TABLE OF CONTENTS Tao Zhang, University of California, Berkeley, Berkeley, CA
Gordon Smith, University of California, Berkeley, Berkeley, CA
Ken Goldberg, University of California, Berkeley, Berkeley, CA
For many industrial parts, their resting pose differs from the orientation desired for assembly. It is possible in many cases to compensate for this difference using a parallel-jaw gripper with fixed orientation. The idea is to arrange contact points on each gripper jaw so that the part is reoriented as it is grasped. We analyze the mechanics of compensatory grasping based on a combination of toppling, jamming, accessibility, and form closure and describe an algorithm for the design of such grasps based on the constrained toppling graph.
Industrial parts on a flat worksurface will naturally come to rest in one of several stable orientations [1], but it is often necessary to rotate a part into a different (unstable) orientation for assembly [2].
This paper proposes an inexpensive (minimalist) method for compensating for these differences in orientation by reorienting the part during grasping. As illustrated in Figure 1, the part is initially in stable orientation (a); it then is rotated by the gripper to orientation (b) for assembly onto the peg. We refer to this as a compensatory grasp.
We achieve this using a simple parallel-jaw gripper with four tips as shown in Figure 2. First, toppling tip A and pushing tip A' make contact with the part and topple...
