Research On Multi-parameter Control And Trajectory Accuracy Of Two-dimensional Precision Aerostatic Bearing Motion Stage

Precision aerostatic bearing motion stage is a complex kinematics system, which has characteristic of high precision, high speed,high acceleration etc. This system adopts two key technologies:the linear drive and aerostatic guideway technology,which significantly improves the kinematecs performance of precision motion stage. Nevertheless,its performance is still affected by electromechanical characteristics of the linear drive, mechanical characteristics of the aerostatic slide and load disturbance.Two-dimensional precision aerostatic bearing motion stage provides an experimental platform for researching the structure and advanced control technology of NC machine. In order to improve the running performance of precision aerostatic bearing motion stage,the factors that affect the running performance are analyzed. The system stability and trajectory accuracy are important standards to measure the performance of precision aerostatic bearing motion stage.For improving the trajectory accuracy of two-dimensional precision aerostatic bearing motion stage,the control performance and trajectory accuracy were studied in terms of simulation and experiment in this paper. The main research contents are as follows:1、The structure characteristics of two-dimensional precision aerostatic bearing motion stage were analyzed, and a three closed loop control model of two-axis (the X axis and Y axis) linear motor was established,which includes current loop controller,velocity loop controller and position loop controller.Mathematical model and open-loop transfer function for each loop were derived. The system stability and characteristics of frequency domains were analyzed by MATLAB simulation,the result indicated that phase margin γ≥60° and magnitude margin Kg≥10db.which are good enough to meet the stability requirements of the engineering control.2、According to the load condition of two-dimensional precision aerostatic bearing motion stage, this paper analyzed the effects of different loads and PID parameters on the step response characteristics,A model of servo control system with speed feedforward and acceleration feedforward established. And the effects of feedforward compensation on the slope response of servo system analyzed.Based on the software PMAC Tuning Pro2 and PMAC Plot Pro2,Analyses were conducted on the effects of feedforward parameters on kinematic characteristics under different load conditions.3、Based on PMAC Tuning Pro2, the PID parameters and feedforward parameters were tuned. And we got a suitable range of parameters,so that we could prepare for measurement of trajectory accuracy of aerostatic bearing motion stage by experiment in the next step.4、Laser interferometer was used to measure the positioning accuracy and repeatability of the X axis of aerostatic bearing motion stage under different loads, And the correctness of the range setting of the speed feedforward gain parameter and the acceleration feed forward gain parameter is verified Furthermore, the relationship between the positioning precision of single axis and arc trajectory accuracy of two axes coordinated simultaneously were analyzed Finally,the influence of speed feedforward parameter and acceleration feedforward parameter on arc trajectory error of two axes coordinated simultaneously was studied,and the trajectory accuracy by setting the parameters is improved.