Parallel Mechanisms Applied to the Human Knee Passive Motion Simulation

Abstract

This paper proposes a new mathematical solution of the forward kinematics of a one-degree of freedom mechanism for passive knee motion simulation that has been presented in the recent literature. The equivalent mechanism of the knee joint relies upon the assumption that fibers within the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL) and the medial collateral ligament (MCL) are isometric in passive relative motion of the femur and tibia condyles which, in turn, are modeled as spherical and planar surfaces respectively, with a single point of contact in the medial and lateral compartments. The paper also presents the mathematical model of a new mechanism that allows the modelling of spherical tibial condyles, thus overcoming the limitation of the previous mechanism. Finally, comparison with experimental results shows the benefits of the new mechanism.