Topology optimisation and customisation of a prosthetic knee joint design

Abstract

Designing light weight and easily customisable prosthetic knee joints that can withstand high impact load while walking is a major challenge. This article will take the typical four bar linkage prosthetic knee joint as an example and tries to improve the design by using topology optimisation. In order to simulate the damping effect of cartilage in a human knee joint, one component of the four bar linkage prosthetic knee joint is redesigned in two steps. Firstly, this component is topology optimised as a compliant mechanism by using a modified Solid Isotropic Material with Penalisation (SIMP) interpolation scheme. After this step, the component not only has the desired damping effect, but also has a lightweight structure, which is still capable of withstanding the prescribed loads. The second step attempts to achieve customisation for users with different body weights. This step is implemented by simply attaching a soft component made of materials such as elastomers, which is customised for different users' weights. The optimisation results are validated by the stress and displacement analysis in ANSYS. This study is the first report applying a tailor made SIMP scheme to optimise prosthetic knee joint.

Keywords:

• topology optimisation
• prosthetic knee joint
• compliant mechanisms
• bionic mechanism design
• design customisation

Acknowledgement

This research has been supported by a CRCG grant from the University of Hong Kong.