An Inductive Sensor for Real-Time Measurement of Plantar Normal and Shear Forces Distribution

Goal: The objective of this paper is to demonstrate a multiplexed inductive force sensor for simultaneously measuring normal force and shear forces on a foot. Methods: The sensor measures the normal force and shear forces by monitoring the inductance changes of three planar sensing coils. Resonance frequency division multiplexing was applied to signals from the multiple sensing coils, making it feasible to simultaneously measure the three forces (normal force, shear forces in x- and y-axis) on a foot using only one set of measurement electronics with high sensitivity and resolution. Results: The testing results of the prototype sensor have shown that the sensor is capable of measuring normal force ranging from 0 to 800 N and shear forces ranging from 0 to 130 N in real time. Conclusion: With its high resolution, high sensitivity, and the capability of monitoring forces at different positions of a foot simultaneously, this sensor can be potentially used for real-time measurement of plantar normal force and shear forces distribution on diabetes patient's foot. Significance: Real-time monitoring of the normal force and shear forces on diabetes patient's foot can provide useful information for physicians and diabetes patients to take actions in preventing foot ulceration.