 Anti-lock braking system 1
No, it wasn't called that from the beginning. Originally it was called 'Automatischer Blockierverhinderer', but 'Anti-Blockier-System' is shorter and easier to understand and results in the same combination of initial letters in
English. However, the term is protected by Bosch. At first glance, it probably seemed easier to implement at the time than in cars, where you couldn't simply drain the brake fluid into the open.
', but anti-lock braking
system is shorter and easier to understand and results in the same combination of initial letters in English.
But that soon turned out to be a mistake, because the normal car weighs around 2 tons and the possible payload is at most a third of the empty weight. This is very different for a truck and especially its trailer. The wheels
that have to be put back into motion after a blockage also have a much larger mass.
Not to mention the greater axle load distribution when braking, the different bodies, number of axles and wheelbases. And it is not uniformly a pneumatic or hydraulic brake on board, but sometimes a combination. Just
look in the next chapter to see how much more dangerous a trailer or semitrailer swerving sideways seems to us.
As with petrol injection, analogue electronics began in the early 1970s. So there was no talk of characteristic maps and possible diagnostics. WABCO states that the transition to digital electronics also enabled them to
save components, installation space and costs. This 'new generation' was then introduced in 1981, matching the Daimler-Benz truck series of the same name built from 1973 to 1988
No manufacturer will ever admit it, but during the first tests in Lapland there were truck drivers who, thanks to particularly sophisticated braking, achieved results that were just as good as those achieved by the ABS that
was then being developed. However, it was not just the development of ABS for trucks that was exciting, but also the justification for its necessity.
Let me digress for a moment. I was still a teenager and we lived at the foot of a small mountain. The road was quite wide in the steep part because of parking spaces. Luckily for a fairly busy bus that needed this snow-
covered, thankfully empty space in the middle of winter to come across us on the way down.
I think I will never forget the image because you could see the people in the bus and at the same time has to fear that it would tip over at any moment with unforeseeable consequences. You guessed it, everyone escaped
with just a fright. Fortunately, the bus stopped sideways just before the end of the parking lot.
If he had had ABS back then, he probably wouldn't have gotten into this predicament. The driver's counter-steering would have had an effect and left the bus in a maneuverable position. Because as you know, the aim of
ABS is not the shortest braking distance, but maintaining steering ability. This cannot be emphasized enough.
With buses and trucks, the even greater braking force is an additional problem, which still quickens over-braking of the wheels. Articulated trucks, even more so than semi-trailers, can prove to be particularly unstable.
There is this video of the so-called death stretch, where the truck would have made it through the narrow section but was dragged down by the falling trailer.
As the tests in Lapland show, it is assumed that even on icy roads, no wheel will lock, no matter how hard the driver brakes. The systems are now so sophisticated that even the best 'brake stutterers' can no longer match
the performance of ABS systems. For a while, the experienced drivers had to be trained to switch from stuttering to full throttle.
It is also important to mention the beneficial effect of ABS on the tires for trucks, which continue to rotate when braking and thus do not wear out in one place. This is called a brake plate, and is immediately noticeable due
to a more unstable chassis. Another advantage is the unusually low control limit of 5 km/h.
The additional number of components required for the ABS remains manageable, which also limits the troubleshooting. Each braked wheel, including the one on the trailer, has a solenoid control valve (2 - 5) and a sensor
with a pole wheel. In addition, there is of course the control unit (1), warning lights and a trailer socket.
The speed of the respective wheel is determined by counting the contactless passing teeth of the pole wheel and communicated to the control unit. This also calculates the deceleration or acceleration from possibly
changing values. It determines the speed of the vehicle from the signals from all sensors, which means that a wheel approaching the locking limit is noticed.
Coming back to the example with the bus, ABS would have prevented the bus from turning by limiting the activation of the wheel brake cylinders on the side to which the rear was threatening to turn. If the other two then
build up proportionally more braking force, there is no longer any danger of the vehicle turning, especially since the vehicle also reacts to steering movements.
| 
