The vehicle controller includes two major components, hardware and software. Its core software and programs are generally developed by manufacturers, while auto parts suppliers can provide vehicle controller hardware and underlying drivers. At this stage, foreign research on the vehicle controller of pure electric vehicles mainly focuses on pure electric vehicles driven by in-wheel motors . For pure electric vehicles with only one motor, it is usually not equipped with a vehicle controller, but the motor controller is used to control the vehicle. Many large foreign companies can provide mature vehicle controller solutions, such as Continental, Bosch, Delphi, etc.
1. The composition and principle of the vehicle controller
The vehicle control system of pure electric vehicle is mainly divided into two schemes: centralized control and distributed control.
The basic idea of the centralized control system is that the vehicle controller completes the collection of input signals alone, analyzes and processes the data according to the control strategy, and then directly issues control commands to each actuator to drive the normal driving of the pure electric vehicle. The advantages of the centralized control system are centralized processing, fast response and low cost; the disadvantage is that the circuit is complicated and it is not easy to dissipate heat.
The basic idea of the distributed control system is that the vehicle controller collects some driver signals, and communicates with the motor controller and the battery management system through the CAN bus. The motor controller and the battery management system respectively collect the vehicle signals through the CAN bus. passed to the vehicle controller. The vehicle controller analyzes and processes the data according to the vehicle information and combined with the control strategy. After the motor controller and the battery management system receive the control command, they control the motor operation and battery discharge according to the current state information of the motor and battery. The advantages of distributed control systems are modularity and low complexity; the disadvantage is relatively high cost.
The schematic diagram of a typical distributed vehicle control system is shown in the figure below. The top layer of the vehicle control system is the vehicle controller. The vehicle controller receives the information of the motor controller and the battery management system through the CAN bus, and provides information to the motor controller and battery. The management system and the in-vehicle information display system send control commands. The motor controller and the battery management system are respectively responsible for the monitoring and management of the driving motor and the power battery pack, and the on-board information display system is used to display the current status information of the vehicle.
Schematic diagram of a typical distributed vehicle control system
The figure below shows the composition principle of the pure electric vehicle controller developed by a company. The hardware circuit of the vehicle controller includes modules such as microcontroller, switch quantity conditioning, analog quantity conditioning, relay drive, high-speed CAN bus interface, and power battery .
Schematic diagram of the composition of the pure electric vehicle vehicle controller developed by a company
(1) Microcontroller module The microcontroller module is the core of the vehicle controller. Considering the function of the pure electric vehicle vehicle controller and the external environment of its operation, the microcontroller module should have high-speed data processing performance, rich The characteristics of the hardware interface, low cost and high reliability.
(2) Switch quantity conditioning module The switch quantity conditioning module is used for level conversion and shaping of the switch input quantity, one end of which is connected with a plurality of switch quantity sensors , and the other end is connected with the microcontroller.
(3) Analog conditioning module The analogue conditioning module is used to collect the analog signals of the accelerator pedal and the brake pedal, and send them to the microcontroller.
(4) Relay driving module The relay driving module is used for driving a plurality of relays, one end of which is connected to a microcontroller through an optoelectronic isolator, and the other end is connected to a plurality of relays.
(5) High-speed CAN bus interface module The high-speed CAN bus interface module is used to provide a high-speed CAN bus interface, one end of which is connected to the microcontroller through an optoelectronic isolator, and the other end is connected to the system high-speed CAN bus.
(6) Power supply module The power supply module provides isolated power supply for the microprocessor and each input and output module, monitors the battery voltage, and is connected to the microcontroller.
The vehicle controller manages, coordinates and monitors all aspects of the electric vehicle power chain to improve the energy utilization efficiency of the vehicle and ensure safety and reliability. The vehicle controller collects the driver’s driving signal, obtains the relevant information of the drive motor and power battery system through the CAN bus, analyzes and calculates, and gives the motor control and battery management instructions through the CAN bus to realize the vehicle drive control and energy optimization control. and brake energy recovery control. The vehicle controller also has a comprehensive instrument interface function, which can display vehicle status information; it has complete fault diagnosis and processing functions; it has vehicle gateway and network management functions.
2. Basic functions of the vehicle controller
The vehicle controller collects driving information such as accelerator pedal signal, brake pedal signal and gear switch signal, and simultaneously receives the data sent by the motor controller and battery management system on the CAN bus, and analyzes the information in combination with the vehicle control strategy and judgment, extract the driver’s driving intention and vehicle running state information, and finally send out commands through the CAN bus to control the work of each component controller to ensure the normal driving of the vehicle. The vehicle controller should have the following basic functions.
(1) The function of controlling the driving of the vehicle The drive motor of the electric vehicle must output the driving or braking torque according to the driver’s intention. When the driver depresses the accelerator pedal or the brake pedal, the drive motor needs to output a certain driving power or regenerative braking power. The greater the pedal opening, the greater the output power of the drive motor. Therefore, the vehicle controller should reasonably explain the driver’s operation; receive feedback information from the subsystems of the vehicle to provide decision-making feedback for the driver; and send control commands to the subsystems of the vehicle to achieve the normal driving of the vehicle.
(2) Network management of the whole vehicle The vehicle controller is one of the many controllers of electric vehicles and a node in the CAN bus. In vehicle network management, the vehicle controller is the center of information control, responsible for information organization and transmission, network status monitoring, network node management, and network fault diagnosis and processing.
(3) Recovery of braking energy The important feature of pure electric vehicles that is different from internal combustion engine vehicles is that they can recover braking energy. This is achieved by operating the motor of pure electric vehicles in a regenerative braking state. The analysis of the vehicle controller The driver’s braking intention, power battery pack status and drive motor status information, combined with the braking energy recovery control strategy, send motor mode commands and torque commands to the motor controller under the conditions of braking energy recovery, so that the drive The motor works in the power generation mode, and the energy recovered by the electric braking is stored in the power battery pack without affecting the braking performance, so as to realize the braking energy recovery.
(4) Vehicle energy management and optimization In pure electric vehicles, the power battery not only supplies power to the drive motor, but also supplies power to the electric accessories. Therefore, in order to obtain the maximum driving range, the vehicle controller will be responsible for the entire vehicle’s power supply. Energy management to improve energy utilization. When the SOC value of the battery is relatively low, the vehicle controller will send commands to some electric accessories to limit the output power of the electric accessories to increase the driving range.
(5) Monitoring and display of vehicle status Information such as power, total voltage, cell voltage, battery temperature and fault, and then send these real-time information to the vehicle information display system through the CAN bus for display. In addition, the vehicle controller regularly detects the communication of each module on the CAN bus. If it finds that a node on the bus cannot communicate normally, it will display the fault information on the vehicle information display system, and take reasonable measures for corresponding emergency situations. processing to prevent the occurrence of extreme conditions, so that the driver can directly and accurately obtain the current operating state information of the vehicle.
(6) Fault diagnosis and processing Continuously monitor the vehicle electronic control system for fault diagnosis. The fault indicator indicates the fault category and some fault codes. According to the fault content, timely carry out corresponding safety protection processing. For less serious faults, it is possible to drive at a low speed to a nearby maintenance station for maintenance.
(7) The external charging management realizes the connection of charging, monitors the charging process, reports the charging status, and ends the charging.
(8) On-line diagnosis and offline detection of diagnostic equipment is responsible for the connection and diagnostic communication with external diagnostic equipment, and realizes UDS diagnostic services, including reading of data streams, reading and clearing of fault codes, and debugging of control ports.
The figure below is an example of a pure electric vehicle vehicle controller. It determines the driver’s intention by collecting control signals during driving and charging, manages and schedules the vehicle’s electronic control equipment through the CAN bus, and uses different models for different models. Control strategy to realize vehicle drive control, energy optimization control, braking energy recovery control and network management. The vehicle controller adopts technologies such as microcomputer, intelligent power drive and CAN bus, and has the characteristics of good dynamic response, high sampling accuracy, strong anti-interference ability and good reliability.
Example of pure electric vehicle vehicle controller
3. Vehicle Controller Design Requirements
Sensors that directly send signals to the vehicle controller include accelerator pedal sensor, brake pedal sensor and gear switch, wherein the accelerator pedal sensor and brake pedal sensor output analog signals, and the output signal of the gear switch is a switch signal. The vehicle controller indirectly controls the operation of the drive motor and the charging and discharging of the power battery by sending commands to the motor controller and the battery management system, and realizes the on-off of the on-board module by controlling the main relay.
According to the composition of the vehicle control network and the analysis of the input and output signals of the vehicle controller, the vehicle controller should meet the following technical requirements.
① When designing the hardware circuit, the driving environment of the electric vehicle should be fully considered, electromagnetic compatibility should be paid attention to, and the anti-interference ability should be improved. The vehicle controller should have a certain self-protection ability in software and hardware to prevent the occurrence of extreme situations.
② The vehicle controller needs to have enough I/O interfaces to be able to quickly and accurately collect various input information, and at least two A/D conversion channels to collect accelerator pedal signals and brake pedal signals. A digital input channel is used to collect the vehicle gear signal, and there should be multiple power drive signal output channels for driving the vehicle relay.
③ The vehicle controller should have a variety of communication interfaces. The CAN communication interface is used to communicate with the motor controller, the battery management system and the vehicle information display system. The RS232 communication interface is used to communicate with the host computer, and an RS-485 communication interface is reserved. /422 communication interface, which can be compatible with devices that do not support CAN communication, such as some models of car touch screens.
④ Under different road conditions, the car will encounter different shocks and vibrations. The vehicle controller should have good shock resistance to ensure the reliability and safety of the car.
Post time: Nov-09-2022