Walk the Walk: A Lightweight Active Transtibial Prosthesis

Active transtibial prostheses that can overcome the deficiencies of passive prostheses are gaining popularity in the research field. In addition to the advantages in joint torque and gait symmetry, terrain adaptation and total weight are other benefits that can help push active prostheses into the commercial market. In this article, we present a lightweight robotic transtibial prosthesis with damping behaviors for terrain adaptation. The proposed prosthesis, which mainly consists of a low-power motor, weighs only 1.3 kg, excluding the battery. It focuses on terrain adaptation instead of providing positive work at the stance phase. A damping control strategy is proposed to enable the prosthesis to manipulate the ankle impedance during stance with little power consumption. Experiments with three amputee subjects using the robotic prosthesis on different terrains show similar angle trajectories to the intact limb during the controlled flexion (CF) period as well as improved gait symmetry and walking stability compared with the robotic prosthesis in the maximal damping mode. The average power consumption of the prosthesis during one gait cycle is around 3.5 W, and a 0.28-kg rechargeable lithium-ion (Li-ion) battery can sustain a usage duration of more than 12 h or 20,000 steps.