Design and development of mobile vehicle tracking system

The mobile vehicle tracking system refers to the comprehensive application of advanced communication technology, automatic control technology and computer technology to the management system, thus establishing a comprehensive real-time, accurate and efficient integrated management and control system [1]. The system can monitor the running track and state of the vehicle, and has convenient debugging, obvious economic and social benefits, and can be widely applied to special vehicles, such as long-distance passenger vehicles, bank cash transport vehicles, public security vehicles, and public transportation intelligent traffic management.

1 system design and communication protocol

1.1 System design

The mobile vehicle tracking system is mainly composed of a vehicle-mounted mobile terminal, a monitoring station and a control center, as shown in FIG. 1 . The vehicle-mounted mobile terminal is mainly responsible for collecting vehicle data, that is, the vehicle running condition, and receiving commands from the control center; using the wireless transmission network as a carrier of data transmission, the monitoring point collects data, and sends the information to the control center. The monitoring center is the core of the management system. The trajectory can display the visual location of the vehicle and monitor the mobile vehicle.


1.2 Communication principle

Wireless communication refers to communication between a mobile terminal and a monitoring point, and it is the hub of the entire design. The vehicle condition information of the running vehicle is constantly changing. To enable the control center to know the driving condition of the vehicle in time, the vehicle-mounted mobile terminal should be able to transmit the vehicle condition information data to the corresponding monitoring point, and transmit it to the control center through the communication between the monitoring points. When communicating, the monitoring points are distinguished by different vehicles, and the running vehicles are numbered. In addition, since the transmission and reception share the same physical channel, when there are multiple running vehicles arriving at the same monitoring point, it is necessary to prevent communication competition of the vehicle [2].

When the system is running, the microprocessor on the monitoring point sets the frequency synthesizer on the wireless module, and switches to three different frequencies in a time-sharing manner. The monitoring point cyclically detects whether the communication port has information to receive or transmit. The types of information are classified into positioning codes, response commands, and control commands. The positioning code includes the number of the vehicle and the running status information of the vehicle. The response command is divided into a positioning response code and a control response code. If the information is successfully sent to the other party's monitoring point, the other party's monitoring point sends a response code indicating that the data has been received, otherwise the sender resends the message. The control command is a dispatch command issued by the control center to the monitoring vehicle. The communication principle is shown in Figure 2.

2 system hardware design

2.1 Car mobile terminal

The vehicle mobile terminal periodically sends a signal, and does not need to wait for the receiving monitoring point to send a response signal to send the next message. The schematic diagram of the car mobile terminal circuit is shown in Figure 3. The vehicle terminal is based on the 8051 single-chip microcomputer, which mainly completes the processing and transmission of signals. The LED digital tube is used to display the speed and number of kilometers of the moving vehicle.

2.2 Monitoring points

The monitoring point analyzes and judges the received signal of the moving vehicle, and then sends the signal to the next monitoring point through the wireless signal until the signal is transmitted to the control center. During a certain time interval, the frequency synthesizer of the monitoring point automatically adjusts the frequency to the network of the monitoring point to complete the information exchange with the adjacent monitoring point. At the same time, the monitoring point receives the control command sent by the control center. Figure 4 is a circuit schematic of the monitoring point.

3 system software design

The software of the system mainly includes two parts: (1) data acquisition and wireless transmission, mainly based on 8051 single-chip microcomputer as the core for programming, which can be divided into communication between vehicle mobile terminal and monitoring point and communication between monitoring points. (2) Design of monitoring center management software. The monitoring center data management interface is programmed in VB6.0, and the program is written in C language based on the Keil development platform. This can shorten the development cycle, reduce development costs, make the program easy to debug and maintain, high reliability, readability and portability [3].

3.1 Software implementation of data transmission

Data transfer is a core part of system software design. Program initialization includes initialization of the serial port and timer. The serial port initialization sets the serial port of the 8051 MCU to work mode 1, that is, 8 bit data bits and 1 bit stop bit. The timer selects the working mode 1 of the timer 0, that is, the 16 bit timer is selected, the crystal frequency is 12 MHz, and the initial value of the timer 0 is TH0=0xEC and TL0=0x78, respectively.

After initialization, the receiving end cyclically detects the change of the serial port potential. When it is detected that the serial port level changes from low to high, there may be a signal input. In order to ensure that the serial port input is not an interference signal, when detecting a potential jump of the serial port, after extending 100 pulses (1 ms per pulse), the input signal is detected again. If it is still high, it indicates that there is Data input, not external interference. After the serial port detects a low potential, after 15 pulses, the input signal is detected again. If it is still low, it is confirmed that this is the “starting bit”, and there is data input to start receiving data. After receiving the 8 bit data bit, if the serial port receives the stop bit, it will send the data bit into the data register and display it through the LED digital tube. Otherwise, the data will be received incorrectly and the data will be discarded.

3.2 PC serial communication program design

The control platform program is developed under the Visual Basic environment. The MSCOMM control has a full-featured serial data transmission and reception function and a good human-machine interface. MSCOMM provides both query and event-driven methods for handling communication problems. The query mode queries the events and errors by checking the value of the CommEvent property. The event-driven mode is to use the MSCOMM control to send OnComm events to capture serial communication errors or events, and write programs in the OnComm event for corresponding processing. This method is timely and reliable. High [4]. In this system, serial communication is implemented through an event-driven method. The OnComm event is triggered when MSCOMM receives the data.

The mobile vehicle tracking system adopts advanced computer software and hardware technology, and designs and manufactures a low-cost information vehicle management system, which takes advantage of the data transmission of the wireless communication network and improves the cost performance of the system. The system is designed around the specific conditions of vehicle management to ensure the advanced, flexible and expansive system, which can meet the long-term development of vehicle management system and adapt to the rapid development of information technology. Economic and practical [5].

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