Designing robot grippers: optimal edge contacts for part alignment

Mike Tao Zhanga1 c1 and Ken Goldberga2

a1 AzFSM (Fab 12/22/32) Industrial Engineering, Intel Corporation, Mail Stop: OC2-254, 4500 S. Dobson Road, Chandler, AZ 85248, USA

a2 Department of Industrial Engineering and Operations Research and Department of Electrical Engineering and Computer Science, University of California, Berkeley, CA 94720-1777, USA


Although parallel-jaw grippers play a vital role in automated manufacturing, gripper surfaces are still designed by trial-and-error. This paper presents an algorithmic approach to designing gripper jaws that mechanically align parts in the vertical (gravitational) plane. We consider optimal edge contacts, based on modular trapezoidal segments that maximize contact between the gripper and the part at its desired final orientation. Given the n-sided 2D projection of an extruded convex polygonal part, mechanical properties such as friction and center of mass, and initial and desired final orientations, we present an O(n3 log n) numerical algorithm to design optimal gripper jaws. We also present an O(n log n) algorithm to compute tolerance classes for these jaws, and report on an online implemented version of the algorithm and physical experiments with the jaws it designed. This paper extends earlier results that generated optimal point contacts [M. T. Zhang and K. Goldberg, “Gripper point contacts for part alignment,” IEEE Trans. Robot. Autom. 18(6), 902–910 (2002)].

(Received October 20 2006)

(Online publication November 30 2006)


  • Grasp;
  • Gripper;
  • Geometric Computation;
  • Manipulation


c1 *Corresponding author. E-mail: