Research On Surface Error Compensation Machining Technology Of Complicated Optical Mirrors Based On Fast Servo Tool

With the development of optoelectronic information technology,high-performance optical systems have put forward higher requirements on the surface accuracy of optical mirrors.However,because complex optical elements are prone to clamping errors and cutting errors during processing,the processing accuracy of complex optical elements is limited.Fast servo tool systems based on piezoelectric actuators are widely used in compensation processing of high-precision and complex optical components.The higher the working frequency and tracking accuracy of the fast servo tool system,the more complex the error compensation processing of complex optical components can be achieved.However,in actual use,due to the natural frequency of the mechanical structure,the hysteresis effect of the piezoelectric actuator,and the phase delay of the control system,the high-frequency movement of the fast servo tool system based on the piezoelectric actuator often has a large tracking error.In order to improve the error compensation accuracy of complex optical components,this thesis studies a fast servo tool system with high frequency response and low tracking error.Firstly,a high bandwidth fast servo tool system is built by analyzing the key technologies affecting the high frequency motion of the fast servo tool system.Then a composite control algorithm is proposed to improve the tracking accuracy of the fast servo tool system.Finally,a process flow for error compensation of complex optical components is proposed,including the compensation of clamping error and cutting error.The main research contents and results are summarized as follows:(1)Fast servo tool system performance analysis and system modelingAccording to the working principle of the fast servo tool,the performance of key components is analyzed and designed,and the key factors affecting the drive performance of the system are analyzed from the natural frequency of the system,real-time tracking,and the load curve of the power amplifier.The performance evaluation of the key components of the servo tool system.The experimental results show that the system’s natural frequency,hinge stiffness,driver performance and other key component performance indicators all meet the high-frequency response motion requirements of the fast servo tool system with a working frequency of greater than1000 Hz.Finally,the actual model of the fast tool servo system is established through the frequency sweep experiment and system identification,which lays the foundation for the research of the servo control algorithm.(2)Research on control algorithm of fast servo tool systemIn order to improve the tracking performance of the fast servo tool,the composite control algorithm of the fast servo tool system is studied for the hysteresis effect of the piezoelectric actuator and the high frequency phase delay and amplitude attenuation of the fast tool system.First study the hysteresis modeling mechanism of piezoelectric actuators,and establish the hysteresis inverse model of piezoelectric actuators;then combine the PID control algorithm with the established hysteresis inverse model to overcome the hysteresis effect of piezoelectric actuators;finally design a zero-phase controller to reduce The phase error and amplitude attenuation of the system.Through comparative experiments comparing different control algorithms,compared with the traditional PID control algorithm,the proposed composite control algorithm has significantly improved tracking accuracy for input signals in various frequency bands.Experimental results show that the tracking error of the system is less than 10% under the operating frequency of 0-1000 Hz.(3)Error compensation processing experiment based on fast servo tool systemIn order to improve the machining accuracy of complex optical components,aiming at the clamping error and cutting error in the ultra-precision turning process,the error compensation strategy for complex optical components based on FTS is studied.First,the clamping is obtained by analyzing the change process of the mirror surface topography.Error and cutting error compensation strategy.Through the combination of real-time monitoring and theoretical simulation,the elastic deformation of the weak-rigidity mirror is accurately extracted to realize the compensation of the clamping error,and the compensation of the cutting error is realized through iterative machining.Finally,use the built fast servo tool system to process a typical complex optical element twice.The final PV value of the machined surface is 0.7μm,which effectively solves the clamping error(PV=5.2μm)and cutting error(PV=1.6μm)arising from the machining process of complex optical components,and verifies the performance of the fast servo tool and the feasibility of the error compensation process.