Design and Control of a Passive Compliant Piezo-Actuated Micro-Gripper with Hybrid Flexure Hinges

This article presents the design, control, and test of a piezo-based passive compliant micro-gripper capable of combining position and force control. The gripper's structure is compact due to a super-large amplification ratio of 52 that is achieved by a two-stage displacement amplifier. The position/force switching control strategy is utilized for the position and force regulation. Particularly, a dual feedforward controller combining Gaussian process regression based hysteresis compensator and input shape technique based vibration suppressor is employed to the position regulation, while a hybrid controller composed of dual feedforward and PID feedback is used for the precision force control. Compared to the conventional design, the system is simplified because displacement sensor is removed. In order to protect the micro-object from contact, the passive compliance design method is introduced to the gripper tip. An experimental study, executing grasp-hold-release operations of a gold wire, is carried out to validate the feasibility of the gripper system. The result confirms that the proposed scheme is feasible and the stable clamping operations can be achieved.