Figure 12.

Experiment results of adaptive hierarchical compliance control with four human subjects who were asked to increase active contribution each time from phase A to phase D. Human active effort (A) was calculated using Eq. 20, ankle movement error (B) was obtained from using Eq. 22, joint nominal pressure (C) was regulated based on human participation by Eq. 19, end-effector admittance (D) was adjusted to human movement error (Eq. 21), and average robot force (E) was the mean value of four muscles’ pulling forces. Blue, red, green, and dark lines represent the results of S1, S2, S3, and S4, respectively.