Research On Ultra Precision Coarse-fine Drive Positioning Technology Base On Disturbance Observer

With the development of ultra-precision processing equipment and manufacturing technology of large scale integration, there are more and more great demand of the positioning system performance with accuracy, speed and acceleration. Coarse/fine dual-drive can satisfy the large travel range and high precision at the same time, which is difficult to traditional driving method.Coarse and fine stage simultaneous motion is an efficient strategy of coarse/fine dual-drive, and is able to achieve continuous precision tracking positioning. However the control is relative complicated, and need high dynamic characteristics of coarse and fine stage. Especially in the case of high acceleration, the interaction force between coarse and fine stage seriously affect the positioning accuracy. When coarse/fine dual-drive system do continuous step action, the relative displacement between coarse and fine stage most likely cause the move of fine stage exceed it's travel range and affect the stability of it.In order to suppress this reaction disturbance, the purpose of this subject is to improve the dynamic characteristics of coarse drive using the combination of Disturbance Observer and PI controller in coarse drive servo system, and reduce the impact of interaction force disturbance on the system.Based on deep analysis of the basic principle and form of Disturbance Observer, this paper point out that the design points of Disturbance Observer are Q filter and disturbance collection. Q filter can filter out the sampling error, also offset the phase advance of reconstruction model, and it's design is fulfilled through a comprehensive consideration of the stability and the disturbance rejection ability of Disturbance Observer. Sampling the current and speed can get the equivalent amount of disturbance, this subject was designed and implemented over current over sampling and speed measurement with MT method, to improve the accuracy of current and speed of collection, thereby enhancing the positioning accuracy of the three closed-loop system and the observed disturbance capacity of Disturbance Observer.This subject has simulated Disturbance Observer in coarse/fine dual-drive system based on Matlab/simulink, and experiment in coarse/fine dual-drive stage. The results are that linear motor positioning noise is reduced by 0.3μm, and jitter of linear motor is reduced by 1.1μm. It contains that bringing Disturbance Observer in linear motor drive servo system can improve the positioning accuracy and the disturbance rejection ability, and it's important to improve the dynamic characteristics of coarse/fine dual-drive system.