Sensorless positioning control using simple external circuit in piezo-actuated systems

This paper presents a sensorless positioning control approach for piezo-actuated systems, using a simple external circuit. To achieve high-precision positioning with a piezoelectric actuator, a feedback control system using a high-resolution position sensor in incorporated, to cancel nonlinearities and disturbances. However, sensorless control is desirable to reduce cost and space utilization in micro- and nano-positioning systems. In this study, a simple external circuit using a capacitor and resistances is used to indirectly estimate the displacement of the actuator. A position feedback controller is designed based on the estimated displacement signal. Vibration detection is achieved based on a self-sensing technique using a virtual bridge circuit, where a position estimation circuit is used. A minor feedback loop is designed to suppress the resonant vibration modes based on the detected signal. The proposed sensorless control approach was verified by conducting experiments using a commercial piezo-actuated stage system.