Wearable conductive fiber sensors for measuring joint movements

This paper describes a technique that uses conductive fibers as part of a wearable sensor for continuous monitoring of joint movements. Conductive fibers are incorporated into flexible fabrics that fit tightly around a joint, and resistance changes in the fibers caused by skin extension can be measured, and related to joint motion. An overview of the sensor design, including functional requirements and design parameters, are presented, as well as preliminary results from a prototype sensor design. A single-axis joint model is also presented to illustrate the implementation of an extended Kalman filter to estimate joint angle. The Kalman filter also estimates parameters associated with misalignment errors that may be created every time the subject takes off and puts on the wearable sensor, allowing a sensor to be calibrated only once, with no need for re-calibration for all future uses.