Development of New Energy Vehicle Controller Scheme_ VCU_ HCU

Development of New Energy Vehicle Controller Scheme_ VCU_ HCU

As a green means of transportation, new energy vehicles have many incomparable advantages in environmental protection, energy conservation and driving performance. They are a complex system composed of multiple subsystems, mainly including battery, motor, brake and other power systems and other accessories. Almost all subsystems complete their functions and objectives through their own control unit VCU. In order to meet the goals of vehicle power, economy, safety and comfort, on the one hand, it must have intelligent human vehicle interaction interface, on the other hand, all systems must also cooperate with each other to optimize the matching. This task needs to be completed by the vehicle controller in the control system. The distributed control network based on bus is an ideal way to realize the cooperative control of many subsystems. Because CAN bus has the advantages of low cost, high transmission rate, high security and reliability, strong error correction ability and good real-time performance, it has been widely used in the real-time distributed control network of middle and low price automobiles. With more and more automobile manufacturers adopting CAN protocol, CAN has gradually become a universal standard. The use of bus network can greatly reduce the connection signal harness between equipment and improve the system monitoring level. In addition, it is convenient to add new control units and expand network system functions without reducing its reliability.

1、 Vehicle controller control system structure

The new energy vehicle controller designed and developed by the company includes micro controller, analog input and output, switching value conditioning, relay drive, high-speed CAN bus interface, power supply and other modules. The vehicle controller manages, coordinates and monitors all links of the power chain of new energy vehicles to improve the energy utilization efficiency of the vehicle and ensure safety and reliability. The vehicle controller collects driver driving signals, obtains relevant information of motor and battery system through CAN bus, analyzes and calculates, gives motor control and battery management commands through CAN bus, and realizes vehicle drive control, energy optimization control and brake feedback control. The vehicle controller also has integrated instrument interface function, which can display vehicle status information; Complete fault diagnosis and handling functions; It has vehicle gateway and network management functions.

The functions of each module are briefly described as follows:

1. Switching value conditioning module

The switching value conditioning module is used for the level conversion and integer of the switching input value. One end of the module is connected to a plurality of switching value sensors, and the other end is connected to the microcontroller;

2. Relay driver module

The relay driving module is used to drive multiple relays, one end of which is connected with the microcontroller through a photoelectric isolator, and the other end is connected with multiple relays;

3. High speed CAN bus interface module

The high-speed CAN bus interface module is used to provide high-speed CAN bus interface. One end of the module is connected to the microcontroller through a photoelectric isolator, and the other end is connected to the high-speed CAN bus of the system;

4. Power module

The power module can provide isolated power supply for the microprocessor and each input and output module, monitor the battery voltage, and connect with the microcontroller;

5. Analog input and output module

Analog input and output module can collect 0~5V analog signal and output 0~4.095V analog voltage signal.

6. Pulse signal input and output module

Pulse signal can be collected and conditioned, with the range of 1Hz-20KHZ and amplitude of 6-50V; Output PWM signal range: 1HZ-10KHZ, amplitude: 0-14V.

7. Fault and data storage module

Ferroelectric memory can store calibrated data, fault codes, vehicle characteristic parameters, etc., with a capacity of 32K.

2、 Function description of vehicle controller

New energy vehicle controller basically has the following functions:

1. Functions of vehicle driving control

The power motor of new energy vehicles must output driving or braking torque according to the driver's intention. When the driver steps down the accelerator pedal or brake pedal, the power motor shall output a certain driving power or regenerative braking power. The greater the pedal opening, the greater the output power of the power motor. Therefore, the vehicle controller shall reasonably explain the driver's operation; Receive feedback information from all subsystems of the vehicle to provide decision feedback for drivers; Send control commands to all subsystems of the whole vehicle to realize normal driving of the vehicle.

2. Network management of the whole vehicle

In modern cars, there are many electronic control units and measuring instruments. There are data exchanges between them. How to make such data exchange fast, effective and trouble free transmission become a problem. In order to solve this problem, German BOSCH Company developed the Controller Area Network (CAN) in the 1980s. In electric vehicles, electronic control units are more and more complex than traditional fuel vehicles. Therefore, the application of CAN bus is imperative. Vehicle controller is one of many controllers of electric vehicle and a node of CAN bus. In the vehicle network management, the vehicle controller is the center of information control, responsible for the organization and transmission of information, the monitoring of network status, the management of network nodes, and the diagnosis and treatment of network faults.

3. Brake energy feedback control

The motor is used as the output mechanism of driving torque for new energy vehicles. The motor has the performance of feedback braking. At this time, the motor acts as a generator and uses the braking energy of the electric vehicle to generate electricity. At the same time, this energy is stored in the energy storage device. When the charging conditions are met, the energy is recharged back to the power battery pack. In this process, the vehicle controller judges whether the braking energy feedback can be carried out at a certain time according to the opening of the accelerator pedal and brake pedal and the SOC value of the power battery. If it can be carried out, the vehicle controller sends a braking command to the motor controller to recover part of the energy.

4. Vehicle energy management and optimization

In a pure electric vehicle, the battery not only supplies power to the power 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 energy management of the vehicle to improve the energy utilization. When the SOC value of the battery is low, the vehicle controller will issue 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

The vehicle controller shall 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 through the sensor and CAN bus, drive the display instrument, and display the status information and fault diagnosis information through the display instrument. The display contents include: motor speed, vehicle speed, battery power, fault information, etc.

6. Fault diagnosis and treatment

Continuously monitor the vehicle electronic control system for fault diagnosis. The fault indicator lamp indicates the fault category and some fault codes. Timely carry out corresponding safety protection treatment according to the fault content. For less serious faults, drive to the nearby maintenance station at low speed for maintenance.

7. External charging management

Realize charging connection, monitor the charging process, report the charging state and end the charging.

8. Online diagnosis and offline detection of diagnostic equipment

Be responsible for connection and diagnostic communication with external diagnostic equipment, and realize UDS diagnostic services, including data flow reading, fault code reading and clearing, and control port debugging.