Impedance Sliding-Mode Control Based on Stiffness Scheduling for Rehabilitation Robot Systems

Area of Science:

• Robotics
• Rehabilitation Engineering
• Control Systems

Background:

• Rehabilitation robots aim to replicate therapist movements for patient training.
• Existing methods face challenges with model dependence and system uncertainties.
• Adaptive control is crucial for tailoring rehabilitation to individual patient conditions.

Purpose of the Study:

• To propose a novel impedance sliding-mode control method for rehabilitation robots.
• To enable application in both active and passive rehabilitation training modes.
• To enhance patient safety and training effectiveness through adaptive impedance control.

Main Methods:

• Developed a free-model-based sliding-mode control strategy to minimize model dependence and limb shaking effects.
• Implemented a stiffness-scheduled law to automatically adjust robot impedance based on patient-exerted force.
• Compared the proposed method against fixed and variable stiffness impedance control techniques.

Main Results:

• The proposed stiffness-scheduled impedance control method demonstrated superior performance compared to fixed and variable stiffness approaches.
• The free-model-based sliding-mode control effectively reduced system uncertainties.
• Experimental validation on an actual rehabilitation robot confirmed the method's feasibility and stability.

Conclusions:

• The developed impedance sliding-mode control with stiffness scheduling offers a robust and adaptive solution for rehabilitation robotics.
• This method enhances rehabilitation training by personalizing robot impedance to the patient's real-time condition.
• The findings support the broader adoption of advanced control strategies in robotic rehabilitation to improve patient outcomes.