Car 101: anti-lock braking is 40 years old, but many still don't know how to use it

Tuesday, 28 August 2018

It was 40 years ago this month that Mercedes-Benz and specialist automotive electronics company Bosch introduced the anti-lock braking system (ABS) to the world.

In August 1978, the two companies demonstrated ABS at the Daimler-Benz plant in Unterturkheim, in Germany. It was the single greatest active safety advance in the history of motoring and arguably the moment when car technology took its first step into the digital age.

ABS was offered as an optional extra on the Mercedes-Benz S-class before the end of the same year and was made available in every one of the brand's models by 1980. In 1981 the company also added it as an option to its commercial vehicles. By 1992 it was standard across the M-B range.

Many cardboard boxes were murdered by Mercedes-Benz in the 1970s. Only ABS technology could save them.

Today, it's a core piece of safety equipment in most modern cars. It's certainly fitted to every new vehicle sold in New Zealand, because electronic stability control is mandatory - and ABS is one of the fundamental building blocks of that technology.

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So ABS has been around for four decades and it's very likely the car you drive every day is fitted with it.

ABS still works the same now as it did back then: prevents wheel lockup, allows you to steer out of trouble.

But do you know what it is and how to use this potentially life-saving piece of technology?

Mercedes-Benz's explanation of ABS in its brochures 40 years ago still covers the basics today: 'The anti-lock braking system uses a computer to monitor the change in rotational speed of each wheel during braking. If the speed slows too quickly (such as when braking on a slippery surface) and the wheel risks locking, the computer automatically reduces the brake pressure. The wheel accelerates again and the brake pressure is increased again, thereby braking the wheel. This process is repeated several times in a matter of seconds'.

In short, if you brake hard enough for the wheels to lock, ABS will take over and 'pulse' the brakes of each wheel many times per second, meaning you stay in control and can even still steer around obstacles.

Sounds simple, but for many modern drivers ABS is still a hard thing to get to grips with in an emergency situation. The key thing is to press the brake pedal hard enough to make the wheels lock - and then get the benefit of ABS while still stopping in the shortest possible distance.

Advancing driving instructors often tell us that teaching people to brake as hard as they can and then maintain that pressure is a very difficult thing to do, because it's natural to panic, push hard - and then release to try and regain control. This is especially true when ABS kicks in initially, because the graunching sound coming from underneath the car sounds like something is badly broken. It's not: that's just ABS at work.

That's why it's so important to sit correctly - with your seat base in a position where you can lift your bottom up with your right leg on the brake pedal, knee still slightly bent. That way you know you can apply maximum brake pressure when needed.

As for keeping it there: if you know you have a car with ABS (and you really should know that), it's a great idea to go and find a quiet piece of road and practice using it. Get to know how it feels and what noises it makes. Then you'll be much more likely to use it properly in an emergency because you'll know what to expect.

The latest cars have lots of technology to help with ABS stops.

There's brake assist for example, which overcomes all the issues above by applying maximum ABS force automatically and holding it, if the system detects a sudden braking action by the driver. And of course many new cars now have various forms of Autonomous Emergency Braking (AEB), which can take over even if you panic and forget to hit the brake pedal altogether.

But these are all aids and there's still no substitute for knowing how ABS works and knowing how to use it.

WHOSE IDEA WAS THIS THEN?

In 1953, Hans Scherenberg, then head of design at Mercedes-Benz, applied for a patent on a system to stop a vehicle's wheels locking under braking.

Although similar solutions already existed in aviation (anti-skid) and on the railways (Knorr anti-slip protection), the automobile was a highly complex system with especially high demands on sensors, signal processing and control. For example, the components needed to register the rotational deceleration and acceleration of the wheels without error, including when cornering, on irregular surfaces and in very dirty conditions.

An intensive, continuous exchange of knowledge between the Group' s own research and development and industrial partners ultimately led to success, with 1963 seeing the start of concrete work on an electronic-hydraulic brake control system in the Advance Development department of what was then Daimler-Benz AG.

In 1966, the company began collaborating with the Heidelberg electronics specialist Teldix, which was later taken over by Bosch. The result premiered in 1970, when Hans Scherenberg, now head of development at Daimler-Benz, presented the analogue-electronic 'Mercedes-Benz/Teldix Anti-Bloc System' to the media at the test track in Unterturkheim.

The launch in 1970 delivered the proof that the system worked. Yet the developers realised that a digital controller was the right approach for a mass-produced ABS – more reliable, less complex while also much more powerful than analogue electronics. Together with Bosch, which was responsible for the digital control unit, this led to the digital, second-generation ABS.

Engineer Jürgen Paul, head of the ABS project at Mercedes-Benz, later described the decision in favour of digital microelectronics as the breakthrough moment in the development of ABS.