| The traditional micro-positioning platform mechanism such as sliding guide rail,ball screw,rolling guide and so on have the complex structure,inertia,slow response and poor stability which cannot meet the requirements of the micro-positioning platform,which including small size,large travel and so on.The Piezoelectric ceramic actuator has the characteristics of simple structure,small volume,large output force and high resolution.At the same time,the flexible hinge has the characteristics of no mechanical friction,compact structure and high sensitivity and so on.Therefore,the micro-positioning platform composed by PZT actuator and flexible hinge is widely used in engineering practice with its advantages such as simple structure,large stroke,and high resolution and so on.However the piezoelectric ceramic actuator is a capacitive load which seriously affects the dynamic response of the micro-positioning system.At the same time,the hysteresis and creep properties of the piezoelectric ceramics make the positioning accuracy of the micro-positioning system decrease,and there is steady-state error.In this thesis,piezoelectric ceramic micro-positioning system is designed according to the characteristics of piezoelectric ceramics,including driving power,flexible hinge amplification mechanism and control algorithm.In the aspect of driving power supply,the driving power of piezoelectric ceramics is analyzed and compared.The DC amplifier driving scheme with precision operational amplifier OP07 and high voltage amplifier PA92 is proposed.The stability of the driving power is guaranteed by zero phase advance compensation method.Finally,the drive power is simulated by Multisim,and the simulation results show that the proposed scheme is feasible.In the flexible hinge amplification mechanism,the stiffness analysis of the straight flexible hinge is done,the two lever-type amplification mechanism is designed with straight flexible hinge,and the magnification is obtained from the static analysis.The dynamic model of the amplification mechanism is established,and the formula of its natural frequency is obtained.Finally the static simulation of flexible hinge amplifier is done by ANSYS,which verified that the theoretical calculation of the magnification is correct.The mathematical model of the micro-positioning system includes the driving power supply,the piezoelectric ceramic hysteresis,the flexible hinge amplifier and so on,and the piezoelectric ceramic's hysteresis model is established by least squares polynomial fitting.The fuzzy control algorithm of micro-positioning system is compiled by Lab VIEW,and the fuzzy closed-loop control simulation platform with feed-forward link of micro-positioning system is established and simulated by simulation control and simulation module.Among the feedforward link adopts the displacement-voltage linear inverse model of piezoelectric ceramics.The simulation results show that the nonlinear and dynamic characteristics of the micro-positioning system are improved by the fuzzy closed-loop control with the feed-forward link,which reduces the steady-state positioning error and improves the positioning accuracy.The simulation results verified the effectiveness of the control algorithm,which can be used as a reference in the practical application of micro-positioning system. |
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