Reaction force estimation of piezoelectric actuator by charge observation

Stacked piezoelectric actuators are suitable for micro manipulation, because they have high resolution and large thrust force. However, thrust force of the actuator contains hysteresis. The hysteresis deteriorates robust control performance and the accuracy of reaction force estimation. Hysteresis compensation methods using models have been proposed, although the accuracy of the model is deteriorated in high-frequency input. Hence, disturbance observer (DOB) and reaction force observer (RFOB) without hysteresis model are proposed in this paper. The RFOB estimates reaction force by observing accumulated charge on the actuator. In order to verify the validity of the proposal, experiments were performed. Experimental results showed that proposed method enabled robust control and reaction force estimation.