Railway Crossing Monitoring System in Mining Areas Based on Single Chip Microcomputer and GPRS

1. Introduction

The railway in the mining area is the intermediate link between the national railway and the mining area, and is an important part of the railway transportation network. According to relevant statistics, the current domestic mining area railway exceeds 20,000 kilometers and there are usually multiple crossings along the line. Since most of the crossings are located inside mining enterprises far away from the urban area, and there are many and scattered crossings, as well as long distances between crossings, coupled with the cross-operation of various means of transportation in the mining area and the irregular flow of vehicles and personnel, the safety management of railway crossings in the mining area has become a very prominent issue. In order to enable the management departments of mining areas at all levels to grasp the safety of each crossing in a timely and accurate manner, this paper designs a railway crossing monitoring system with Atmega128 and MC55 as the core, and realizes the automation, digitization and networking of railway crossing monitoring management. This is of great significance to ensure the normal production of mining areas, improve the economic benefits of mining enterprises, and the safety of vehicles and pedestrians passing through the crossings.

2. System composition

The whole system is composed of the crossing monitoring center. From the functional point of view, the system can be divided into five parts: signal acquisition part, crossing part, signal transmission and sending part and crossing monitoring center.

2.1 Signal acquisition part

The signal acquisition part is mainly used to collect train approach and departure signals, and provide decision signals for automatically retracting and releasing guardrails. At present, there are several ways to detect incoming vehicle signals in the crossing system, such as vibration sensors, radio frequency sensors, GPS+ ARM+ GPRS, video monitoring equipment or pedal switches, each of which has its own advantages and disadvantages. The signal acquisition part of this system consists of 4 magnetoelectric sensors, which are placed in pairs on the inner side of the rails on both sides of the crossing. When a train passes through this position, the magnetoelectric sensor can detect the incoming vehicle signal, and after the amplification circuit and A/D conversion circuit, it is directly sent to the single-chip microcomputer Atmega128.

2.2 Crossing

The crossing is equipped with two sets of crossing signal machines, sound and light alarms and barrier devices, which are used to indicate the train is about to arrive, sound and light alarms and perform the barrier release operation. An automatic control box is set at the crossing, which can be remotely controlled by the PC in the center of the crossing monitoring room in the mining area, or manually operated by the operator on site. The alarm is composed of an audio circuit board, a cylindrical speaker and a revolving warning light, which is used to remind the drivers of passing vehicles and pedestrians to pay attention to safety and not to cut in.

2.3 Signal transmission and sending part

The magnetoelectric sensor is installed about 500 m away from the crossing. When it detects the signal of an incoming vehicle, it transmits the signal to the single-chip Atmega128 in the automatic control box of the crossing through a copper cable. MC55 is the main device for sending signals. It packages the data collected by the single-chip and transmits it to the mine crossing monitoring center through the GPRS network. The crossing monitoring center further analyzes and processes the data.

2.4 Mine crossing monitoring center

The mine crossing monitoring center is equipped with a PC, which is mainly used to receive data on the running status of trains at each crossing. The monitoring center uses dynamic IP combined with DNS domain name resolution networking to achieve remote monitoring of the crossing. This method first requires contacting the DNS service provider to apply for a domain name for the monitoring center and write this domain name into the single-chip Atmega128. After the monitoring center is connected to the Internet, it connects to the DNS server and reports the current dynamic IP to the DNS server. The DNS server then finds the public network dynamic IP of the monitoring center, so that a communication connection can be established between the two.

3 System Hardware Design

The system hardware design mainly refers to the hardware design of the crossing control part. According to the signal flow, it can be roughly divided into three hardware modules, namely sensor signal amplification and A/D conversion circuit design, single-chip microcomputer Atmega128 and MC55 interface design, and driver

The interface circuit design of various equipment on site, among which the Atmega128 and MC55 interface circuit is the focus and feature of the hardware design of the monitoring system. Figure 2 shows the circuit diagram of the monitoring station hardware system with the interface circuit as the core. Both ATmega128L and MC55 have standard RS232 interfaces, so the hardware design is relatively simple. It only needs to connect PE5 of Atmega128L with IGT of MC55 to start the MC55 module, and connect TX0/RX0 of Atmega128L with TX0/RX0 of MC55 for data input and output; RING0 of MC55 is connected to the interrupt line of ATmega128L as the interrupt signal of data transmission. Atmega128 is an 8-bit high-performance microcontroller launched by Atmel. It has 128KB of program memory, 4KB of data memory, 4KB of EEPROM, 8 10-bit ADC channels, 2 8-bit and 2 16-bit hardware timer J counters, 8 PWM channels, programmable watchdog timer and on-chip oscillator, on-chip analog comparator, JTAG, UART, SPI, and I2C bus interfaces, as well as six power saving modes that can be selected by software. In this design, ATmega128L is the core of the entire data acquisition system, mainly completing the sensor signal acquisition, software filtering, data calculation and various control functions of the signal. MC55 is a GPRS dual-band module produced by Siemens. In addition to the original functions of the GSM module, it also supports packet service functions and has an embedded TCP/IP protocol; its data input/output interface is actually a serial asynchronous transceiver that complies with the RS232 interface standard and has fixed parameters: 8 data bits and 1 stop bit, no parity bit. It works together with Atmega128 to complete the remote transmission of data. [page]

4 System Software Design

The software is divided into several relatively independent functional modules by modular software design, and appropriate entry and exit parameters are arranged for each module, so that the modules can be connected and combined flexibly and conveniently. The software design of the entire monitoring system mainly consists of the crossing automatic control subsystem and the mining area monitoring center subsystem.

4.1 Design of automatic crossing control software

The entire program of the crossing automatic control subsystem is programmed in a combination of C language and assembly language, using a modular structure. It is well organized and the program volume is concise, which optimizes the speed of Atrnega128 and the capacity of the compiler program. Its main function is to trigger the output pulse of the magnetoelectric sensor, drive various alarm devices on site through the single-chip microcomputer, and send the running status data of the train passing through the crossing to the monitoring center through MC55. The subsystem software can be divided into timer initialization module, interrupt management initialization module, MC55 initialization module, interrupt signal filtering and processing module, train status data calculation module, data communication module with the host computer, and various equipment modules on site according to its function. Its software design mainly includes two parts: the main program and the interrupt service subroutine. Among them, the interrupt signal filtering and processing module, the module for driving various equipment on site and the module for calculating the train status data are implemented in the interrupt service subroutine, and the remaining modules are implemented in the main program. Figure 3 shows the main flow chart of the automatic control subsystem software.

4.2 Software Design of Mine Monitoring Center

The main function of the mining area monitoring center subsystem is to receive, display and print the current speed, approach distance to the crossing and other related train operation data transmitted from each crossing in real time through the GPRS network. This subsystem is programmed in the high-level language VC.

The software has a friendly user interface, can store all collected data into a database, and can display and analyze waveforms. According to the functions, it can be divided into system login module, system management module, data communication module with the lower computer, train data real-time display module, train data storage module and train historical data query module.