Basic knowledge about electronically controlled suspension and chassis[Copy link]
The suspension mainly affects the vertical vibration of the car. Traditional car suspension is not adjustable, and the change of the height of the car body during driving depends on the deformation of the spring. Therefore, there is a natural phenomenon that the ground clearance of the car body is different when the car is unloaded and fully loaded. In particular, some cars use relatively soft coil springs. The deformation stroke of the spring will be relatively large after full load, resulting in a difference of tens of millimeters in the ground clearance between the unloaded and fully loaded cars, which affects the car's passability.
Different driving states of the car have different requirements for the suspension. Generally, a softer suspension is required for comfort when driving, and a harder suspension is required for stability when making sharp turns and braking. There is a contradiction between the two. In addition, the requirements for the height of the car body are also different in different driving environments. The unchanging suspension cannot meet this contradictory demand, and can only be solved in a compromise way. Driven by the development of electronic technology, engineers have designed an electronically controlled suspension that can be adjusted within a certain range to meet this demand. This suspension is called an electronically controlled suspension. At present, the more common form is the electronically controlled air suspension.
In the past, air suspension was mostly used on buses. When parking, the suspension dropped to reduce the ground clearance of the car, which was convenient for passengers to get on and off the car. When driving, the suspension rose to facilitate traffic. This air suspension system consists of an air compressor, valves, springs, air chambers (air bags), and shock absorbers. The height of the vehicle is directly adjusted by the valve to control the air flow in and out of the air chamber. The
electronically controlled suspension used in cars now introduces the air suspension principle and electronic control technology, combining the two together. A typical electronically controlled suspension consists of an electronic control unit (ECU), an air compressor, a vehicle height sensor, a steering angle sensor, a speed sensor, a brake sensor, an air spring element, etc. The
air spring element is composed of an electronically controlled shock absorber, a valve, and a double air chamber. There is a small motor on the top of the electronically controlled shock absorber, which can be used to turn a control lever that adjusts the size of the measuring hole to divide the damping into multiple levels, thereby achieving the purpose of controlling the damping. The valve also acts as a regulator of airflow. Usually, the two air chambers are connected, and the total volume together acts as an air spring, which is relatively soft. However, when the valve between the two air chambers is closed, the capacity of one air chamber will bear the role of the air spring, which will become hard. Therefore, the valve plays a role in controlling the "spring" to become softer or harder.
When the electronically controlled suspension is working, the interaction of the valves controls the air flow to the air spring element. The sensor detects the driving state of the car and feeds back to the ECU. The ECU calculates and outputs instructions to control the motor and valve of the air spring element based on these feedback information, so that the electronically controlled suspension changes with the driving and road conditions: in general driving, the air spring becomes softer and the damping becomes weaker, so as to obtain a comfortable ride; in sharp turns or braking, it quickly converts into a hard air spring and stronger damping to improve the stability of the vehicle body. At the same time, the electronically controlled shock absorber of the system can also adjust the height of the vehicle, and can reduce the height of the vehicle body (reduce ground clearance) as the speed increases, reduce wind resistance to save energy; when the speed is relatively slow, the height of the vehicle body can return to normal.
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