Research On Control System Of Precision Air-bearing Turntable

Precision turntable is an integrated optical and mechanical equipment for precise positioning of objects.Precision turntable is widely used in various precision processing and testing systems.In precision machining and detection system,precision turntable is an essential equipment,its performance directly affects the quality of machining and detection.Precision air-bearing turntable is a kind of precision turntable with air-bearing.The positioning accuracy and tracking accuracy of precision air-bearing turntable are easily affected by nonlinear friction,rotor micro vibration,motor harmonic torque and other disturbances.The motion accuracy of precision air-bearing turntable limits its further application in precision machining detection system.Therefore,it is of great value to study the control system of precision air-bearing turntable and improve the motion accuracy of turntable.In order to realize the low-speed accurate control of precision air-bearing turntable and improve the positioning accuracy and dynamic response performance of turntable,the turntable control system is studied.The main contents of this thesis are as follows:(1)The overall scheme of control system for precision air-bearing turntable is designed.The technical specifications of the control system of precision air-bearing turntable are analyzed.The key components of the control system,such as precision air-bearing turntable,driving motor,angular position feedback device and control driver,are selected.The control system model is established,and the common control algorithms are analyzed according to the control system model.The overall scheme of the control system with vector control as motor control strategy and linear adaptive disturbance rejection control as turntable control strategy is established.(2)The research on the control strategy of turntable based on the linear adaptive disturbance rejection control is carried out.The structure and principle of linear disturbance rejection control are studied.The observation error of linear extended state observer is analyzed.An observer bandwidth adjustment method is proposed to improve the dynamic performance of the turntable step response.The linear adaptive disturbance rejection control is designed and the simulation of turntable control is carried out in Matlab/Simulink.The simulation results show that the linear adaptive disturbance rejection control can realize the precise position control of the turntable and has good disturbance rejection.The proposed observer bandwidth adjustment method can improve the dynamic performance of the turntable step response.(3)Experimental research was carried out.The experimental platform of precision air-bearing turntable control system was built.The control software was designed.The turntable control experiment were carried out.The experimental results show that the proposed observer bandwidth adjustment method reduces the overshoot of the turntable and improves the dynamic performance of the turntable step response;the positioning error of the turntable is ≤± 0.0007° and the tracking error is ≤± 0.0008° when the speed command is 1.2°/s.It meets the requirements of micro nano CT system for turntable.The turntable has been used in micro nano CT.