Research Of Train Signal Loop Current Detection Technology

This thesis is based on computer railway signal machine monitoring system, and mostly focused on the sub-system of train signal loop current collector.The train signal loop current gathering device measures the current of four signal machines simultaneously, and sends out four effective current values according to the requirements of the host machine. Because each current gathering device has a unique address and monitors different train signal, the host machine can easily get each signal machine's status and help to amend failed machines timely. Therefore the loop current gathering device of train signal is of great importance to making the railway system operate effectively and safely.There are five major sections in this thesis:Firstly, introduce the principle of loop current gathering device and its history.Secondly, describe circuit hardware design of loop current gathering device, which includes linear processing of input signal, optocoupler application and using voltage transformer to separate power supply system. Moreover, circuit designs of processor power supply, AD conversion module comparative voltage and watchdog are also contained in this part.Thirdly, a new computational algorithm of how to acquire the effective loop current component is proposed and several other common algorithms are analyzed and compared, as well. Besides, this thesis describes the whole software system design and how it works specifically. The application of MODBUS communication is stated, too.Fourthly, this thesis does not only study on system design, it but also introduces a concept of health degree of train signal machine, which can help the host machine notice the aging problem of signal machine timely. Therefore, predicting and alarming the potential risks become possible.Lastly, by conducting a real test, the train signal loop current gathering device is proved reliable, and has better performance in measuring current more accurately and predicting the failure tendency. Meanwhile the problems co-existing in test are still analyzed and trouble-shooting approaches are raised in the end of the thesis.All in one, this Cortex-M3 based hardware design platform has comparative advantages in energy consumption,processing speed and easy flexibility. Moreover, this system works stably and precisely, and has bright capability for future development.