Comparison of Different Actuation Concepts for the Knee Joint During Stair-Climbing

Maximizing efficiency and minimizing metabolic expenditure are pivotal in advancing transfemoral prosthetics. Designing an energy store/release mechanism emerges as a critical pursuit within this scope. This study mainly compares the performance of the direct drive (DD), series elastic actuator (SEA), and parallel elastic actuator (PEA) concepts for a knee joint during the stair-climbing task. Additionally, the conceptual design of an actuator utilizing a mechanism to transfer the generated force by the actuator to the knee joint is proposed. It is shown that the actuator's weight of the proposed robotic knee (Rnee) prosthesis is 68%, 60%, and 31% lighter than the DD, SEA, and PEA concepts, respectively. Notably, a comprehensive scoring method evaluating mass, complexity, backdrivability, and inertia solidifies the Rnee as a beacon of efficiency. Its overall score surpasses the DD, SEA, and PEA concepts by 162%, 23.5%, and 5%, respectively.