Ambulatory measurement of foot kinematics using wearable ultrasonic sensors.

In this paper, an ultrasonic-based system for foot parameters measurement has been proposed and investigated. An extended Kalman filtering-based methodology has been developed to extract foot parameters including step length, stride length and cycle time from horizontal displacement during walking. The system comprises of one ultrasonic transmitter (mobile) and four ultrasonic receivers (anchors) with fixed known positions. A Radio Frequency (RF) module is used in our system not only to provide synchronization clock between the mobile and anchors, but also to transmit collected data wirelessly to reduce the wires used. To evaluate the performance of the proposed system, the 2-dimensional foot displacement and the foot parameters were measured and validated against the reference camera motion capture system. These experiment results demonstrate the capability of the proposed system being used as a gait analysis tool for rehabilitation and other medical applications.