A Dual-Module-Driven Method for Foot Posture Indirect Measurement With Potential Application in Rehabilitation Robots

Currently, wearable systems have become mainstream in human motion analysis due to their low cost, minimal environmental constraints, and capability for prolonged monitoring. However, wearable inertial sensors can only directly measure motion data at their mounting locations, which necessitates increasing the number of sensors in the network to capture multi-limb data. This, in turn, diminishes the advantages of lightweight design and minimal motion interference. To address this issue, this paper proposes a dual-module driven indirect estimation method for foot orientation. The approach is based on two significant factors in foot orientation changes during gait: the direct driving from the shank and the foot’s intrinsic fine adjustment. Accordingly, two driving modules are constructed, and real-time adjustable weight factors are applied. Validation on 7 healthy subjects and 11 pathological subjects yielded a root mean square error (RMSE) of 3.81 ± 1.21 and an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> value of 0.95. Compared with similar studies, the proposed method not only is applicable to healthy subjects but also demonstrates high robustness in pathological gait. Moreover, the hardware system, consisting solely of two inertial measurement units (IMUs) mounted on the shank, offers significant clinical value.