The Cybathlon RehaBike: Inertial-Sensor-Driven Functional Electrical Stimulation Cycling by Team Hasomed

Our Team Hasomed joined the functional electrical stimulation (FES) bike race at the very first Cybathlon, which was organized by the Swiss Federal Institute of Technology in Zurich (ETH Zurich). This article describes our technical approach regarding the tricycle, the stimulator, and the inertial-sensor-based control strategy used for training and during the race. Due to the cycling device's independence, the same setting and stimulation pattern can be used for either regular or ergometer-based cycling. Regarding the bike architecture, the focus was on using standard components as much as possible and enabling an easy and autonomous transfer between the wheelchair and the tricycle. Together with our paraplegic pilot [spinal cord injury (SCI) lesion level T5/6, American Spinal Injury Association (ASIA) Impairment Scale Grade A], we developed a training plan and an electrode setting that was continuously improved upon over the course of 18 months. Right before the Cybathlon, our pilot was able to cycle the full race distance of 750 m five times with 5-min rests in between in a gymnasium. At the Cybathlon, our athlete completed the 750-m race, taking fourth place with a new personal record of 6 min and 44 s. With our work, we showed that an inertial-sensor-based joint-angle estimation can be used for smooth and effective FES cycling.