Guo Xie

A Prediction Method Based on Stepwise Regression Analysis for Train Axle Temperature

The axle temperature of the high speed train is the most direct reflection of the train operating conditions while it is also affected by many factors. The factors which significantly affect the axle temperature are screened out by using the stepwise regression analysis and the prediction equation of the axle temperature is established, so as to compare the predicted data and the measured data. The validity of the coefficients in the equation is verified through R-squared, F test and T test. The experiment shows that R-squared is between 0.81 and 0.93, indicating a high degree of fitting prediction equations, and F test results show that the overall equation is significantly better. The results of T test indicate that the velocity, the carrying capability and the ambient temperature have significant influence on the change of axle temperature. But the traction and the power of traction have less effect. The result shows that this method can reflects the variation trend of axle temperature, which can provide support to the operation and maintenance of axle.

Study on Formal Specification of Automatic Train Protection and Block System for Local Line

This paper presents a formal specification of an Automatic Train Protection and Block (ATPB) model for local line railway system in Japan proposed by the author [12], and validates the model by internal consistency proving and systematic testing. The system consists of two parts, the on-board subsystem and ground subsystem. The former is to detect the basic state of train, such as position, speed and integrity, monitor the speed, communicate with ground equipment and record the relative events. And the latter is responsible for communicating with train, controlling the route and interlocking, and decision-making for train operation adjustment. The main purpose of this project is to improve the efficiency and guarantee that there is no collision, no derailment and no over speeding at the same. The formal language used in this project is VDM++. And the state and specification of operation are all checked and validated using VDMTools. The results confirm the correctness of this system and the model throws new light on practical system design.

Fairness-power consumption re-topology strategies for mobile botnet

Mobile botnets have recently evolved due to the rapid growth of smartphone technologies. In this paper, we designed a region C&C server selected algorithm for the atomic network of the heterogeneous multi-layer mobile botnet. The nodes are divided into two categories based on the energy threshold division. The Gini coefficient is introduced to estimate the current power gap of nodes in the atomic network. And we assign the probability of being selected as region C&C server to each kind node. Experimental results indicate that the method we proposed can effectively prevent the reduction of network size due to improper node selection.

Data-Based Axle Temperature Prediction of High Speed Train by Multiple Regression Analysis

Axle is a key equipment of high speed train, and affects the safety of train operation. The fault of axle is commonly detected by comparing the current axle temperature with a fixed temperature threshold. Owing to the complex mechanism of axle temperature rising, the axle temperature has a wide variation range even working in normal condition. Therefore, the shortcomings of the method with a fixed temperature threshold are obvious: a high threshold may leads to missing alarm, existing potential safety risk, on the contrary, a low one can ensure the safety, but easily leads to failing alarm, causing unnecessary troubleshooting and maintenance. In view of the problem, a model for the calculation of dynamical temperature threshold is proposed in this paper by relational analysis of monitoring data. Specifically, after analyzing the characteristic of axle temperature changing, the temperature prediction process is divided into three stages according to its running modes, i.e. acceleration, stable running and deceleration. Then the temperature prediction model is established and validated, and the results denoted the effectiveness and practicability.

Data-Based Health State Analysis for the Axle of High Speed Train

Taking into account that the present popular methods, such as the judgement of the axle failure based on temperature threshold, and the early warning of axle based on real-time temperature analysis, cannot analyze the changing of performance trends, a health state analysis method for the axle of high-speed train based on long-term temperature monitoring data is proposed in this paper, which including the following main steps: (1) Preprocessing of the original data to correct the singular zero value and complement the missing values, (2) Smoothing of the processed data in order to automatically extract the beginning and end points of every temperature rising stage of axles, (3) Establishment of the calculation method of temperature rising rate, and evaluating the health sate of axles based on the temperature rising rate. Finally, the proposed method is validated based on the data from a test line, the results demonstrate the effectiveness and practicability of the method.

Formal Analysis of Automatic Train Protection and Block System for Regional Line Using VDM

This paper introduced a novel railway system, Automatic Train Protection and Block (ATPB) briefly, which is proposed to improve the efficiency of existing regional train lines with low cost in Japan. The biggest superiority of ATPB system is a great use of universal and mature technologies, such as GPS and regular mobile telephone networks, so that there is nearly no increment of trackside equipments in the reconstruction. Then in order to guarantee the system safety, a formal model of ATPB is established and analyzed by formal method VDM++. Firstly, the specification is specified by VDM++ formally without ambiguity. Secondly, its internal consistency is proved by discharging the proof obligations. And finally, its satisfiability is checked by systematic testing, which executes specification and checks the outputs against corresponding inputs.

A UDP-based way to improve data transmission reliability

In real-time control systems, a fast and reliable data transmission mechanism is necessary. This paper analyzes the advantages and disadvantages of the existing data transmission protocol and proposes a data transmission protocol called Deque-ERUDP (Deque Efficient and Reliable Protocol Based on UDP) which can guarantee data transmission reliability and efficiency. The proposed protocol uses double sub-queue data transmission and acknowledgment mechanism. This protocol controls TIQ (Timeout Interval of Queue) and TIP (Timeout Interval of Packet) dynamically to avoid network congestion. By comparing the results of simulation experiment, it really verifies the feasibility of Deque-ERUDP and improves the reliability of data transmission very well.

A Feasible Control Strategy for LQG Control Problem with Parameter and Structure Uncertainties

Previous efforts have mainly been made on Linear Quadratic Gaussian (LQG) control problem with parameter uncertainties. However, in practice the change of system environment and parameters usually leads to the change of system structure. On the basis of a receding horizon strategy forth LQG control problem with unknown parameters, this paper provides a solution to LQG control problems which involve both parameter and structure uncertainties. When system parameters are estimated and updated gradually, this method considers the impact of the change of system structure on the performance index. It realizes parameters estimation based on posterior probability by Bayesian theorem, eliminates the correlation between system structures by changing the weighted symmetric matrices, obtains control gain minimizing the performance index and learns the future information at the same time. Finally, simulation results illustrate the effectiveness and accuracy of the proposed method.

A Strategy to Formalize Specification and Its Application to an Advanced Railway System

This paper proposes a novel strategy for formally analyzing functional requirements specification (FRS) and applies it to the Automatic Train Protection and Block (ATPB) system, which is proposed t...

Theory and methodology of object-oriented formal modelling

Although formal methods (FMs) are highly recommended by several International Standards for safety critical systems, almost all of the existing work on FMs focused on formal models which only have internal inconsistencies. How to guarantee the external consistency (or correctness) of a formal model, i.e., satisfying the expectations of users, is a great challenge. In this paper, a strategy to improve the correctness of formal models is proposed by establishing, validating and verifying the function model and data structure separately, and fusing them finally, as the following steps. Firstly UML models are created to graphically express the system structure, and examine the structural completeness and reasonability. Secondly, hybrid automata are created to characterise system behaviours and analyse system action properties. Lastly, an object-oriented VDM++ model is established based on the transformation from hybrid automata to VDM++ functions, and from UML model to VDM++ data structure.