New Directions in Automotive SmartsApril 1, 2006 By: Dean McConnell, Continental Automotive Systems Sensors
Do you dread stopping on a hill? Worry about wet brakes? The Mercedes-Benz S-Class automobiles are showcasing a family of remarkable new safety features.
Television ads are doing automotive engineering a disservice, focusing as most do on snappier looks, more horsepower, and occasionally on some mysterious quality that not even alert viewers can figure out. The truth is that the automotive industry is taking the lead in making its products more reliable, more efficient, more comfortable—and, in particular, safer.
Antilock braking systems, introduced in 1978, were a significant improvement over their stomp-and-skid precursors. The mid-1990s saw the introduction of electronic stability control (ESC, Figure 1), which became the foundation for further advances in smart automotive design.
Figure 1. The ESC sensor cluster
In addition to instrumenting many of a vehicle's mechanical components with intelligent sensors, ESC establishes channels of communication among them. Continental calls this the Total Safety Approach. Let's take a closer look at some of the ways this technology is being showcased in the 2007 Mercedes-Benz S-Class automobiles.
Advanced Braking System
The MK25E5 brake control system (Figure 2) incorporates a brake pressure sensor at each wheel and another on the master cylinder. The infinitely variable apply-and-release valves provide extremely sensitive brake pressure signals that improve the vehicle's forward and side-to-side dynamics. This advantage translates into shorter stopping distances, barely perceptible braking intervention, and improved driving stability when maneuvering in hazardous situations. And there are additional comfort and safety functions.
Figure 2. The MK25E5 brake control system
Hill Start Assist. This feature, reminiscent of the "hill-holder" last offered in a domestic auto by Studebaker in the 1960s, prevents the vehicle from rolling backward when it's stopped on an incline. Directional wheel-speed sensors detect any rearward travel (Figure 3). When the driver steps on the brakes, cylinder pressure is maintained even after the brake pedal is released. The vehicle stays put. Once the driver applies the gas, the brake is released. No need to worry about that split second while your foot is changing pedals.
Figure 3. Active wheel-speed sensors
Automatic Brake Disc Drying. If the sweep of windshield wipers alerts the system to wet weather conditions, a minimal amount of brake pressure (2–3 bar) is automatically applied to the wheel and dries the brake discs. This ensures that the brake calipers and linings are ready for a braking maneuver. The entire operation is invisible to the driver.
Ready Alert Brakes. This function causes a signal from the gas pedal to alert the system to a quick release after an emergency hard braking. It then prefills the brake hydraulics to make the system ready for another such event—with minimal refreshing time. The benefit is that your brakes are ready to stop you when the next inattentive or rash driver cuts you off.
Distance Control System
The driver-assist adaptive cruise control (ACC, Figure 4) is a radar-supported system that operates at speeds between zero and 200 km/hr. (124 mph). All you need to do is set the speed you want to travel and ACC will maintain a safe distance from the vehicle ahead.
Figure 4. Radar-based adaptive cruise control
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