Use of Dynamic FEA for Design Modification and Energy Analysis of a Variable Stiffness Prosthetic Foot

Abstract

Different tasks and conditions in gait call for different stiffness of prosthetic foot devices. The following work presents a case study on design modifications of a prosthetic foot, aimed at variable stiffness of the device. The objective is a proof-of-concept, achieved by simulating the modifications using finite element modeling. Design changes include the addition of a controlled damping element, connected both in parallel and series to a system of springs. The aim is to change the stiffness of the device under dynamic loading, by applying a high damping constant, approaching force coupling for the given boundary conditions. The dynamic modelling simulates mechanical test methods used to measure load response in full roll-over of prosthetic feet. Activation of the element during loading of the foot justifies the damped effect. As damping is in contrast to the main design objectives of energy return in prosthetic feet, it is considered important to quantify the dissipated energy in such an element. Our design case shows that the introduction of a damping element, with a high damping constant, can increase the overall rotational stiffness of the device by 50%. Given a large enough damping coefficient, the energy dissipation in the active element is about 20% of maximum strain energy.

A Reduced-Order Computational Model of a Semi-Active Variable-Stiffness Foot Prosthesis

“…The VSF is an ideal device for studying the effects of prosthesis stiffness on gait mechanics because it can readily exhibit a range of forefoot stiffness values, thereby eliminating the need to purchase or manufacture multiple prostheses as in [26][27][28]. In doing so, this also eliminates confounding variables that accompany a foot-switching compared the angular stiffness response of a finite element foot prosthesis model to data from mechanical tests [13].…”

“…Simulations based on computational models can be powerful tools for evaluating potential biomechanical interventions, such as the implementation of a novel ESR prosthesis. Recently, simulations have been used to aid in the iterative design process and improve user-specificity [11][12][13]. Inverse simulations provide the ability to estimate values that cannot be measured in vivo (e.g.…”

Design and Analysis of The Energy Storage and Return (ESAR) Foot Prosthesis Using Finite Element Method

“…The fabrication method used is the EMRCC (Extended Manufacturer Recommended Curing Cycle) method. In this prosthesis leg, the design must meet the criteria of being able to withstand a weight of 70 kg with a loading of 1.2 times the weight for normal walking activities [15] So this prosthesis leg must be able to withstand a maximum weight of 84 Kg, so that the static loading on the Ansys Software uses a force of 823.7 N.…”

“…as in Table 1. In this prosthesis leg, the design must meet the criteria of being able to withstand a weight of 70 kg with a loading of 1.2 times the weight for normal walking activities [15].…”

Application of the Finite Element Method in the Analysis of Composite Materials: A Review

“…Some applications of FEM for composites in the sport sector: (a) a tennis racket, (b) a bicycle and (c) a prosthetic. Reproduced with Creative Common License[331].…”