Design and Implementation of a High-Precision Motor Control System for Adjustable-Stiffness Biomedical Treadmills

This paper presents a novel motor control system for a biomedical treadmill featuring adjustable stiffness, tailored to enhance rehabilitation and gait training. Unlike conventional treadmill systems, the proposed design incorporates an advanced dual-stepper motor configuration with scissor lift mechanism for precise side stiffness adjustment. Alongside an adaptive position control system based on model predictive control with dynamic weight compensation, the resultant system is enabling accurate and responsive body positioning under varying operation conditions. This innovative control system delivers rapid, accurate, and versatile stiffness modulation, offering significant improvements in adaptability and user experience for clinical and research applications. A <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{7 0 0} \mathbf{~ W}$</tex> platform prototype has been developed to showcase the system's capabilities, bridging the gap between theoretical insights and practical implementation. The system's performance is rigorously validated through simulation and experimental testing, demonstrating exceptional dynamic response within 0.5 seconds, a maximum stepper motor speed of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3,657.6$</tex> RPM, and track displacement accuracy of 0.025 mm. The experimental results align closely with theoretical predictions, highlighting the system's robustness and reliability. This work introduces a control approach for next-generation rehabilitation treadmills, that are able to adjust surface stiffness.