Assembly of complex shaped objects: A stiffness control with contact localization

Abstract

This paper presents a compliant control method for insertion of complex objects with concavities. The control algorithm presented here is capable of generating satisfactory compliant motion control in spite of changing contact states. During the execution of a nominal motion plan, it computes the actual position of the contact point from the force/torque sensor reading using a contact localization algorithm. It then dynamically updates the center of compliance to the computed contact point, and minimizes the chance of jamming and unwanted collisions. The control scheme has been implemented on hardware and tested on the task of inserting a T-shaped object into a C-shaped cavity with a very tight tolerance. The insertion motion, which involves a sequence of 2 translational and 1 rotational compliant motions, was successfully executed by the proposed compliant motion controller.