A Low Cost Coarse/Fine Piezoelectrically Actuated Microgripper with Force Measurement Adapted to Eupass Control Structure

Over the last few years the demand for miniature objects and devices has continuously increased. So the need for MEMS (Micro Electro Mechanical Systems) and MOEMS (Micro Opto Electro Mechanical Systems) in various fields has become more and more important. New micromanipulation technologies must be developed that take into account the specificities of MEMS and MOEMS. For performing manipulation tasks, gripping is one of the fundamental functions. In this paper, the design and the control of a microgripper dedicated to very high precision tasks are presented. The LAB (Laboratoire d'Automatique de Besançon) has developed a microgripper based on the piezoelectric properties [1]. This gripper is equipped with a precise sensor for force measurement. Force measurement is very important in order to avoid damaging or destroying the fragile object. Various approaches were used to model and calibrate the microgripper. The control of the gripper is done using the EUPASS Control Structure [6]. 1 Structure of the system To handle micro-objects in a wide range of sizes, the designed microgripper is made up of two different parts (see Figure 1): A mobile part, shown in Figure 2, composed of a coarse positioning device using a piezomotor from PiezoMotor and a piezoelectric bending cantilever for fine positioning. This cantilever is the first finger of the gripper. A fixed part, linked to the main support which constitutes the second finger of the gripper. A Low Cost Coarse/Fine Piezoelectrically Actuated Microgripper with Force Measurement Adapted to the EUPASS Control Structure 236 Handled object 1cm Main support Fixed part Piezoelectric cantilever Mobile part Fig.1. Structure of the microgripper 2 Force measurement To perform force measurement, a strain gauge (length: 1.27mm, width: 0.38mm) is glued on every side of the piezoelectric cantilever (see Figure 2) which is bonded on a PCB. The force measurement depends on the gauge properties and the physical characteristics and dimensions of the cantilever. Other principles of force measurement are also possible [2] [3] [4]. coarse positioning device Piezoelectric cantilever (fine positioning device) Strain gauges