New energy electric vehicle control system

火辣西米秀

New energy electric vehicle control system [Copy link]

Regarding the automotive electronic control system, it is actually not exclusive to new energy electric vehicles. Fuel vehicles also have it, but the electronic control system of new energy electric vehicles is more complex and more powerful.

The automotive electronic control system is the general term for a system controlled by modules. It is composed of hardware and software. Electronic control is actually the general term for the software + hardware of all electronic control systems of a vehicle. We can understand the entire electronic control system as the nervous system of the vehicle. This system can control the vehicle's operating ability, so the more powerful the electronic control system, the better the vehicle's control and driving ability. Today, let's talk about the vehicle control system of new energy vehicles.

The vehicle control system consists of input signal sensors such as accelerator pedal position sensor, brake pedal position sensor, electronic shifter, control modules such as vehicle control unit (VCU), motor controller (MCU), battery management system (BMS), and actuators such as drive motor and power battery.

Application Diagram

Composition structure diagram

These controllers on the car communicate through the CAN network. CAN, the full name of which is "Controller Area Network", is one of the most widely used field buses in the world. Initially, CAN was designed as a microcontroller communication in the automotive environment, exchanging information between the various electronic control units ECU on the vehicle to form an automotive electronic control network. For example: CAN control devices are embedded in the engine management system, transmission controller, instrument equipment, and electronic backbone system.

Functions of vehicle control system

1. Driver driving intention analysis

It mainly analyzes and processes the driver's operation information and control commands, that is, converts the driver's throttle signal and brake signal into the required 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

Based on the driver's control input to the vehicle (accelerator pedal, brake pedal and gear selector switch), vehicle status, road and environmental conditions, after analysis and processing, corresponding instructions are issued to the vehicle management system to control the driving torque of the motor to drive the vehicle to meet the driver's requirements for the dynamic performance of the vehicle drive; at the same time, according to the vehicle status, corresponding instructions are issued to the vehicle management system to ensure safety and comfort.

3. Braking energy feedback control

The vehicle controller determines whether braking energy feedback can be performed at a certain moment based on the opening of the accelerator pedal and the brake pedal, the vehicle driving status information, and the status information of the power battery (such as the SOC value), and recovers part of the energy under the premise of meeting the safety performance, braking performance, and driver comfort. This includes motor braking torque control during coasting braking and braking.

4. Vehicle energy optimization management

By coordinating and managing the electric vehicle's motor drive system, battery management system, transmission system and other on-board energy and power systems (such as air conditioning, electric pumps, etc.), the energy utilization efficiency of the entire vehicle can be improved and the driving range can be extended.

In pure electric vehicles, the battery not only supplies power to the drive motor, but also to other electrical appliances. Therefore, in order to obtain the maximum driving range, the vehicle controller will be responsible for the energy management of the vehicle to improve the energy utilization rate. When the battery SOC value is relatively low, the vehicle controller will issue instructions to other electrical appliances to limit the output power of other electrical appliances, or shut down some auxiliary equipment to increase the driving range.

5.Charging process control

Work together with the battery management system to control the charging power during the charging process. After the vehicle controller receives the charging signal, it should prohibit the high-voltage system from powering on to ensure that the vehicle is in a driving lock state when charging; and limit the charging power according to the battery status information to protect the battery.

6. Power on and off control of the electric control system

1. High voltage power on

The ignition key is in the ON position, the BMS and MCU are in normal status, and there is no serious problem with the vehicle during the previous power on and off process.

Fault

1. BMS and MCU initialization completed, VCU confirms status

2. Close the battery relay

3. Close the main relay

4.MCU high voltage power on

5. If the gear is in N gear, the instrument display Ready light is on

2. Power-off sequence

To power off a pure electric vehicle, just turn the ignition key to the OFF position to achieve normal power off of high-voltage and low-voltage electricity.

1. Turn the ignition key to OFF position, the main relay is disconnected, and the MCU is powered off at low voltage.

2. Auxiliary systems stop working, including DC/DC, water pump, air conditioning, and heater

3. BMS new battery relay

4. Vehicle Controller Power Off (VCU) The vehicle controller will store the fault information that occurred during driving before powering off.

7.Electric auxiliary system management

The electrified auxiliary systems include electric air conditioning, electric brakes, and electric power steering. The vehicle controller should monitor the DC/DC and electrified auxiliary systems according to the status of the power battery and low-voltage battery.

8. Real-time monitoring and display of vehicle status

The vehicle controller should detect the vehicle status in real time and send the information of each subsystem to the on-board information display system. The process is to detect the vehicle status and the status information of each subsystem related to the power system and related electrical accessories through sensors and CAN bus, drive the display instrument, and display the status information and fault diagnosis information through the digital instrument.

9. Fault diagnosis and troubleshooting

Continuously monitor the vehicle's electronic control system, perform fault diagnosis, and promptly perform corresponding safety protection processing. According to the sensor input and other information such as motors, batteries, and chargers communicated through the CAN bus, various faults are judged, classified, and alarmed; fault codes are stored for viewing during maintenance. The fault indicator light only shows the fault type and some fault codes. During driving, fault diagnosis and processing are performed according to the fault content.

The fault level of the whole vehicle is divided into 4 levels:

10. Remote Control

(1) Remote query function

Users can check the vehicle status in real time through the mobile phone APP, and understand the vehicle's condition in real time, including: remaining SOC value, driving range, etc.

(2) Remote air conditioning control

Whether in the hot summer or the cold winter, users can remotely control the air conditioning cooling, heating and defrosting functions through mobile phone commands before going out.

(3) Remote charging control

When the user leaves the vehicle, he inserts the charging gun into the charging pile. Instead of charging immediately, he can take advantage of the electricity price trough and check the SOC value in real time at home. When charging is needed, he can send remote charging instructions through the mobile phone APP to perform charging operations.

11. Vehicle CAN bus gateway and network management

The CAN bus system of 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 through the CAN bus to achieve the sharing of sensor measurement data, the sending and receiving of control instructions, etc., and to improve the control performance of each, thereby improving the control performance of the system. The communication and information types between them are information class and command class. The information class mainly sends some information, such as sensor signals, diagnostic information, and system status. The command class is mainly sent to other actuators.

12. Online matching calibration based on CCP

The CCP-based online matching calibration protocol adopts a master-slave communication mode. The master device is connected to multiple slave devices through the CAN bus. The master device is a measurement and calibration system, and the slave device is the ECU that needs to be calibrated. 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 host. After the slave device executes the master device command, it returns a message containing information such as the command response value or error code. At the same time, the slave device can transmit variable information to the master device at a regular time according to the list information set by the master device through the control command. 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

The DC/DC converter is a branch of switching power supply technology that converts DC voltage into another DC voltage. It is composed of a semiconductor power device as a switch tube, a diode, an inductor, a capacitor, a load and a DC power supply. By connecting and disconnecting the load circuit with a filter and the DC voltage from time to time, another DC voltage is obtained on the load.

(2) EPS control

The electric power steering system of a car uses the torque generated by the motor to assist the driver in power steering after the steering system decelerates and the transmission mechanism converts it. Although the EPS structural components of different cars are different, the basic principles are the same. After detecting the effective car ignition signal, when the steering shaft rotates, the torque or angle sensor outputs the detected torque and angle signals to the electronic control unit ECU

The ECU analyzes and calculates the torque, angle signal, vehicle speed, axle load signal, etc. to determine the direction of the power-assisted motor and the size of the target power-assisted current, thereby achieving power-assisted steering control.

14. Gear shift control function

The shift control function is related to the driver's driving safety. The correct understanding of the driver's intention and the identification of the vehicle's reasonable gear position are well optimized in the gear management module developed based on the model. It can take corresponding measures to ensure the safety of the entire vehicle when a fault occurs, and remind the driver through the instrument when the driver makes a gear misoperation, so that the driver can make corrections quickly.

15. Anti-slip function control

When a pure electric vehicle starts on a slope, the vehicle may slide backwards from the time the driver releases the brake pedal to the time the driver steps on the accelerator pedal. During the slope, if the driver does not step on the accelerator pedal deeply enough, the vehicle speed will gradually drop to 0 and then slide backwards. Therefore, in order to prevent the vehicle from sliding backwards when starting and running on a slope, an anti-slip function is added to the vehicle control strategy.

The anti-slip function can ensure that the vehicle will not slide backward by less than 10CM when starting on a slope; if the power is insufficient during the operation of the vehicle on the slope, the vehicle speed will slowly drop to 0, and then maintain 0 speed without sliding backward any more.

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As a newcomer to the automotive electronics industry, I would like to read the posts of the great masters and actively learn and improve myself.