An Adaptive Controller Design for Flexible-joint Electrically-driven Robots With Consideration of Time-Varying Uncertainties

In the Constant Turning Force Adaptive Control system, the cutting process is nonlinear time-varying; besides, the stability cannot be assured by classical control theory since the cutting tools usually cut a workpiece at various cutting depths. In this paper, based on the small gain theorem, we propose a new method to design a PI controller with high robustness to stabilize the force feedback control system against the nonlinear time-varying gain perturbation in the cutting process. A simple design procedure will be presented and several illustrative simulation results are given. The practical experimental results of a converted lathe with the PI controller designed with this method also show a good robustness and good reliability.

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A new control method of flexible-joint manipulator with harmonic drive

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406219899697 ◽

2020 ◽

Vol 234 (9) ◽

pp. 1868-1883

Author(s):

Guocai Yang ◽

Yechao Liu ◽

Minghe Jin

Keyword(s):

Control Method ◽

Controller Design ◽

Joint Stiffness ◽

Adaptive Controller ◽

Harmonic Drive ◽

Flexible Joint ◽

Assignment Method ◽

Uncertain Dynamics ◽

Tracking Controller ◽

Flexible Joint Manipulator

Considerable elasticity and nonlinear friction caused by harmonic transmission challenge the performance of flexible-joint manipulators. The uncertain dynamics of manipulator and the inadequate measurable states also limit the controller design. A new control method is proposed to address these problems, achieving the precise motion control of the flexible-joint manipulator. The method consists of three cascaded controllers: an adaptive controller, a torque-tracking controller, and a motor controller. The adaptive controller was adopted to generate the desired torque ensuring the robustness for uncertain dynamics. The torque-tracking controller derived the position compensation for motor control according to the torque error. As the elastic torque is under control, the vibration caused by harmonic drive can be eliminated. The motor was controlled based on poles-assignment method and friction compensation. The Kalman observer based on the Brownian motion model observed both velocity and the high-order derivatives of torque sensing. The stability of the control method was strictly proved. Calibration was performed on each joint to obtain the required joint stiffness and motor friction parameters. The control method was verified on a single joint and the frequency response of the system was obtained. The results show that the controller has good performance. The controller was realized on the self-developed seven-degree-of-freedom manipulator. The results reveal that the controller has high-precision tracking performance.

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Adaptive controller design for flexible joint manipulators

Automatica ◽

10.1016/0005-1098(96)85559-2 ◽

1996 ◽

Vol 32 (2) ◽

pp. 273-278 ◽

Cited By ~ 51

Author(s):

Shuzhi S. Ge

Keyword(s):

Controller Design ◽

Adaptive Controller ◽

Flexible Joint

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Robust Adaptive Control of Uncertain Nonlinear Systems With Time-Varying Input Delay

Volume 4B: Dynamics, Vibration, and Control ◽

10.1115/imece2017-71255 ◽

2017 ◽

Author(s):

W. X. Deng ◽

J. Y. Yao

Keyword(s):

Nonlinear Systems ◽

Controller Design ◽

Adaptive Controller ◽

Robust Adaptive Control ◽

Input Delay ◽

Time Varying ◽

Uncertain Nonlinear Systems ◽

Bounded Disturbances ◽

Robust Adaptive ◽

Adaptive Feedforward

In this paper, a robust adaptive controller is proposed for a class of uncertain nonlinear systems subject to time-varying input delay, parametric uncertainties and additive bounded disturbances. The desired trajectory based adaptive feedforward technique and a predictor-like robust delay compensating term are integrated via backstepping in the controller design. The proposed controller theoretically ensures semi-global uniformly ultimately bounded tracking performance based on Lyapunov stability analysis by employing Lyapunov-Krasovskii (LK) functionals. Simulation results are obtained to illustrate the effectiveness of the proposed control strategy.

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