways • Relational Methods • Associative Methods • Case Study of Topological Navigation with a Hybrid Architecture • Summary

  4. Overview Route representations fall into one of two approaches : • Relational • most popular • giving the robot an abbreviated, “connect the dots” graph-style of spatial memory • use an explicit representation, support path planning • focus on the graph-like representation of spatial memory • Associative • better for retracing known paths • focus on coupling sensing with localization

  5. Landmarks and Gateways • Landmark • one or more perceptually distinctive features of interest on an object or locale of interest • not necessarily a single • can be a grouping of objects McDonald’s stand of aspen trees

  6. Landmarks and Gateways • Landmark • be either artificial or natural • “artificial” and “natural” ≠ “man-made” and “organic” • artificial landmark • set of features added to an existing object or locale in order to either support recognition of the landmark or some other perceptual activity

  7. Landmarks and Gateways • Landmark • natural landmark • configuration of existing features selected for recognition which were not expressly designed for the perceptual activity

  8. Landmarks and Gateways • Landmark • must satisfy three criteria • Be readily recognizable • Support the task dependent activity • Be perceivable from many different viewpoints • good landmark’s characteristics • passive in order to be available despite a power failure • should be perceivable over the entire range where the robot might need to see it • should have distinctive features, and, if possible, unique feature

  9. Landmarks and Gateways • Gateway • an opportunity for a robot to change its overall direction of navigation • critical for localization, path planning, and map making

  10. Relational Methods • Relational methods • represent the world as a graph or network of nodes and edges • Nodes • gateways, landmarks, or goals • Edges • a navigable path between two nodes • can attach additional information • direction(N,S,E,W), approximate distance, terrain type, the behaviors needed to navigate that path

  11. Relational Methods • Earliest relational graphs for navigation(Smith and Cheeseman)

  12. Relational Methods • Earliest relational graphs for navigation(Smith and Cheeseman)

  13. Relational Methods • Relational graphs for navigation(Kuipers and Byun)

  14. Relational Methods • Distinctive places • landmark that the robot could detect from a nearby region called a neighborhood

  15. Associative Methods • Associative methods • create a behavior which converts sensor observations into the direction to go to reach a particular landmark • assumption • perceptual stability : that views of the location that are close together should look similar • perceptual distinguishability : that views far away should look different

  16. Associative Methods • Visual homing • work done by Nelson, and later by Engelson • image signature • created by partitioning an image into sections • possible measurement • edge density • dominant edge orientation • average intensity • so on…

  17. Associative Methods • Visual homing

  18. Associative Methods • Visual homing

  19. Associative Methods • QualNav(qualitative navigation) • the ideas from Levitt and Lawton • for outdoor navigation over large distances as part of the Defense Advance Research Projects Agency (DARPA) Autonomous Land Vehicle (ALV) project in the late 1980’s

  20. Associative Methods • QualNav(qualitative navigation)

  21. Case Study of Topological Navigation with a Hybrid Architecture • Case study of topological navigation using the SFX architecture in 1994 AAAI Mobile Robot Competition by a team of undergraduates form the Colorado School of Mines

  22. Case Study of Topological Navigation with a Hybrid Architecture • placed in a random room • navigate out of the room and to another room within 15 minutes • be given a topological map • How the topological map was entered the activities of Cartographer • How scripts were used to simplify behavioral management, and the lessons learned

  23. Case Study of Topological Navigation with a Hybrid Architecture • Path planning a sample topological map • start nodes • direction • blockages • landmark

  24. Case Study of Topological Navigation with a Hybrid Architecture • Path planning • Cartographer • input : a gateway type, start node, goal node • output : a list of nodes representing the best path • preprocessing • reclassifying (a hall to door connection as Hd) • eliminates extraneous gateways • Task Manager • select the appropriate abstract navigation behavior d

  25. Case Study of Topological Navigation with a Hybrid Architecture • Path planning

  26. Case Study of Topological Navigation with a Hybrid Architecture • Path planning

  27. Case Study of Topological Navigation with a Hybrid Architecture • Path planning

  28. Case Study of Topological Navigation with a Hybrid Architecture • Path planning

  29. Case Study of Topological Navigation with a Hybrid Architecture • Navigation scripts • used to specify and carry out the implied details of the plan • navigate-door ANB

  30. Case Study of Topological Navigation with a Hybrid Architecture • navigate-hall ANB

  31. Case Study of Topological Navigation with a Hybrid Architecture • navigate-foyer ANB

  32. Case Study of Topological Navigation with a Hybrid Architecture • Lessons learned • critical to build the abstract navigation behaviors out of robust primitives (biggest problem is quality of the primitive behaviors) • contention for sensing resource • metric distance problem • impact of obstacles

  33. Summary • Landmarks • simplify the ‘Where am I?’ problem • Gateways • special landmarks which reflect a potencial for the robot to change directions • navigation methods • relational • distinctive places(nodes), local control strategies(lcs) • associative • viewframe

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