We developed a soft power assist device named "Smart Suit" for reducing horse trainers' physical fatigue in their horse training works in order to prevent their spine or legs injuries. The smart suit is a kind of semi-active and flexible power assist devices. The semi-active assist mechanism consisting of rubber belt and small DC motor is our original technology and it is in patent pending. The assist force is basically gained by the elastic force of rubber belt, and it is controlled by tuning the length of the rubber belt by using DC motor. In order to gain the suitable assist force for periodical horse trainers' motion, the assist force control method based on the periodical input control was developed in this study. Also, for stabilizing their horse riding motion, we developed the assist force control method considering their dynamic stability by controlling their center of gravity on the zero moment point (ZMP) which is the dynamic stable point. Experimental results showed that the smart suit installing these control method was effective to reduce the activities of muscles in the thigh. The assist ratio evaluated by EMG was 40-50%. Moreover, a prototype of Smart Suit Light of which the assist force is manually controllable was also developed. The smart suit light was also effective for horse trainers. In actual horse training, the assist ratio of back muscle, quadriceps femoris and hamstrings were 15%, 58% and 10% respectively.

DESCENTE SPORTS SCIENCE Vol.30/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE