New robust position and force regulation for a compliant microgripper

This paper reports a new robust control scheme for the regulation of both position and grasping force of a piezo-driven compliant microgripper with integrated position and force sensors. Based on a detailed analysis of the grasping process, the problem of position/force control is converted into the position control along with force monitoring. Then, a strategy of sliding mode-based robust position control is presented and its stability is demonstrated analytically. As compared with the traditional position/force switching control which usually induces an unstable transition, the switching problem is eliminated by the presented scheme. Moreover, only a piecewise position trajectory planning is needed for the robust position controller. The effectiveness of the proposed control scheme is validated by experimental investigations. The scheme provides a sound base for the execution of practical microassembly tasks.