Stiffness change of ankle joint during different activations of tibialis anterior muscle

摘要

Impedance control plays an important role in the control of human-machine control system, especially in rehabilitation devices. It is essential to estimate patient's limb stiffness to adjust the impedance parameters of controller. A large number of studies showed that muscle co-contraction would influence the limb stiffness. This study aimed to investigate the change of ankle joint stiffness using only tibialis anterior electromyography (EMG) during different activations of tibialis anterior. Four young subjects were recruited to keep the activation of tibialis anterior at four ranges (0~10%, 10~20%, 20~30%, 30~40%) with a PD-controlled ankle exoskeleton system, as well as minimize the activation of gastrocnemius as much as possible. An EMG-driven Hill-type neuro-musculoskeletal model was used to predict the torque of tibialis anterior. Moving Window Multiple Linear Regression (MWMLR) was applied to calculate the stiffness coefficient of the ankle joint with or without considering the variation of the torque of tibialis anterior. The results showed that the variance of estimated stiffness was smaller without considering the variation of muscle torque. And a significant relationship between the activation of tibialis anterior and the stiffness coefficient of the ankle joint was found.