Hysteresis Nonlinearity Modeling And Control Research Of Piezoelectric Actuator Based On Hammerstein Model

With the development of micro and nano manufacturing technology,the strict control accuracy is demanded in the fields,such as biological,microelectronics,MEMS manufacturing,and so on.Piezoelectric actuators are extensively used in precision applications due to their fast response,high control accuracy and high reliability.However,piezoelectric ceramics are inherently hysteretic and exhibit non-linear properties such as multiple mapping and rate-dependent.The hysteresis characteristic may dramatically affect the precise control performance,lead to undesirable oscillations in the system,and even destabilize the system.Therefore,one needs to first obtain an accurate hysteresis model of the piezoelectric actuator,and then design a controller with good performance to eliminate the effects of hysteresis.This thesis focuses on corresponding research on the modelling,identification and control of piezoelectric actuators.The content of its research is valuable for the development of micro and nanotechnology fields.The main research contents are summarized as follows:(1)A piezoelectric hysteresis model based on a tangent butterfly function is proposed.First,the proposed static hysteresis model is directly described in terms of butterfly function.The proposed butterfly hyperbolic tangent function carries the memories of turning points and can accurately describe the slope transformation of hysteresis curve.The necessary conditions for the hysteresis model,i.e.,wiping out and congruency properties of the proposed model are proved theoretically and experimentally.Then,the static hysteresis model with memory properties and a dynamic model are cascaded to form a Hammerstein system to descript rate-dependent hysteresis.(2)A decoupling identification method for the Hammerstein system model of piezoelectric actuators based on an extended state observer is proposed.The Hammerstein system is composed of a non-linear part and a linear dynamic part,and the coupling of the two parts causes difficulties in the identification of the model parameters.Therefore,this thesis proposes a method to decouple the linear and non-linear parts of Hammerstein by combining the performance of an extended state observer.Finally,it is demonstrated through comparative experiments that the proposed hysteresis model parameters identified by the proposed decoupling method can adequately describe the rate-dependent hysteresis characteristics.The effectiveness of the modelling and identification method techniques is verified.(3)An adaptive feedforward-feedback composite controller with inverse hysteresis compensation is designed.First,based on the constructed piezoelectric actuator model,a feed-forward hysteresis inverse compensation scheme is proposed Therefore,in order to better achieve precision motion control,a feedforward-feedback composite control scheme is introduced to reduce errors.Where the feedback controller is a adaptive controller based on backstepping recursion,treating hysteresis,creep,compensation error and other such disturbances as an unknown but bounded disturbance signal.Experiments were conducted to verify the effectiveness of the proposed control schemes.