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Image-based Control Convergence issues

Image-based Control Convergence issues. CMPUT 610 Winter 2001 Martin Jagersand. Notes:. Please hand in project proposal on Thu. See me if there are any problems. Some on-line search engines for papers: http://www.cora.whizbang.com/ http://citeseer.nj.nec.com/cs. Recall: Visual Servoing.

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Image-based Control Convergence issues

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  1. Image-based ControlConvergence issues CMPUT 610 Winter 2001 Martin Jagersand

  2. Notes: • Please hand in project proposal on Thu. • See me if there are any problems. • Some on-line search engines for papers: • http://www.cora.whizbang.com/ • http://citeseer.nj.nec.com/cs

  3. Recall: Visual Servoing • Observed features: • Motor variables: • Local linear model:

  4. Recall again: Visual Servoing Steps • Solve: • Update and move: • Read actual visual move • Update Jacobian: repeat

  5. Recall again: Visual Servoing Steps • Solve: • Update and move: • Read actual visual move • Update Jacobian: repeat

  6. How to specify a visual task?

  7. Visual specifications • Point to Point task “error”: Why 16 elements?

  8. Visual specifications 2 • Point to Line Line:

  9. E (y) = wrench y - y y - y 4 2 5 7 y • (y  y ) y • (y  y ) 8 6 2 4 3 1 ParallelComposition example (plus e.p. checks)

  10. Serial CompositionSolving whole real tasks • Task primitive/”link” • Acceptable initial (visual) conditions • Visual or Motor constraints to be maintained • Final desired condition • Task =

  11. “Natural” primitive links • Transportation • Coarse primitive for large movements • <= 3DOF control of object centroid • Robust to disturbances • Fine Manipulation • For high precision control of both position and orientation • 6DOF control based on several object features

  12. Example: Pick and place type of movement 3. Alignment??? • To match transport final to fine manipulation initial conditions

  13. More primitives 4. Guarded move • Move along some direction until an external contraint (e.g. contact) is satisfied. 5. Open loop movements: • When object is obscured • Or ballistic fast movements • Note can be done based on previously estimated Jacobians

  14. Solving the puzzle…

  15. Summary • Servoing alone does not solve whole tasks • Parallel composition: Stacking of visual constraints to be simultaneously satisfied • Serial composition: Linking together several small movements into a chain of continuous movements

  16. Convergence? • Convex function? • Convex domain? • Convergent method?

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