Design of bicycle anti-theft tracking system on campus

1 Introduction
In recent years, with the continuous progress of wireless communication, sensor technology and embedded computing, the development of low-cost and low-power Internet of Things technology has been promoted, making the Internet of Things technology an active research field today [1]. The Internet of Things is composed of a large number of cheap micro sensor nodes deployed in the monitoring area. It is a network system formed by wireless communication. Its purpose is to collaboratively sense, collect and process the information of the sensed objects in the network coverage area and send it to the observer. Wireless sensor networks have broad application prospects in both military and civilian fields [2]. The Internet of Things (IoT) refers to the ubiquitous terminal devices and facilities, including sensors with "intrinsic intelligence", mobile terminals, industrial systems, building control systems, home smart facilities, video surveillance systems, etc., and "external enablers", such as various assets with RFID, individuals and vehicles carrying wireless terminals, etc. "intelligent objects or animals" or "smart dust" [3]. Through various wireless long-distance or short-distance communication networks, interconnection, large-scale application integration, and cloud computing-based SaaS operation models are achieved, providing safe, controllable and even personalized real-time online monitoring, positioning and tracing, alarm linkage, dispatching and command, plan management, remote control, security prevention, remote maintenance, online upgrades, statistical reports, decision support, leadership desktop and other management and service functions, realizing the integration of "management, control and operation" of "everything" with "efficiency, energy saving, safety and environmental protection" [4]. The key technologies, architecture, system model, network system and service system of the Internet of Things have become current research hotspots [5]. This paper introduces the Internet of Things technology into the campus bicycle anti-theft system, and gives a design scheme for a campus bicycle anti-theft system based on the Internet of Things to provide protection for the management of bicycles on campus.
The structure diagram of the Internet of Things Information Processing Center is shown in Figure 1:

Sensor network: The sensor network is the basic component of this system. It uses ZigBee network. The protected object contains a device node composed of a ZigBee node and an accelerometer. The sensor network is responsible for locating the device nodes entering this network. The device nodes will record the location information. When someone moves the bicycle, the accelerometer responds, triggering the device node to calculate the location information again. When the position is displaced to a certain extent, an alarm message is sent to the ZigBee network coordinator, and the local alarm response is made at the same time. After the bicycle is stolen, the device node will also calculate its latest location information in the sensor network in real time and upload it to the information processing center.
Perception platform: The perception platform consists of the coordinator of the ZigBee network and a protocol conversion platform. The protocol conversion platform is composed of a dedicated MCU. As an information aggregation node, the perception platform is responsible for aggregating the data of each ZigBee network, and then using the TCP/IP protocol to send the data to the IoT information processing center through wired or wireless means.
Internet of Things Information Processing Center: Analyze and process the data transmitted by the sensing platform, respond to the alarm information, transmit the alarm information to the owner through the mobile network, and transmit the alarm information and the latest location information of the object to the school security department, activate the monitoring equipment at the corresponding location, and dispatch security personnel to handle it. In addition, the Internet of Things Information Processing Center can be further expanded to serve as the data processing center of the Internet of Things information of the whole school, manage the sensor network throughout the school, and truly realize the perception campus and smart campus.

3 Hardware Design
The core of the hardware design of the campus bicycle anti-theft system is the design of wireless network nodes. According to the tasks undertaken in the system, it can be divided into general sensor nodes and perception platforms. However, these two categories are only slightly different, and there is no essential difference in hardware. They are all these major parts (as shown in Figure 2).

(1) Microprocessor
This design uses CC2430 as the main processor. CC243 is a true system-on-chip COMS solution that combines a high-performance 2.4GHz DSSS RF transceiver core with an industrial-grade compact and efficient 8051 controller. The design of CC2430 combines 8Kbyte RAM and powerful peripheral modules. In this design, there is no need for external memory expansion. Its low cost and low power consumption are also important reasons for using this processor.
(2) Information acquisition module
The MEMS accelerometer is selected here. It is a dual-axis acceleration measurement device integrated according to CMOS technology. The working principle of the device is based on thermal convection. It works like other accelerometers, but it is a bubble in a MEMSIC device. A single heat source is suspended in a closed space in a single crystal silicon, and groups of thermocouples are evenly spaced around the heat source. When there is no acceleration, the temperature gradient around the heat source is the same, so the temperature at all thermocouples is the same, and the output voltage of the thermocouples is also the same. Due to the arbitrariness of heat convection, each direction of the accelerometer may break the temperature balance and show nonlinearity. Due to temperature changes, the output voltages of the four thermocouples are different. Different accelerations are directly proportional to different output voltages. The accelerometer has two identical acceleration signal lines, which are used to measure the acceleration of the X and Y axes respectively.
It forms a complete sensor system through mixed signal processing and integrated IIC bus (the working sequence diagram is shown in Figure 3), which can be directly connected to the microprocessor without A/D conversion. The MXC6202xG/H/M/N chip measures the acceleration range of ±2g, and the accuracy can reach g/512-g/128 when working in a 3.0V25℃ environment. Both dynamic and static acceleration can be measured. Taking advantage of the acceleration of the bicycle when it is stolen, the AT89S51 microcontroller is used to collect the sensor information, and the stolen bicycle is judged after a period of time, and then the information is sent to the wireless device. [page]

(3) Transparent transmission module
The advantage of the transparent transmission module is that the user does not need to consider how the program in the module runs. The user only needs to send his data to the module through the serial port, and then the module will automatically send the data wirelessly and communicate with the destination address node in the network according to the pre-configured network structure. The receiving module will verify the data. If the data is correct, it will be sent through the serial port. In actual operation, it is very simple and convenient.
(4) Other modules
The power module serves the entire node system and supplies power to its own system; the key module is mainly used to set the system status. The entire system can only run when each module is operating normally and in a normal coordinated state.
The actual experiment is shown in Figure 4:

4 Software System Design
(1) Network Description:
Network Access:
When a bicycle equipped with a device node enters the sensor network, the user turns on the device node to put it in working state. At this time, the device node sends a broadcast signal, and all the Router nodes that receive the broadcast signal reply with a signal. The device node selects from the received reply signals. Because there may be multiple sensor networks at the location of the device node, the device node will choose a network with better signal quality to join.
After entering the network, the device node will repeatedly send a one-hop signal to all anchor nodes in the network. After all anchor nodes receive this one-hop signal, they will calculate the average signal strength received. Based on this average signal strength and the coordinate information set by the anchor node itself, the location information of the device node is calculated and told to the device node.
After obtaining the location information, the device node will connect to the coordinator through the Router node, and send its location information and the network number of the sensor network it is in to the IoT information processing center through the perception platform. At this time, the IoT network center can know the specific location of the object to be protected on campus.
The entire network access process is shown in Figure 5:

Alarm:
When the device node is turned on and initialized, and has informed the IoT information processing center of its own location information, the device node is already in an alert state.
When someone moves an object, it will affect the acceleration sensor to react and trigger the device node. The device node is now in a high alert state and continuously sends signals to the anchor node to obtain its own location information. The interval sending time is set to 1 second. When others move without malicious intent, such as moving a bicycle so that others can store other bicycles, it can be understood in the processing flow that the object has only moved a short distance, and it is considered to be a non-malicious movement, and no alarm response is made. When the object moves a long distance and exceeds the threshold value, it is considered that theft has occurred, and the alarm response is immediately activated. At the same time, the alarm information will be uploaded to the IoT information processing center through the coordinator, and the owner will be notified through the mobile network, and the school emergency plan will be activated.
Tracking:
When the device node of an object confirms that it has been stolen, the device node will continuously send broadcast signals. According to the strength of the reply signal collected from the Router node, it will determine which sensor network it is currently located in, and then send a signal to the anchor node in this sensor network to confirm its location in this network. After that, the device node will upload its latest location information to the information processing center through the coordinator and the sensing platform, thereby realizing the tracking function. At the same time, combined with the existing monitoring resources on campus, it can effectively help security personnel prevent thieves from succeeding.
The entire alert, alarm, and tracking process is shown in Figure 6.

(2) Host computer design
The host computer is the information processing center and a central server responsible for managing each sensor network and analyzing and processing the data transmitted from each network. When the device node is connected to the network, the information processing center records its location information, including which sensor network it belongs to and its location in the sensor network. When the device node issues an alarm, it uploads the alarm information to the information processing center and activates the closed-circuit monitoring equipment in the area. The various systems are linked to prevent theft. [page]
The graphical interface is developed using Visual Basic 6.0 software, which provides a good human-computer interface and facilitates human-computer interaction. The software supports visual programming and object-oriented technology. The design and implementation of the VB software is to first complete the communication between the PLC and the host computer according to a specific communication protocol, so that the host computer can correctly read the content of the PLC specified data area, and then display the data.
The actual effect is shown in Figure 7:

5 Scope
of application This system can be transplanted and applied in various anti-theft places, such as the management of archives in the archive room, the anti-theft of student notebooks, the anti-theft of gold and silver jewelry, the anti-theft of valuable equipment in small factories, etc. The main function of the system is anti-theft, so in terms of anti-theft of items, the application of this system can reduce a lot of trouble for people.
The layout diagram of this system actually applied in some areas of Daqing Petroleum College is shown in Figure 8:

6 Conclusion
At present, more and more school students complain about the problem of lost bicycles. This system mainly uses gravity acceleration sensors to determine the loss of bicycles, and uses the characteristics of ZigBee wireless transmission and positioning for bicycle anti-theft on campus, which can help students solve the problem of lost bicycles. This anti-theft system can also be implanted in other application fields, which can realize the monitoring of items, facilitate people's management, and make science and technology better serve mankind.

References:
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