Research On Fault Diagnosis For Railway Jointless Track Circuits

A jointless track circuit is the fundamental infrastructure in Chinese Train Control System, it is a typical safety critical system and is a key issue affecting the efficiency of railway transport. However, fault diagnosis and maintenance methods for track circuits cannot meet the urgent needs of the development of railway transport in China, some "inertia faults" even become prominent weaknesses in production of railway safety. It is significantly important to carry out systematic research on fault diagnosis for track circuits.In this paper, the ZPW-2000A jointless track circuit is used as the study object which is widely used in China railway system. An equivalent circuit model of an unoccupied track circuit is established based on two-port network theory, the correctness of the model is validated using experiment data based on track circuit physical mode and real data based on Signal Centralized System, then the main fault modes are summarized and relationships between fault modes and monitoring variables are investigated. Similar work is done for a track circuit under occupied condition. In particular, the wheel-rail contact resistance which is a key factor to cause shunt disfunction of a track circuit is modeled and investigated using Electrical Contact Theory, then the mechanism of shunt disfunction is analyzed in the view of theory.Based on these results, fault diagnosis methods for typical fault modes for the unoccupied track circuit are studied. Firstly, a fault diagnosis method which combines Support Vector Machine and Combination-based multi-class strategy is proposed, a multi-class probability estimation algorithm and an amendment algorithm considering the loss for misclassification for diagnosis results are presented. Furthermore, In order to obtain the information of the location of faulty compensation capacitor, that cannot be got from the above method, a fault diagnosis method for compensation capacitors is proposed which is based on Ensemble Empirical Mode Decomposition and Phase Space Reconstruction Theory, in which the signal from on-board monitoring system for an occupied track circuit is used as the analyzed object. Three different sources of data: simulated data based on track circuit model, experiment data based on track circuit physical model and real data from monitoring system are used to test the preference of the diagnosis methods, Experiments’results show that the fault models can be well diagnosed using the approach, and the preference is not sensitive to interference. The innovations of the dissertation are as follows:(1) The study investigates the relationships between fault models and monitoring variables of a jointless track circuit which combines Signed Directed Graph, Independent Component Analysis and linear fit method and so on, this work provides the necessary prior knowledge for fault diagnosis research.(2) The study proposes a wheel-rail contact resistance model based on Electrical Contact Theory, based on the model the variation mechanism of the wheel-rail contact resistance and relationship between the resistance and influence factors are investigated quantitatively, this work provides a theoretical basis for the prediction and elimination of shunt disfunction.(3) The study proposes a fault diagnosis method for track circuits based on Support Vector Machine and Combination-based multi-class stratagem, in which the signal from ground monitoring system for an unoccupied track circuit is used as analyzed object. The adaptability and generalization ability of this method can comply with the requirements of maintenance.(4) The study proposes a multi-class probability estimation algorithm for diagnosis results using Sigmoid function model and generalized Bradley-Terry model, in doing so, the expression of diagnosis results is more reasonable.(5) The study proposes a fault diagnosis method for compensation capacitors in track circuit based on Ensemble Empirical Mode Decomposition and Phase Space Reconstruction theory, in which the signal from on-board monitoring system for an occupied track circuit is used as analyzed object. This method is effective for incipient fault of a compensation capacitor, and is not sensitive to interference.