Abstract
By analyzing the mechanism of pure air emergency brake for high-speed train, the discrete emergency brake model is established. Aiming at the problem that time-varying hidden parameters cannot be observed directly, the sliding window-based expectation maximization is proposed, and the unobserved time-varying brake parameters are identified. Firstly, the position and size of the sliding window are selected; then, the sliding window-based expectation maximization is used for brake parameter identification; finally, combined with the gradient optimization, the optimal identifications of emergency brake parameters are obtained. The simulation results show that the brake parameters can be identified quickly and accurately by the proposed method. Under uniform noise, the identification errors of friction coefficient and braking ratio are ±0.0068 and ±0.0349, respectively, and the maximum relative errors between the identifications and true values are 2.4807% and 1.3154%, respectively, which can meet the actual requirements of the brake system. The effectiveness and practicability of the proposed model and method are verified.
Highlights
As an important part of the rail transportation system [1,2,3], high-speed train plays an important role in national economic development, cultural exchange, and urban construction [4,5,6]
Accurate dynamic modeling is the basis of precise braking. rough the real-time accurate estimation of the performance parameters of braking model, the realtime performance state of the train can be obtained, which greatly ensures the driving safety and improves the driving efficiency [7,8,9]. erefore, it is of great significance to study on high-speed train emergency brake modeling and online identification of time-varying parameters
In order to effectively utilize the regenerative energy of braking train and reduce the actual energy consumption during running, a cooperative train braking control model was put forward by Su et al, which can minimize the actual energy consumption effectively [12]
Summary
As an important part of the rail transportation system [1,2,3], high-speed train plays an important role in national economic development, cultural exchange, and urban construction [4,5,6]. Erefore, it is of great significance to study on high-speed train emergency brake modeling and online identification of time-varying parameters. In order to solve the problem of tracking and controlling the position and speed of high-speed train connected by couplers, an elastic collision dynamics model reflecting the nonlinear traction/braking and driving faults of asymmetric vehicles was proposed by Song and Song [13]. For the dynamic model of high-speed train, a generalized weighted parameter estimation was proposed by Wang et al, and the controller was designed according to the estimation error [15]. Aiming at the time-varying hidden variable parameters which are difficult to observe in the model, an online identification of hidden variable parameters based on sliding window and maximum expectation is proposed, which realizes the real-time acquisition of dynamic characteristics and running state of high-speed train
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