0 Preface
Energy shortages and climate change have made electric vehicles with energy-saving and environmental advantages a global concern. Electric vehicles use clean energy as power, which is a long-term solution for future transportation [1]. For individual users, charging needs to be charged to the nearest charging station or charging post, and the charging time is longer. If the battery is quickly charged, the battery is damaged. If the current battery in the car is low and the time is tight, you need to keep a spare battery ready for replacement. Electric vehicle batteries are large in size, difficult to operate, and costly. For example, individuals purchasing spare batteries will inevitably lead to an increase in personal basic investment, making it difficult for electric vehicles to be promoted among individual users. Therefore, the charging station or the battery rental company keeps a plurality of batteries, and the company uniformly charges and maintains the battery, and performs battery replacement for the user according to the demand. The electric energy supplement of the electric vehicle is mainly based on the electric exchange mode.
The method has the following advantages: reducing the basic input of the user; prolonging the service life of the battery; improving the utilization rate of the battery; helping to solve the emergency situation outside the charging network; the rental company uses the peak and valley electricity to uniformly charge, which is beneficial to the overall power grid. The deployment and so on. Since the power-exchange mode is used, the battery will be circulated among multiple users and multiple regions, and the tariff will be settled according to the battery condition when the battery is replaced. Therefore, the electric vehicle battery needs to be linked with information of different users (such as license plate number, etc.). On the one hand, it is necessary to ensure that the user's personal information is not leaked; on the other hand, it is necessary to ensure the safety of the battery when the battery is in circulation. At this time, the owner of the battery asset (such as a charging station or a battery rental company) has greatly improved the safety requirements for battery management of the electric vehicle.
In this paper, the ESAM security module is combined with the RF module to form a new and more secure battery safety module RF transceiver, which is installed in the electric vehicle battery. At the same time, the handheld terminal is provided with the ESAM security module. At this time, the user's personal information and battery asset information are stored in the ESAM security module, not only the personal information is encrypted, but also the ESAM security module and the smart grid in the battery when charging or changing power. The background sales system is certified, and the charging and replacement can be performed normally after the certification is passed, thus ensuring the safety of the battery assets.
1 system structure
In order to realize the battery management of electric vehicles, the whole system is divided into the following parts: battery safety RFID module for battery terminals of electric vehicles, handheld computers, fixed read heads, and background management systems.
A battery safety RFID module is added to the electric vehicle battery, referred to as a battery module. The module is used to implement functions such as battery information storage, data encryption and decryption authentication, and data interactive transmission, and is mainly composed of an MCU, an ESAM, and a radio frequency transmitting RF transceiver. The system organization structure is shown in Figure 1.
2 Battery-side battery safety RFID module
2.1 ESAM Security Module
ESAM (Enbedded Secure Access Module) embedded security control module is a dedicated high-performance security microprocessor as a hardware platform, with an independent embedded operating system (Card OperaTIng System, referred to as COS) embedded security products, in addition to anti-detection In addition to hardware features such as anti-attack and self-destruction, it also has secure file key management and perfect security mechanism, as well as standard encryption and decryption computing functions. The internal structure includes a microprocessor, a cryptographic coprocessor, a true random number generator, ROM, RAM, EEPROM, and data I/O ports [2].
Since the ESAM security module has the above security features, the key data of the electric vehicle battery is stored in the ESAM module. For different battery data classification management, set to transparent file or opaque file according to security requirements, that is, whether to encrypt when data communication.
2.2 Master MCU function
On the battery module, select the appropriate MCU as the MCU. At present, the module uses the STM32 chip as the MCU, including multiple peripheral interfaces, which can simultaneously connect the BMS system, ESAM security module and RF transmitting RF transceiver of the car itself. Data interaction between multiple modules, while performing data processing operations on data during data interaction.
2.3 RF Transceiver
The RF transceiver on the battery module is connected to the MCU through the SPI interface. At the same time, the same RF transceiver is configured on the handset side, and the same wireless communication frequency is set to realize wireless data communication.
At the same time, since the RF transceiver can realize simultaneous processing of multiple tags, a fixed wireless communication read head can also be set at the door of the battery management warehouse to facilitate the management of the storage and storage of the warehouse.
3 handheld / fixed read head
The handheld/fixed read head is a device for reading and writing information on the battery module. The difference is that the handheld device is a mobile reading and writing device, which is mainly used for occasional emergency power exchange in the field or inventory check in the storage, etc., and has high portability. It includes peripheral aids such as display screen, keyboard and human-computer interaction system, which is convenient for operators to apply. The fixed read head is mainly used for fixed locations such as warehouse access and storage, and the RF transceiver can realize the characteristics of simultaneous reading and background processing of multiple tags, and quickly perform inbound and outbound management.
The optional GPRS module is provided on the handheld device, and the data can be updated in time by the GPRS and the background main station after the handheld device collects the information. For key data, it is encrypted when transmitting over the GPRS public network, so as not to be intercepted or tampered by others during the transmission of the public network [3].
The PSAM card is required to be installed in the terminal of the handheld device or the fixed read-head device. The PSAM card is the Purchase Secure Access Module (Purchase Secure Access Module), which is used for terminal devices such as merchant POS, network terminal, and direct connection terminal. Safety control of the machine [4]. The PSAM card is issued in association with the ESAM in the battery module for encryption and decryption operations in data exchange.
4 background management system
Since the electric vehicle battery may be circulated among multiple users and multiple regions when it is in operation, the background management system is mainly used for storing and managing all information. The information can be read from the battery security module through the handheld or fixed read head, and finally integrated in the background management system, facilitating unified asset control and information management.
The encryption machine is installed in the background system to cope with the encryption and decryption of the uploaded data.
5 ESAM security implementation mechanism
According to the data security requirements, the data exchange between the battery module and the outside world can adopt the following four modes: plaintext, ciphertext, plaintext plus checksum or ciphertext plus check mode. Encryption of the data guarantees the reliability of the data, while data integrity and authentication to the sender are achieved by using a check code. The encryption mode is to encrypt and transform the message data to be transmitted and then transmit; the verification mode is to use an algorithm to encrypt the message data to be transmitted to obtain a 4 B check code MAC, which is packaged into the data to be transmitted and transmitted together. After receiving the data, the receiver discriminates the data according to the MAC; and the encryption check mode takes the length of both [5].
5.1 Identity Certification
The random number is taken in the battery module ESAM and the encryption calculation is performed to generate the authentication data, which is uploaded to the handheld terminal, and then the internal authentication ciphertext is calculated by the PSAM card in the handheld terminal, and the internal authentication ciphertext generated by both parties is checked to be consistent. The terminal equipment authenticates the legality of the battery module. The process is shown in Figure 2.
The random number is generated by the true random number generator built in ESAM. The real random number generator uses the internal electromagnetic white noise to generate random numbers, which eliminates the possibility that the pseudo random number is predicted due to periodicity, thus ensuring the security of the encryption process. Sex [6].
5.2 Data Interaction Process
After the identity authentication is passed, the next step of data interaction can be entered, that is, the battery module communicates with the external handset or charging pile for data communication and data interaction.
For the data stored in the battery module, the data is classified according to the importance degree of the data file, and the permission settings for reading and writing operations are performed according to different security levels. The higher the security requirement, the higher the encryption level, and the higher the encryption mode level during communication; the lower the security requirement, the lower the encryption level, that is, the corresponding encryption method can be reduced or transparent and not encrypted. Communication speed and reduced redundancy calculation. Therefore, according to the different requirements of the security level, the communication method adopts four modes: plaintext, ciphertext, plaintext+checking, ciphertext+checking.
In the ESAM of the battery module, the key file encryption level is the highest. Since the ESAM security chip used in the battery management system is hard-encrypted, all key files are unchangeable, but they are free to use and have the highest security level. Encryption and decryption of transmitted data.
The rest of the data, such as application information files, are divided into transparent files and opaque files according to the security level. For example, charging documents, asset information, etc., because of the important information related to the ownership of the assets and the number of times of charging and the amount of money, the security requirements are high. This part of the file is an opaque file. When interactive communication is used, the ciphertext + verification method is used. In order to ensure that it can not be deciphered and modified by third parties during the space transmission process; some battery operation information files do not need to perform mac verification, and use cipher text to communicate; such as battery address inquiry, broadcast time and other query operations, due to Without the user or owner's private information, the clear text can be directly communicated between the primary station and the battery module without EMS encryption and decryption, thereby saving communication time.
5.3 Security Management System
Due to the encryption and decryption function of the security module, the electric vehicle battery will be connected with the background master station through the matching key system during the circulation process, thereby realizing the asset control of the electric vehicle battery.
When the electric vehicle battery is being charged, the electric vehicle internal module communicates with the charging post through the BMS, and the charging pile will charge the battery only after the identity authentication is passed. At the same time, during the interaction process, the charging pile can also read the relevant information in the battery module and transmit it to the back-end system for backup. The operator can query the circulation of the battery at any time through the background system.
The same read/write device can also be configured on a fixed read head or handset to manually query battery asset information in and out of the library.
In addition to ensuring security in the program algorithm flow, in the application management system, login passwords with different permission levels are respectively set on the background system software and the handheld device for secure management of information in the system.
6 Conclusion
As one of the development directions of possible vehicles in the future, the development of electric vehicles is particularly attractive. Among them, electric vehicle battery is one of the most important components and core technologies in electric vehicles. Based on ESAM security module and handheld terminal, this paper introduces an improved design method for electric vehicle battery management system, improves battery asset management security, makes it more systematic, safe and convenient, and has a deep focus on the further promotion and application of electric vehicles in the future. Impact.
references
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[3] Chen Songsong, Wang Lili, Xiang Bin, et al. Application of ESAM in electric vehicle charging piles [J]. Power System Communications, 2012, 33(234): 42-43.
[4] China Financial IC Card Pilot Project Implementation Team. China Financial PSAM Card Application Specification Part I: Document Structure [S]. 1999.
[5] China Financial Integrated Circuit (IC) Card Standard Revision Working Group. China Financial Integrated Circuit (IC) Card Specification Part 1: Card Specification [S]. 2004.
[6] Tao Weiqing, Huang Junxiang, Cao Jun, et al. Application of ESAM security module in prepaid electricity meter [J]. Electrical Measurement and Instrumentation, 2010, 47 (539): 60.
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