Gait velocity estimation for a smartwatch platform using Kalman filter peak recovery

A gait velocity estimation algorithm using the inertial sensors of a smartwatch is proposed. The peaks of accelerometer and gyroscope norms are detected at first. Then a Kalman Filter is employed to recover the peaks that are missed because of the arm swing. The Kalman filter combines the accelerometer and gyroscope norm peaks and robustly detect walking step events even in cases where there is a large arm swing. Walking velocity is then estimated using the step duration. It will be shown in this work that the gait velocity has a good correlation with the inverse of the square of the step duration. The model parameters are calculated by collecting the training data from 25 subjects: each subject walked 50 m six times with different walking speed and different arm swing speed. The standard deviation of walking velocity estimation error is 0.1009 m/s (without person dependent calibration) and 0.0630 m/s (with person dependent calibration). The average precision of 91.7% was achieved for the gait speed testing on the smartwatch platform over all the speed scenarios.