A chaotic bio-mechanics model of dairy cow leg.

The real knee joint is very complex. When the knee joint performs the leg bending action, the relative motion between the lower surface of the femur and the upper surface of the tibia includes rolling and sliding. Therefore, a simple hinge pair model cannot correctly represents the real knee joint motion. In this work, we build a structure model of cow leg with both sliding and hinge pairs firstly; Then, according to the second kind of Lagrange equation of the structural model with the potential force and dissipative force, the system dynamics model is established. Third, the environmental noise, such as the elasticity of the ground which exerted on the cow's feet directly, is taken into the nonlinear model, so, a more practical dynamic model of cow leg is constructed. Numerical simulation shows that the model has strong chaotic motion characteristics,and the model with noises is better than one without noises. For the chaotic model, small parameter changes will lead to large changes in the phase orbit diagram, which built a foundation for us to study and identify the pathology of dairy cows based on the dynamic weight time series signals during the process of dairy cows' progress. • The chaotic structural model of cow leg with sliding and rolling is established. • The environment noises is embed into the model to improve the practical performances. • The mathematical model of chaotic dynamics of the cow leg is constructed. [ABSTRACT FROM AUTHOR]