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Robotics

Robotics. Reprise on levels of language Movement in a crowded workspace Review for midterm Lab: Complete pick up, travel, deposit exercise. Homework: study for midterm. Post proposal for library research project. Movement. Move to position P. Note: position P may involve

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Robotics

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  1. Robotics Reprise on levels of language Movement in a crowded workspace Review for midterm Lab: Complete pick up, travel, deposit exercise. Homework: study for midterm. Post proposal for library research project.

  2. Movement • Move to position P. Note: position P may involve • 2D (planar) position, • 2D+orientation, • 2D+orientation+positioning/setting of gripper or other tooling • 3D (space) position, • 3D position + orientation (3 dimensions) • 3D position + orientation + positioning of tooling + (maybe) state of tooling (on or off)

  3. How do we get there? • Called: movement in crowded workspace • Two approaches: • Assuming the workspace is known, calculate path (trajectory) ahead of time • advantages: more efficient during operations • Disadvantages: difficult calculation. Objects may have moved—that is, workspace may not be known. • Move incrementally, using sensors, may involve backtracking

  4. AI terms • Brute force • Try everything • Heuristics • Use some special method, may not get the best answer • Closed form, algorithmic solution • Guaranteed best approach

  5. Backtracking • Brute force (but efficient brute force) • Enumerate (all at once or incrementally) solutions to problem and try them out • Implicit or explicit tree representing solutions • If there is a failure, mark solution as bad and go back to last known branching point. • Applications other than robotic movement: • Sudoku (see Flash examples on my site) • Position 8 queens on chess board so no 2 are on same horizontal, vertical or diagonal line • Stage in compilation that examines if sentence satisfies a rule in a grammar

  6. Geometry • Polygon is closed planar figure with straight lines as sides • Polygon is set of vertices and edges, each vertex connected to exactly 2 edges and the line segment defining each edge intersects with exactly two other edges • Convex polygon is such that for any two points inside the polygon, the edge/line segment connecting those points also is in the polygon • A concave polygon is one that is not convex

  7. Class exercise • Draw a polygon • Draw a figure with straight edges that is not a polygon • Draw a convex polygon • Draw a concave polygon.

  8. Polyhedron • Vertices, edges, faces, indication of presence of material (typically done using normals: outward pointing vectors) • Flat sides • Nominally curved surfaces (spheres, conic sections) approximated using facets

  9. Back to robots • Moving through a crowded workspace also called: the piano mover’s problem, wayfinding, moving in a crowded workspace, motion planning. • Many approaches involve ‘growing’ the obstacles and shrinking the piano/robot and doing this in multiple dimensions. • Growing may be in high[er] dimension space. • Many approaches involve general AI techniques, including backtracking and A* • Possible research paper topic! • Possible posting topic

  10. Sources • A* article http://www.policyalmanac.org/games/aStarTutorial.htm • Obstacle avoidance article http://www.aboutjens.com/dump/Reading/AI/Navigation/Automated_Static_and_Dynamic_Obstacle_Avoidance_in_Arbitrary_3D_Polygonal_Worlds1.pdf • Program http://code.google.com/p/straightedge/ • Animations http://gamma.cs.unc.edu/videos/robotics/

  11. Midterm review • ?

  12. Library research project • Proposal due March 22 REQUIRED • Please make constructive comments on each other’s proposals. • Paper and presentation due April 9 • 1 page: summary (abstract), 1 illustration, standard bibliography, proof-read! • Formal presentation: PowerPoint and/or other visuals • Try prezi.com

  13. [Way to get to] Topics • Postings (and/or my suggestions for postings) • Something you want to explore and work on in the future

  14. Lab • Complete pickup, travel, deposit, move away exercise. • use sensor or absolute value for pickup location • deposit in known absolute or relative location • understand which! • Start planning for parallel parking • tribot plus side mounted ultrasonic, optionally bumper • travel along parking lane determining where there is a spot. • back up / swivel. May use recorded path moves.

  15. Homework • Study for midterm: see on-line guide, review lecture charts, postings, suggested questions by students. • Prepare proposal for library research project

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