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Dynamic Modelling and Control Strategy Analysis of a Lower-Limb Exoskeleton
Huanrong Xiao1, Teng Ran1, Afang Jin1
1College of Mechanical Engineering, Xinjiang University, Ürümqi 830047, China.
Sensors (Basel, Switzerland)
|April 14, 2026
Summary
This study introduces a new dynamic model for lower-limb exoskeleton robots, improving control accuracy for rehabilitation and assistance. The computed torque method significantly enhances joint angle tracking compared to traditional PD control.
Area of Science:
- Robotics
- Biomechanics
- Rehabilitation Engineering
Background:
- Lower-limb exoskeletons are crucial for rehabilitation and assistive augmentation.
- Existing dynamic models often neglect ankle dynamics and pelvic translation, limiting performance.
Purpose of the Study:
- To develop a comprehensive sagittal-plane dynamic model of the human lower limb and exoskeleton system.
- To design and evaluate advanced control strategies for precise trajectory tracking.
Main Methods:
- A seven-segment kinematic model was created using modified Denavit-Hartenberg parameters.
- Lagrangian formulation derived dynamic equations for the coupled human-exoskeleton system.
- Simulations compared PD control, PD with gravity compensation, and computed torque control using real gait data.
Main Results:
- The computed torque method achieved a joint angle tracking RMSE of 0.59°, an 86.3% improvement over PD control.
- Low control torque RMS of 4.44 N·m was maintained.
- Stable tracking performance was demonstrated across walking speeds from 0.4 to 1.45 m/s.
Conclusions:
- The proposed dynamic model and computed torque control strategy effectively enhance exoskeleton performance.
- This advancement holds significant potential for improving lower-limb exoskeleton applications in rehabilitation and assistance.
