In this paper, a model of the electropneumatic brake used on subway trains is developed; it facilitates brake system analysis, fault diagnosis and controller design. This objective is met by decomposing an electropneumatic brake into smaller modules and developing detailed models at three levels. The basic subcomponent models of the electropneumatic brake are built using a lumped parameter method. Then individual models are developed based on the subcomponent models. Finally, a complete model of the electropneumatic brake is developed by assembling all the valve models. Simulation models of these three levels are built using Matlab-Simulink. Important subcomponent models are verified by comparison with experimental results. Furthermore, a test rig is set-up to validate the complete brake model. Experimental and simulated results suggest that the model is able to closely predict the behaviour of the electropneumatic brake: brake filling and releasing time differences between experimental and simulated results are less than 10%; the cause of steady state pressure error of a real electropneumatic brake can be explained using the model; other behaviour of a real electropneumatic brake (sharp pressure jump and drop, pressure oscillation, thermal exchange) can be predicted and better understood using the proposed model.
Instead of using knowledge-based controllers, which need a lot of experience and experimental data to form a reliable knowledge base, a model-based controller is proposed in this article based on a sliding mode control method to control the brake cylinder pressures of an electropneumatic brake on subway trains. The complicated structure of the electropneumatic brake is simplified, and an order-reduced nonlinear model of the plant is built. An equivalently continuous technique based on pulse width modulation is used to deal with the discontinuity of the plant model, which is derived from the discontinuous nature of On/Off valves. The nonlinear sliding mode controller is designed for air charging and discharging periods, respectively. Measures such as continuous approximation and control dead zone are introduced into the controller to improve control performance. This article concerns mainly about the theoretical part of the whole research. Plant parameter identification and controller tests are performed in a sequel article.
This paper proposes the design of an aerodynamic braking device for a high-speed train. The design is based on the parameters of the high-speed train and the working principles of airplane wings. The proposed device is a unidirectional opening model driven by hydraulics. The prototype uses hard-wired signals to transmit braking commands on eight levels. The important characteristics of the device include a synchronous action and a fault-oriented security design. Its functions include service braking, gradual braking, emergency braking and self-checking. Simulation results show that deceleration in the high-speed zone between 250 and 500 km/h can be improved by between 8 and 60%. When the train runs at 500 km/h, the braking deceleration rate can be improved by 0.12 m/s 2 . The simulation results are found to agree with wind tunnel test results. The braking characteristics are also investigated using a test bed, which mimics the aerodynamic load exerted on the prototype when the train is running between 0 and 550 km/h. It is clearly demonstrated that the proposed principle of the aerodynamic braking system is feasible and its design scheme is reasonable. The aerodynamic braking device can survive a 50,000 N aerodynamic load, and the time taken to achieve the maximum braking capacity, which is the time taken to take the brake panel from its closed position of À5 to the maximum angle of 75 , is less than 3 s. The proposed prototype therefore offers an important step in the design of practical systems.
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