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Kinematic calibration of bracket type parallel posture alignment mechanism considering the gravity effect

Zhihao Wang (College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China)
Wenliang Chen (College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China)
Min Wang (College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China)
Qinghe Xu (College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China)
Can Huang (College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China)

Industrial Robot

ISSN: 0143-991x

Article publication date: 17 July 2019

Issue publication date: 21 August 2019

Abstract

Purpose

The purpose of this study is to improve the position and posture accuracy of posture alignment mechanism. The automatic drilling and riveting machine is an important equipment for aircraft assembly. The alignment accuracy of position and posture of the bracket type posture alignment mechanism has a great influence on the operation effect of the machine. Therefore, it is necessary to carry out the kinematic calibration.

Design/methodology/approach

Based on analysis of elastic deformation of the bracket and geometric errors of the posture alignment mechanism, an improved method of kinematic calibration was proposed. The position and posture errors of bracket caused by geometric errors were separated from those caused by gravity. The method of reduction of dimensions was applied to deal with the error coefficient matrix in error identification, and it did not change the coefficient of the error terms. The target position and its posture were corrected to improve the error compensation accuracy. Furthermore, numerical simulation and experimental verification were carried out.

Findings

The simulation and experimental results show that considering the influence of the elastic deformation of the bracket on the calibration effect, the error identification accuracy and compensation accuracy can be improved. The maximum value of position error is reduced from 5.33 mm to 1.60 × 10−1 mm and the maximum value of posture error is reduced from 1.07 × 10−3 rad to 6.02 × 10−4 rad, which is superior to the accuracy without considering the gravity factor.

Originality/value

This paper presents a calibration method considering the effects of geometric errors and gravity. By separating position and posture errors caused by different factors and correcting the target position and its posture, the results of the calibration method are greatly improved. The proposed method might be applied to any parallel mechanism based on the positioner.

Keywords

Acknowledgements

This research is supported by National Natural Science Foundation of China (Grant No. 51605221). The authors would like to acknowledge the editors and the reviewers for their insightful comments.

Citation

Wang, Z., Chen, W., Wang, M., Xu, Q. and Huang, C. (2019), "Kinematic calibration of bracket type parallel posture alignment mechanism considering the gravity effect", Industrial Robot, Vol. 46 No. 5, pp. 581-598. https://doi.org/10.1108/IR-09-2018-0183

Publisher

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Emerald Publishing Limited

Copyright © 2019, Emerald Publishing Limited