Compact MR Rotary Brake for Prosthetic Applications

Abstract

Controllable stiffness can greatly improve the usefulness of a prosthetic foot and its users comfort. In this thesis the feasibility of using a magnetorheological rotary brake in conjunction with carbon fiber blades to provide variable stiffness in a prosthetic foot is investigated. For the brake to be effective in a prosthesis it needs to be compact. A known reference design, currently used in a prosthetic knee, is scaled down and a finite element analysis applied to investigate the effect chosen parameters have on the torque output. The size is investigated with regard to the radius of the brake because of limited space as well as weight restrictions. The minimum torque output needs to be high enough to provide a range for the stiffness to be considered variable and have an effect on the prosthesis behavior. The results show that a magnetorheological brake retains enough braking torque after being scaled down to be considered an option in a foot prosthesis.