@CONFERENCE\{IMM2006-05848,
    author       = "H. True",
    title        = "On Nonlinear Railway Vehicle Dynamics",
    year         = "2006",
    month        = "oct",
    pages        = "149-166",
    booktitle    = "Workshop: Track for High-Speed Railways, 12. and 13. October 2006, {FEUP} Porto, Portugal",
    volume       = "",
    series       = "",
    editor       = "",
    publisher    = "Civil Engineering Department, Faculty of Engineering of the University of Porto",
    organization = "",
    address      = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/5848-full.html",
    abstract     = "In this article we first outline the most important properties of nonlinear dynamic systems and contrast them with known properties of linear dynamic systems. Vehicle systems are nonlinear.
Next some important features of the vehicle dynamic systems that are caused by their nonlinear nature are presented. That section is followed by a description of the most important contributions to the nonlinearities in railway vehicle dynamics. They include first of all the kinematic and dynamic contact relations in the wheel/rail contact area. The elements in the suspension systems of the vehicles all have nonlinear constitutive mechanical laws, and the response of the track also contribute with nonlinearities. Some of the nonlinearities are explained in some detail.

The vehicle models can very often be formulated in a coordinate system that is fixed to the vehicle and moves with its speed, which may be time dependent. The speed of the vehicle is then a natural external control parameter in the dynamic problem.

Last we mention some problems that are connected with the numerical analysis of the dynamics of the railway vehicles with their rather high number of degrees of freedom. Special attention must be paid to non-smooth systems – and most vehicle dynamic problems are non-smooth.

The article ends with concluding remarks and a list of references."
}