The use of ABS in automobiles is now a matter of course for almost all manufacturers worldwide. But when the anti-lock braking system was first offered in the top-of-the-range Mercedes-Benz in 1978, it ushered in the revolution in driving assistance…
Text & photos: DR
A world first for Mercedes-Benz and Bosch
The history of ABS (from the German “AntiBlockierSystem”, literally “anti-lock braking system”) begins in 1953, when Hans Scherenberg, then head of design at Mercedes-Benz, applied for a patent for a system to prevent ABS from locking the wheels vehicle in the event of braking. Although similar solutions already existed in aviation (slip protection) and in railways (Knorr anti-slip protection), application in automobiles required a specific, very complex system with particularly high demands on sensors, signal processing and control. For example, the components that are needed to accurately record rotational deceleration and wheel acceleration, even when cornering, on uneven surfaces and in heavy dirt.
In 1966, Daimler-Benz AG began collaborating on this topic with the Heidelberg electronics specialist Teldix (a merger of the two project partners Telefunken and Bendix), which was later taken over by Bosch. A year later, the exotic English Jensen FF coupe entered production, adopting the Dunlop Maxaret mechanical brake control system originally developed for aviation. Unfortunately, the Dunlop-Ferguson system quickly proved to be as complex and expensive as it was unreliable… In 1970, Hans Scherenberg, then head of development at Daimler-Benz, finally presented the fruits of his labor to the media, the anti-electronic lock “Mercedes-Benz/ Teldix” on the Untert-Kockheim test track.
The presentation in 1970 provided evidence that the German system worked well. But then developers realized that a digital controller was the right approach for a mass-produced ABS system – more reliable, less complex and at the same time much more powerful than the analog electronics used in the demonstration prototype. Together with Bosch, who was responsible for the digital control unit, the second generation digital ABS (ABS2) was created. Engineer Jörgen Paul, head of the ABS project at Mercedes-Benz, later described this switch to the microprocessor as the decisive moment in the development of ABS.
We had to wait until October 1978 for the electronic anti-lock braking system to become available in a Mercedes-Benz production model. Bosch ABS makes its debut as an option in the Mercedes-Benz S-Class (W116), a few weeks before the BMW 7 Series. Two years later, ABS was available as an option in all Daimler cars. And from October 1992, ABS was installed as standard in all cars of the brand with the star.
ABS comes into play!
With the opening of the new Nürburgring on May 12, 1984, Mercedes used ABS in racing for the first time: 20 drivers competed in the “Race of Champions” with barely modified Mercedes-Benz 190 E 2.3-16s, all equipped with ABS. Grand- Prix drivers, former winners of the 1,000-kilometer race at the Nürburgring and some young drivers fought on a wet track to promote Mercedes' new sports sedan. The winner will be a certain Ayrton Senna, who was still largely unknown at the time, who finished just ahead of F1- Star Niki Lauda reaches the finish…
During preliminary tests behind the wheel of the “Baby Benz”, the presence of the ABS initially bothered the Brazilian considerably: “The brakes are broken,” he complained to Gerhard Lepler, who was responsible for using the 190E in this historic opening race. This was not the case, but the driver was irritated by the pulsation in the brake pedal when the ABS was activated! Gerhard Lepler had to calm him down by explaining that he just had to “keep his foot on the pedal.” Niki Lauda, on the other hand, had a much more positive opinion of the system, saying at the time: “ABS is the greatest invention since the wheel”.
However, Lepler was not entirely satisfied with the system in racing. In addition to the pulsation of the brake pedal, the sudden loss of braking on bumps was particularly disturbing. The reason for this was that the sensors detected that the wheels had lost contact with the road and reported icing to the control unit. This scenario resulted in brake pressure first being drastically reduced and then restored, albeit too slowly for a racer. Enough to give some people a few scares…
Nevertheless, Mercedes-Benz ST “sport technik” insisted on the use of ABS in competition and in 1990 a new version of the system was tested in a DTM race in Kyalami, South Africa, using a specially prepared 190 E 2.5-16 Evolution II. Against strong competition, works driver Roland Asch won the second race and the overall ranking in this race, which, however, was not included in the DTM championship ranking. The 190 E 2.5-16 Evolution II was internally codenamed M7. Prepared specifically for this race by the company's sports department, the engine was even optimized for use at an altitude of 2,000 meters above sea level, recalls former project manager Gerhard Lepler.
But the real strength of this 190 Evo II M7 was its electronic anti-lock braking system. Roland Asch, who over the years drove almost all of the test vehicles developed for the DTM at Mercedes-Benz, was enthusiastic about this new racing ABS system. “At first we kept it secret that the car was secretly equipped with this in Kyalami,” the driver explained. “When other drivers asked me about the steering wheel button that turned the ABS on and off, I simply told them about a brake adjustment.” The driver smiled mischievously as he remembered the reactions of the competitors on the track when they were overtaken while braking. Roland Asch, DTM runner-up in 1988 and 1993, quickly brought his Mercedes 190 to the front of the grid. “I still can’t believe how hard you can brake with racing ABS,” he said after the test. “I can concentrate entirely on driving and only have to brake at the last moment.” Formula 1 has also been working with ABS brakes for several years. However, ABS was eventually banned in the highest classes of motorsport in order to place more emphasis on the driver's skill.
How does ABS work?
Maintain full control over the steering of the vehicle even during emergency braking because the wheels do not lock: the anti-lock braking system (ABS) can do this. The anti-lock braking system uses a computer to monitor the change in speed of each wheel during braking. If the speed decreases too quickly (e.g. when braking on slippery surfaces) and the wheel threatens to lock, the computer automatically reduces the brake pressure. The wheel accelerates again and the brake pressure is increased again, slowing the wheel down. This process is repeated several times within a few seconds.
The ABS system consists of a speed sensor for each wheel (see “1” in the picture), an electronic computer unit (2) and a hydraulic brake pressure control (3). The system can pump brake fluid from both brake circuits to the master cylinder to reduce pressure until the wheel is released. As soon as the wheel finds its footing again, the brake pressure is increased again. By performing a very rapid sequence of locking/unlocking operations controlled by the computer, the system is able to regulate the optimal braking force around the locking point wheel by wheel.
What might have seemed complicated in the age of analog electronics was, however, completely convincing in practice: even in wet, ice, snow or difficult conditions, the ABS enabled the equipped vehicle to develop maximum power. Braking is physically possible without the wheels locking, while the vehicle remained steerable during emergency braking. This system redefined the role of the vehicle, which became increasingly active when driving and offered the driver increasingly important support for his safety.
What are the symptoms of ABS block failure?
An ABS light on the dashboard is usually the first sign of a faulty ABS system. Then it could simply be a defective ABS sensor on one of the wheels or, even worse, a complete failure of the ABS unit. Beyond the warning light coming on, an ABS problem can result in brake loss or imbalance with a non-braking wheel, lack of brake pressure, or a hard or soft brake pedal.
Since this problem can immediately endanger your safety and that of other road users, it is therefore important to quickly check the correct functioning of your ABS if you have the slightest doubt. In the event of a proven breakdown, you can either have the entire ABS unit replaced with a new one or go to a specialist to repair this very technical part. For example, professionals like diag-engine.fr have powerful equipment and qualified technicians to offer a quick and efficient repair service for your ABS unit, especially if the vehicle has not passed the technical inspection, and at a lower cost than a full replacement ABS unit.