Dynamics of a Running Below-Knee Prosthesis Compared to Those of a Normal Subject

Document Type: Research Paper


1 Mechanical Engineering, Tarbiat Modares University, Tehran

2 Sharif University of Technology, Tehran

3 Biomechanics, Mechanical Engineering Sharif University

4 Mechanical Engineering Department, University of Tehran


The normal human running has been simulated by two-dimensional biped model with 7 segments. Series of normal running experiments were performed and data of ground reaction forces measured by force plate was analyzed and was fitted to some Fourier series. The model is capable to simulate running for different ages and weights at different running speeds. A proportional derivative control algorithm was employed to grant stabilization during each running step. For calculation of control algorithm coefficients, an optimization method was used which minimized cinematic differences between normal running model and that of the experimentally obtained from running cycle data. This yielded the estimated torque coefficients of the different joints. The estimated torques and the torque coefficients were then applied to specific below-knee prosthesis (a SACH foot) to simulate healthy-running motion of joints. Presently the SACH foot is designed for amputee’s walking; our data was used to modify such construct for running purposes. The goal was to minimize the differences between normal human model and a subject wearing a SACH foot during running. Kinematical curves of models for the obtained optimum mechanical properties indicated that prosthetic leg can reasonably produce the kinematics of normal running under normal joint driving torques.


[1] Stein J. L., Flowers W. C., 1987, Stance phase control of above-knee prostheses: knee control versus SACH Foot design, Journal of Biomechanics 20(1):19-28.

[2] Blumentritt S., Werner S. H., Michael J., Schmalz T., 1998, Transfemoral amputees walking on a rotary hydraulic prosthetic knee mechanism: a preliminary report, American Academy of Orthotists & Prosthetists10(3): 61-70.

[3] Sutherland J. L., Sutherland D. H., Kaufman K., Teel M., 1997, Case study forum: gait comparison of two prosthetic knee units, American Academy of Orthotists & Prosthetists 9(4): 168 -173.

[4] Pejhan S., Farahmand F., Parnianpour M., 2008, Design optimization of an above-knee prosthesis based on the kinematics of gait, Proceedings of the 30th Annual International Conference of the IEEE EMBS, Vancouver, British Columbia, Canada.

[5] Peasgood M.E., 2007, Stabilization of a dynamic walking gait simulation, Journal of Computational and Nonlinear Dynamics 2(1):65-72.

[6] Tsai C.S., Mansour J.M., 1986, Swing phase simulation and design of above-knee prostheses, Journal of Biomechanical Engineering, 108(1): 65-72.

[7] Dundass C., Yao G.Z., Mechefske C.K., 2003, Initial biomechanical analysis and modeling of transfemoral amputee gait, American Academy of Orthotists & Prosthetists 15(1): 20-26.

[8] Gard S.A, Childress D.S., Ullendahl J.E., 1996, The influence of four-bar linkage knees on prosthetic swing-phase floor clearance, American Academy of Orthotists & Prosthetists 8(2), 34 -40.

[9] Wojtyra M., 2000, Dynamical analysis of human walking, 15th European ADAMS Users Conference, University Technology, Warsaw.

[10] Iidaa F., Rummel J., Seyfarth A., 2008, Bipedal walking and running with spring-like biarticular muscles, Journal of Biomechanical 41(3):656-667.

[11] Peter S., Grimmer S., Lipfert W., 2009, Variable joint elasticities in running, Informatik Aktuell, Autonome Mobile Systeme 2009:29-136.

[12] Gerrit S., Mombaur K., Knöthig J., 2010 , Modeling and optimal control of human-like running, IEEE/ASME Transactions on Mechatronics 15(5).

[13] Akbari M., Farahmand F., Zohoor H., 2008, Dynamic simulation of the biped normal and amputee human gait, 12th International Conference on Climbing and and Walking Robots and the Support Technologies for Mobile Machines, Istanbul, Turkey.