Cable Tension Sensing System

Overview

AirStep is a cable-driven gait rehabilitation robot at the UCI Biorobotics Lab. I developed a sensing system that compensates for spring displacement during dynamic motion, achieving compliance within 0.03 mm during walking cycles.

What I worked on

• Designed and 3D-printed a compact spring-based sensing and rack-and-pinion mechanism with a rotary encoder.
• Integrated AMT102-V rotary encoders at 2048 PPR resolution to quantify dynamic cable tension.
• Implemented a closed-loop tension monitoring approach using spring constant calibration and encoder position data.
• Modeled the mechanism in SolidWorks and integrated it into the master CAD assembly for AirStep.
• Validated the device through iterative testing and clinical trials at Rancho Los Amigos National Rehabilitation Center.

Takeaways

Working in a lab environment showed me how careful instrumentation and a small mechanism can unlock entirely new capability for a much larger system.