Locomotive adhesion control + rail friction field measurements = ?

The design and validation of a locomotive adhesion control system is a very complex multi-disciplinary engineering problem that not only requires consideration of the electrical system but also requires to go very deeply into mechanical and material engineering as well as tribology. The typical approach for advanced locomotive traction studies focuses on the development of the following models and algorithms: train dynamics modelling, multibody locomotive model, traction power system model, adhesion control algorithms, wheelrail contact modelling and track models. These are required to cover all the physical processes present in the system. One of the complicated parts of this system is how to represent the creep force characteristics at the wheel-rail interface properly without measurements being performed on existing or modified/upgraded locomotives under traction or braking because any locomotive field measurements involve high testing costs. This paper discusses how this can be avoided using friction measurement data obtained in the field with an experimental tribometer and how that data should be interpreted for locomotive studies, and how it might affect locomotive performance outcomes considering locomotive adhesion control strategies. Numerical experiments have been performed by the co-simulation of two full traction control systems developed in Simulink, and two locomotive mechanical models developed in Gensys multibody software, representing two standard gauge heavy haul locomotives running under traction operational scenarios. All possible limitations and results observed during the development and implementation studies have been discussed.