At present, there are three types of automobile active collision avoidance systems researched and developed: (1) Vehicle active collision avoidance warning CWS (collisionwarning) system, this system gives an alarm to the detected hazards. The United States has already implemented commercial use on some heavy-duty trucks and bus vehicles. (2) Vehicle adaptive cruise control ACC (adapTIvecruisecontrol) system, this system can achieve active collision avoidance and cruise control in simple traffic situations, some car companies have begun to use ACC technology on high-end models. (3) A compound vehicle intelligent control system. This system is aimed at complex traffic conditions, especially the urban traffic environment, and uses an ACC system supplemented by a vehicle stop & go system to improve the practicality of vehicle intelligent control. At present, most domestic and foreign researches on automotive active collision avoidance systems focus on the longitudinal control of the collision avoidance system. The key technologies of the system include target vehicle identification and movement information acquisition, safe distance model and collision avoidance control system modeling in the driving environment. Analysis of the technology development of automobile active collision avoidance system Driving environment recognition The key to driving environment identification is distance measurement. At present, the technical methods used in distance measurement include ultrasonic measurement, infrared distance measurement, laser measurement, machine vision and radar technology. The real-time performance and accuracy of radar measurement are good. The millimeter-wave vehicle radar system currently working in the millimeter wave band is considered to be a better solution to the problem of control detection under the condition of active collision avoidance of automobiles. Many companies' ranging technology has entered practical use. The collision avoidance alarm system being researched by GM uses lidar technology; the MEAR laser ranging system developed by Germany ’s Wild Hebrüger Company can provide the driver with the distance and relative distance to other vehicles and obstacles. Speed ​​data, while providing video images; Mercedes-Benz, Nissan and other auto companies are using the millimeter-wave radar system produced by the German ADC company. Safe state judgment The safe distance logic algorithm is mostly used to judge the safe state, and different safe distance models are established based on factors such as kinematic analysis of vehicle braking process, riding comfort, workshop time, driver characteristics and other factors. Among them, the safety distance model based on the workshop time distance does not take into account the fact that the driver ’s actual feeling that the workshop distance should be maintained is also related to the relative speed, and the judgment result does not conform to the driver ’s subjective perception. Therefore, researchers in Japan have established a driver preview safety distance model. However, under the typical working conditions of the collision avoidance system of the front vehicle braking, the acceleration of the model is fixed, which results in the judgment result of the model not conforming to the driver's subjective feelings. In response to this problem, the driver's optimal preview acceleration model is studied. Collision avoidance system control The active collision avoidance control methods of automobiles mainly include upper control and lower control. The former is based on the safety distance, and the control algorithm is used to obtain the deceleration that the vehicle should have in the current situation from the perspective of kinematics; the latter is based on the target parameters such as the target deceleration of the vehicle determined by the upper control algorithm, combined with the vehicle braking system model , Application of control algorithms to achieve precise control of throttle, braking, steering, etc., to achieve the goal of higher control requirements. The control algorithms include fuzzy control and neural network control, which are suitable for nonlinear mode sliding mode control algorithm and Back-stepping method. Problems in active collision avoidance system Current research considers very few side targets and other types of distance targets. The system has problems such as redundant alarms, false alarms, and insufficient consideration of driver characteristics. In the control model, only the longitudinal control model is considered. For the dangerous working conditions such as high-speed steering braking and overtaking of the vehicle, a dynamic model that considers lateral control must be established. In terms of the controller design of the model, the existing higher-level controller design considers that the driver's driving characteristics are not enough, while the lower-level controller has poor robustness and cannot meet the needs of the collision avoidance system, which needs further research and solution.
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