Research Of Controlling Unit For Piezoelectric Oscillating Mirror

In order to achieve the coaxial beam of different wavelengths of laser beam,each laser is equipped with two-dimensional piezoelectric oscillating mirrors to bear combined mirror.Piezoelectric ceramic has the advantages of small structure size and high control precision,and is widely used in micro positioning.However,due to piezoelectric ceramics with hysteresis and creep and some other non-linear characteristics,so as to increase the difficulty of the precise control of piezoelectric ceramics or even it makes the system out of control seriously.By studying the hysteresis model and the control algorithm of the piezoelectric oscillating mirror,the precise control of the oscillating mirror can be realized,so as to meet the requirements of the control system.In the project requirements,the maximum range of the piezoelectric oscillating mirror deflecting around the two perpendicular axes is ±1mrad,positioning accuracy must be within 5μrad.In this paper,the nonlinear characteristics of piezoelectric ceramics,such as hysteresis,creep and temperature characteristics,are studied theoretically,and the microscopic polarization mechanism of piezoelectric ceramics is analyzed.The mechanical structure of the piezoelectric oscillating table,including the internal displacement amplification and precise deflection mechanism,the electrical connection structure of the piezoelectric oscillating table,and the signal acquisition sensor are analyzed theoretically.The design principle of each circuit module in the drive control system is described,including the control module,the drive module and the detection module.The control module includes main control chip DSP,serial-parallel conversion interface FPGA,digital-analog conversion chip D/A and A/D and theirs peripheral circuit.And the voltage signal outputted by the control module is amplified by the high-voltage power operational amplifier to drive the rotation of the oscillating table.The detection module adopts a two-stage operational amplification structure to amplify and feedback the micro-deformation signal of the piezoelectric ceramic collected by the sensor to the control module.Then the linearity,output stability and zero repeatability of the drive control system hardware circuit are tested.The PI hysteresis model and parameter identification are established for the piezoelectric oscillating table by designing the piezoelectric oscillating mirror control driving hardware platform.The PI hysteresis inverse model and its parameters are solved and the feedforward controller is designed to control the piezoelectric ceramic actuator.Then through the introduction of PID feedback loop can achieve compound precise control for the piezoelectric oscillating mirror to further improve the control accuracy.Experimental results show that the maximum positioning error of compound controlling for the piezoelectric oscillating table is 2.2μrad,in line with system requirements.The research work in this paper is helpful to realize the precise control of the piezoelectric ceramic in the oscillating mirror,and it has a certain theoretical and practical value for the wide application of the two-dimensional piezoelectric oscillating mirrors.