Wireless in-shoe force system [for motor prosthesis]

In this paper we present a Wireless In-shoe Force System (WIFS) to acquire, process, and transmit foot-floor force information which has been proven feasible for use with normal and paraplegic subjects. The WIFS is a portable system, intended for ambulatory use in a variety of locations (rather than in a laboratory setting). It measures times of foot contact occurrence, the approximate weight on each foot, and the center of pressure (COP) on each foot (as a function of time). This was done using a set of thick-film force sensors (for each foot), mounted in multi-layer shoe insoles (fitted to each foot and shoe, and worn inside the shoe). Information obtained by these insoles is transmitted (broadcast) from small, battery powered transmitters mounted on the shoe to a receiver. The system operates in the 902-928 MHz carrier frequency which allows data transmission rates of up to 50 Kbaud over a range of up to 500 meters. We proved that four force sensors, arranged under the supporting bones of the foot and mounted inside the shoe, obtained accurate COP information which was telemetered to the receiver.