amirhosein javanfar

In this paper, the rigid four-bar linkage with clearance joint has been examined. The effects of design parameters have been analyzed separately. Considering chaotic behaviour and undesirable vibrations of the system induced by joint clearance, it has been suggested to use compliant joints for improving these undesirable behaviours. Therefore, rigid four-bar linkage with clearance joint and compliant joint is investigated by pseudo-rigid-body model. Subsequently, the nonlinear behaviour of the compliant mechanism is examined, using fast Fourier transform analysis, Poincare sections, and bifurcation diagram. Comparative analysis of results clearly shows that using appropriate compliant joints causes notable improvements in the behaviour of the system, reduction of sudden impacts, and lower accelerations. 6 cycles simulations of mechanisms demonstrate the decreasing 207 impacts to 33 impacts using compliant joint. Moreover, the results report 87% decrease in follower top acceleration and 64% in clearance joint top contact force. Although using the compliant joint makes limitations in the workspace, but the appropriate and optimized design of the compliant joint results in good improvement in the performance of the system.

Biomechanical modeling of human joints has been considered for a long time by researchers due to its high importance and application. Therefore, methods of modeling joints, and kinematic and dynamic analysis of human movement have continuously been developing. In this paper, a biomechanical human knee model is developed, and a generic procedure for dynamic analysis of contact problems in combination with the musculoskeletal model is introduced. The development of this knee dynamic model includes the geometric expression of collision curves and an algorithm for determining collision points. This presentation addresses cartilage penetration depth and contact force calculation through nonlinear discontinuous contact law. Therefore, the femur and tibia's relative motion is modeled through the combined collision reactions of cartilage and bone in the knee. Moreover, two knee models, the novel curve fitted-plane contact model, and the spherical-plane contact model, have been compared, and a personalized model has been developed for such cases as knee osteoarthritis. There is a difference (average 12%) between the results of the enhanced model and the sphere on the plane model in the cartilage penetration. In the simulation, maximum penetration depth in a healthy knee is reported to be 0.705mm, while in a 75% KOA is 0.521mm, including 0.5mm cartilage-cartilage contact and 0.021mm bone-bone contact. The contact force is not increased in KOA despite the general belief. The cartilage penetration depth exceeds cartilage thickness, and the bone-bone contact leads to pain. It is a suitable tool for the analysis and control of the auxiliary device in order to control the relative motion of the tibia femur and their separation in patients with osteoarthritis of the knee.