Research On Detection Method Of Rail Fracture Based On Singular Value Decomposition Of TCR Record Information

Rail fracture is one of the common faults of railway lines,which seriously threatens the safety of railway.Once the running train have an anccident because of rail fracture,the consequences are very serious.The ZPW-2000 A jointless track circuit is widely used to realize the rail broken detection of each track circuit section.It is one of the important means of the rail broken detection system in China.However,this method is only used to detect the broken rail state of track circuit.The fracture state of track circuit with cracks and the electrical connection is still not detected.At the same time,it can not determine the specific location of the rail fracture.In this thesis,to solve these problems,the change laws of the track circuit reader(TCR)induced voltage signal of ZPW-2000 A jointless track circuit at fracture state of track circuit is studied,and a method to detect the rail fracture is presented by using the mutation characteristics of TCR induced voltage amplitude envelope curve.The main contents of this thesis are listed as follows:Firstly,four terminal network model of fracture state of ZPW-2000 A jointless track circuit under the condition of shunt state is established.A short rail with a fracture point is equivalent to an impedance series connects in the circuit.Then,the main track circuit is divided into different state units by compensating capacitance,and the transmission characteristics are represented by different four terminal networks.The distribution coefficient method is used to solve the four terminal network coefficients.Finally according to the four terminal network theory,the four terminal network model of fracture state of ZPW-2000 A jointless track circuit under the condition of shunt state is established.The TCR induced voltage amplitude function of the fault state is obtained based on the model.Combined with the electrical parameters of ZPW-2000 A jointless track circuit,the TCR induced voltage magnitude function of fracture state is simulated and analyzed by using Matlab.With the ballast resistance and fracture position and fracture point equivalent impedance as variables,the influence of these factors on the envelope curves of the TCR induced voltage amplitude of fracture state is analyzed.The results show that,regardless of the variation of these variables,the TCR induced voltage amplitude envelope curve always occurs mutation at the fracture point of the rail.Therefore,it can be used to detect the fault of rail fracture according to the mutation characteristics of TCR induced voltage curve.At last,in order to accurately detect the position of the mutation point of TCR induced voltage amplitude envelope curve at fracture state,the signal singularity detection method of multi-resolution singular value decomposition(MRSVD)is studied.The MRSVD algorithm is used to decompose the TCR induced voltage amplitude signal in different levels,and the MRSVD detail signals at different levels are obtained.Then,according to the “zero crossing point” of the detail signal,the position of the mutation point of the signal is more accurately located.The simulation results show that the mutation point of TCR induced voltage amplitude envelope curve can be accurately detected by the detail signals of each layer.The feasibility of using this method to detect rail fracture is verified.