Control systems and control strategies of active wheelset steering of railway vehicles

QC251028

Abstract

This doctoral dissertation focusses on active wheelset steering of railway vehicles. Active wheelset steering is a mechatronic solution for a solid-axle wheelset that has been proven to improve curving performance. Several aspects are investigated including control strategies, control systems and steering control in turnouts. This aims to explore the interaction of all elements in mechatronic running gear with active steering capability. 

Active wheelset steering can be executed by various control strategies and one of the widely recognised is control strategies for perfect steering condition. Several control variables can be used to achieve such a condition such as wheelset yaw angle and lateral displacement. For instance, wheelset lateral displacement control requires a lateral displacement feedback signal and a knowledge of the wheel-rail contact parameter, that is equivalent conicity of the wheelset. Hence, the estimator based on the dual extended Kalman filter technique is designed to estimate vehicle states and wheelset equivalent conicity. This estimator can potentially be applied for active wheelset steering with lateral displacement feedback. To ease the required sensing and estimation, control strategies for active wheelset steering aiming at achieving perfect steering condition are proposed by considering wheelset angular velocity as a control variable which is easy to obtain through direct measurements. The control strategy is first introduced by considering the main objective to minimise longitudinal creepages in curve. Influence of wheel-rail combinations are investigated as it greatly affect the proposed control strategies. Subsequently, the simplified control strategy and the control strategy based on equal wheelset angular velocity are proposed as alternative solutions to solve challenges from wheel-rail pairs. In addition, a robust control for active wheelset steering is studied as railway vehicles are subjected to disturbances from track inputs and uncertainties mainly from wheel-rail parameter variation. The design and development of robust control system is based on sliding mode control with equivalent control. The complexity of the derived controller is mainly from the required signals. Then, the simplified sliding mode control (SSMC) is investigated. The application of the simplified controller as passive fault-tolerant control is analysed with a consideration of one actuator fault with zero force. The adaptive sliding mode control is proposed to support the full mitigation to actuator failure effect. Another contribution of this thesis also includes steering control in switch and crossing as railway turnout is an important track component that guides movement of the vehicles. The characteristics of turnouts challenge to active wheelset steering system in various aspect. Thus, the optimised steering control in turnouts is proposed to further improve steering performance. The preview of train position is incorporated by using the map-based train positioning. This proposed method can dramatically reduce peaks in wheel-rail wear in switch and crossing.

In conclusion, this research contributes to the advancement in active wheelset steering of railway vehicles in several aspects including control strategies, robust control system and control approach in turnouts for active wheelset steering. The contributions in this thesis would facilitate the practical implementation of active wheelset steering and further performance improvement in railway turnouts.

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