机器人 2023, Vol. 45 Issue (1): 48-57 0

WANG Chongchong, YANG Guilin, CHEN Chinyin, XIN Qiang, SUN Xianbei, WANG Weijun. Speed Ripple Suppression Based on an Adaptive Disturbance Observer for Collaborative Robot Joint[J]. ROBOT, 2023, 45(1): 48-57.

1. 中国科学院宁波材料技术与工程研究所, 浙江 宁波 315201;
2. 中国科学院大学, 北京 100049

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.
Keywords: collaborative robot joint    double-stator motor    harmonic drive reducer    disturbance observer    adaptive algorithm

1 引言（Introduction）

2 基于双定子永磁力矩电机的关节集成设计（Integrated design of the joint based on a double-stator permanent magnet torque motor）

 图 1 双定子永磁同步电机样机的电流－力矩曲线 Fig.1 Torque-current curve of the double-stator permanent magnet synchronous motor prototype

 图 2 一体化关节模块 Fig.2 The integrated joint module
3 关节性能分析（Performance analysis on the joint）

3.1 关节开环响应特性分析

 图 3 驱动力矩到电机速度的频率响应曲线 Fig.3 Frequency-response curves from the drive torque to the motor velocity

 图 8 系统模型偏差以及DOB滤波器的幅频响应 Fig.8 Amplitude-frequency response curves of the system model error and filters in DOB

 \begin{align} &L =\min p\\ \rm{s.t.\; }\; &\sum\limits_{i=p}^5 {\sqrt{\hat{a}_{i}^{2} +\hat{b}_{i}^{2}}} \leqslant \tau_{1} \\ &\tau_{{\rm m, 1}} =\sum\limits_{i=5}^L {\hat{d}_{{\rm{rip}}, i}} \\ &\tau_{{\rm m, 2}} =\tau_{\rm m}^{*} -\tau_{{\rm m, 1}} \end{align} (6)

4.2 关节速度控制实验

 图 9 电机速度阶跃响应和速度稳态波动FFT分析 Fig.9 Motor speed step-response and FFT analysis on steady-state speed fluctuations

 图 10 关节低速跟踪性能 Fig.10 Low-speed tracking performance of the joint

5 结论（Conclusion）