An Infrared Sensor-Based Instrumented Shoe for Gait Events Detection on Different Terrains and Transitions

This paper presents a low-cost wireless gait event detection system that incorporates infra-red range sensors mounted laterally at a specific anatomical location on the shoe. This system uses foot clearance information to extract heel strike (HS) and toe-off (TO) events. A subject-specific algorithm based on signature curve matching was developed to estimate the HS and TO in six able-bodied subjects and three transfemoral amputees. The data were acquired in a real-life environment while the subject walked on level ground and ramp terrains, including the transitions. The HS and TO in the level ground were detected with an accuracy of 22.87± 9.93 ms and 10.42± 6.70 ms, respectively, in able-bodied participants. The accuracy of 37.91± 12.36 ms and 20.41± 11.23 ms in HS and TO, respectively, was observed in amputees during level ground walking. Further, within the ramp terrain, the HS and TO were detected with an accuracy of 23.33± 11.20 ms and 13.36± 9.5 ms respectively in able-bodied subjects and 40.35± 12.64 ms and 47.51± 19.23 ms in amputees. This method reports comparable accuracy, with minimal standard deviation, to other existing methods based on accelerometer, gyroscope, electromyography, and force myography. This system is robust, easy to operate, and avoids direct contact with the body. The developed system offers a movable sensor platform in two degrees of freedom that facilitates the adaptability of the proposed system for different heel height and shoe sizes.