Defect free optimization of a polycentric prosthetic knee design using imperialist competition-inspired optimization method
The disability of lower limbs is one of the biggest problems facing human lives. In order to restore the missing functionality and aesthetic feature of the amputee's locomotion, finding the optimal design of the human lower limb knee prosthesis is crucial. This paper focuses the design optimization of a four bar knee mechanism (FBKM) capable to reproduce the complex flexion/extension knee joint motion in the sagittal plane with variable instantaneous centre of rotation (ICR) positions. Thus an optimization approach with appropriate constraints is formulated in order to consider the degree of compatibility between the trajectories of the human reference knee joint ICR and the ICR of the FBKM. To solve this high nonlinear optimization problem, an algorithm based on multi-objective modified imperialist competitive method (MOMICA) is proposed where all the constraints are managed with the penalty method. The obtained MOMICA results showed a capability to reach a small error between the reference knee ICR and the ICR of the FBKM. The obtained results prove the effectiveness of the proposed optimization approach and MOMICA method for the optimal synthesis of the FBKM, compared with other literature techniques.