Year1
After more than ten years of development, the design of the power system of electric vehicles, At present, the only model with the most practical value and commercial operation is hybrid electric vehicles. The hybrid power system assembly has developed from the original discrete structure of the engine and motor to the integrated structure of the engine, motor and gearbox, that is, an integrated hybrid powertrain system. The main function of the power management of electric vehicles is to give full play to the combustion efficiency of the fuel, so that the engine works near the optimal operating point, and to timely adjust the relationship between the vehicle operating conditions and external road conditions through the energy reserve and output of the electric motor and battery. matching relationship. Therefore, only the power management situation of the hybrid system is considered here. From a functional perspective, the power management of the hybrid system needs to achieve the following two goals: Make full use of the vehicle's inertial energy. When the vehicle decelerates, brakes, or travels downhill, the inertial force of the wheels drives the electric motor. At this time, the electric motor becomes a generator, which can charge the battery in reverse direction, saving fuel. () Ensure the best working condition of the engine and avoid inefficient operation of the engine. The engine can usually be adjusted to operate stably near the optimal operating point, and the output of the battery and electric motor can be adjusted to adapt to changes in various external road conditions. For example, when the vehicle is in low speed, coasting, and idling conditions, the battery pack drives the electric motor. When the vehicle is in starting, accelerating, and climbing conditions, the engine-motor set and battery pack jointly provide electric energy to the electric motor. In this way, the efficiency of the engine is improved because the engine avoids idling and low-speed operation, which not only reduces exhaust emissions but also saves power. Statistics show that under road conditions above 10%, an ordinary car that only utilizes its power potential will fall to 100% in urban areas, while electric vehicles that use optimized power management, such as Toyota R car, its power performance has exceeded the level of similar cars, and it saves fuel.
related to energy consumption and energy conversion.
. .Figure bus-based energy management and control network topology
. .Through the bus, the upper master control node composed of the on-board computer system controls the entire The energy management and control network is connected, and through a specialized software system, data collection, data analysis and control strategy output are carried out to achieve optimal matching between external driving resistance and engine energy adjustment, and to achieve energy conversion within the vehicle. Utilize to realize energy saving, energy storage and supplementary energy regulation of motor and battery systems. The powertrain system is mainly used to optimize engine operation. Under normal driving conditions, the energy of the engine is divided into two channels. One channel is transmitted to the vehicle transmission and propulsion system to drive the vehicle to operate normally, and the other channel drives the motor to work and supplies power to the battery. At this time, the auxiliary power system composed of the motor and the battery is equivalent to an energy regulating device. Through the battery motor controller and the driving resistance test device, the adjustment and distribution of the two output energy of the engine are realized according to changes in external road conditions. The kinetic energy conversion device works together with the driver's control monitoring system and the battery motor controller. When the driver steps on the brake pedal, the brake motor first approaches the rotating device to be braked, such as the transmission shaft, consuming the vehicle's inertial energy and converting it into electrical energy. At the same time, when the control monitoring system detects the brake pedal movement, it charges the battery. The circuit is adjusted to realize the storage of electric energy transferred from the braking motor. < ., the structure and communication process of each monitoring node based on the bus
The bus node structure is generally divided into two categories: one uses appropriate The matching card is connected to the machine to realize the communication between the host computer and the bus. The other type is composed of microcontroller, controller and driver. As a type of node, it transmits data with the bus. In the energy management and control system designed in this article, the upper master control node The first type of bus node structure is adopted, and each key monitoring/control system adopts the second type of bus node structure. The structure of each node and the connection method of the system are shown in the figure. Two resistors are configured at both ends of the bus. Their function is to match the bus impedance, which can increase the stability and anti-interference ability of bus transmission and reduce the error rate in data transmission. For each lower-level monitoring node, a series of microcontrollers can usually be used as the primary monitoring signal processing center device of the node and used as the controller. , is a commonly used interface between a transceiver and a physical bus, which mainly provides differential transmission capabilities to the bus and differential acceptance capabilities to the controller. The circuit diagram of a lower monitoring node composed of the above three components is shown in the figure. The three-layer structure model of the bus is: < .Physical layer, data link layer and application layer
. The functions of the physical layer and data link layer are completed by. After the power-on hardware is reset, it must be software initialized before data communication can be carried out. Its main function is to define the bus speed, acceptance mask code, output pin drive mode, bus mode and clock division. During the communication process of the entire energy management and control system, each controller sends data (vehicle speed, battery voltage, current, driving resistance, engine speed, etc.) to the bus in a prescribed format and period, and also receives information from other controllers. Other controllers on the bus take the required messages as needed. For receiving data, the system uses interrupts. Once an interrupt occurs, the received data is automatically loaded into the corresponding message register. At this time, the mask filtering method can also be used, using the mask filter register to selectively compare the identifier of the received message with the identifier set in advance when the receive buffer is initialized. Only messages with matching identifiers can enter. Receive buffer, those messages that do not meet the requirements will be shielded from the receive buffer, thereby reducing the burden of processing messages. The process of the host computer receiving relevant data using interrupt mode is shown in the figure. , Conclusion As a reliable automobile computer network bus, the bus has begun to be applied in automobiles, allowing each automobile computer control unit to share all information and resources through the bus. , to achieve the purpose of simplifying wiring, reducing the number of sensors, avoiding duplication of control functions, improving system reliability and maintainability, reducing costs, and better matching and coordinating various control systems. The bus-based electric vehicle energy management and control system communication solution designed in this article can basically achieve the purpose of saving energy and optimizing engine efficiency. The technology is relatively mature, has high flexibility, simple scalability, excellent anti-interference and The ability to handle errors is of great significance to improving the power, operational stability and safety of the car.
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