2 System principle and design requirements
1: Principle of hybrid electric vehicle
Hybrid electric vehicle uses the traditional internal combustion engine and motor as the power source, and drives the vehicle through the mixed use of thermal energy and electric power systems, so as to save fuel and reduce exhaust pollution. The internal combustion engine used includes diesel engine and gasoline engine. The common characteristics are small displacement, light weight, high speed and good emission. The key of hybrid electric vehicle is hybrid power system. Its performance is directly related to the whole vehicle performance of hybrid electric vehicle. The schematic diagram of hybrid power system is shown in Figure 1.
Hybrid power system is divided into series type, parallel type and hybrid type. Series hybrid electric vehicle is mainly composed of engine, generator, drive motor, battery pack and other components. The engine is only used to generate electricity. The electric energy generated by the generator is supplied to the motor, which drives the car. Part of the electric energy generated by the generator charges the battery to extend the driving range of the hybrid electric vehicle. In addition, the battery can also separately provide electric energy to the motor to drive the electric vehicle, so that the hybrid electric vehicle can run under the state of zero pollution. See Figure 2 for the series schematic diagram.
Parallel hybrid electric vehicle is mainly composed of engine, generator / motor, battery pack and other components. The parallel drive system can use the engine or motor as the power source alone, or use the motor and engine as the power source to drive the vehicle at the same time. See Figure 3 for the schematic diagram of the parallel drive system.
Hybrid electric vehicle is mainly composed of engine, generator, motor, planetary gear mechanism, battery pack and other components. The hybrid drive mode is to connect the engine, generator and motor through a planetary gear device. The power is output from the engine to the planet carrier connected to it. The planet carrier transmits part of the torque to the generator and the other part to the motor and output to the drive shaft. At this time, the vehicle is not series or parallel, but between series and parallel, making full use of the advantages of the two driving modes. See Figure 4 for the schematic diagram of hybrid connection.
2: Hybrid electric vehicle battery control unit system setting requirements.
1: Touch screen design requirements
The system adopts weinviewmt8070ih touch screen, which is 7 "wide screen and 400MHz CPU. 128M super large capacity flash, which can quickly respond to system instructions.
The picture language shall be switchable between Chinese and English, and the picture shall have animation effect. For example, the charging and discharging process of the battery shall be synchronized with the actual situation and expressed in animation effect.
The touch screen adopts a 7-inch wide screen, and the main screen can intuitively show the working conditions of the user's fuel cell unit, as well as the working conditions and relevant parameters of each group of batteries and each battery. For this battery management unit, there are 10 groups in total, with 12 batteries in each group. It is required to display the voltage, current and temperature parameters of these 120 batteries. If the parameters exceed the range, an alarm must be given.
2: Set alarm voltage range:
When it is detected that the voltage of any string in the battery pack exceeds 3.00-3.65v, the voltage submenu and warning triangle symbol shall flash. Enter the voltage submenu, and the battery pack exceeding the standard shall flash. Click the menu on the third page of the corresponding battery pack, and the string exceeding the standard shall flash.
3: Set alarm temperature range:
When the temperature of any battery in the battery pack exceeds 70 , the temperature submenu and warning triangle symbol shall flash. Enter the temperature submenu, and the battery pack exceeding the standard shall flash.
4: Calculation of battery capacity:
Calculation method: total current x total voltage x time = charge and discharge capacity; The touch screen is required to accurately display the charge and discharge data.
3 Screen design of touch screen system
1: Design of touch screen main monitoring screen
The Chinese and English images of the main monitoring screen of the touch screen are shown in the figure below. There are battery symbols on the whole screen, marked with positive and negative poles, which can display the current capacity of the battery. The first dial on the screen is an ammeter, which can display the charge and discharge of the battery unit; The second meter is a voltmeter, which mainly displays the voltage of the battery pack after inversion. The temperature and voltage controls on the screen can be used as alarm display and function keys to enter the next level of directory.
2: Design of touch screen temperature monitoring screen
Click the temperature button on the main screen to enter the battery module temperature monitoring screen, in which we can see the temperature of 10 groups of batteries. For batteries with 12 sections in each group of batteries, the temperature sensor measures the temperature of every 4 batteries, so there are three temperature sensors in a group of batteries, which can be read out through the touch screen. When the temperature is abnormal and exceeds the working temperature of the battery, the icon of the corresponding battery will flash, which is convenient for the driver to view. The battery temperature monitoring screen is shown in the figure below.
Battery temperature monitoring
3: Design of touch screen temperature and voltage picture
Click the voltage button on the main screen to enter the battery module voltage monitoring screen, in which we can see the voltage of each subsection of each battery in each group of batteries. In the quick selection bar on the left of the screen, you can switch other battery packs arbitrarily and view the detailed voltage of the battery pack.
In the battery unit, when the voltage range of one battery exceeds 3.00-3.65v, the corresponding battery icon will flash for relevant alarm; It is convenient for operators and drivers to query.
4 Establishment of communication between touch screen and controller
1: Development of communication protocol
The customer's controller is developed with single chip microcomputer, so mt8070ih and its communication must have a communication protocol to communicate with single chip microcomputer. The communication parameters of the single chip microcomputer have been set at the single chip microcomputer. Please see the following figure for the communication parameters of the touch screen.
2: Communication debugging and data test
After the communication test is successful, we will test the correctness of the data. Firstly, the parameters of all battery units should be read through the software of single chip microcomputer; Then use the touch screen to communicate with the MCU to test whether the read data is consistent with the parameters read by the MCU software. The software screen for reading data of single chip microcomputer is shown in the figure below. On the screen, we can read the parameters of each battery.
3: Test of alarm system
For the alarm test, we can set the alarm on the touch screen, including the battery voltage alarm range, the battery temperature alarm range and the battery capacity alarm range. In this way, it is convenient for the commissioning personnel to test whether the alarm is normal, because the parameter voltage of some batteries may be less than 3V in the commissioning stage, so the self setting of the alarm range is more conducive to the communication test between mt8070ih and the controller.
The system adopts the control system composed of weinviewmt8070ih touch screen and single chip microcomputer. When applied to hybrid electric vehicles, the fuel saving effect can reach 30%. The energy conversion effect is good. It can supplement the kinetic energy when the fuel system is lack of power. When braking, it can convert the kinetic energy of braking into electric energy and save it through the battery. At present, the application of new energy vehicles is in its infancy, but this application is not only in line with the development trend of transition from fuel drive to electric drive in the future, but also greatly increases the environmental protection degree of the automobile industry, which is of great significance to the improvement of human living environment.