In the advanced driver assistance of the car, the automatic cruise system (CCS) is one of the driving control systems for the car and plays a very important role in the safety control of the car. The cruising control system (CCS) refers to an electronic control device that can ensure that the car runs stably at a set speed without controlling the accelerator pedal within a certain range of vehicle speed. Specifically, the cruise control system has the functions of cruise constant speed, acceleration and deceleration. The system is mainly composed of command switches, sensors, ECUs and corresponding actuators.
Years ago, Bosch introduced a new generation of automatic cruise control system, Adaptive Auto Cruise System (ACC), to the BMW 3 Series. This system adds the ACC system itself to the original CCS, in addition to the vehicle's own speed cruise control. Control modules (such as obstacle detection systems, cruise control system throttles, etc.), brake systems, specifically including radar sensors, direction angle sensors, wheel speed sensors, brake controllers, torque controllers, and Engine controller and other components. ACC combines anti-lock brake system (ABS), traction control unit (TCS) and enhanced vehicle stability system (VSE), which is more intelligent than traditional automatic cruise, and the driver does not step on the brake pedal in time. In this case, the ACC can also automatically complete the brakes.
Today, Xiaobian will briefly talk about how to do a complete automatic cruise system. First, let's talk about the basic principles of the automatic cruise system before the opening:
How the cruise control system works:
Cruise control system work flow chart
The cruise control system is a typical closed loop control system. The control principle of the electronically controlled cruise control system is shown in the figure above. There are two signals for inputting the CCS ECU of the cruise control unit: one is the cruise speed command signal set by the driver through the cruise switch according to the driving condition, and the other is the actual vehicle speed feedback signal input by the vehicle speed sensor.
When the cruise speed command signal and the actual vehicle speed feedback signal are input to the cruise control unit CCS ECU, the comparator A of the CCS ECU can obtain the difference between the two signals by comparison operation, which is called an error signal. After the error signal is subjected to the proportional operation and the integral operation, the control signal for controlling the throttle opening degree is obtained by the amplification process, and the CCS ECU sends the control command to the actuator, and the actuator can drive the throttle cable to adjust the engine throttle. The size of the opening speed quickly adjusts the actual vehicle speed to the speed value set by the driver, thereby achieving constant speed control, that is, achieving cruise control.
During the control process, when the actual vehicle speed is lower than the cruise speed value set by the driver, the cruise electronic control unit CCS ECU will issue an instruction to increase the throttle opening to the actuator to increase the actual vehicle speed to the cruise speed. Conversely, when the actual vehicle speed is higher than the cruise speed value set by the driver, the cruise control unit CCS ECU will issue an instruction to the actuator to reduce the throttle opening, so that the actual vehicle speed is reduced to the cruising speed, so that the actual vehicle speed is basically Keep the cruise speed value set by the driver unchanged.
Cruise control system
(1-power supply, 2-master switch, 3-cruise control ECU, 4-actuator, 5-connected throttle, 6-speed sensor, 7-brake light switch)
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