Analysis of the whole vehicle control system
of new energy vehicles
Regarding the automobile 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 automobile electronic control system is the automobile electronic control system. It is a general term for systems controlled by modules. It consists of hardware and software. Electronic control is actually the general term for the software + hardware of all electronic control systems of the vehicle. 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. Therefore, the more powerful the electronic control system is, the better the control and driving ability of the vehicle will be.
The whole vehicle control system consists 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 actuators such as drive motor and power battery.
These controllers on the car communicate through the CAN network. CAN, the full name of "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 various electronic control devices 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 trunk system.
Functions of the vehicle control system
1. Driver driving intention analysis
It is mainly to analyze and process the driver's operation information and control commands, that is, to convert 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
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, corresponding instructions are issued to the vehicle management system to control the motor's driving torque 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. Including motor braking torque control during coasting and braking.
4. Vehicle energy optimization management
Through the coordination and management of the electric vehicle's motor drive system, battery management system, transmission system and other on-board energy power systems (such as air conditioning, electric pumps, etc.), the energy utilization efficiency of the vehicle is improved and the driving range is extended.
In pure electric vehicles, in addition to powering the drive motor, the battery also powers 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's 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 turn off some auxiliary equipment to increase the driving range.
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 semiconductor power devices as switch tubes, diodes, inductors, capacitors, loads and DC power supplies. By connecting and disconnecting the load circuit with a filter and the DC voltage, another DC voltage is obtained on the load.
(2) EPS control
The electric power steering system of an automobile uses the torque generated by the motor to assist the driver in power steering after deceleration of the steering system and conversion by the transmission mechanism. 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 signals, vehicle speed, axle load signals, etc., and obtains the steering direction of the power motor and the size of the target power current, thereby realizing power steering control.
