Compensation of hysteresis in piezoceramic actuators and control of nanopositioning system.

摘要

In this thesis, a recursive form of the classical Preisach model for voltage-to-displacement dynamics in piezoceramic stack actuators has been developed for applications where the load is relatively small and the range of frequencies of the voltage excitation is limited. The limitations of the classical Preisach model in modeling piezoceramic stack actuators were also experimentally assessed. It was shown that the classical Preisach model accuracy deteriorates as the load applied to the actuator increases or the voltage signal applied to the actuator contains frequencies that are not close to the frequencies contained in the voltage signal used to generate the database of first order reversal functions used for the implementation of the classical Preisach model. In order to account for the rate-dependent nature of the voltage-to-displacement dynamics in piezoceramic stack actuators, a novel model for dynamic hysteresis was also developed by explicitly introducing the rate of change of the voltage signal in the voltage-to-displacement model. The model for dynamic hysteresis is shown through experiments to offer high accuracy under voltage excitations covering a wide frequency band. A two-input hybrid model based on neural networks is also developed to model dynamics in piezoceramic stack actuators when they are subject to persistently exciting load and voltage signals. The two-input model is also shown experimentally to offer good accuracy.; Two application cases are explored in this thesis: vibration suppression and tracking control. For the vibration suppression case, a hysteresis compensation technique based on the classical Preisach model was used in conjunction with an LTI controller to implement vibration suppression of a cantilever beam. Experimental results show that a “linearized” piezoceramic actuator is more effective in vibration suppression than a regular piezoceramic actuator as it seems that hysteresis acts as a nonlinear filter and reduces the effectiveness on the vibration controller. For the tracking control application, an inverse dynamic hysteresis model was developed and implemented to develop “linearized” piezoceramic actuators. A closed-loop controller that includes a PID regulator and a feedforward hysteresis compensator based on the dynamic hysteresis model is developed and is shown experimentally to offer very high accuracy.