Design of new prosthetic leg damper for above knee amputees using a magnetorheological damper activated permanent magnet only

Magnetorhological fluids (MR) have been applied to numerous devices or systems which require forward or feedback control to achieve desired performances. One of applications is the rehabilitation device. MR dampers applied to artificial joints are implemented with two phases; stance phase: motion to support the feet on the ground, and swing phase : motion to step out. In case of stance phase, the damping force should be increased by applying the magnetic field to support the body. On the other hand, in case of swing phase, the damping force should be removed by not applying the magnetic field so that the prosthesis can be easily rotated by the motor. In this study, a special mechanism of MR damper is proposed to make a prosthetic leg which can derive on/off mode using permanent magnet only. The design mechanism is undertaken and damping force is analyzed to validate the effectiveness of the proposed damper system for the patient’s motion without control device.