Identification and compensation of hysteretic dynamics of piezoelectric actuators for accurate and fast scanning

Abstract

The scanning and tracking accuracy of piezoelectric mechanisms over broadband frequencies are limited due to inherent dynamic hysteresis. This phenomenon has been a key bottleneck in the use of piezoelectric mechanisms in fast precision scanning applications. This paper presents a systemic model identification and composite control strategy without hysteresis measurement for such applications. First, least squares estimation using harmonic signals is applied to achieve the Preisach density function. Next, the hysteresis output is estimated using the identified Preisach model. Then, the non-hysteretic electric and vibration dynamics are identified. The discrete composite control strategy is proposed with a feedforward-feedback structure. The feedforward controller is the primary component designed for the performance. The secondary PI feedback controller is used to suppress the offset and disturbance for robustness. Finally, the identification and composite control strategy is implemented with a dSPACE 1104 board for a real piezo setup. The experimental results show that adequate scanning performance can be sustained at frequencies higher than the first resonant frequency.