Research On Fault Detection Technology Of Railway Traffic Signal Cable

Railway traffic signal cable plays a more and more important role in the process of railway transportation industry to the direction of automation and intelligence,but also affects the safe and stable operation of railway traffic,which makes the normal transmission of railway traffic signal cable working signal is more and more important.When the signal cable is faulty,it can quickly locate the fault location,diagnose the fault type,and shorten the fault occurrence time,which is of great significance for the reliable operation of trains.Therefore,the main purpose of this research is to design a set of hardware and software system for fault diagnosis and location of railway traffic signal cables.On this basis,the cable fault detection technology is studied.The Logistic chaos test sequence is adopted to realize the design of cable fault detection method based on extended spectrum time-domain reflectometry(SSTDR),and the location of cable fault points and the judgment of fault types are completed.Logistic chaotic sequence is used as random sequence in SSTDR cable fault detection method,which improves the recognition ability of cable fault reflection signal.Based on the propagation law of traveling wave in cable,the characteristics of traveling wave when it meets different cable fault points are analyzed in detail,and a physical platform is built to verify the theory of traveling wave reflection method.On this basis,the principle of SSTDR for online cable fault detection is further studied,and the feasibility of applying Logistic chaotic sequence to SSTDR is analyzed in detail,instead of the traditional pseudo-random sequence as the test sequence of SSTDR.A hardware and software system for railway signal cable fault detection is designed using FPGA as the main controller.The hardware part mainly includes Logistic chaos test signal generation circuit,fault reflection signal extraction circuit,fault reflection signal acquisition circuit,completed the prototype of the cable fault detector.In the software part,QT Creator is used to design the upper computer user operation and display interface.The designed cable fault detection terminal uses a differential operational amplifier,which effectively eliminates the test signal in standing wave and improves the contrast of the output crest and sidelobes of the correlator.The design of RTL code of each function module of cable fault detector based on FPGA is realized.It mainly includes Logistic chaotic sequence generator and BPSK modulation of sinusoidal signal generated by DDS frequency synthesis technology.A cross-correlation fault location algorithm module based on FPGA is designed,and the time delay between reference signal and fault reflection signal is preliminarily calculated.TCP protocol is used for data transmission between the upper computer and the lower computer with high transmission rate,which can quickly upload the results of cross-correlation algorithm to the upper computer for processing,and carry out data saving,fault distance calculation and type judgment at the terminal.The practical test of the designed railway traffic signal cable fault detector shows that the cable fault detector has high positioning accuracy and long positioning distance.When the fault distance reaches 2000 meters,the positioning error can still be kept within ±1%.