Research On Signal Acquisition And Communication Subsystem Of Real-time Detection System For Broken Rail

Detection track circuit is a detection device for broken rail without track circuit, whichhas an importance of ensuring operation security of trains. In order to check rail integrity,according to the principle of broken rail detection, it is required to collect and analyze theinduced voltage signal of the current sensor for receiving end of detection track circuit. Inorder to make manager of tunnel monitoring center know well the rail’s condition of thetunnel, the detection message is needed to transmit real-time and reliably to the remotemonitoring center. The dissertation studies acquisition and communication problems of theinduced voltage signal of the current sensor for detection track circuit.By describing the basic working principle of detection track circuit, design indices ofacquisition and communication systems are determined. Under the premise of not consideringthe impact of the parameters of the current sensor in the receiving end of the detection trackcircuit and the equivalent impedance of the receiving circuit on detection track circuit, thetransmission equations of the equivalent model of detection track circuit in normal and brokenrail operation modes are simplified and change rules and characteristics of the signal current inthese modes are analyzed. Because of Controller Area Network (CAN) having excellentcharacteristics of real-time, reliability and other in data transmission, using CAN network totransmit the detection message is put forward, and the distributed acquisition and communicationsystem’s structure based on CAN bus is built.According to the characteristics of the current sensor and its input signal, thecharacteristic of the output signal of the current sensor is analyzed. To facilitate thesubsequent signal acquisition, the output signal of the current sensor is processed withresonance, amplification, filtering and AC-DC conversion. Multi-functional data acquisitioncard USB-M08222C10based on USB bus is selected to complete data acquisition so thatusing Matlab software directly processes the collected data. Because of the unbalance tractioncurrent of the rail affecting the normal work of detection track circuit, in order to ensure thenormal work of detection track circuit, anti-interference circuit is designed on the basis of theresistance to electrification interference principle. Simulation results show that the amplitudeof the interference signal is decreased. It don’t affect the detection result. The quality of thedetection signal is improved.Because of the plastic optical fiber having excellent anti-interference performance andadvantage in short distance communication, in order to transmit detection message to remotemonitoring center real-time and reliably, and satisfy the requirements of real-time andreliability of the detection message, a communication interface for the plastic optical fiber ofCAN bus is designed. The correctness of the communication interface is verified through experiment. Results of experiment data show using the plastic optical fiber of CAN bus totransmit the detection message improves real-time and anti-interference of the system. Inorder to meet communication needs of detection system for broken rail, a CAN applicationlayer protocol suitabled for its is proposed.