Engineering development and control design of a system for paraplegic tricycling

The aim of this study was the design of a cycle device to be used by patients with Spinal Cord Injury (SCI), using the technique of Functional Electrical Stimulation (FES). A complete literature review of former projects in the areas of Design Engineering, Control Engineering, Physiologic and Psychologic investigations in SCI FES cycling was done. All results achieved so far were summarized. Based on the review, a commercially available tricycle was modified for the demands of SCI people. A 10 Bit shaft encoder was used to feed back information from the tricycle and the cyclist. A software for the stimulation of the muscles in the lower limbs was developed. The Real Time Toolbox of Matlab was used for the data acquisition between the tricycle and the PC. A simple approach was invented to find a good first approximation of the individual stimulation pattern for the Gluteal, Hamstring, and Quadriceps muscle groups. Initial experiments were done. A velocity compensation routine, which was part of the software as well, allowed a healthy subject, stimulated via FES, to increase the pedal frequency to more than 100 rev per minute. A closed loop controller, based on system identification and analytical controller design, was implemented into the software as well. Experiments showed that the controller was able to fix the pedal frequency to a constant value on one hand, but also to solve dynamic tasks on the other hand. This is a significant original contribution, as this type of feedback controller has not previously been applied in FES cycling. The system described in the thesis is currently being used in a pilot study of FES cycling with three paraplegic subjects at the Southern General Hospital in Glasgow.