• If ESC is not installed, the direction stability cannot be maintained during
emergency braking. At this time, the lateral adhesion of the ground is very small,
and the steering wheel cannot be operated to avoid obstacles ahead; when
there is ESC emergency braking, turn the steering wheel at the same time, at this
time, the vehicle will drive in the direction controlled by the steering wheel and
stop smoothly.
• For vehicles without ESC system, slight steering wheel rotation or small external
lateral force can lead to understeer and oversteer when the vehicle is running
at high speed; with ESC system, if the vehicle is understeer or oversteer, it will
actively brake the vehicle to prevent vehicle rollover, etc.
• Although the ESC system is installed, it is still necessary to drive carefully on
slippery or icy roads and when emergency braking on curves.
Operating Principle of ESC System
Experienced drivers all know that when driving on a slippery road or when the
speed is very high, emergency braking must be carried out continuously by gently
pressing the brake pedal to keep the vehicle under control. Through analysis and
research, it is found that when the wheel is locked, the road friction in both the
longitudinal and transverse directions of the wheel decreases greatly. At this time,
the slip rate is 100%, and the vehicle deviates, spins or even loses its steering ability.
However, when the wheel is in a semi-rolling and semi-sliding state, the friction
between the road surface and the wheel is the best. At this time, the braking effect
is the best, and its slip rate is between 10% and 30%.
ABS works according to this principle. First, it measures the speed signal of each
wheel through the sensor and sends it to the controller. The controller analyzes
and calculates the input signal and sends the brake pressure control command to
the air pressure regulator according to the movement of the wheel. When it finds
that a wheel is going to lock, it immediately lets the regulator discharge the brake
air appropriately to reduce the friction between the brake hub and the brake shoe,
make the wheel speed increase properly. When the controller finds that the wheel
speed increases too fast, it will stop the exhaust of the regulator and reduce the
wheel speed. During this process, the regulator can have up to 3-5 control cycles
per second. Through the cyclic regulation of brake pressure of "lock-release-lock-
release", the wheel slip rate is always kept within the ideal range, thus achieving the
best braking effect.
As an extension function of ABS, the principle of ESC: SAS monitors the driver's
driving intention to adjust the steering wheel, and YRS monitors the actual posture
of vehicle body movement; combined with the wheel speed sensor of ABS, the
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