Elasto-geometrical error modeling and compensation of a five-axis parallel machining robot |
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| Affiliation: | 1. Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin University, Tianjin 300072, China;2. Chair of Mechanics and Robotics, University of Duisburg-Essen, Duisburg 47057, Germany;3. School of Engineering, The University of Warwick, Coventry CV4 7AL, UK;1. Department of Mechanical Engineering, Institute of Manufacturing Engineering, Tsinghua University, Beijing 100084, China;2. Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA;3. Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipment and Control, Tsinghua University, Beijing 100084, China;1. Institute of Electromechanical Engineering, Beijing Information Science & Technology University, 12 Xiaoying East Road, Qinghe, Haidian District, Beijing, 100192, China;2. Key Laboratory of Modern Measurement & Control Technology, Ministry of Education, Beijing Information Science & Technology University NO.12 xiaoying East Road, Qinghe, Haidian DistrictBeijing100192China;3. National NC System Engineering Research Center, Huazhong University of Science & Technology, 1037 Luoyu Road, Wuhan 430074, China;1. Institute of Instrument Science and Technology, Department of Precision Instrument, Tsinghua University, Beijing 100084, China;2. State Key Laboratory of Tribology and Institute of Manufacturing Engineering, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;3. Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipment and Control, Beijing 100084, China |
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| Abstract: | Parallel manipulators have the potentials of high efficiency and high precision in the field of machining and manufacturing. However, accuracy improvement of the parallel manipulator is still an essential and challenging issue, encountering two important problems. Firstly, the ignorance of elastic deformation caused by gravity or deviations of static stiffness model restricts further improvement of accuracy. To solve this problem, an elasto-geometrical error modeling method is proposed. The comprehensive effects of structural errors, elastic deformation under gravity and compliance parameter errors on pose deviations are disclosed. On this basis, the identification equation of actual structural errors and compliance parameter errors can be established. Secondly, the ill-conditioned identification matrix and the identification equation with anisotropic residual error can lead to inaccurate identification results. To solve this problem, a weighted regularization method is proposed. The identification equation with isotropic residual error is built, and accurate identification can be realized with the regularization method. Based on the proposed methods, the error compensation experiment is conducted on the prototype of a five-axis parallel machining robot using a laser tracker. Experiment results show that the accuracy of the machining robot is significantly improved after compensation. An M1_160 test piece and an S-shaped test piece are machined and measured to further validate the effectiveness of the proposed methods. The elasto-geometrical error modeling method and the weighted regularization method can be applied to other parallel manipulators’ accuracy improvement. |
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| Keywords: | Elasto-geometrical error model Weighted regularization method Error compensation Parameter identification Five-axis parallel machining robot |
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