Gripper point contacts for part alignment

The initial resting pose of many industrial parts differs from the orientation desired for assembly. We show that it is possible to align parts during grasping using a standard parallel-jaw gripper. A solution is an arrangement of four gripper point contacts that will align the part in the vertical plane as the jaws close. Given a n-sided polygonal part and k uniformly distributed sample points on each side, we present an O(n⁴k⁴) numerical algorithm to compute a set of solutions or a report that no solution exists. The algorithm combines toppling, accessibility, and form-closure analysis. We have implemented the algorithm and report sensitivity data from physical experiments.