Towards a force-controlled microgripper for assembling biomedical microdevices

This paper presents recent results on the development and control of a micr ogripper based on flexure joints, fabricated by LIGA and instrumented with semiconductor strain-gauge force sensors. The microgripper is the end-effec tor of a workstation developed to grasp and manipulate tiny objects such as the components of a typical biomedical microdevice. The development of the force control in the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities requi red to perform assembly tasks for biomedical microdevices. As a step towards the definition of the force control strategy, system iden tification techniques have been used to model the microgripper. Results ind icate that a proportional integral (PI) controller could be used to assure, at the same time, closed-loop stability of the system, and a bandwidth sui table for the intended applications. The force control is based on strain-g auge sensors which have been integrated in the microgripper and experimenta lly characterized. Sensor response in the idling condition and during grasp showed that they can provide useful information for force control of the m icrogripper.