Position control of a SMA microgripper

Abstract

A SMA microgripper system with an integrated optical position sensor is presented. The microgripper consists of two actuation units and an optical slit fabricated from one piece of SMA material with overall dimensions of 2 × 5.8 × 0.23 mm3. The gripper is sandwiched by two substrates with an aligned photodiode and a photosensor, respectively. This transmission setup allows position sensing with a spatial resolution of 1 μm per 2.5% optical signal change. By feedback of the position signal to a PI controller a position error of 0.3% is achieved. The typical time constant for reaching stationary positions is about 140 ms.