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In today's era of rapid development of science and technology, automobiles, as an indispensable means of transportation in our lives, are constantly improving and innovating. In particular, the electronic control system, the core component, has become a key indicator to measure the performance of a car. The electronic control system is not the unique technology of new energy electric vehicles, fuel vehicles are also equipped with this system, but in new energy vehicles, it shows more complex and powerful functions. Just like the nervous system of the human body, the electronic control system is responsible for the coordination and control of various operating functions of the vehicle, and its advanced or not is directly related to the driving performance and driving experience of the vehicle.
This article will lead you to an in-depth understanding of the vehicle control system of new energy vehicles - this highly integrated intelligent network. It is not just a simple combination of a series of sensors and controllers, but a sophisticated information and instruction processing center that enables efficient communication between components via a CAN network. From the analysis of the driver's driving intention, to the vehicle drive control, to the energy feedback and optimization management, every step reflects the subtlety and efficiency of the electronic control system.
Let's explore what this system consists of, what it does, and how it can support the intelligence, safety, and comfort of electric vehicles.
01 One
Introduction to the vehicle control system
Regarding the automotive electronic control system, it is not exclusive to new energy electric vehicles, fuel vehicles also have, but the electronic control system of new energy electric vehicles is more complex and more powerful.
Automotive electronic control system, is the automotive electronic control system, is a module control of the system general term, it is composed of hardware and software, electronic control is actually the general name of all the electronic control system of the vehicle software + hardware, we can understand the entire electronic control system as the nervous system of the vehicle, this system can control the operation ability of the vehicle, so the more powerful the electronic control system, the better the control and driving ability of the vehicle. Today, let's talk about the vehicle control system of new energy vehicles.
The vehicle control system is composed of input signal sensors such as accelerator pedal position sensor, brake pedal position sensor, electronic shifter, vehicle controller (VCU), motor controller (MCU), battery management system (BMS) and other control modules and drive motors, power batteries and other actuators.
Application diagram
Composition Diagram
These controllers in the car communicate via a CAN network. CAN, the full name of "Controller Area Network", is one of the most widely used fieldbuses in the world. Originally, CAN was designed as a microcontroller communication in the automotive environment, exchanging information between the various electronic control devices and ECUs in the vehicle to form an automotive electronic control network. For example, the engine management system, transmission controller, instrumentation equipment, and electronic backbone system are embedded with CAN control devices.
02 Two
The function of the vehicle control system
1. Analysis of the driver's driving intention
It is mainly to analyze and process the driver's operation information and control commands, that is, to convert the driver's accelerator signal and braking signal into the demand torque command of the motor according to certain rules. Therefore, the response performance of the drive motor to the driver's operation depends entirely on the throttle interpretation result of the vehicle control, which directly affects the driver's control effect and operation feeling.
2. Vehicle drive control
According to the driver's control input to the vehicle (accelerator pedal, brake pedal and gear selection switch), vehicle status, road and environmental conditions, after analysis and processing, the corresponding instructions are issued to the vehicle management system to control the driving torque of the motor to drive the vehicle, so as to meet the driver's dynamic requirements for vehicle drive; At the same time, according to the state of the vehicle, the corresponding instructions are issued to the vehicle management system to ensure safety and comfort.
3. Braking energy feedback control
According to the opening of the accelerator pedal and the brake pedal, the driving status information of the vehicle and the status information of the power battery (such as SOC value), the vehicle controller judges whether the braking energy can be fed back at a certain time, and recovers part of the energy under the premise of satisfying the safety performance, braking performance and driver comfort. This includes motor braking torque control during coasting braking and braking braking.
4. Optimized management of vehicle energy
Through the coordination and management of the motor drive system, battery management system, transmission system and other on-board energy power systems (such as air conditioning, electric pumps, etc.) of electric vehicles, the energy utilization efficiency of the whole vehicle can be improved and the driving range can be extended.
In a pure electric vehicle, the battery supplies power to other electrical appliances in addition to the drive motor.
Therefore, in order to get the maximum driving range, the vehicle controller will be responsible for the energy management of the whole vehicle to improve the utilization of energy. When the SOC value of the battery is relatively low, the vehicle controller will issue instructions to other electrical appliances to limit the output power of other electrical appliances, or turn off some auxiliary equipment to increase the driving range.
5. Charging process control
After receiving the charging signal, the vehicle controller should prohibit the high-voltage system from powering on to ensure that the vehicle is in a driving lock state in the charging state; And limit the charging power according to the battery status information to protect the battery.
6. Power up and down control of the electronic control system
6.1 High voltage power-on
The ignition key is in the ON file, the current state of the BMS and MCU is normal, and there is no serious failure of the vehicle in the previous power-on and power-off process
-The BMS and MCU initialization is complete, and the VCU confirms the status
- Closed battery relay
-Close the main relay
-The MCU is powered on at high voltage
-If the gear is in N gear, the meter shows that the Ready light is on
6.2 Power-off sequence
When the pure electric vehicle is powered off, it only needs to hit the ignition key to the OFF gear to achieve the normal power-off of high-voltage and low-voltage electricity
-The ignition key is in OFF mode, the main relay is disconnected, and the MCU is powered off at low voltage
- Auxiliary systems stop working, including DC/DC, water pumps, air conditioners, heaters
-BMS new battery relay 4.Vehicle controller power off (VCU)The vehicle controller will store the fault information that occurs during the driving process before powering off
7. Electrification assistance system management
Electrified assistance systems include electric air conditioning, electric braking, and electric power steering. The vehicle controller should monitor the DC/DC and electrification assistance systems according to the status of the power battery and the low-voltage battery.
8. Real-time monitoring and display of vehicle status
Vehicle controller should carry out real-time detection to the state of vehicle, and the information of each subsystem is sent to the vehicle information display system, and its process is through the sensor and CAN bus, detect the state of the vehicle and its power system and related electrical accessories related to the state information of each subsystem, drive the display instrument, and the status information and fault diagnosis information are displayed by the digital instrument.
9. Fault diagnosis and treatment
Continuously monitor the electronic control system of the whole vehicle, diagnose faults, and carry out corresponding safety protection treatment in time. According to the input of the sensor and other information such as the motor, battery, charger and other information communicated through the CAN bus, various faults are judged, classified and alarmed. Fault codes are stored for review during repairs. The fault indicator is only the fault type and part of the fault code. In the process of driving, fault diagnosis and treatment are carried out according to the fault content.
The fault level of the whole vehicle is divided into 4 levels:
10. Remote control
10.1 Remote query function
Users can query the status of the vehicle in real time through the mobile APP, and understand the status of the vehicle in real time, including: remaining SOC value, driving mileage, etc.
10.2 Remote air conditioning control
Whether it is in the hot summer or the cold winter, users can realize remote air conditioning refrigeration, air conditioning heating and defrosting functions through mobile phone commands before going out.
10.3 Remote charging control
The user plugs the charging cable into the charging pile when leaving the vehicle, and instead of charging immediately, he can take advantage of the trough of the electricity price and stay at home.
11. Vehicle CAN bus gateway and network management
The CAN bus system for electric cars consists of a central controller, a battery management system, a motor control system, a brake control system, and an instrument control system. Each controller communicates with each other through the CAN bus to realize the sharing of sensor measurement data, the sending and receiving of control instructions, etc., and the control performance of each controller is improved, so as to improve the control performance of the system. The types of communication and information between them are information and command. The information class mainly sends some information, such as sensor signals, diagnostic information, and the status of the system. Command classes are mainly commands that are sent to other executors.
12. Online matching calibration based on CCP
The online matching calibration protocol based on CCP adopts master-slave communication mode, the master device is connected with a plurality of slave devices through the CAN bus, the master device is a measurement and calibration system, the slave device is the ECU that needs to be calibrated, and the master device first establishes a logical link with one of the slave devices. After the logical connection is established, all data transmission between the master and slave devices is controlled by the master, and the slave device returns packets containing information such as command response values or error codes after executing the master command, and the slave device can periodically transmit variable information to the master device according to the list information set by the master device through the control command, and the data transmission is initialized by the master device and executed by the slave device, and is triggered by a fixed cyclic sampling frequency or event.
13. DC/DC control and EPS control
(1) DC/DC control
DC/DC converter is a branch of switching power supply technology that converts DC voltage into another value of DC voltage. It is composed of a switch tube, a diode, an inductor, a capacitor, a load and a DC power supply as a semiconductor power device, and another DC voltage is obtained on the load by making the load circuit with a filter and the DC voltage sometimes turn on and off.
(2) EPS control
The electric power steering system of the automobile uses the torque generated by the electric motor, which is converted by the deceleration and transmission mechanism of the steering system to assist the driver in power steering. Although the EPS structural components of different vehicles are different, the basic principle is the same. After detecting a valid vehicle ignition signal, the torque or angle sensor outputs the detected torque and angle signals to the ECU when the steering shaft turns.
The ECU analyzes and calculates the torque and angle signals, vehicle speed, axle load signals, etc., and obtains the steering of the booster motor and the target booster current, so as to realize the power steering control.
14. Shift control function
The shift control function is related to the driver's driving safety, correctly understands the driver's intention, and identifies the reasonable gear of the vehicle, which is well optimized in the gear management module developed based on the model. In the event of a failure, the corresponding treatment can be made to ensure the safety of the whole vehicle, and the driver can be prompted by the instrument when the driver has a gear misoperation, so that the driver can quickly make corrections.
15. Anti-slip function control
When a pure electric vehicle starts on a hill, the driver will slide backwards from the time he releases the brake pedal to the time he steps on the accelerator pedal. In the process of driving on a hill, if the driver does not press the accelerator pedal deep enough, the vehicle will gradually reduce its speed to 0 and then roll backwards. Therefore, in order to prevent the car from rolling backwards when starting and running on a slope, the anti-slip function is added to the vehicle control strategy.
The anti-slip function can ensure that when the vehicle starts on the slope, the backward slip is less than 10CM; If the power is insufficient during the vehicle slope operation, the vehicle speed will slowly drop to 0, and then maintain the vehicle speed at 0 and no longer slide backwards.