Hysteresis Modeling And Adaptive Control Method Of Piezoceramic Micro-positioning Platform

With the rapid development of ultra-precision machining,micro-driving and micro-positioning,the requirements for high-precision control technology are getting higher.The piezoceramic micro-positioning platform which has the advantages of high positioning accuracy,fast response and large output force is widely applied in the fields of precision manufacturing,bioengineering and microelectronics.Hence,the improvement in terms of performance and accuracy of the piezoceramic micro-positioning platform has become an urgent problem needs to be solved in micro-nano positioning and control applications.Due to its inherent hysteresis nonlinearity characteristics,the positioning accuracy of piezoceramic micro-positioning platform is inevitably decreased and even causing the oscillation easily to occur in the actual positioning process.Therefore,eliminating the hysteresis nonlinearity in piezoceramic micro-positioning platform is a severe task in practical applications.This paper first introduced the structural composition and working principle of the piezoceramic micro-positioning platform,and then summarized both the modeling and control methods for hysteresis nonlinearity existed in the piezoceramic micro-positioning platform.In order to accurately describe the hysteresis nonlinearity characteristics of the platform,this paper mainly studied from two aspects.First,the rate-dependent Bouc-Wen model was established to accurately describe and predict the hysteresis nonlinearity of the piezoceramic micro-positioning platform.Then,effective controllers were designed to suppress the influence of the hysteresis nonlinearity characteristics on the positioning accuracy during the positioning control process.The traditional Bouc-Wen model had the insufficiency of capturing the rate-dependent hysteresis nonlinearity of the platform.In this paper,the Bouc-Wen model was improved by cascading the ARX function(i.e.rate-dependent Bouc-Wen model)to describe the above property.The parameters of the static nonlinear part and linear dynamic part of the rate-dependent Bouc-Wen model were identified by two-population differential evolution algorithm based on cross mutation strategy and recursive least squares method,respectively.Experimental results proved the effectiveness of the rate-dependent Bouc-Wen model.To reduce and eliminate the influence of hysteresis nonlinearity on the positioning accuracy of the piezoceramic micro-positioning platform,this paper firstly identified the inverse Bouc-Wen model and used it as an inverse compensation feedforward controller to realize inverse compensation control.The availability of the control system was confirmed under different reference frequencies of sine waves and triangular waves.The experimental results showed that the inverse compensation feedforward control could effectively compensate the hysteresis nonlinearity of the platform.However,it is difficult to determine the parameters of hysteresis model.To avoid this complexity and uncertainty,the model reference adaptive control method based on inverse compensation was designed to further improve the positioning accuracy,and the stability of the system was proved by Lyapunov function.Experiments showed that the control performance in positioning accuracy of adaptive control method outperformed that of feedforward control.In order to further improve the positioning accuracy and more effectively suppress the influence of inherent hysteresis nonlinearity on the piezoceramic micro-positioning platform,this paper proposed an inverse compensation hybrid adaptive control strategy with unmodeled dynamics considering the modeling uncertainty of the system.Firstly,the piezoceramic micro-positioning platform was compensated by the inverse compensation controller,and by this simplification,it could be described by dynamic linear part and unmodeled dynamics.Then the hybrid adaptive controller was designed to further compensate the hysteresis nonlinearity of the piezoceramic micro-positioning platform.Subsequently,the tracking experiments under different reference displacement signals were conducted to prove the validity of the controller.It could be seen that the inverse compensation hybrid adaptive control strategy with unmodeled dynamics proposed in this paper could effectively eliminate the inherent hysteresis nonlinearity in the piezoceramic micro-positioning platform and had the prominent capacity to positioning precisely.