title: The Effects of the Inertial Properties of Above-Knee Prostheses on Optimal Stiffness, Damping, and Engagement Parameters of Passive Prosthetic Knees.
abstract: Our research aims to design low-cost, high-performance, passive prosthetic knees for developing countries. In this study, we determine optimal stiffness, damping, and engagement parameters for a low-cost, passive prosthetic knee that consists of simple mechanical elements and may enable users to walk with the normative kinematics of able-bodied humans. Knee joint power was analyzed to divide gait into energy-based phases and select mechanical components for each phase. The behavior of each component was described with a polynomial function, and the coefficients and polynomial order of each function were optimized to reproduce the knee moments required for normative kinematics of able-bodied humans. Sensitivity of coefficients to prosthesis mass was also investigated. The knee moments required for prosthesis users to walk with able-bodied normative kinematics were accurately reproduced with a mechanical system consisting of a linear spring, two constant-friction dampers, and three clutches (R2=0.90 for a typical prosthetic leg). Alterations in upper leg, lower leg, and foot mass had a large influence on optimal coefficients, changing damping coefficients by up to 180%. Critical results are reported through parametric illustrations that can be used by designers of prostheses to select optimal components for a prosthetic knee based on the inertial properties of the amputee and his or her prosthetic leg.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 e-mail: ynarang@seas.harvard.edu.
authors.forename: Yashraj S
authors.initials: YS
authors.lastname: Narang
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 e-mail: murthya@mit.edu.
authors.forename: V N
authors.initials: VN
authors.lastname: Murthy Arelekatti
authors.affiliation: Mem. ASME Assistant Professor Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 e-mail: awinter@mit.edu.
authors.forename: Amos G
authors.initials: AG
authors.lastname: Winter
mesh_terms: D000054:Acceleration; D000672:Amputation Stumps / Q000503:physiopathology* / Q000601:surgery*; D000674:Amputees / Q000534:rehabilitation; D001186:Artificial Limbs; D003198:Computer Simulation; D017076:Computer-Aided Design; D055119:Elastic Modulus; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017276:Friction; D005684:Gait; D007719:Knee Joint / Q000503:physiopathology*; D007720:Knee Prosthesis; D008954:Models, Biological; D014783:Viscosity