Capacitive Sensing-Based Continuous Gait Phase Estimation in Robotic Transtibial Prostheses

Gait phase plays an important role in controlling wearable robot. This paper focuses on the continuous gait phase estimation by using capacitive sensing method for one transtibial amputee wearing robotic prosthesis. First, the capacitive sensing signals are used to record muscles' contraction and relaxation to detect two gait events (heel strike and toe off) as the start points (reset 0 rad) of one gait cycle. Secondly, continuous gait phase estimation is conducted based on the detected gait events (heel strike and toe off, respectively) with adaptive oscillators. In this study, the heel strike and toe off in each gait cycle can be detected with 100% accuracy based on linear discriminant analysis algorithm. The delay ratios for heel strike and toe off are less than 1% within one gait cycle. The root-mean-square errors of continuous gait phase estimation based on the different reset timings (heel strike and toe off) are 0.15 rad and 0.19 rad. The results show the feasibility to estimate the gait phase for amputee based on the residual muscles' capacitive signals.