Bond graph modeling of rail wheelset on curved track

This paper presents a bond graph model of a free rail wheelset rolling on flexible curved track, considering six degrees of freedom without linearity approximations. Modeling of engineering systems through bond graphs is based on exchange of power amongst the basic elements of a system and several energy domains can be represented in a unified manner. In this paper, the modeling approach is based on creating subsystem bond graph models or capsules representing various analytical aspects of wheelset dynamics. The model is finally converted to a wheelset capsule, which can be further used for the development of truck and carbody models with suspension elements. The model can accommodate any creep force formulation for the rail-wheel contact forces. In this work, both Kalker's linear theory and heuristic modification based on non-linear formulation by Vermeulen and Johnson are used separately in a comparative study. Both these formulations allow the creep forces to be modeled by a non-linear bond graph R elements acted upon by the corresponding slip velocities between the wheel and track. Kinematic analysis of the wheelset is carried out to determine velocities of the contact points. The bond graph is created using software SYMBOLS 2000 and simulated for a set of parameter values.