When it comes time to stop avehicle, most drivers slowly press on the brake pedal. Even during anemergency situation, studies have shown that almost all drivers willpress only partially on the brake pedal for the first few millisecondsuntil their brain has time to analyse the situation and then the brakepedal is pressed firmly. This slight delay in braking enables thevehicle to travel several metres further and can mean the differencebetween a controlled stop and a fender bender. There are several otherfactors that delay the vehicle's response to a braking situation.Mercedes-Benz is trying to reduce or eliminate as much as possiblethese factors with their new brake systems. They call it SensotronicBrake Control. I call it Smart Braking.
Mercedes-Benz first introducedthe Sensotronic brake system on their SL-Class sports car. Now thistechnology has been introduced to the E-Class sedans and wagons. Thebrake system is integrated into the car's stability control andtraction control systems to predict the amount of braking forcerequired at each wheel of the car. Rather than simply reacting to theslip of a tire on the road, the brake controller anticipates themaximum potential braking force all the time the car is rolling downthe road. This ensures optimum braking performance at each wheel whenneeded.
Actual brake application beginslong before the driver pushes on the brake pedal. By monitoring theaccelerator pedal position, the brake computer can measure the rate atwhich a driver releases the pedal. If a driver is removing their footquickly, then it could be in response to an emergency situation. Thebrake controller reacts by applying slight hydraulic pressure to eachbrake caliper to move the brake pads toward the brake rotor,eliminating any delay in applying braking force.
By now, the driver has startedto step on the brake pedal but probably not firm enough for anemergency stop. The computer measures the rate of brake pedalapplication by the driver and if the response is rapid, the computerwill apply the brakes fully, even before the driver realizes thatmaximum braking effort is required. The computer can vary the amount ofhydraulic pressure at each wheel to provide maximum deceleration evenwhen the vehicle is on a turn or in a rapid evasive manoeuvre. If atire should happen to lock up because of changes in road surfacetraction, the ABS system will work to get the tire rolling again sothat maximum brake pressure can be applied. In conjunction with thestability control and ABS systems, the Sensotronic brake system cankeep the car stable even during the most severe brake applications ondiffering road surfaces.
Rain poses another problem forbraking. Water coats the surface of the brake rotors and acts as a lowfriction surface between the brake pad and rotor. The Sensotronicsystem overcomes this by slightly applying the brake pads against therotors for a short time every few minutes so that the water film issqueezed off the brake rotor and the rotor is heated by the friction tokeep it dry. How does the computer know the brakes are wet? It uses thewindshield wiper input. If you have the wipers on, the road surfacemust be wet.
The Mercedes-Benz Sensotronicbrake system is a good example of how technology can make our carssafer. Here is a system that anticipates rather than reacts. Itcontrols the pressure at each wheel independently for maximum stoppingpower and it does all this without changing the way we operate ourvehicles. I like to think of the system as a great equaliser. Eveninexperienced drivers can have braking control approaching that of theworld's best race-car drivers. Now that is 'smart braking'!
[ 本帖最後由 carwing 於 2009-2-10 10:41 PM 編輯 ] |
發表於 2009-2-9 01:42 PM
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