Research on adaptive trajectory following of lower limb rehabilitation exoskeleton based on sliding mode control

Lower limb rehabilitation exoskeleton robots have the characteristics of nonlinearity and strong coupling, and they are easily disturbed during operation by environmental factors. Thus, an accurate dynamic model of the robot is difficult to obtain, and achieving trajectory tracking control of the robot is also difficult. In this article, a self-adaptive-coefficient double-power sliding mode control method is proposed to overcome the difficulty of tracking the robot trajectory. The method combines an estimated dynamic model with sliding mode control. A nonlinear control law was designed based on the robot dynamics model and computational torque method, and a compensation term of control law based on double-power reaching law was introduced to reduce the disturbance from model error and environmental factors. The self-adaptive coefficient of the compensation term of the control law was designed to adaptively adjust the compensation term to improve the anti-interference ability of the robot. The simulation and experiment results show that the proposed method effectively improves the trajectory tracking accuracy and anti-interference ability of the robot. Compared with the traditional computed torque method, the proposed method decreases the tracking error by more than 71.77%. The maximum absolute error of the hip joint and knee joint remained below 0.55° and 1.65°, respectively, in the wearable experiment of the robot.

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Impedance Control Based Sliding Mode for Lower Limb Rehabilitation Robot

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.672-674.1770 ◽

2014 ◽

Vol 672-674 ◽

pp. 1770-1773 ◽

Cited By ~ 1

Author(s):

Fu Cheng Cao ◽

Li Min Du

Keyword(s):

Dynamic Response ◽

Sliding Mode Control ◽

Lower Limb ◽

Control Method ◽

Sliding Mode ◽

Impedance Control ◽

Rehabilitation Robot ◽

Active Rehabilitation ◽

Limb Rehabilitation ◽

Lower Limb Rehabilitation

Aimed at improving the dynamic response of the lower limb for patients, an impedance control method based on sliding mode was presented to implement an active rehabilitation. Impedance control can achieve a target-reaching training without the help of a therapist and sliding mode control has a robustness to system uncertainty and vary limb strength. Simulations demonstrate the efficacy of the proposed method for lower limb rehabilitation.

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Sliding Mode Control of an Actuated Knee Joint Orthosis

Current Signal Transduction Therapy ◽

10.2174/1574362415999210104223820 ◽

2021 ◽

Vol 15 ◽

Author(s):

Imen Saidi ◽

Asma Hammami

Keyword(s):

Sliding Mode Control ◽

Lower Limb ◽

Sliding Mode ◽

Position Tracking ◽

Sliding Mode Controller ◽

Mechanical Device ◽

Tracking Errors ◽

Mode Control ◽

Speed Tracking ◽

Human Morphology

Introduction: In this paper, a robust sliding mode controller is developed to control an orthosis used for rehabilitation of lower limb. Materials and Methods: The orthosis is defined as a mechanical device intended to physically assist a human subject for the realization of his movements. It should be adapted to the human morphology, interacting in harmony with its movements, and providing the necessary efforts along the limbs to which it is attached. Results: The application of the sliding mode control to the Shank-orthosis system shows satisfactory dynamic response and tracking performances. Conclusion: In fact, position tracking and speed tracking errors are very small. The sliding mode controller effectively absorbs disturbance and parametric variations, hence the efficiency and robustness of our applied control.

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Periodic event-triggered sliding mode control for lower limb exoskeleton based on human–robot cooperation

ISA Transactions ◽

10.1016/j.isatra.2021.05.039 ◽

2021 ◽

Author(s):

Jie Wang ◽

Jiahao Liu ◽

Gaowei Zhang ◽

Shijie Guo

Keyword(s):

Sliding Mode Control ◽

Lower Limb ◽

Sliding Mode ◽

Lower Limb Exoskeleton ◽

Mode Control ◽

Robot Cooperation ◽

Event Triggered

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Design of M-G modal space sliding mode control for lower limb exoskeleton robot driven by electrical actuators

Mechatronics ◽

10.1016/j.mechatronics.2021.102610 ◽

2021 ◽

Vol 78 ◽

pp. 102610

Author(s):

Jinsong Zhao ◽

Tao Yang ◽

Zhilei Ma ◽

Chifu Yang ◽

Zhipeng Wang ◽

...

Keyword(s):

Sliding Mode Control ◽

Lower Limb ◽

Sliding Mode ◽

Lower Limb Exoskeleton ◽

Mode Control ◽

Exoskeleton Robot ◽

Modal Space

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Fault tolerant control based on backstepping nonsingular terminal integral sliding mode and impedance control for a lower limb exoskeleton

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

10.1177/09544062211035792 ◽

2021 ◽

pp. 095440622110357

Author(s):

Majied Mokhtari ◽

Mostafa Taghizadeh ◽

Pegah Ghaf Ghanbari

Keyword(s):

Sliding Mode Control ◽

Lower Limb ◽

Fault Tolerant ◽

Sliding Mode ◽

Impedance Control ◽

Fault Tolerant Control ◽

Integral Type ◽

Lower Limb Exoskeleton ◽

Mode Control ◽

Control Scheme

In this paper, an active fault-tolerant control scheme is proposed for a lower limb exoskeleton, based on hybrid backstepping nonsingular fast terminal integral type sliding mode control and impedance control. To increase the robustness of the sliding mode controller and to eliminate the chattering, a nonsingular fast terminal integral type sliding surface is used, which ensures finite time convergence and high tracking accuracy. The backstepping term of this controller guarantees global stability based on Lyapunov stability criterion, and the impedance control reduces the interaction forces between the user and the robot. This controller employs a third order super twisting sliding mode observer for detecting, isolating ad estimating sensor and actuator faults. Motion stability based on zero moment point criterion is achieved by trajectory planning of waist joint. Furthermore, the highest level of stability, minimum error in tracking the desired joint trajectories, minimum interaction force between the user and the robot, and maximum system capability to handle the effect of faults are realized by optimizing the parameters of the desired trajectories, the controller and the observer, using harmony search algorithm. Simulation results for the proposed controller are compared with the results obtained from adaptive nonsingular fast terminal integral type sliding mode control, as well as conventional sliding mode control, which confirm the outperformance of the proposed control scheme.

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