Assembly Line Part Handling Algorithm

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Feeding Polyhedral Parts
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Feeding Polyhedral Parts
Related Work Paul (1973), Birk (1974), Salisbury
(1982) Fearing (1986), Nguyen (1986) Tournassound,
Lozano-Perez, and Mazer (1987) Ponce and
Faverjon (1992), Rus (1992) Erdmann, Mason, and
Vanecek (1993)
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Pivoting
Animation
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Pivoting Gripper
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Problem Choose Grasp Axis
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Problem Definition

• Stable poses of the polyhedron
• Hard-finger contacts
• resists forces and torques,
• except about grasp axis.

Input

• Shape of polyhedral part with n faces,
• Center of mass,
• Coefficient of friction,
• Initial and Desired poses.

Criteria

• Grasp Axis is parallel to workable,
• Grasp wont slip,
• Part will rotate due to gravity when lifted,
• When replaced, part will assume desired pose.

Output

• Pivoting Axis for each pair of stable poses
• m x m Transition Matrix

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Rao, Kriegman, Goldberg (1996)
Complete Algorithm Computes m x m Transition
Matrix in time O (m2n log n).
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Result
1. We can find candidate grasps in time O (n3)

• Slicing part at critical heights,
• Effective ?,
• Nguyen regions,
• Algebraic formulation of stability f (z) 0

2. A pivoting grasp always exists if

• Part is convex with interior com, and
• no slip.

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Future Work

• Capture Regions
• Active Pivot Grasps (APGs)
• Avoiding Collisions with Nearby Parts
• Toppling
• Learning Transition Probabilities