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More than 30 years: ABS - ready for production in 1978 *
01.02.2009 - 00:00

German version

More than 30 years: ABS, ready for production in 1978

Commercial vehicles included: After the world premiere in passenger cars in 1978, Mercedes-Benz presented the anti-lock braking system in a touring coach in 1979.

In August 1978 Mercedes-Benz presented the second-generation anti-lock braking system (ABS), developed together with Bosch, to the press in Untertürkheim. The world-first enables a driver to retain steering control even during emergency braking. From December the innovation became available, initially in the S-Class sedans (116 series).

Eight years before, in 1970, the first-generation anti-lock braking system for passenger cars, a system that had been developed together with TELDIX, had its world premiere. ABS is thus an example of the great staying power sometimes required to bring a product up to production standard – a responsibility which the Mercedes-Benz brand takes upon itself again and again with its numerous innovations.

Development over decades

An anti-lock braking system had been on the automotive engineers' list of wishes for decades – it was, after all, expected to improve handling safety drastically by retaining steerability during braking. As early as 1928 the German Karl Wessel had been granted a patent on a braking force regulator for automobiles, but this design only existed on paper.

In 1941, an anti-lock regulator was tested with which, however, "only modest successes were achieved," as the "Automobiltechnisches Handbuch" (Automotive Engineering Manual) reported.

Nevertheless, these first attempts set the course: an anti-lock braking system had to have sensors for measuring the speeds of each front wheel, as well as a control unit for recording and comparing the data measured by the sensors. This control unit was to correct excessive deviations by individually controlling the brake pressure at every wheel up to the point at which the wheel is about to lock.

However, the transfer of the idea into hardware for use on the road proved to be significantly more difficult than expected. The sensors did work satisfactorily as early as 1952, in an anti-skid system for aircraft, and in 1954 in a Knorr braking system for railways.

But in the car, the demands on the mechanical friction wheel sensors were much higher: they had to register decelerations and accelerations in wheel speeds, they had to react reliably in corners and on rough ground and work perfectly even when heavily soiled and at high temperatures.

Induction instead of mechanics

The problem was tackled not only by Daimler-Benz engineers but also at TELDIX GmbH in Heidelberg. The two companies did not make any headway with mechanical sensors, so they had to look for another, new solution.

In 1967, they came up with a solution to the problem in a joint effort – in the form of contactless speed pickups which operate on the principle of induction. Their signals were to be evaluated by an electronic unit which controlled brake pressure via solenoid valves.

At the time, electronics still worked on the basis of analogue technology which was relatively susceptible to failure and consisted of complicated circuitry. Integrated modules did not yet exist. And yet, this proved to be a first, promising approach.

For this reason, Daimler-Benz introduced this first generation of an anti-lock braking system for cars, trucks and buses to the public on the test track in Untertürkheim on December 12, 1970 – with a resounding echo by an enthusiastic expert world and press. The principle had been found to be convincing.

Development of the production ABS

Another eight years passed before Daimler-Benz was able to offer a reliably functioning anti-lock braking system for production cars; this time was required to give the prototype the degree of technical maturity and reliability that is indispensable for large-scale production. In development, the engineers benefited from the revolution in electronics. It was not until the invention of integrated circuits that small, robust computers could be built, capable of recording wheel sensor data in next to no time and reliably actuating the valves for adjusting brake pressure.

It took development partner Bosch five years to supply the first digital control unit to Untertürkheim for test purposes. Digital instead of analogue: this meant fewer components with the advantage of the risk of malfunction being reduced down to virtually zero.

Thanks to digital technology, the electronic components were capable of recording, comparing, evaluating and transforming sensor data into governor pulses for the brakes' solenoid valves within milliseconds. What's more, not only the front wheels but also the rear wheels were included in the control operations.


Despite an emergency braking maneuver on a wet road, the bus equipped with ABS (top) retains its steerability, directional stability and safe tire-to-road contact. It is effectively decelerated whereas the bus without ABS (bottom) skids across the wet road surface without being decelerated as strongly as with ABS intermittent braking.

1978: The world's first production ABS

Thus, it had taken a long, long time before Mercedes-Benz became the world's first motor manufacturer in August 1978 to officially launch the second-generation anti-lock braking system and to offer it as an option from December 1978 – initially in the S-Class at a surcharge of DM 2,217.60. Since 1984, ABS has been standard equipment on Mercedes-Benz passenger cars. Ten years after the introduction, as many as one million Mercedes-Benz cars with ABS were being operated on the roads throughout the world.

Mercedes-Benz also adopted a pioneering role where ABS for commercial vehicles was concerned. As early as 1981 ABS was offered for compressed-air brakes, a joint development with Wabco. ABS has been standard equipment on all touring coaches of the brand since 1987 and on all trucks of the brand since 1991. In late 1990, ABS also found its way into the Mercedes-Benz racing cars for the German Touring Car Championship.

25 years of standard ABS at Setra

Also with Setra one worked on the abs system and 1984, exactly 20 years ago, the company introduced the anti-lock braking system (ABS) in all its touring coaches as standard equipment. A technical advance that was preceded by a development and testing phase lasting over ten years.


Twenty-five years ago, this sticker – seen here on the rear of a Setra S 215 HD – informed following traffic that this coach is fitted with an anti-lock braking system.

It was as early as 1970 that the Ulm-based company had started its pioneering development work in the area of improved braking performance for buses in close cooperation with the electronics manufacturer Bosch. One year later – in 1971 – the first Setra, an S 200, was ready for practical trials. The principle was that when braking, one or more wheels were to be prevented from locking up so that handling stability was assured even in critical situations. By maintaining the ability to steer the vehicle, the driver was to be capable of avoiding any sudden obstacles at all times while keeping the braking distance to a minimum. In 1982 the company first demonstrated the effectiveness of ABS in two and three-axle buses, and in 1984 all Setra buses were equipped with the system as standard.


The ABS system was put through long-term testing in the Setra S 200.


Basis for innovations

ABS development never stops. The complete control system is becoming ever smaller, ever more effective, ever more robust. The initial, typical pulsating of the brake pedal, indicating ABS activation, has largely been eliminated today. However, the system not only optimally decelerates the car and retains its steerability, it also serves as the basis and pulse generator for the acceleration skid control (ASR) system, the Electronic Stability Program ESP®, the Brake Assist and of course also for the electro-hydraulic brake system, Sensotronic Brake Control (SBC™).


Photos:
Daimler AG
Kässbohrer Fahrzeugwerke GmbH
Video-clip:
Kässbohrer Fahrzeugwerke GmbH


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