ESP is a driving safety system. The purpose of ESP is to ensure the stabilisation of the vehicle in critical, unstable driving situations (driving manoeuvres).
Curves which are taken too quickly and violent steering movements give rise to lateral forces, which may result in the excessive rotation of the vehicle about the vertical axis. This causes the vehicle to swerve and control of the vehicle is usually lost.
- Straight ahead driving
- Driving in curves
| D | Centre of pressure | F cl | Centrifugal force |
|---|---|---|---|
| O | Reference point | F S | Lateral force |
| S | Centre of gravity | v F | Vehicle speed |
| F SW | Side force due to wind | r K | Curve radius |
| M Z | Yawing moment | ||
| l | Vehicle length | ||
| d | Distance of centre of pressure |
Due to constant vehicle monitoring and vehicle information evaluation (approx. 25 times per second) ESP can stabilise the vehicle with the onset of a loss of control through targeted manipulation of the brake and engine management systems. The ESP control, which is integrated into the ABS control unit, receives the required vehicle data from the existing ABS 5.3/TC components and from additional sensors such as pressure, steering angle and yaw rate / acceleration sensors.
The individual wheel braking plays an important role. ESP can generate precisely metered braking force at each individual wheel (1 = braked wheel), which attempts to pull the vehicle back on course in the event that it no longer responds to the steering.
| I | Without ESP | II | With ESP |
In the case of understeer (I, front of vehicle pulls towards outside of curve) and for vehicles with ESP (2), the rear wheel on he inside of the curve is braked, stabilising the vehicle in curves, whereas a vehicle without ESP (1) is thrown out of the curve.
In the case of oversteer (II, vehicle pulls towards outside of curve) and for vehicles with ESP (4), the rear wheel on he outside of the curve is braked, stabilising the vehicle, whereas a vehicle without ESP (3) is thrown out of the curve.