Phase plane analysis of walking with applications in controlling bipeds and prostheses

In the Human Machine Integration laboratory, we have been designing wearable robots. For our robotic systems, the user’s walking pattern and intent must be determined to generate appropriate motor outputs. In the past, we have used tunable gait patterns, variable stiffness patterns, and a tibia based controller. In this paper, we focus on understanding human gait and the underlying patterns by studying phase curves. For example, we use the progression of the shank phase angle as a metronome to determine the user’s percent gait cycle. We go one step further by studying the phase angle of the shank as a function of the phase angle of the foot. A signature pattern between the two phase angles is shown. The pattern seems to be invariant to different tasks such as walking, walking quickly, and walking on slopes. In the future, it is hoped that a shank phase angle with a unique orientation and angular speed can be used to determine a unique foot phase angle allowing the generation of appropriate motor outputs.