Model Reference Adaptive Control of Train Dynamic Braking

Model Reference Adaptive Control (MRAC) is developed to control the amount of current through the traction motors under various wheel/rail adhesion conditions while braking. More accurate estimation and control of train braking distance will allow the trains to be run with closer spacing. In order to minimize the braking distance of a train, dynamic braking forces need to be maximized while maintaining good wheel/rail adhesion. Wheel/rail adhesion coefficient plays an important role in safe train braking. Excessively large dynamic braking can cause wheel lockup that can damage the wheels and the rail. In addition, it can cause large buff loads that cause derailment or coupler damage. Dynamic braking force is directly proportional to the current supplied to the traction motors. In this study, a multibody formulation of a locomotive and three railcars is used to develop a model reference adaptive controller for adjusting the current provided to the traction motors such that the maximum dynamic braking is achieved, without wheel lockup. Aerodynamic drag and air brake forces are included in the model. The coupler forces are also considered in the control model to ensure that they remain within acceptable levels. The results indicate that the MRAC system significantly improves braking distance while maintaining better wheel/rail adhesion and coupler dynamics during braking.