Stride Length Estimation Based on a Single Shank's Gyroscope

An inertial measurement unit based stride length estimation remains as a challenging problem despite many researchers have tried to use frequency, vertical acceleration, and/or angle to estimate the stride length. In this letter, we propose three new features that can be extracted from a single shank's gyroscope for an stride length estimation. We first noticed that the shank's horizontal displacement increases mainly during its extension, while remains almost unchanged during its flexion. The horizontal displacement s during the shank's extension was treated as a linear increment, and therefore, a linear kinematic equation s = 0.5(u + v)t could be applied. The initial velocity u is estimated as the average angular velocity during shank's flexion, while the final velocity v is estimated as the summation of angular velocity during the whole stride. The time t is estimated as the duration of the shank's extension rather than the duration of the whole stride. This proposed method had resulted in a low mean absolute error of 4.2 cm with a standard deviation of 5.5 cm.