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How exactly does ABS work?



Assistance systems help prevent accidents. In a new series on VisionZeroWorld we explain how ESP & Co. work. This time it’s the turn of the Anti-Lock Braking System.

It’s pouring with rain, and the windshield wipers are giving their all. It’s getting dark, too, so visibility is poor on this country road. All of a sudden, a deer darts out from behind a tree. The driver hits the brakes and the car comes to a standstill just in time – an all-too-familiar situation on our roads. The vehicle occupants – and the deer – owe their well-being to an invention that’s been around for 40 years now: the Anti-Lock Braking System, or ABS for short. Development partners Bosch and Mercedes launched the first ABS generation back in 1978. Today, Continental too is playing a leading role in developing new ABS solutions. These systems prevent the wheels from locking up under emergency braking or when braking on wet or slippery surfaces. The braking force is still effectively transmitted, the vehicle remains steerable, and the braking distance is minimized. So just how does this tried-and-tested system work?

Continental demonstrated the effectiveness of the new ABS3 Anti-Lock Braking System at a presentation in Arvidsjaur, Sweden. Photo: Continental


A modern ABS consists of four sensors, a control unit and a hydraulic unit. The sensors on the wheel suspension measure the rotational speed of each individual wheel and convey this information to the control unit. If a wheel shows signs of locking up when the driver brakes hard, the system momentarily reduces the braking force applied to this wheel until it rotates more freely and the force can be increased once more. This process is repeated up to forty times per second – until the driver eases the pressure on the brake pedal or the wheels are no longer locking up. As a result, braking distances are reduced, even on slippery roads, and the car remains maneuverable. The driver can tell that the system is active from the stuttering vibrations in the brake pedal. Like many new developments, ABS was first introduced in high-end models and then soon became available as a cost option in the compact class as well; that remained the case until 2004 when automakers committed to making this safety system a standard feature on all cars. ABS is now also available for motorcycles and even for bicycles.

With ABS3, the new-generation Anti-Lock Braking System from Continental, the vehicle is easier to steer under emergency braking, even in adverse conditions. Photo: Continental


Continental recently presented ABS3, its third-generation Anti-Lock Braking System. With this new development the technology company is meeting the demands placed on modern braking systems and aiming to achieve a further increase in road safety in another step toward the long-term goal of Vision Zero, the vision of accident-free driving. The new generation adapts the braking pressure even more rapidly and precisely to changing road conditions: When braking on mixed surfaces, with wet leaves at the edge of the road and good grip at the center for instance, the ABS triggers very different braking forces at the two sides of the vehicle; this ensures maximum efficiency while at the same time keeping the car steerable. “To maintain optimal braking efficiency and maneuverability at all times under varying conditions, ABS3 computes changes more rapidly and reliably, and regulates the wheel dynamics accordingly,” says Felix Bietenbeck, who heads up the Vehicle Dynamics business unit at Continental. In other words, ABS3 reacts faster than the previous generation to sudden changes in the level of grip that the road surface offers.