Development of a sliding mode controller with chattering suppressor for human lower extremity exoskeleton robot

Exoskeleton robot-based human upper and lower extremity rehabilitation is an appealing solution for many disabled individuals. To deliver the desired form of physical therapy efficiently, robots with streamlined maneuverability are needed. Sliding mode control is a robust control scheme that works e...

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Bibliographic Details
Published in:Results in control and optimization 2022-06, Vol.7, p.100123, Article 100123
Main Authors: Hasan, S.K., Dhingra, Anoop K.
Format: Article
Language:English
Subjects:
Chattering phenomena
Exoskeleton robot
Lower extremity dynamic model
Robot joint friction
Sliding mode control
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Summary:Exoskeleton robot-based human upper and lower extremity rehabilitation is an appealing solution for many disabled individuals. To deliver the desired form of physical therapy efficiently, robots with streamlined maneuverability are needed. Sliding mode control is a robust control scheme that works efficiently for a nonlinear system such as a serial link manipulator. The main limitation of the sliding mode control system is the chattering phenomenon. Chattering leads to rough movements and often causes actuator saturation leading to reduced actuator life and an energy-inefficient system. A sliding mode control system without a chattering suppressor needs more powerful actuators that make the manipulator heavy. In this paper, a seven degrees of freedom human lower extremity dynamic model for an exoskeleton robot is presented first. To control the robot dynamics, a sliding mode controller (SMC) is employed. To study the effects of chattering phenomenon, dynamic simulations are done with and without continuous mode chattering suppressor. A continuous mode chattering suppressor is introduced. A realistic friction model is included in the human lower extremity dynamic model to simulate joint friction effects. Simulation results show the effectiveness of the developed Sliding mode controller with continuous mode chattering suppressor while tracking trajectories involving sequential as well as simultaneous joint movements. A performance comparison of the developed Sliding mode controller with linear (PID) and nonlinear control techniques (Computed torque controller) is presented.
ISSN:2666-7207
2666-7207
DOI:10.1016/j.rico.2022.100123