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IMU-based Smart Knee Pad for Walking Distance and Stride Count Measurement

To calculate the knee angle, stride counts, and walking distance, we propose a system, iKneePad, fusing two 9-axis sensors with Bluetooth equipped on the thigh and shank segments. The changing rates of hip and knee angles are used to determine the beginning and the ending of a stride. The thigh length, shank length, hip angle, and knee angle are used to calculate the walking distance. The experimental results show that the accuracy of stride count is 100%, the absolute mean errors of knee angle are 2.99° and 1.42° for the maximum and minimum flexion angles, respectively. For walking distance, the mean error rates are −2.40% and −2.26% for short (10m) and long (33m) distances, respectively. The proposed system also instantly provides feedback to users by showing on an Android smartphone when conducting rehabilitation or exercise with iKneePad.