New solution for remote vehicle monitoring based on OBD system

The Internet of Vehicles refers to the electronic tags installed on vehicles, which use identification technologies such as wireless radio frequency to extract and effectively utilize the attribute information and static and dynamic information of all vehicles on the information network platform, and effectively supervise the operating status of all vehicles and provide comprehensive services according to different functional requirements.
The concept of Internet of Vehicles has appeared in developed countries and regions such as the United States, Europe and Japan in the 1960s, and ITS, IVHS, RTI, VICS and other Internet of Vehicles systems have been developed. In China, the concept of Internet of Vehicles was first proposed at the Fourth National GPS Operator Conference and was recognized by a large number of professionals; at the China International Internet of Things Conference held in Wuxi, the state listed the Internet of Vehicles as an important project in the third special project of China's major projects, and China's Internet of Vehicles started from then on. To date, the in-vehicle systems provided by some suppliers have basically realized functions such as intelligent navigation, maintenance appointments, and consultation inquiries, which are more convenient for vehicle travel and improve the driving experience to a certain extent.
In addition to providing users with a better driving experience, the development of the Internet of Vehicles should also be able to provide powerful background data feedback services for automobile manufacturers or 4S stores and other institutions. This is also meaningful for their business expansion and service extension. Powerful data feedback can respond to sudden abnormal conditions of vehicles in a timely manner and provide a basis for analyzing the maintenance quality of vehicles; historical data can provide targeted and personalized maintenance services for specific types of vehicles.
The paper provides a solution with powerful background data feedback functions such as real-time vehicle condition information monitoring, abnormal vehicle condition alarm, and driving data recording. That is, the vehicle system collects vehicle condition information and uploads it to the server. The administrator can log in to the information center of this solution system and use functions such as remote monitoring of vehicle conditions, remote capture of abnormal conditions, and vehicle driving logs to widely collect driving data. Through active analysis of data, automobile manufacturers can not only provide car owners with higher quality and more proactive vehicle maintenance services, but also clearly understand the operating conditions of a certain model or series of vehicles, which has a significant contribution to the improvement and optimization of vehicle types, and can also improve the production efficiency of automobile manufacturers and reduce vehicle maintenance costs.

1 Framework analysis of the solution
The solution implementation framework diagram is shown in Figure 1. The entire system is composed of two server/client (C/S) architecture subnets. The vehicle system and the server form a vehicle/service information interaction network through the GPRS network; the information center and the server form an information interaction network through a multi-network including TCP/IP protocols. In view of the lack of security in open networks, the information interaction between the two subnets uses an encrypted communication solution to ensure the basic security of communication data.

2 Definition of the main functional modules of the scheme
2.1 Definition of vehicle system functions
(1) As the source of feedback data, it is the main provider of basic data required by the information center for upper-level services, and exchanges information with the OBD system to obtain the latest status information of the car in real time.
(2) Accept task requests from the data server and passively provide data feedback of specific vehicle status information.
(3) According to the settings and fault definition rules, when an abnormality is detected in the vehicle system, the abnormal information of the vehicle is promptly and actively fed back to the data server.
(4) It is the direct executor of the real-time recording of vehicle travel information, and regularly uploads the travel record to the data server, and combines with the data server to form a complete system for vehicle travel records. The vehicle travel record is temporarily stored in the local Flash area of ​​the vehicle system. The Flash area has a relatively large storage space and has a power-off retention function, which can act as a black box. When the car has an accident and there is no time to upload the abnormal information, the latest information at the time of the accident can still be saved in time.
(5) It supports security-related mechanisms such as communication encryption and key exchange.
2.2 Definition of data server functions
(1) As the core role of the feedback data sharer. The large amount of feedback data received provides structured data storage. Structured data facilitates secondary data processing and is suitable for logical storage isolation from data of different meanings. It realizes the functions of a remote database server.
(2) It accepts data access from a remote information center, correctly executes task requests from the information center, and accepts delegations from the information center to access data from vehicle system nodes. The delegation mechanism can improve the response speed to information center requests through the cache mechanism.
(3) It accepts information from vehicle system nodes and uses the received information to update database data according to certain rules. And the agent completes the task of accessing data from the vehicle system nodes delegated by the information center.
(4) It provides authentication services for the information center and vehicle system nodes, and provides security mechanisms such as data access control.
(5) It supports security-related mechanisms such as communication encryption and key exchange.
2.3 Definition of information center functions
(1) It is the main role for in-depth application of feedback data. It legally accesses the data server and converts the data into information meaningful to the administrator after parsing, including vehicle fault information, vehicle operating parameters, etc. The use of local data processing and analysis can enable communication to use code communication that condenses a large amount of information, thereby reducing network data communication volume and reducing the computing burden of the database.
(2) Provide an interface for administrators of the information center to perform remote legal operations on the data server, including basic application interfaces such as obtaining information requests, recording operation requests, login authentication, and task delegation, and abstract macro-application layer functions such as remote vehicle condition monitoring and remote vehicle condition abnormality timely response through software.
(3) Support security-related mechanisms such as communication encryption and key exchange.
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3 Feasibility analysis of the scheme
3.1 Feasibility analysis of the implementation of the vehicle system scheme
The on-board diagnostic circuit (OBD) can obtain the internal parameter status of the vehicle. OBD was originally used as a displacement monitor to control vehicle emissions. By detecting the engine status and the content of pollutants in the exhaust gas, it prompts the driver to maintain the vehicle. Later, it gradually developed into a complete comprehensive vehicle monitoring system. If the manufacturer implements all the PID functions in the OBD standard, OBD can provide information on tire pressure, air flow, pedal position, etc.
Since the OBD system cannot notify the user of the cause of the error, the detected OBD data needs to be sent to the remote manufacturer for analysis, and then the information is fed back to the user.
The OBD system can provide a comprehensive understanding of the condition of the car. The standard OBD provides 9 services.

The current state parameters of the car are mainly obtained through the Model, such as tire pressure, battery voltage, engine speed, vehicle speed, etc. The current fault code is obtained through Mode3, and the freeze frame related to the fault code is returned through Mode2. Error codes that may occur in the future are found through Mode7.
The OBD protocol supports multiple physicals and uses a 29-bit extended CAN bus. OBD has 4 communication frames. The implementation of these 4 communication frames on the CAN protocol is shown in Figure 2. Figure 2 (a) is the format of point-to-point communication, and Figure 2 (b) is the broadcast communication format.

ELM327 is used as the protocol translator for communication with OBD. The chip supports ISO15 764 protocol and the corresponding CAN bus physical layer, ISO9141, ISO14230 protocol and the corresponding K-line physical layer, SAEJ1850 protocol and the corresponding PWM&VPW physical layer, and converts them into standard serial port protocols. Using ELM327 can improve versatility. SIM300 is used as the GPRS communication module, STM32F103RB is used as the main control chip of the vehicle end, and 128 kB of Flash can meet the needs of fault information storage.

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