Design of semi active knee joint with magnetorheological (MR) damper

In this study, electronic above knee prosthesis using magnetorheological (MR) cylinder is developed. The prosthesis structure having a proper knee mechanism is used for MR cylinder damping produced for experimental studies. Movement of knee joint originated from hip is damped with these cylinders and through a control algorithm running on microcontroller the system achieves the motion closer to the natural movement of leg. The performance of MR cylinder in the prosthesis are examined while a healthy subject wearing a custom designed socket mounted to prosthesis walks interchangeably at predetermined speed. According to the results obtained by the image based Motion Analysis System (MAS) the walk with the prosthesis using the MR damper is closer to the natural gait in terms of gait cycle duration and phases. On the other hand, in terms of the required maximum knee angle, the prosthesis with pneumatic damper performs better when the natural gait cycle is considered.