7.4.5 ESP (vehicle stability system)
Let’s consider the following situation: in mid-November, you went on a long trip. The road is great as a mirror, but in the blink of an eye your car suddenly falls off the trajectory, it is thrown from side to side. The active rotation of the steering wheel does not provide the desired result, but everything works out, the consequences are expressed by trembling hands due to a surge of adrenaline and shaky nerves. The reason for such an unpredictable car behavior is ice. During the movement, the wheels on the right side hit a thin imperceptible layer of ice. The car differential reacted instantly, "throwing" the moment on the wheel, which lost traction. There was a turning moment and the car started actively "fishtailing" on the road.
The story described above ended without any consequences. But this, unfortunately, is not always the case in real life. In order to eliminate and/or minimize all the factors that influence the change in the trajectory of the car, the designers created and implemented a car stabilization system - ESP.
This system allows one to virtually eliminate such a dangerous maneuver of the car as skidding (which in most cases cannot be controlled). This system uses all the elements of the anti-lock braking system and additionally has its "own" sensors: the sensor of lateral accelerations, the sensor of car fishtailing, an angle of turn of wheels, etc.
While collecting data from all sensors, in case of a car skid or loss of wheel traction due to weather conditions, the system "decides" which of the wheels shall brake in order to compensate for the torque, and if necessary, reduces engine speed.
Example
In case if the car when passing the turn to the right at high speed front wheels start "carrying away" from the set trajectory in the direction of action of centrifugal forces of inertia, i.e. on radius bigger, then the radius of turn. The ESP system in this case will start braking the rear wheel, which goes on internal radius of turn. This provides the car with big turning ability and directs it, as if screwing it in turn. At the same time in case of the increased danger ESP system will reduce engine turns. In case if the rear side of the vehicle skids while turning, ESP system activates the left front wheel brake on the outer turning radius.
ESP is currently the most effective active safety system; thus most cars do not have the ability to disable it.
Note
The stabilization system has different names for different car manufacturers. Below is a list of names of this system by different companies:
- ESP (Electronic Stability Program) system on most cars in Europe and the USA;
- ESC (Electronic Stability Control) system on Honda, Kia, Hyundai cars;
- DSC (Dynamic Stability Control) system on BMW, Jaguar, Rover cars;
- DTSC (Dynamic Stability Traction Control) system on Volvo cars;
- VSA (Vehicle Stability Assist) system on Honda and Acura cars;
- VSC (Vehicle Stability Control) system on Toyota cars;
- VDC (Vehicle Dynamic Control) system on Infiniti, Nissan, Subaru cars.
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