Railway vehicle speed control in a mountainous track
The vehicle speed has a large impact in the wheel wear evolution. In curve negotiations, the vehicle is subjected to higher accelerations, namely, in the transversal direction and hence the occurrence of flange contact is more probable. In longitudinal accelerations and decelerations, the wheel slip is more prone to occur which lead to wheel wear issues. To simulate realistically a railway vehicle running in a realistic railway track, not only detailed models of the vehicle and the track are required, but also the action of the vehicle powertrain, that is, the axial moment applied on the traction wheelsets that accelerate and decelerate the vehicle, must be considered. This work proposes an approach to simulate the vehicle at prescribed speed for three-dimensional tracks. To control the vehicle speed, a driver constraint is applied in the traction wheelsets. This constraint requires a database that contains the vehicle speed and acceleration as function of time. This database can be obtained experimentally or it can be deduced since the vehicle speed depends on the track geometry, namely, the track curvature and cant angle as function of the track length. The approach proposed here to obtain the vehicle speed profile for an arbitrary railway track considers the vehicle speed constant in tangent and curve negotiations, while the speed variations, which occurs before and after curve negotiations, are assumed linear. The speed for the track curves is found based on the non-compensated acceleration principle. To demonstrate the applicability of the proposed method, the light rail vehicle is simulated in a realistic railway track, fully three-dimensional and with track irregularities, with an extension close to 2.5 km. The wheel-slip, the non-compensated acceleration and the moment developed by the powertrain of the vehicle are discussed.