Research On Tracking Control Of Lorentz Force Type Fast Tool Servo System

Optical free-form surface parts are widely used in aerospace,military,power electronics,scientific research and civil fields because of their good working performance.The main way to achieve high precision,high efficiency and low cost of optical free-form surface is diamond ultra-precision turning technology.The core of this technology is Fast Tool Servo(FTS).In this thesis,the Lorentz force motor--Voice Coil Motor(VCM)is used as the actuator of FTS,tracking and restrain periodic problems by modern control methods with sliding mode and repetitive control.Its specific analysis are as follows:Firstly,a large number of reference in domestic and abroad are collected and consulted to the main driving ways of FTS,established the mathematical model of the voice coil motor,which drives FTS to operate,analyze the FTS relevant control strategies and describes the factors,which affecting the control accuracy of voice coil motor.Secondly,if run into cutting force disturbance in the operation of FTS,proxy-based sliding mode control is adopted.This is an extension of PID control and combines sliding mode control and PID control.A hypothetical virtual stroke position,which called proxy is added between the actual position and the desired position of VCM with PID controller.The proxy stroke position tracking the desired position by sliding mode controller,and the discontinuous symbolic function in proxy-based sliding mode control law is needed to convert to saturation function,with the purpose of improving the tracking accuracy and disturbance rejection.The effectiveness of the control strategy is verified by modeling,simulation and comparative analysis based on the theoretical control strategy designed by Matlab/Simulink.Finally,due to the operation of FTS,the tracking accuracy will be affected by the long troke and high frequency.In order to improve the tracking accuracy deeply,a super-twisting repetitive compensation PID control is used.This is a control strategy,which combines repetitive compensation PID control and super-twisting PID sliding mode control,which can action independently.The repetitive compensation PID control can improve the tracking accuracy with periodic signal.If encountered disturbance as given periodic sinusoidal signal or cutting force,adding the super-twisting PID sliding mode control on base of repetitive compensation PID control.Using PID controller to sliding mode surface,and design sliding mode control law according to Lyapunov function arrival condition.Super-twisting PID sliding mode control is a kind of continuous second-order sliding mode control with well restrain disturbance ability.Super-twisting repetitive compensation PID control has strong robustness and high tracking accuracy in long stroke and high frequency environment.The designed control strategy is modeled,simulated and compared in Matlab/Simulink to prove the feasibility of the control strategy.