The influence of the hip joint formulation on the kinematic response of the model of human gait is investigated throughout this work. To accomplish this goal, the fundamental issues of the modeling process of a planar hip joint under the framework of multibody systems are revisited. In particular, the formulations for the ideal, dry, and lubricated revolute joints are described and utilized for the interaction of femur head inside acetabulum or the hip bone. In this process, the main kinematic and dynamic aspects of hip joints are analyzed. In a simple manner, the forces that are generated during human gait, for both dry and lubricated hip joint models, are computed in terms of the system's state variables and subsequently introduced into the dynamics equations of motion of the multibody system as external generalized forces. Moreover, a human multibody model is considered, which incorporates the different approaches for the hip articulation, namely, ideal joint, dry, and lubricated models. Finally, several computational simulations based on different approaches are performed, and the main results are presented and compared to identify differences among the methodologies and procedures adopted in this work. The input conditions to the models correspond to the experimental data capture from an adult male during normal gait. In general, the obtained results in terms of positions do not differ significantly when different hip joint models are considered. In sharp contrast, the velocity and acceleration plotted vary significantly. The effect of the hip joint modeling approach is clearly measurable and visible in terms of peaks and oscillations of the velocities and accelerations. In general, with the dry hip model, intrajoint force peaks can be observed, which can be associated with the multiple impacts between the femur head and the cup. In turn, when the lubricant is present, the system's response tends to be smoother due to the damping effects of the synovial fluid.
Influence of the Hip Joint Modeling Approaches on the Kinematics of Human Gait
Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received May 11, 2015; final manuscript received October 14, 2015; published online January 29, 2016. Assoc. Editor: Zhong Min Jin.
Costa, J., Peixoto, J., Moreira, P., Pedro Souto, A., Flores, P., and Lankarani, H. M. (January 29, 2016). "Influence of the Hip Joint Modeling Approaches on the Kinematics of Human Gait." ASME. J. Tribol. July 2016; 138(3): 031201. https://doi.org/10.1115/1.4031988
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