TITLE: A Wireless Sensor System for Real-Time Measurement of Pressure Profiles at Lower Limb Protheses to Ensure Proper Fitting PRINCIPAL INVESTIGATOR: Keat

A force m onitoring system consisting of stress-sensitive magnetoelastic strips forremotely measuring the force profile across a hard surface is described. Under the excitation of amagnetic AC field, the m agnetoelastic strips generated higher-order harmonic fields (magneticAC fields at multiple frequencies of the excitation field), allowing remote measurement of theirresponses without interference fr om the excitation field. Due to their magnetoelastic properties,these higher-order harmonic fields were also dependent on the applied force and, as a result,variations in force/stress could be tracked vi a changes in th e field am plitudes. These changeswere monitored using a detection system featuring a set of m agnetic detection coils, whichcaptured the response of the m agnetoelastic strips. To dem onstrate the functionality of thissensor system, a three-strip m agnetoelastic sensor array was fa bricated on a flat polycarbonatesubstrate. The substrate, placed within a customized mechanical loader, was exposed to a varietyof force loading conditions. Experim ental results demonstrated a proportional relationshipbetween the amplitude of the 2 order harmonic field and the applied f orce. An algorithm wasdeveloped to identify the m agnitude of the applied force. The novelty of this system lies in itswireless and passive nature, which is ideal for applications in which wir es and internal powersources are prohibited or discouraged. Moreover, the sensing com ponent of this system is anarray of th in magnetoelastic strips, allowing f or minimal modifications to existing structuresduring implementation.