On the influence of wheel-rail combination on active wheelset steering control with wheelset angular velocity feedback and countermeasures

Active wheelset steering using wheelset angular velocity feedback has been proposed and proven effective in achieving one of the goals for perfect steering condition, i.e. minimising longitudinal creep forces and thus wear. This control strategy relies on the contact parameters of wheel-rail pairs to generate a desired angular velocity by using the wheel rolling radii. Some wheel-rail combinations give a non-monotonic function of the average rolling radius with respect to curve radius, which therefore poses a difficulty in controlling active steering with the angular velocity feedback. This study aims to investigate the effect of different wheel-rail combinations and wheel wear. Worn wheels in general tend to cause a non-unique function whereas the original profile gives a monotonic one. Two countermeasures are then investigated to cope with the raised challenges. First, the reference signal generated from the approximated average rolling radius method has proven to be effective for both the original and the least worn profile; however, a wheel with higher wear depths would require a new tuned scaling factor. The control strategy based on equal wheelset angular velocity is then investigated with two schemes: equal wheelset angular velocity within the same running gear and equal angular velocity of all wheelsets within the vehicle. Both schemes provide significant wear number reduction, but the second approach results in better distribution of wheel-rail lateral forces among all wheelsets. This control strategy can also relax the demanded knowledge of wheel-rail contact properties and vehicle travelling speed.