Adaptive sliding mode repetitive learning control of the upper-limb exoskeleton with unknown dynamics

2021 ◽  
pp. 095965182110087
Author(s):  
Yan Zhang ◽  
Jian Liu ◽  
Yuteng Zhang ◽  
Ying Zhou ◽  
Lingling Chen
Keyword(s):  
Upper Limb ◽  
Control Strategy ◽  
Sliding Mode ◽  
External Disturbance ◽  
Tracking Error ◽  
Learning Control ◽  
Lyapunov Theory ◽  
Adaptive Sliding Mode ◽  
Upper Limb Exoskeleton ◽  
Repetitive Learning

This article proposes a new adaptive sliding mode repetitive learning control strategy. The proposed controller can obtain satisfactory position tracking performance in the presence of unknown dynamics and external disturbance. The unknown dynamics parameters of the exoskeleton system can be estimated via an adaptive algorithm, which is used to design the sliding mode control law. Besides, the periodic external disturbance of the system can be compensated by repetitive learning to reduce the tracking error. The stability of the proposed method is demonstrated rigorous by the Lyapunov theory. Using an upper-limb exoskeleton model, simulation results demonstrate the effectiveness of the control strategy. The proposed method has a better control performance than other methods.

scholarly journals Prescribed Performance Control for the Upper-Limb Exoskeleton System in Passive Rehabilitation Training Tasks

2021 ◽  
Vol 11 (21) ◽  
pp. 10174
Author(s):  
Zhirui Zhao ◽  
Jichun Xiao ◽  
Hongyun Jia ◽  
Hang Zhang ◽  
Lina Hao
Keyword(s):  
Upper Limb ◽  
Control Method ◽  
Controller Design ◽  
Sliding Mode ◽  
Tracking Error ◽  
Adaptive Sliding Mode Control ◽  
Model Parameters ◽  
Prescribed Performance ◽  
Upper Limb Exoskeleton ◽  
Model Free

In this study, a model-free adaptive sliding mode control method was developed in combination with the prescribed performance method. On this basis, this study attempted to fulfill the joint position tracking trajectory task for the one-degree of freedom (DOF) upper-limb exoskeleton in passive robot-assisted rehabilitation. The proposed method is capable of addressing the defect of the initial error in the controller design and the application by adopting a tuning function, as compared with other prescribed performance methods. Moreover, the method developed here was not determined by the dynamic model parameters, which merely exploit the input and output data. Theoretically, the stability exhibited by the proposed controller and the tracking performance can be demonstrated. From the experimental results, the root mean square of the tracking error is equal to 1.06 degrees, and the steady-state tracking error converges to 1.91 degrees. These results can verify the expected performance of the developed control method.

scholarly journals Switching Gain Reduction in Adaptive Sliding Mode Control for Rigid Spacecraft Attitude Maneuvers

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Zhen Chen ◽  
Binglong Cong ◽  
Xiangdong Liu
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
External Disturbance ◽  
Tracking Error ◽  
Adaptive Sliding Mode Control ◽  
System Response ◽  
Spacecraft Attitude ◽  
Adaptive Sliding Mode ◽  
Mode Control ◽  
Rigid Spacecraft

This paper investigates the overadaptation problem in current adaptive sliding mode control (ASMC) for rigid spacecraft attitude maneuvers. The inertia matrix uncertainty and external disturbance are taken into account, and an adaptive scheme is employed for the switching gain calculation. A detailed analysis of existing ASMC design reveals the fact that the switching gain would be overestimated if the ASMC algorithm is developed in the framework of conventional sliding mode control (SMC), owing to the unrelated adaptation caused by initial tracking error. The global sliding mode concept of integral sliding mode control (ISMC) is exploited to solve such a problem. The advantages of the proposed strategy are twofold. First, a much smaller switching gain is generated as compared to conventional ASMC. Second, the resulting small switching gain would not slow down the system response. The advantages of the proposed strategy are verified by both theoretical analysis and simulation results.

scholarly journals Adaptive sliding mode control with gravity compensation: Application to an upper-limb exoskeleton system

2019 ◽  
Vol 261 ◽  
pp. 06001
Author(s):  
Sana Bembli ◽  
Nahla Khraief Haddad ◽  
Safya Belghith
Keyword(s):  
Upper Limb ◽  
Sliding Mode ◽  
Robustness Analysis ◽  
Stability Study ◽  
Adaptive Sliding Mode Control ◽  
Parametric Uncertainties ◽  
Gravity Compensation ◽  
Adaptive Sliding Mode ◽  
Upper Limb Exoskeleton ◽  
Flexion Extension

This paper presents a robust control algorithm with gravity compensation in presence of parametric uncertainties. The application deals with an upper limb exoskeleton system, aimed for a rehabilitation application. The treated system is an robot with two degrees of freedom acting on the flexion / extension movement of the shoulder and elbow. An adaptive sliding mode algorithm with gravity compensation has been developed to control the upper limb exoskeleton system. A Stability study is realized. Then, a robustness analysis in the presence of parametric uncertainties using Monte Carlo simulation is developed. To prove the performance of the gravity compensation approach, a comparison study is done. Simulation results are presented to highlight the performances and the effectiveness of the proposed controller using gravity compensation.

A New Approach for Simultaneous Vehicle Handling and Path Tracking Improvement Through SBW System

2010 ◽  
Author(s):  
Amir Ali Janbakhsh ◽  
Reza Kazemi
Keyword(s):  
Sliding Mode ◽  
External Disturbance ◽  
Precise Determination ◽  
Path Tracking ◽  
Lyapunov Theory ◽  
Adaptive Sliding Mode Control ◽  
Adaptation Algorithm ◽  
Vehicle Handling ◽  
Adaptive Sliding Mode ◽  
Steering Mechanism

A nonlinear adaptive sliding mode control for simultaneous vehicle handling and path tracking improvement through the Steer-By-Wire system is presented in this paper. The proposed adaptive sliding mode controller, which is insensitive to system uncertainties, offers an adaptive sliding gain to eliminate the precise determination of the bound of uncertainties. The sliding gain value is calculated using a simple adaptation algorithm which does not require extensive computational load. A driver control model is also presented according to the preview or look-ahead strategy to generate the appropriate steering angles using the vehicle states feedback and the future information about the path to be followed. Moreover, because of the inertia and viscous damping in the steering mechanism and the effects of coulomb friction and self-aligning moment of the front tires, the steering system controller based on the proposed adaptive sliding mode scheme, is designed to control the front steering angle. A complete stability analysis based on the Lyapunov theory is presented in order to guarantee the closed loop stability. Eventually, the simulation results confirm that the proposed adaptive robust controller not only improves the vehicle handling and path tracking performance but also reduces the chattering problem in presence of uncertainties in the tire cornering stiffness and the external disturbance.

Finite-time disturbance observer–based funnel voltage control strategy for vehicle-to-grid inverter in islanded mode

2021 ◽  
pp. 095965182110173
Author(s):  
Yuchen Dai ◽  
Liyan Zhang ◽  
Guofu Liu ◽  
Dezhi Xu ◽  
Chengshun Yang
Keyword(s):  
Control Strategy ◽  
Finite Time ◽  
Disturbance Observer ◽  
Sliding Mode ◽  
Tracking Error ◽  
Voltage Control ◽  
Lyapunov Theory ◽  
Voltage Control Strategy ◽  
Power Sources ◽  
Vehicle To Grid

Based on vehicle-to-grid technology, electric vehicles can be used as power sources in the case of power failure. With the aim to reduce voltage overshoot and improve the anti-disturbance ability of the vehicle-to-grid inverter, a high-performance voltage control strategy based on funnel control and finite-time disturbance observer is developed. First, the dynamic model of the inverter in dq-frame is established, and the lumped disturbance including the unmodeled part is considered. Next, a novel funnel variable is proposed to ensure that the voltage tracking error can be stabilized within the prescribed funnel boundary, and thus enhance the transient performance. Then, a novel finite-time disturbance observer is designed to estimate the lumped disturbance in the system such as load fluctuations, and improve the anti-disturbance ability of the controller. Moreover, the second-order sliding mode differentiator is introduced to estimate the derivative of the virtual control law and eliminate the explosion of complexity problem in the derivation process. Finally, the finite-time stability of the proposed voltage control strategy is analyzed via the Lyapunov theory. The effectiveness of the proposed control strategy is verified by two cases.

Novel Adaptive Reaching Law for Sliding Mode Control of an Upper Limb Exoskeleton Robot*

2020 ◽  
Author(s):  
Brahim Brahmi ◽  
Khaled El-Monajjed ◽  
Mohammad Habibur Rahman ◽  
Tanvir Ahmed ◽  
Claude El-Bayeh ◽  
...  
Keyword(s):  
Sliding Mode Control ◽  
Upper Limb ◽  
Sliding Mode ◽  
Reaching Law ◽  
Mode Control ◽  
Upper Limb Exoskeleton ◽  
Exoskeleton Robot

scholarly journals Control of an IPMC Soft Actuator Using Adaptive Full-Order Recursive Terminal Sliding Mode

Actuators ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 33
Author(s):  
Romina Zarrabi Ekbatani ◽  
Ke Shao ◽  
Jasim Khawwaf ◽  
Hai Wang ◽  
Jinchuan Zheng ◽  
...  
Keyword(s):  
Sliding Mode ◽  
External Disturbance ◽  
Tracking Error ◽  
Working Environment ◽  
Parametric Uncertainties ◽  
Metal Composite ◽  
External Disturbances ◽  
Terminal Sliding Mode ◽  
Positioning Accuracy ◽  
Soft Actuator

The ionic polymer metal composite (IPMC) actuator is a kind of soft actuator that can work for underwater applications. However, IPMC actuator control suffers from high nonlinearity due to the existence of inherent creep and hysteresis phenomena. Furthermore, for underwater applications, they are highly exposed to parametric uncertainties and external disturbances due to the inherent characteristics and working environment. Those factors significantly affect the positioning accuracy and reliability of IPMC actuators. Hence, feedback control techniques are vital in the control of IPMC actuators for suppressing the system uncertainty and external disturbance. In this paper, for the first time an adaptive full-order recursive terminal sliding-mode (AFORTSM) controller is proposed for the IPMC actuator to enhance the positioning accuracy and robustness against parametric uncertainties and external disturbances. The proposed controller incorporates an adaptive algorithm with terminal sliding mode method to release the need for any prerequisite bound of the disturbance. In addition, stability analysis proves that it can guarantee the tracking error to converge to zero in finite time in the presence of uncertainty and disturbance. Experiments are carried out on the IPMC actuator to verify the practical effectiveness of the AFORTSM controller in comparison with a conventional nonsingular terminal sliding mode (NTSM) controller in terms of smaller tracking error and faster disturbance rejection.

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