Design of a Transtibial Prosthesis Utilizing Active and Passive Components in Conjunction with a Four-Bar Mechanism

This thesis outlines the design and testing of a powered ankle prosthesis which utilizes a four-bar mechanism in conjunction with a spiral torsion spring and a servo motor that mimics non-amputee (normal) ankle moments during the stance phase of gait. Previous research has shown that this novel approach is feasible, but the proof-of-concept prototype was not designed to be able to be worn by an amputee due to size, strength and mobility limitations. The goal of this research was to redesign the transtibial prosthesis to fit the requirements of the targeted amputee population. A preliminary virtual prosthesis was designed using a computer-aided engineering (CAE) program; it was then subjected to a dynamic motion simulation (equivalent to the bench testing standards) where reaction forces between components were recorded. A finite element analysis (FEA) was then performed on crucial components to ensure safety, aid in material selection, and reduce weight. With a thorough FEA complete, components of the prosthesis were machined, and then the prosthesis was constructed and bench tested for the foot-flat through toe-off portion of gait (stance phase). A prosthesis was designed, optimized, fabricated, and tested with the purpose of demonstrating its ability to match crucial ankle moments during the stance phase of gait