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“Automobiles are an important means of transportation in modern society, providing people with convenient and comfortable travel services. However, traditional fuel vehicles generate a large amount of harmful exhaust gas during use, and increase their dependence on non-renewable resources of petroleum. As a major energy consumer, my country’s situation is even more severe, with massive imports of energy endangering the normal operation of the national economy and national energy security. In terms of the environment, transportation energy consumption is also one of the main causes of local environmental pollution and global greenhouse gas emissions.
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I. Overview
Automobiles are an important means of transportation in modern society, providing people with convenient and comfortable travel services. However, traditional fuel vehicles generate a large amount of harmful exhaust gas during use, and increase their dependence on non-renewable resources of petroleum. As a major energy consumer, my country’s situation is even more severe, with massive imports of energy endangering the normal operation of the national economy and national energy security. In terms of the environment, transportation energy consumption is also one of the main causes of local environmental pollution and global greenhouse gas emissions.
In order to cope with the global energy crisis and climate change, countries around the world have accelerated the transformation and upgrading of the automobile industry in recent years, and electric vehicles as an alternative to traditional fuel vehicles have gradually become a research hotspot. However, battery and battery management are the bottleneck restricting the development of electric vehicles. When the battery’s own capacity has been determined, effective monitoring and management of the battery pack has become an important means to extend the service life of the battery pack and increase the mileage of electric vehicles. .
Combining the characteristics of the automotive electronics industry, this article mainly introduces the application of the KINCO bus type (CAN bus) touch screen in the battery monitoring unit (BMS).
2. System structure
1. Principles of electric vehicles
All or part of the vehicles driven by electric motors and equipped with large-capacity electrical energy storage devices are collectively referred to as electric vehicles, including three types of pure electric vehicles (PEV), hybrid electric vehicles (HEV) and fuel cell electric vehicles (FCV). A pure electric vehicle is a vehicle that is powered by a rechargeable battery and driven by an electric motor and a motor control system.
The storage battery provides electric energy for the driving motor of the electric vehicle. The electric motor converts the electric energy of the power supply into mechanical energy, and drives the wheels and working devices through the transmission device or directly. The schematic diagram of a pure electric vehicle (see Figure 1).
2. Battery Management System (BMS)
BMS battery management system (Battery Management System or Battery Control Unit) refers to the software and hardware equipment used to safely monitor and effectively manage battery packs. The system includes self-diagnosis, data collection, charge and discharge management, balanced charging, heat management, and safety Management, data communication, battery monitoring, abnormal alarm, abnormal protection, Display of remaining capacity (SOC, State of Charge, battery state of charge estimation is an important function of the electric vehicle battery management system, accurate and effective SOC estimation is important to promote the core technology of electric vehicles Development is of great significance), battery health (SOH) and other functions; it also uses algorithms to control the maximum output power according to the voltage, current and temperature of the battery to obtain the maximum mileage, and uses the algorithm to control the charger to charge with the best current, through CAN The bus interface communicates with the vehicle master controller, motor controller, energy control system, vehicle display system, etc. in real time. Figure 2 shows the basic structure of BMS.
The battery management system is an important part of the related technologies of electric vehicles. Its advantages and disadvantages can promote or limit the development of electric vehicles. Therefore, the research on BMS is particularly important.
3. Features of KINCO Bus HMI (MT5423T-CAN)
Human-machine interface is used in all walks of life as a medium for transferring and exchanging information between humans and machines. With its stable performance and integration of CAN bus, the HMI HMI has been paid attention to by customers in the electric vehicle industry. Good application experience.
1. CAN bus interface function. The CAN bus is widely used in the automotive industry as a solution to the data exchange between the control and test instruments in modern cars, and the SAE J1939 protocol based on the CAN bus is widely used in the truck and bus industry. According to customer needs , SAE J1939 protocol is integrated in the self-developed EV5000 software (Figure 3).
2. Integrated SD card and USB HOST interface. Pure electric buses use as many as hundreds of cells, some even more, and the voltage, temperature and other parameters of these cells and battery packs must be collected and stored in real time. The internal storage space of ordinary touch screens is far from enough. MT5423T-CAN can store a large amount of data through an external SD card (8G).
3. High brightness and high resolution. The resolution of up to 800*600 can clearly display various parameters and pictures.
4. Up to 520MHz CPU and embedded operating system can quickly process large amounts of data.
Four, monitoring interface design
In this solution, the customer uses 6 data acquisition boards and a main control board to collect information such as battery voltage and temperature at a high speed through the CAN bus, thereby achieving high-efficiency balance of the battery. The voltage/current and temperature of the battery, the estimation of battery health and residual current, and fault alarm information are all displayed in graphics and text through the HMI.
1. Main control interface
The main monitoring screen of the touch screen can be designed to display in multiple languages. The total voltage and total current of the battery can be monitored on the entire monitoring screen, and information such as the battery state of charge (SOC) can be monitored; click other buttons to enter the corresponding interface, for example, click “Real-time data query” button, you can observe various data values of the battery at a specific time.
2. Data collection interface
Click the data collection button on the main control interface to enter the temperature and voltage monitoring interface of each battery module. On the monitoring interface, you can easily monitor the voltage of each single battery. Each battery module has 20 single cells, and the temperature sensor measures the temperature of every 5 cells, so in each data collection interface, you can see the data collection values of 20 cell voltages and 4 temperature values. Or when the voltage is abnormal, the monitoring will automatically enter the fault alarm interface.
3. Fault alarm interface
Enter the fault alarm interface, to display 40 fault codes (the fault code is determined by the 5 bytes received by the HMI, and each bit corresponds to a fault code. If the bit is 1, the alarm is issued, and the alarm is 0 to cancel the alarm). The alarm information mainly includes: discharge current overcurrent alarm, voltage alarm information, charging current information alarm, and CAN message receiving overtime alarm.
Five, summary
The application of MT5423T-CAN in the electric bus industry takes full advantage of its stable performance, open and flexible CAN bus, and a large amount of data storage. At present, the product runs stably on customer buses. With the country’s strong support for the new energy industry, the future development of the electric vehicle industry will speed up, and the company will continue to work hard to develop better and more cost-effective HMI products for customers.
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