Measurement of Absolute Vehicle Speed With a Simplified Inverse Model

This paper presents the study of a sensing technique for the measurement of the absolute speed of railway vehicles, which is achieved by detecting the time shift of the track random excitations between two wheelsets of a bogie (or truck). A simplified inverse model is designed to extract particular features of motion at the wheelsets from two inertial sensors mounted onto a bogie frame. The time delay in the estimated motions from one wheelset to the other is detected by the means of cross-correlation calculations. The development of the proposed technique is detailed, and the design of an inverse model for the estimation of wheelset motions is presented. The performance of the measurement method is evaluated based on a comprehensive vehicle model using one of the standard multibody simulation packages widely used by vehicle manufacturers and compared with the International Union of Railways (UIC) requirement for wheel slide protection. There is no need to use conventional position encoders, and therefore, difficulties associated with inaccuracy in wheel slip/slide conditions or limited resolutions of the encoders are eliminated. The method presented in the study may provide a reliable and accurate measurement of the absolute vehicle speed essential for railway traction and braking control systems and may also be extended for automotive applications.