Design Of ZPW-2000A Track Circuit Inspection System

ZPW-2000 A uninsulated track circuit,which is widely used in signal infrastructure of high-speed railway in China,mainly used for inspection of train occupancy,communication of ground and train,and check of broken track.The stability of the circuit plays an essential role in the security and workpiece of high-speed railway.Its structure is composed of transmitter,receiver,cable and so on.In general,the environment around the track circuit is complicated,which is susceptible to the interference of natural conditions and human factors.Therefore,faults often occur and human inspection is required.ZPW-2000 A uninsulated track circuit relies on frequency shift signal to realize information transmission,so the acquisition and measurement of frequency shift signal has become the top priority for fault diagnosis of it.The purpose of this paper is to develop a set of measuring ZPW-2000 A type uninsulated track circuit frequency shift signal detection equipment,which can easily measure the frequency shift signal of the upper and lower side frequency,low frequency and effective voltage.The main research contents are as follows:(1)Uninsulated track circuit of ZPW-2000 A working principle and characteristics of frequency shift signal as the basic theory,analyzes frequency shift signal’s principle of generation and transmission,signal characteristics.Based on the AD9833—the high precision programmable signal generator,design a set of equipment to simulate ZPW-2000 A uninsulated track circuit to produce a variety of different frequency shift signal generator,is advantageous for the subsequent research of acquisition and measurement of ZPW-2000 A uninsulated track circuit signal.(2)Based on uninsulated track circuit of ZPW-2000 A checking system function and technical requirements,according to the characteristics of the FSK keying frequency shift signal,design a signal filter circuit based on digital filter MAX7490,and a automatic control circuit of orbital signal amplitude based on the digital potentiometer MCP41100,is advantageous for the sampling system to more accurate signal acquisition.(3)According to the technical requirements,in view of the current situation that the frequency domain measurement method has a large amount of computation and the timefrequency domain measurement method is not mature,a patrol inspection system for extracting the characteristics of the frequency shift signal of ZPW-2000 A track circuit is developed in the time domain based on STM32F407 single-chip microcomputer,and the method of capturing the signal edge with the single-chip timer is used.A new demodulation algorithm suitable for the characteristics of ZPW-2000 A uninsulated track frequency shift signal is designed,and the accurate measurement of the upper and lower side frequencies and low frequency information of various frequency shift signals generated by ZPW-2000 A uninsulated track circuit is realized.The measurement accuracy can reach 0.01 Hz,and the measurement error also satisfies the demand.The calculation method of frequency shift signal amplitude is designed based on the trapezoidal formula of numerical integration,which can measure the effective value of voltage amplitude of frequency shift signal.(4)The inspection system is equipped with GPS module and display module,and the upper computer interface is designed based on Visual Studio.The information of measurement,time and place can be correlated and displayed on the LCD screen or the upper computer.In this thesis,the developed inspection equipment can produce and accurately measure the ZPW-2000 A uninsulated track signal of center frequency of 1700 Hz,2000 Hz,2300 Hz and 2600 Hz,can visually display frequency and voltage,time and place information,provide a basis for fault diagnosis in railway inspection personnel.Compared with the traditional handheld multimeter and frequency shift meter commonly used by patrol personnel,the hardware cost is lower,the signal feature extraction is more perfect,and it has the recording function.As a new type of inspection equipment,it has a strong practical significance in railway engineering departments.