| With the deepening of researchers’ exploration in the field of micro-nano manufacturing,the research on micro-nano manufacturing and positioning technology plays an important role in the development of large-scale integrated circuits,chips,microelectronic technology and other fields.Piezoelectric ceramic actuators are widely used in the micro-nano field because of their advantages of high resolution,high bandwidth,small size,etc.However,their own nonlinear characteristics will cause serious accuracy problems for micro-nano operations.Therefore,the Hysteresis characteristic of piezoelectric actuator is studied in this paper.At the same time,the piezoelectric driven micro-nano positioning stage is the most widely used positioning device in micro-nano positioning technology.In order to make the stage work with higher positioning accuracy,this paper also studies the control problems of the micro-nano positioning stage system.The main contents of this paper are as follows:(1)The hysteresis characteristics of piezoelectric actuators are analyzed.First,an improved PI model is established to describe the hysteresis characteristics of the piezoelectric actuator.The experimental results show that the model can only describe the asymmetric hysteresis characteristics,but cannot describe the rate dependent hysteresis characteristics.Therefore,the Hammerstein model which can describe the dynamic characteristics of the system is established,and a modeling method that uses a fractional transfer function to represent the dynamic link of the Hammerstein model is proposed.At the same time,an improved particle swarm optimization algorithm with variable weights is used to identify the parameters of the fractional order transfer function.The experimental results show that the improved model can not only describe the asymmetric hysteresis characteristics of piezoelectric actuator,but also describe its rate dependence,which improves the modeling accuracy.(2)In order to reduce the adverse effect of hysteresis on the piezoelectric micro-nano positioning stage,the design of the system controller is studied based on the established micronano positioning stage model.First,the Fractional Order PID controller is designed,and the cuckoo algorithm is used to optimize its parameters to improve the control accuracy of the control system.Secondly,in order to realize the adaptive control of the micro-nano positioning stage,the fuzzy theory is introduced into the Fractional Order PID controller,the membership function and fuzzy rules are established,and the fuzzy Fractional Order PID controller is designed,which further improves the control accuracy and adaptability of the system.Finally,for the Fractional Order PID controller,two discretization methods,the finite memory digital realization method and the Oustaloup filter approximation method,are analyzed for practical development.(3)Designed and built a micro-nano positioning stage control system,which is mainly composed of two parts:the upper computer and the lower computer.The host computer is developed with visual studio and displays in the form of human-computer interaction interface.The host computer can complete the functions of sending instructions,serial port configuration,receiving data and displaying graphics.The lower computer is realized by STM32F4 development board,and communicates with the upper computer through serial port.By using the D/A conversion module and timer interrupt module in STM32F4 development board,the functions of signal generation,data transmission and data acquisition can be realized.At the same time,the control system controller of micro-nano positioning stage is also implemented in the lower computer.(4)In view of the fact that it is easier to adjust the parameters with the finite memory digital implementation method,the approximate method is used to discretize the Fractional Order PID.The designed Fractional Order PID control algorithm is integrated into the micro positioning stage control system,and the micro-nano positioning stage closed-loop control system is built.The experimental results show that the micro motion stage control system can realize the functions of serial port detection and different kinds of driving signal generation and so on.At the same time,the designed digital fractional order PID controller can accurately track the micro-nano positioning stage motion under the excitation of different types,different frequencies and different amplitudes of driving signals.Moreover,the micro-nano positioning stage can quickly return to the original state under the control of the controller after adding the interference signal into the system,which verifies the effectiveness of the designed closed-loop control system of the micro-nano positioning stage. |
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