Research on nonlinear friction compensation of harmonic drive in gimbal servo-system of DGCMG

In this paper, a high-accuracy motion control of a torque-controlled motor servo system with nonlinear friction compensation is presented. Friction always exists in the servo system and reduces its tracking accuracy. Thus, it is necessary to compensate for the friction effect. In this paper, a novel controller that combines robust adaptive control with friction compensation based on neural network observer is proposed. An improved LuGre friction model is applied into the friction compensation as it is known as a good model to express the nonlinear friction. A single hidden-layer network is utilized to observe the immeasurable friction state. Then, the robust adaptive controller is used to handle the parametric uncertainty, the parametric estimation error, friction compensation error, and other uncertainties. Lyapunov theory is utilized to analyze the stability of the closed-loop system. The experimental results demonstrate the effectiveness of the proposed algorithm.

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Torque Control in Harmonic Drives with Nonlinear Dynamic Friction Compensation

Journal of Robotics and Mechatronics ◽

10.20965/jrm.2004.p0388 ◽

2004 ◽

Vol 16 (4) ◽

pp. 388-396 ◽

Cited By ~ 8

Author(s):

Rached Dhaouadi ◽

Keyword(s):

Differential Equation ◽

Computer Simulation ◽

Torque Control ◽

Nonlinear Observer ◽

Position Tracking ◽

Friction Compensation ◽

Dynamic Friction ◽

Nonlinear Stiffness ◽

Nonlinear Friction ◽

Harmonic Drive

This paper proposes a nonlinear observer-based controller designed to compensate for friction in harmonic drives with hysteresis. Hysteresis in a harmonic drive is described by a nonlinear differential equation representing the combination of nonlinear stiffness and nonlinear friction. Nonmeasurable friction is derived using a nonlinear observer to provide asymptotic stability and position tracking. The performance of the proposed system is confirmed by computer simulation.

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Nonlinear Friction Compensation of a Flexible Robotic Joint with Harmonic Drive

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.868.39 ◽

2017 ◽

Vol 868 ◽

pp. 39-44

Author(s):

Peng Fei Zeng ◽

Ge Dong Jiang ◽

Chuang Zou ◽

Xian Zhang ◽

Cheng Xuan Xie

Keyword(s):

Control Strategies ◽

Industrial Robot ◽

Friction Compensation ◽

Nonlinear Friction ◽

Harmonic Drive ◽

Stribeck Effect ◽

Compensation Control ◽

Polynomial Fit ◽

Feedback Compensation ◽

Control Accuracy

To suppress the abrupt and unexpected turning velocity fluctuation of the industrial robot under the condition of trajectory tracking, a flexible robotic joint experimental setup with the harmonic drive was established. The measured friction with Stribeck effect and velocity were modeled by a simple polynomial fit method. Two friction compensation control strategies of feedforward and feedback were designed. The friction compensation experiments were carried out on the dSPACE system, the good restraint effect of fluctuation on the turning velocity was verified and the control accuracy of feedback compensation control strategy proved better.

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