A Wearable Device for Ankle Impedance Estimation During Walking

This paper proposes a wearable device for the estimation of ankle joint impedance modulated depending on the gait cycle. The wearable perturbator device is designed as a boots-type and equipped with a low-reduction geared DC motor. The rotation axis of the motor is aligned with the dorsi-plantar flexion axis to ensure little disruption to the natural ankle motion for walking. A binary signal is employed as the torque command, and the dynamic response of the ankle to the external perturbation is extracted from the recorded ankle motion during walking by using a high-pass (band-pass) filter. The ankle impedance is then estimated by the least squares method. Through the experiment with four healthy male participants, the proposed wearable device is verified.