For a healthy individual, the knee and ankle generate a significant amount of power output to support the locomotion. The majority of existing transfemoral (TF) prostheses, however, have been limited to energetically passive devices. The inability to generate net power output poses a serious limitation to their performance in restoring locomotive functions, especially those requiring significant power output, such as walking upstairs and upslope [1,2]. Furthermore, even during level walking, TF amputees fitted with passive prostheses exhibit asymmetric gait, expend more metabolic energy [3], and exhibit a significantly higher amount of hip power and torque [1], in comparison with healthy subjects.
To obtain a TF prosthesis with active power output, developing a compact actuation system is a key challenge. In the early research efforts by Flowers and Mann [4], the active knee was actuated with a hydraulic actuator, which offers...
