Figure 4

Augmentation Factor (AF). The AF was calculated for six devices and compared to the measured metabolic impact for each device [9, 10, 12, 20, 22]. Triangle markers are previously published autonomous devices, square markers are previously published tethered devices, and the circle marker is the presented autonomous exoskeleton of this study. The equation estimated by linear regression is y = 1.1x – 4 with an R² equal to 0.98. In the AF equation, the p⁺ term is calculated by taking the positive work done by an exoskeleton during the gait cycle and dividing by the gait cycle duration. If the net-work done by the exoskeleton is negative, then p^dis is equal to this negative net-work divided by the gait cycle duration, otherwise, p^dis is zero.