Speed Ripple Suppression Based on an Adaptive Disturbance Observer for Collaborative Robot Joint
WANG Chongchong1, YANG Guilin1, CHEN Chinyin1, XIN Qiang1,2, SUN Xianbei1, WANG Weijun1
1. Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：Aiming at the requirements of collaborative robots for high load-to-weight ratio and high-precision speed control, a joint module is designed, which integrates a double-stator permanent magnet synchronous motor and a harmonic drive reducer. The characteristics of the double-stator structure are utilized to increase the torque density of the motor. In order to improve the control accuracy of joint speed, an equivalent input torque disturbance to the joint system is used to describe the lumped effect of all factors acting on the joint speed ripple, including the low-frequency nonlinearities such as friction, the motor torque ripple, and the transmission error of the harmonic drive reducer, and the joint speed ripple is suppressed by compensating this equivalent input torque disturbance. In order to improve the disturbance estimation precision, a method is proposed which utilizes double disturbance observers and an adaptive algorithm. A performance test on the double-stator motor demonstrates that the torque density of the double-stator motor is increased by 11% compared with the single-stator structure. The joint speed control experiment verifies that compared with the conventional proportional-integral (PI) speed controller, the root mean square (RMS) of the joint low-speed steady-state fluctuation errors is reduced by 40%~60%, while the RMS of medium-speed and high-speed steady-state fluctuation errors is reduced by about 30%~40% with the proposed method, and the speed control accuracy is improved.
[1] Albu Schaffer A, Haddadin S, Ott C, et al. The DLR lightweight robot:Design and control concepts for robots in human environments[J]. Industrial Robot, 2007, 34(5):376-385. [2] Burger R, Haddadin S, Plank G, et al. The driver concept for the DLR lightweight robot III[C]//IEEE/RSJ International Conference on Intelligent Robots and Systems. Piscataway, USA:IEEE, 2010:5453-5459. [3] Mikerov A G. Brushless DC torque motors quality level indexes for servo drive applications[C]//IEEE EUROCON. Piscataway, USA:IEEE, 2009:827-834. [4] Chai F, Cui S M, Chen S K. Performance analysis of doublestator starter generator for the hybrid electric vehicle[J]. IEEE Transactions on Magnetics, 2005, 41(1):484-487. [5] Niu S X, Chau K T, Jiang J Z, et al. Design and control of a new double-stator cup-rotor permanent-magnet machine for wind power generation[J]. IEEE Transactions on Magnetics, 2007, 43(6):2501-2503. [6] Niu S X, Ho S L, Fu W N. A novel direct-drive dual-structure permanent magnet machine[J]. IEEE Transactions on Magnetics, 2010, 46(6):2036-2039. [7] 王雅玲.电动汽车用双定子永磁无刷电机研究[D].济南:山东大学, 2014. Wang Y L. Research of dual-stator permanent magnet brushless motors used in electric vehicles[D]. Jinan:Shandong University, 2014. [8] Cheng M, Han P. A dual-stator brushless doubly-fed induction motor for EV/HEV applications[C]//International Conference on Intelligent Green Building and Smart Grid. Piscataway, USA:IEEE, 2014. DOI:10.1109/IGBSG.2014.6835258. [9] Mannen T, Fukasawa I, Fujita H, et al. A new control method of suppressing the DC-capacitor voltage ripple caused by thirdorder harmonic compensation in three-phase active power filters[J]. Electrical Engineering in Japan, 2018, 202(2):54-62. [10] Mannen T, Fujita H. Dead time compensation method based on current ripple estimation[C]//IEEE Energy Conversion Congress and Exposition. Piscataway, USA:IEEE, 2013:775-782. [11] Lam B H, Panda S K, Xu J X. Reduction of periodic speed ripples in PM synchronous motors using iterative learning control[C]//26th Annual Conference of the IEEE Industrial Electronics Society. Piscataway, USA:IEEE, 2000:1406-1411. [12] Mattavelli P, Tubiana L, Zigliotto M. Torque-ripple reduction in PM synchronous motor drives using repetitive current control[J]. IEEE Transactions on Power Electronics, 2005, 20(6):1423-1431. [13] Qian W Z, Panda S K, Xu J-X. Torque ripple minimization in PM synchronous motors using iterative learning control[J]. IEEE Transactions on Power Electronics, 2004, 19(2):272-279. [14] 高云雷,王玉彬,黄瑛.基于自抗扰迭代学习控制的双定子磁场调制电机转矩脉动抑制策略[J].电机与控制应用, 2021, 48(6):10-16. Gao Y L, Wang Y B, Huang Y. Torque ripple suppression strategy of field-modulation double-stator motor based on ILCADRC[J]. Electric Machines & Control Application, 2021, 48(6):10-16. [15] Petrovic V, Ortega R, Stankovic A M, et al. Design and implementation of an adaptive controller for torque ripple minimization in PM synchronous motors[J]. IEEE Transactions on Power Electronics, 2000, 15(5):871-880. [16] Ahn H-S, Chen Y Q, Dou H F. State-periodic adaptive compensation of cogging and Coulomb friction in permanent-magnet linear motors[J]. IEEE Transactions on Magnetics, 2005, 41(1):90-98. [17] Luo Y, Chen Y Q, Pi Y G. Cogging effect minimization in PMSM position servo system using dual high-order periodic adaptive learning compensation[J]. ISA Transactions, 2010, 49(4):479-488. [18] Han C H, Wang C C, Tomizuka M. Suppression of vibration due to transmission error of harmonic drives using peak filter with acceleration feedback[C]//10th IEEE International Workshop on Advanced Motion Control. Piscataway, USA:IEEE, 2008:182-187. [19] Iwasaki M, Yamamoto M, Hirai H, et al. Modeling and compensation for angular transmission error of harmonic drive gearings in high precision positioning[C]//IEEE/ASME International Conference on Advanced Intelligent Mechatronics. Piscataway, USA:IEEE, 2009:662-667. [20] Sasaki K, Okitsu Y, Yajima T, et al. Method for compensating for angular transmission error of wave gear device:US008296089B2[P]. 2012-10-23. [21] Lu Y S, Lin S-M. Disturbance-observer-based adaptive feedforward cancellation of torque ripples in harmonic drive systems[J]. Electrical Engineering, 2007, 90(2):95-106. [22] Lu Y S, Lin S-M, Hauschild M, et al. A torque-ripple compensation scheme for harmonic drive systems[J]. Electrical Engineering, 2013, 95(4):357-365. [23] Kong K, Tomizuka M. Nominal model manipulation for enhancement of stability robustness for disturbance observerbased control systems[J]. International Journal of Control, Automation, and Systems, 2013, 11(1):12-20.
