Precision Control of Force Produced by Ionic Polymer Metal Composite

In this paper, we present the precision feedback control of the force produced by ionic polymer metal composite (IPMC). The high-precision force generation capability of IPMC at low force level makes it ideal for micro-device applications such as micro-grippers. To design fingers for a micro-gripper using IPMC, the study of the adhesion force is also of critical importance. We measured this adhesion force with an atomic force microscope between a glass micro-sphere of 32.43-μm diameter and an IPMC strip, and it was found to be 144 nN. After the implementation of the feedback controller, the settling time was reduced to 1.5 s from 10 s in open loop, and the overshoot was reduced to 30% from 131.62% in open loop. The current force resolution is one the order of 4 μN at 0.904-μN rms force noise. The crossover frequency of this control system is 1.3 Hz limited by the structural resonance of the polymer strip. We have demonstrated high precision force control capability of IPMC for micro-device applications.