Hybrid electric vehicle (HEV) can organically combine engine, motor, power battery and other components.
It can give full play to the advantages of internal combustion engine vehicle and electric vehicle. It is an important method to reduce oil consumption and carbon dioxide emissions. In the development of hybrid electric vehicle, vehicle controller is the ultimate carrier of all kinds of control measures and an important component to meet the cooperative work of vehicle power system. Therefore, attention must be paid to the development of vehicle controller for hybrid electric vehicles. In this paper, combined with ISG hybrid electric vehicle, the vehicle torque requirement, engine working area optimization and vehicle control strategy are analyzed, and a variety of working modes are realized by real vehicle test, which shows that the development of vehicle controller is feasible. Today, with the rapid development of society and economy, the development of the world automobile industry is facing two major challenges, namely, energy shortage and environmental pollution. It is urgent to carry out research on new energy vehicles. Compared with traditional automobiles, hybrid electric vehicles not only have the characteristics of diesel locomotives, but also have the advantages of electric vehicles, which is of great significance in improving the economy and reducing pollution emissions. Hybrid Electric Vehicle (HEV) needs the cooperation of various parts and components, which requires continuous and rapid switching of working mode under certain control measures. Therefore, higher requirements are put forward for the development of vehicle control system. As a key control component of HEV, the vehicle controller should be based on the driver’s acceleration pedal position and gear position. Operations and battery charging status can accurately calculate all the parameters needed for operation, such as the output power of engine and motor, so as to achieve the coordination of all power components and ensure the normal running of electric vehicles. At the same time, it can also use vehicle charging and braking energy recovery to achieve higher energy efficiency. Therefore, the development of vehicle controller has a great impact on the power, economy and reliability of the vehicle. The system structure of a hybrid electric vehicle belongs to a typical single-axle parallel structure. The working mode of the vehicle includes pure gasoline engine drive, hybrid drive, regenerative braking and so on. When the vehicle is running, various hardware line vehicle controllers are used to collect relevant parameters, such as vehicle status, driver intentions, etc. The preset control algorithm and management strategy are implemented through the extremely fast running CPU and control ports, and the instructions and information are transmitted to the executive parts of power system by using CAN bus and switch output ports, so as to achieve effective control. Compared with traditional vehicles, hybrid electric vehicles have basically the same demand for torque, which can be fully reflected by acceleration pedal drivers. Driver driving demand torque can be expressed by formula. The maximum torque of the motor at the current speed can be expressed by Tmmax. The speed of ISG motor can be expressed by n. According to the analysis of the working characteristics of the engine, the engine has lower efficiency and higher fuel consumption at low speed and low load. The minimum, optimum and maximum optimum working torques can be determined by relevant conditions, and the optimum working area of the engine is located in the minimum and maximum optimum working torques curve. By adjusting the ISG motor, the engine can be controlled in the optimum working torque curve and the optimum working area of the engine. If the torque requirement is below the minimum optimum working torque, the throttle opening must be increased appropriately to ensure that the engine works in the optimum working area. ISG motors can be driven by excess torque to generate electricity and charge batteries. For example, when the torque requirement is at the minimum and maximum optimum working torque, the mode is the engine driving mode alone. If the required torque is above the maximum optimum working torque, thermostatic element the engine can work in the optimum working area continuously with the help of motor. If the maximum resistance torque of the motor is still inconsistent with the required torque, the throttle opening should be continuously increased and the engine torque output should be continuously increased to meet the vehicle torque requirements. Software design. Code Warrior 4.6 is the software design environment for vehicle controller, which configures Freescale 16-bit simulator. During the vehicle test, the test data can be collected and recorded in time, and the control strategy parameters in the controller can be updated in time. Based on this, the driver interface reflected by VisuaIC and CAN card is selected to develop data acquisition and on-line debugging software. The software can display, store and play back the relevant information collected in CAN card, and write control strategy parameters in E2ROM through CAN network by on-board computer, so as to update control strategy parameters. Hardware design. The hardware of the controller is the key point in the development of the whole vehicle controller for hybrid electric vehicles. The specific contents are shown in Table 1. Engine start. The ISG motor is selected to replace the traditional starter, such as the START gear as the key switch position.
The ISG motor can receive the speed control mode indication of the vehicle controller, with the target speed of 800 r per minute. The vehicle controller can close the relay and turn on the engine controller, then start the vehicle to achieve the purpose of fuel injection and ignition. Charge the car. The acceleration pedal has about 10% opening between 30 and 50 seconds. If the throttle opens for this purpose, the working efficiency and load of the engine are low. If the throttle opening is increased continuously, the ISG motor can be driven by redundant torque to realize the functions of power generation and battery charging when the throttle opening is about 40%. Pure engine drive. The accelerator pedal is about 33% open between 50 and 70s. At this time, 0 is the demand of charging torque. If the working speed is unchanged and the throttle is 68% open, the demand of driver’s driving torque can be matched. According to the working characteristics of the engine, the efficiency of the engine in this stage is high. Hybrid drive. When the acceleration pedal is between 205 and 215 seconds, its opening is about 100%, which is the maximum opening value. ISG motor works at the same time, and the output torque is about 100N per meter. 252V is bus voltage, 100A is bus current. Parking and charging. When the charging state coefficient of battery pack is low, it is in the parking state. At this time, the engine can be turned on and charged. This process has no response to the acceleration or brake pedal controller. According to the difference between the target charging and the specific charging current, the vehicle controller can adjust the throttle opening properly and form a closed-loop control system. In this system, the working mode of the motor is speed regulation, and the target speed is 1200 r per minute. It ensures that the motor can start at very low engine speed without stalling. In summary, with the rapid development of social economy, China’s energy consumption is becoming more and more serious. In order to alleviate the problem of energy shortage, we must pay attention to the development and utilization of new energy. Compared with traditional automobiles, hybrid electric vehicles have more advantages in environmental protection and energy saving. In order to improve the performance of hybrid electric vehicles, it is necessary to pay attention to the development of vehicle controller, design vehicle controller, and verify the rationality and correctness of the development of vehicle controller and its control strategy through vehicle test, so as to ensure its faster and better development.