Chord error constraint based integrated control strategy for contour error compensation

Abstract

As the traditional cross-coupling control method cannot meet the requirements for tracking accuracy and contour control accuracy in large curvature positions, an integrated control strategy of cross-coupling contour error compensation based on chord error constraint, which consists of a cross-coupling controller and an improved position error compensator, is proposed. To reduce the contour error, a PI-type cross-coupling controller is designed, with its stability being analyzed by using the contour error transfer function. Moreover, a feed rate regulator based on the chord error constraint is proposed, which performs speed planning with the maximum feed rate allowed by the large curvature position as the constraint condition, so as to meet the requirements of large curvature positions for the chord error. Besides, an improved position error compensation method is further presented by combining the feed rate regulator with the position error compensator, which improves the tracking accuracy via the advance compensation of tracking error. The biaxial experimental results of non-uniform rational B-splines curves indicate that the proposed integrated control strategy can significantly improve the tracking and contour control accuracy in biaxial contour following tasks.

Keywords

cross-coupling controller / contour error / tracking error / position error compensator / feed rate regulator

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Acknowledgements

This work is supported by the National Science and Technology Major Project of China (Grant No. 2015ZX04005006), the Science and Technology Major Project of Zhongshan City, China (Grant Nos. 2016F2FC0006 and 2018A10018).

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2020 Higher Education Press