EXPERIMENTS IN ADAPTIVE MODEL-BASED FORCE CONTROL

This article reports recent experiments with a new class of model-base d adaptive force control algorithms for robot arms [6, 3]. The problem addressed in this article is the control of robots whose motion is co nstrained by point contact between the robot tool and a smooth rigid e nvironment or workpiece. Manufacturing applications for force control include a great variety of commonplace tasks, such as grinding, polish ing, buffing, deburring, and assembly operations currently performed e ither manually or by fixed automation equipment. The new force control algorithm provides asymptotically exact tracking of both end-effector position and contact-force [6]. This force control algorithm utilizes a sliding-mode control technique of a type first espoused for the cas e of free (non-contact) robot motion [21]. The stability of the new fo rce control algorithm can be proven with respect to the commonly accep ted nonlinear rigid body dynamical equations of motion. Moreover, its adaptive extension can be shown to adaptively compensate for unknown p lant parameters such as link and payload inertia, joint friction, and friction arising at the contact point between the tool tip and the sur face. In [15,5] the authors report satisfactory performance of this fo rce control algorithm in numerical simulation studies. This article de monstrates the comparative advantages and disadvantages of this contro l algorithm under a variety of conditions in actual working implementa tions.