GPS Vehicle Positioning and Monitoring System Based on GSM

frozenviolet

GPS Vehicle Positioning and Monitoring System Based on GSM [Copy link]

Using GPS (Global Positioning System) for positioning and navigation is the most basic application of GPS. With the expansion of urban construction in my country and the increasing number of vehicles, the management and reasonable dispatch of transportation has become a widely concerned issue, especially after the global positioning system (GPS) was converted from military to civilian use, the application of GPS technology in the monitoring of mobile targets has unparalleled advantages over other monitoring methods. Therefore, the use of GPS technology to monitor and dispatch various vehicles is a new research hotspot.

The overall structure and working principle of the system

The GPS vehicle positioning and monitoring system based on GSM is an ideal solution for vehicle management. The system uses GPS technology to locate mobile targets in real time, uses the GSM digital mobile communication network for real-time data transmission, and uses electronic maps and spatial information systems as support platforms to achieve positioning tracking, monitoring alarms, anti-robbery and anti-theft, command and dispatch, and information query management. The entire system is composed of two major parts: the GPS satellite positioning system and the ground mobile communication system, and the ground mobile communication system is composed of three parts: the command and monitoring center, the vehicle-mounted mobile unit, and the GSM communication network. The vehicle-mounted mobile unit equipment can provide the command and monitoring center with the latest positioning data, operating status, and alarm information of each mobile target in real time, and automatically record this information for subsequent query and analysis, and is a user terminal. The command and monitoring center combines the GIS (Geographic Information System) electronic map to display the geographical location of the currently monitored and commanded vehicles in real time. The GSM communication network transmits data, voice, and images.

System Monitoring Center

The structure of the system monitoring center is shown in Figure 1, which mainly includes GSM communication network, GIS terminal, electronic display screen, monitoring terminal, and main control computer. The monitoring center receives vehicle GPS positioning data information transmitted by the vehicle-mounted mobile unit, and processes the vehicle's alarm and dispatch information. Through GIS map matching, the current precise location of the vehicle can be displayed on the electronic map in real time, so as to conveniently realize the dispatch, monitoring, and command functions of the vehicle; at the same time, various control instructions can be sent to the designated vehicle-mounted station through the GSM wireless communication network to realize remote control and information query services for the vehicle.

Figure 1 GPS vehicle monitoring and command system center structure diagram

Design of the main components of the vehicle-mounted mobile unit

The vehicle-mounted mobile unit is composed of a main controller CPU, a GPS receiver, a GSM wireless communication module, a function control unit (handle) and a liquid crystal display. Its structural principle is shown in Figure 2.

Figure 2 Schematic diagram of the hardware structure of the vehicle-mounted mobile unit

The vehicle-mounted mobile unit receives the positioning signal transmitted by the GPS satellite through the GPS receiving antenna, and after being processed by the CPU main controller, calculates the vehicle's date, time, latitude and longitude, speed and driving direction and other positioning data. The main controller CPU is the core, processing the positioning information sent by the receiver, displaying the positioning information and control information sent by the monitoring center on the LCD screen, and controlling the GSM module to send and receive short messages. The handle control unit realizes remote control monitoring, requesting services, receiving Chinese short messages and making calls. Since the GSM wireless module and the GPS module are connected to the MCU in serial communication mode, the hardware design is relatively simple. In this design, the MCU chooses Winbond's W77E58 because it has two serial ports that can communicate with the GSM module and GPS module at the same time, and its instructions are fully compatible with MCS-51. There are 32k flash MTP ROM and programmable watchdog timer on the chip. Using it can save a lot of peripheral components and improve the stability of the system. The system main controller circuit is shown in Figure 3.

GSM wireless communication

There are two communication modes for GPS vehicle positioning monitoring and management system: dedicated wireless communication network and public GSM network. GPS/GSM vehicle positioning monitoring and management system uses GSM short message service to realize two-way data transmission. Short message service establishes a signaling connection between mobile station and mobile service exchange center, which has priority, extremely high communication rate and extremely low bit error rate. This is the benefit that the private network and cluster network brought by GSM public network cannot match. The biggest advantage of short message for vehicle monitoring is that it is simple to establish connection, fast connection and low service cost, which is suitable for sending positioning information to the monitoring center at regular intervals.

Figure 3 System main controller circuit

Figure 4 WM01-G900/1800 peripheral circuit design block diagram

In practical applications, we choose WM02-G900/1800. Its peripheral circuit design block diagram is shown in Figure 4, and its related performance indicators are shown in Table 1. It uses a standard serial port to communicate with the microcontroller, and the highest baud rate of communication can reach 115 200b/s. The GSM module and the SIM card mainly communicate data through the SIMCLK and SIMDATA signal lines. In order to ensure that the time interval between sending a short message and the arrival of the short message is as short as possible, the selected SIM card is preferably provided by the same telecom operator. When using the GPRS function, it is also necessary to select a SIM card that supports GPRS and activate the GPRS service. The module also supports driving two microphones, two speakers and one buzzer. One of the microphones and speakers can be connected to the handset of the handle to realize the car phone function; the other can realize the monitoring and hands-free functions, but these two cannot work at the same time. If the hands-free mode is required during a call, it can be switched through the AT command: AT+SPEAKER=0 or 1.

The logic level of the I/O interface of WM02-G900/1800 is 3V. When it communicates with the microcontroller serial port, level conversion is required. The author chooses MAX3237/3238 for conversion in the application. If GPRS service is required, you can also choose the TC-45 module produced by Siemens and the GR47 of Sony Ericsson, which support GSM/GPRS format transmission.

Controlling the WM02-G900/1800 module to send and receive short messages and perform voice communications is the key to the design. If you are not familiar with the relevant AT commands, you cannot set them correctly, which will affect the normal operation of the system and bring unpredictable consequences.

GPS receiver and its data format

The GPS OEM board is used to receive signals from GPS satellites and calculate the current location of the vehicle terminal. It consists of a frequency converter, a signal channel, a microprocessor, and a storage unit. The GPS module sends positioning coordinates to the main controller through the serial port; the main controller can also send setting commands to the GPS module to control the status and working mode of the GPS module. The GPS module needs to be equipped with a special GPS antenna to receive GPS satellite signals. Generally, in relatively open areas, more than three GPS satellite signals need to be received for accurate positioning. In the vehicle-mounted GPS intelligent terminal system, placing the antenna on the roof can achieve a better positioning effect. We chose TFAG10 GPS RECEIVER. Its performance indicators are shown in Table 2.

The input and output of the TFAG10 GPS RECEIVER receiver sentence is completed through the RS-232 serial interface, which complies with the NMEA-0183 communication standard format established by the National Marine Electronics Association of the United States. The data format of its communication port should be set to 8 data bits, 1 start bit and 1 stop bit; no parity check; the baud rate is 4800b/s. The output data of the NMEA-0183 communication standard uses ASCII code, and its content includes information such as latitude, longitude, altitude, speed, date, time, heading and satellite status. There are five kinds of sentences. For different applications, the selected sentence records are also different. In this design, we only care about date and time, longitude and latitude, and ground speed, so we only use RMC recording sentences. A $GPRMC statement contains 13 records: statement header, world time, positioning status, latitude, latitude azimuth, longitude, longitude azimuth, ground speed, ground route, date, magnetic declination, checksum and end mark, which takes up a total of 70 bytes (including 11 commas used to separate records). For example:
$GPRMC,161229.487,A,3723.2475,N,12158.3416,W,0.13,309.62,120598,,*10

Power Design

In the power supply design of vehicle-mounted equipment, we focus on the following issues:

● Fully consider the fluctuation and pulse interference of the car power supply and select the appropriate power filter;
● Since the car battery has +12V and +24V, the power supply of the vehicle-mounted equipment should be designed with a wide input voltage (the input voltage range of the power module we selected is 7~35V);
● The vehicle-mounted equipment should use low-power devices and take measures such as powering off the GPS module and GSM module when parking to minimize the power consumption of the vehicle-mounted equipment to avoid damaging the car battery when the car is parked for a long time. For a 50AH car battery, if the standby current of the vehicle terminal is 140mA, it can last for 357 hours, about 15 days, when parked;
● Overcurrent and overvoltage protection measures should be taken.

In this system, we use the LM2596 series switching regulator integrated circuit, whose main performance indicators are shown in Table 3.

It has been proved in actual use that the use of LM2596 series switching voltage regulator integrated circuit as the power module of this system can not only improve the working efficiency of the power supply, reduce energy loss, reduce the thermal damage to the core components, but also reduce the interference of the large fluctuation of the external automobile level voltage on the components, and at the same time reduce the pulse interference entering through the power supply, which can play a multiplier role in ensuring the safety and reliable operation of the system. The power supply circuit is shown in Figure 5.

How system devices work

When the device is powered on for the first time after installation, the vehicle-mounted device starts working.

After the vehicle is turned off, the user uses the remote control to turn on the anti-theft function. At this time, all anti-theft inputs and door opening and closing detection will take effect immediately until the user uses the remote control to disarm. The vehicle's arming/disarming is confirmed by linking the car's taillights and sirens. If the door is not closed properly when armed, it can be prompted by sound and light.
Usually, the GSM module of the vehicle-mounted equipment is in standby mode. When receiving the command from the center, the vehicle-mounted equipment will send a short message according to the command of the center.

Regardless of whether the vehicle is driving or parked normally, once the emergency alarm button on the vehicle is pressed, or the medical help or traffic rescue button is pressed, the vehicle-mounted equipment can immediately and automatically report the location and alarm type to the center via a short message via a mobile phone. The anti-theft alarm sensor connected to the vehicle-mounted equipment will only report the location and alarm type to the center via a short message via the GSM module immediately and automatically when the vehicle is stopped and armed.

The vehicle-mounted equipment can receive the center's instructions on turning off/on the ignition and opening and closing the doors, and complete the corresponding operations through the linked and connected devices.

In addition to normal telephone functions, the handset can be used to set the SMS service center number corresponding to the vehicle-mounted equipment, the SMS called number of the alarm monitoring center and the monitoring service center, monitor the phone number, equipment ID number, password, and can display the received SMS in Chinese.

The ID number of the vehicle-mounted equipment, the short message called number of the alarm monitoring center and the monitoring service center, the data transmission time interval, the speed limit value, the driving area limit value, etc. can be changed through remote control programming.

开始插入图片 zhenwei20060613111846.GIF zhenwei20060613111934.GIF zhenwei20060613112007.GIF zhenwei20060613112028.GIF zhenwei20060613112254.gif 结束插入图片