Cross-coupled control based on real-time Double Circle contour error estimation for biaxial motion system

Li Bo,Wang Peng,Wang Taiyong

doi:10.1177/0020294021993830

Abstract

In contour machining, contour error is a major factor affecting machining quality. In order to improve the performance of contour following, many control techniques based on real-time contour error estimation have been developed. In this paper, a Double Circle contour error estimation method is proposed. First, based on the kinematic information of the reference point on the command trajectory, five interpolation points closest to the actual point are obtained. Then the approximate contour error is obtained by employing the Double Circle approximation method. Compared with the common contour error approximation methods, the proposed method can achieve high precision approximation. In addition, according to the proposed contour error approximation method, the cross-coupled control strategy is improved. Experiments prove the effectiveness of the proposed estimation method and control strategy.

Highlights

Attaining high machining accuracy is a key aspect of CNC (Computerized Numerical Control) machining
Since the contour error of long linear trajectory and long circular trajectory can be accurately calculated and decoupled to each axis for compensation,[16] this paper focuses on the contour error approximation and compensation for continuous free-form trajectory
A Double Circle contour error estimation method is proposed based on the Three-Point Circle method

Summary

Introduction

Attaining high machining accuracy is a key aspect of CNC (Computerized Numerical Control) machining. In the approaches proposed in Zhu et al.,[18] Hu et al.,[19] Wang et al.,[20] Zhao et al.,[21] and Shi and Lou,[22] real-time contour error estimation based on Taylor expansion approximation employed a point-to-curve distance function to calculate directly. As the actual position moves, the Three-Point Circle changes as the nearest interpolation point changes This results in a mutation of the estimated contour error. The interpolation points are cached in the buffer; the relationship between the sampling period and the interpolation period is confirmed; the closest interpolation point in the buffer is calculated according to the actual point position of the current sampling period; the four interpolation points are obtained according to the approximate model of Double Circle estimation, and the approximate contour error is calculated; the gains of cross-coupled controller are calculated. If the adjustment is needed, the adjusted Cc can be use as the initial value in Step 3

Experimental setup

Findings

Conclusion