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Electronic Stability Program

ESP is essential, also for compact cars

The Electronic Stability Programme should prevent the breaking away of a vehicle by specific braking of individual front and/or rear wheels. ESP cannot cancel out the effect of centrifugal force. It can however prevent, if necessary, the danger of tilting (Rollover-Protection) by specific or even sharp braking. The ESP also intervenes through the braking assembly. The combination with certain four-wheel-drive functions, which can also include acceleration, is new.

In point of fact, the system has, apart from the price, only advantages. Consequently, it is represented in more than 90 percent, at least in Germany, of vehicles from the mid-range compact class upwards. There is still some need to include it in the small-car-range, which is favoured by a large number of novice drivers. After all, 50% of all accidents are caused by skidding, of which 80% could be prevented by ESP. For this reason, it is quite incomprehensible, that in 2007 only 20 percent of the small cars were equipped with ESP. The aim should be a blanket solution as there is with ABS.

Focused braking, extension of ABS

An ESP system only functions in connection with ABS (anti-locking braking system). As well as the ABS equipment, a hydraulic pump without additional electric motor, and four magnetic valves are necessary . The ABS sensors become supplemented by longitudinal and lateral acceleration pick-up sensors and a sensor for yawing, the rotary movement around the vertical axis. The steering wheel position must also be included in the calculations. Individual wheels can receive pressure from the additional hydraulic pump and magnetic valves.

If the front of the vehicle breaks out through under-steering in a curve, specific braking of the rear inside wheel can initiate counter steering. Braking the front outside wheel has the same effect when over-steering occurs. Both can also be used stepwise to successfully bring the vehicle on track again and make it more controllable. For this to function, a relatively early intervention is necessary. If the inside wheel, through an extreme rolling motion, loses ground contact, it can have no further braking influence on the yawing.

ESP integrated into the stepwise stiffening of the suspension

In addition, the speed is lowered by the braking manoeuvre. Conservatively set-up ESP prevents the driver from making too risky a manoeuvre. For particularly performance-orientated driving, with calculated drifting required, it can be very tolerantly adjusted and in some cases, for especially racy and riskier driving, can be switched off completely. The second generation Electronic Stability Programme is able to specifically brake several wheels simultaneously. While previously when braking, the ABS function (brake release), respectively, the ESP function, (individual braking) was clearly possible, now a brake release within a function controlled by ESP can also occur if, e.g., by too heavy braking the outside-front wheel loses the necessary grip while cornering.

Also the function of the hand-brake, the drying of the brake discs by brief, gentle braking and the production of increased primary pressure in the braking system can be taken over by ESP. Further developments will probably be in the direction of active regulation, whereby ESP can, when required, also actively influence the steering.

Beware!, actuator diagnosis in the safety system

As with all safety systems, including of course ESP, the actuator diagnostic during test driving is only conditionally possible, as a rule, only at very low speeds. This is perfectly understandable, if a brake is suddenly applied during a test-drive, it could lead to incalculable reactions and therefore, to accidents. 09/08

At very sporty driving, the ESP light flashes frequently. Perhaps therefore it is turned off so often. It would be stupid to build with so much safety equipment on board an accident.