Railway multibody simulation with the knife-edge-equivalent wheel-rail constraint equations

This paper describes a new numerical procedure for the modelling and simulation of the wheel-rail contact in railway dynamic simulations. The method is called knife-edge-equivalent contact constraint method, or simply KEC-method. Using this method, the wheel-rail contact is modelled as rigid or constraint-based using a set of kinematic constraints that eliminates one-degree of freedom of relative wheel-rail motion. The KEC-method uses a transformed but equivalent wheel profile in contact with a single-point rail. This equivalent profile has the property of producing the same wheelset-rail relative kinematics as the real wheel-rail profiles. The method can be used efficiently online while achieving better computational times than using contact lookup tables. Compared with existing constraint methods, the KEC-method has the following advantages: (1) simplification of the wheel-rail contact constraints, (2) simplified wheel-rail profiles, (3) online solution of the contact constraints, (4) reduction of the number of surface parameters, and (5) increased computational efficiency. A comparative study with respect to the use of efficient contact lookup tables in the simulation of Metro de Sevilla (metropolitan train in the city of Sevilla) shows that this contact method is appropriate to simulate the dynamics of a railway vehicle efficiently.