Robotic Assembly across Multiple Contact Stiffnesses with Robust Force Controllers

Abstract

Active Force Control (AFC) is an important scheme for tackling high-precision robotic assembly. Classical force controllers are highly surface-dependent: the controller must be carefully tuned for each type of surface in contact, in order to avoid instabilities and to achieve a reasonable performance level. Here, we build upon the recently-developed Convex Controller Synthesis (CCS) to enable high-precision assembly across a wide range of surface stiffnesses without any surface-dependent tuning. Specifically, we demonstrate pegin-hole assembly with 100 micron clearance, initial position uncertainties up to 2 cm, and for four types of peg and hole materials -rubber, plastic, wood, aluminum -whose stiffnesses range from 10 to 100 N/mm, using a single controller.