Design and Evaluation of a Novel Microprocessor-controlled Prosthetic Knee

Transfemoral amputees demand a mechatronic lower limb prosthesis as technical substitute for restoring their gait functions. Prosthetic knee is the key component of a transfemoral prosthesis. The performance of the prosthetic knee determines the walking ability of the transfemoral amputee. This study proposed a novel microprocessor-controlled prosthetic knee with hydraulic damper and evaluated the performance of the prosthetic knee by function simulation and evaluation platform. The prosthetic knee with electrical-controlled hydraulic cylinder that could modulate knee flexion and extension damping properties independently and continuously by single motor was designed. Gait phase identification system based on knee angle sensor, inertial measurement units mounted on thigh connector and shank and force transducer embedded in shank was proposed. Gait phase identification and damping control strategy were determined by typical gait events during walking. Speed adaption and gait symmetry tests were conducted with a customized gait simulator to evaluate the performance of the proposed microprocessor-controlled prosthetic knee. The angle trajectories of the prosthetic knee were similar under a range of walking speeds. While the symmetry index values indicated that the stance phase was more asymmetry than swing phase, the peak swing flexion knee angles were consistently controlled between 60-70 degrees under different speeds. The knee angle symmetry was observed in different speeds during swing phase. It is suggested that the proposed microprocessor-controlled prosthetic knee could meet the fundamental demands of walking with smooth angular transition across different walking speeds.