Adhesion Control Of High Speed Trains Based On Robust And Adaptive Fault-tolerant

ABSTRACT:With the rapid development of High-Speed Train (HST) program in China, the increasing requirement of safe operation for HST has become the major concern. As the train speed increases, the safety issue is becoming more and more important yet challenging to address. There are many factors that must be taken into account in control design, which include the varying and uncertain operation environment, the unknown nature of the rail surface, and unpredictable geological hazards. For this reason, there still remain certain unexpected problems in this field that are of great theoretical and practical interest from control system point of view. As the key of the safe operation for HST, the stability and reliability of the traction and braking performance play an important role. It is necessary to study adhesion control, because stable and reliable adhesion characteristics between wheel-rail are the guarantee of traction and braking performance. Adhesion is a complex system, and a destroyed adhesion can worsen the performance of traction and braking system, cause wheel slip and the accident of train derailment, or even endanger the HST safety in some emergent situations. Advanced adhesion control of HST plays an important role in enhancing train operation safety. This thesis investigates the adhesion control problem for HST, and the major contributions of the work can be summarized as follows:(1) There are many factors that must be taken into account in establishing more suitable and practical dynamic model, which include the complexity, uncertainty and unpredictability of operation environment, time-varying state of rail surface and unpredictable geological hazards factors.(2) Due to characteristics of HST operation state and adhesion, asymptotic tracking control method is chosen in adhesion control design and an expected tracking target must be prespecified. For this reason, a variable step seeking algorithm is introduced. This seeking algorithm just utilizes the relate states of HST in searching process, and it is unnecessary to get all the adhesion relationship under various HST rail conditions. Moreover, this seeking algorithm has obvious advantages in terms of speed and accuracy.(3) An adhesion control strategy with robust estimation is designed based on the established adhesion system model and expected tracking target. Robust estimator can identify the information of unknown system term, and the controller does not rely on many system parameters. Such control strategy is with simple structure and trivial computations. The closed loop stability of the control strategy is proved through Lyapunov theory.(4) On the basis of the developed adhesion control dynamic model with the actuator faults, a robust adaptive fault-tolerant control strategy is proposed to achieve the adhesion control for HST. The control scheme is not only robust against the modeling uncertainties, the unknown time-varying of the system parameters and the uncertain nature between the rail surface and surrounding environment, but also tolerant the actuator failures. Such control strategy is with simple structure and trivial computations. Little human interference and limited system information are required here. The closed loop stability of the control strategy is proved through Lyapunov theory and numerical simulation with MATLAB is conducted to verify the effectiveness of the control strategy.