RE: PH Origins: Anti-lock brakes

[Fastdruid]

malucnojes said:

Always remember seeing Cavaliers when I was growing up with ABS badges on the back and thinking it was cool for some reason!

Not sure about the Cavalier but it was an optional extra on many things and I think partly a status boast as well as a warning... in the same way once upon a time you got a "disk brakes" badge on the back of Jag MkII's.

Of course once everything started to get them (and they became standard equipment) they stopped fitting the badges.

Not sure when that would have been, I remember my parents Citroen BX's having them (From memory would have been MY1987 and MY1989 ) but don't know when the practise died out.

Edited by Fastdruid on Monday 22 January 21:19

[anonymous-user]

PH said:

His patent, published in 1909, marks the established introduction of the concept of anti-lock braking. Whether Francis's idea ever saw action is unknown but it laid the groundwork for all future anti-lock and traction control systems.

So a single patent, which was never realised and technically infeasible at the time "laid the groundwork"? Hmm, sorry, i'm not convinced! We consider the aircraft systems as the father of vehicle systems because they proved the idea worked, and developed the technology to the point where it was shown to work. Prior art, when that art is just an idea or concept doesn't really come into it. I mean, In the 1st century AD, Hero of Alexandria, came up with the idea for a steam turbine, but it took 1800 years till it was turned into a reality by Parsons, who is correctly identified as the inventor of the (practical) steam turbine


And, with the early 1900's patent by Pierre Cayla, it doesn't take a genius to spot the flaw in the plan:

PH said:

'The braking ceases at the same time as the rotation of the wheel,'

So, the wheel turns a pump which generates pressure to create a braking effect. Ok, that means you can never actually completely stop your car! The closer to zero speed you get, the less pressure you can make, so you can't actually ever brake to a halt, not on the flat and certainly not down a hill.......

[Dr Interceptor]

I think you’d be better looking at things like Carbon Ceramic Brakes. Concorde had them back in 1974, but it also has fans inboard of the wheel hub and brake assembly to cool the brakes during operation.

Just to save the steam train at least one outing as the inventor of everything.

[cahami]

Abs had been fitted to a motorbike in or before 1965

[RoverP6B]

jet_noise said:

olderbutnotwiser said:

The Jensen FF is definitely a nicer looking car than the Prototype Ferguson R5 which also had 4wd & anti lock.

https://www.autocar.co.uk/car-news/anything-goes/t...

Aargh, my eyes!
A Frankencar if ever there was one.

So that's from where Ssanyong got their design cues

Err... I quite like that.

[zeeboy]

Toltec said:

Cannot find it, but I'm sure I saw a post saying traction control was originally developed for trains too.

You're not entirely wrong. Try re-reading paragraph three of the main article.

[wolfracesonic]

So our lives may be safer but at what cost? Won't someone think of all the cardboard boxes sacrificed?

[Amanitin]

Jex said:

I know that if the wheels lock you should release them and re-apply them

1) with the ABS firing the brake distance goes up
2) in a panic situation you probably will not be able to dish out precise and rapid steering inputs to safely avoid sudden obstacles

overall I believe you are better off slamming on the brakes and staying there. And then acting like the spin was intentional.

[LewisR]

IMO, Jensen FF is one of the coolest cars ever. Massively thirsty & unreliable but cool Italian styling and a epic bass note from that V8.

The Mk3 Granada/Scorpio was one of the first models to have ABS fitted as standard, even on the poverty-spec 1.8 L but there were never any ABS badges on it !

[unpc]

Amanitin said:

1) with the ABS firing the brake distance goes up
2) in a panic situation you probably will not be able to dish out precise and rapid steering inputs to safely avoid sudden obstacles

overall I believe you are better off slamming on the brakes and staying there. And then acting like the spin was intentional.

No cadence braking is far more effective than locked wheels and enables the driver to still steer.

[Lewis Kingston]

Dr Interceptor said:

I think you’d be better looking at things like Carbon Ceramic Brakes. Concorde had them back in 1974, but it also has fans inboard of the wheel hub and brake assembly to cool the brakes during operation.

Just to save the steam train at least one outing as the inventor of everything.

Much obliged – I'll have a gander. Does indeed sound interesting, that.

Yes, apologies for the doubling up on that front – but the two were so closely interlinked that, while I had all the research and material to hand, I thought I'd strike while the iron was hot.

[Lewis Kingston]

Max_Torque said:

PH said:

His patent, published in 1909, marks the established introduction of the concept of anti-lock braking. Whether Francis's idea ever saw action is unknown but it laid the groundwork for all future anti-lock and traction control systems.

So a single patent, which was never realised and technically infeasible at the time "laid the groundwork"? Hmm, sorry, i'm not convinced!

With regards to Francis's innovation, I only state it's 'unknown' if it were employed because I don't have categoric proof – and I'm not going to assume. I don't think there was anything infeasible about his concept, though (its operation and the mechanisms required are detailed and illustrated, for example).

In any instance, he subsequently extended his patent by showing how it could be applied to the then-popular Westinghouse air brake system. Westinghouse, either of its own volition or after taking some inspiration, ran with this idea – developing myriad concepts and systems in the '30s (perhaps earlier) and on for locomotive use.

Ultimately, Westinghouse itself – and Lockheed, Hydro-Aire, Dunlop, etc. – applied the anti-locking concept to aircraft as the braking demands increased. As mentioned in the article, many cite Francis's original patent. As you rightly assert, of course, the original concept isn't from the era in which the systems really came of age – but I'm just interested to see where and when the technologies first raised their head.

Max_Torque said:

And, with the early 1900's patent by Pierre Cayla, it doesn't take a genius to spot the flaw in the plan:

PH said:

'The braking ceases at the same time as the rotation of the wheel,'

So, the wheel turns a pump which generates pressure to create a braking effect. Ok, that means you can never actually completely stop your car! The closer to zero speed you get, the less pressure you can make, so you can't actually ever brake to a halt, not on the flat and certainly not down a hill.......

I'm sure Cayla was well aware of this trait, which is perhaps why he primarily envisioned it being used 'for steering wheels of motor vehicles'. As mentioned in the article, 'This system would presumably work in conjunction with a conventional set-up fitted on the driveshaft, or one axle, for parking and hill holds.'

Any ABS, of course, has to 'shut off' at some point so that the vehicle in question can stop entirely. Preaching to the converted, no doubt, with regards to this!

Edited by Lewis Kingston on Tuesday 23 January 11:33

[anonymous-user]

Lewis Kingston said:

Any ABS, of course, has to 'shut off' at some point so that the vehicle in question can stop entirely.

Not at all sure about that - the role of ABS is not to apply the brakes but to RELEASE them and allow them to be re-applied. That's why you have to keep your foot on the pedal when ABS is operating. Braking ceases as soon as you remove your foot pressure from the pedal.

Active braking is an entirely different concept which turns up in the form of modern "anti-collision" systems. It also turns up in those versions of cruise control which apply the brakes if you overspeed when going down hill.

[Lewis Kingston]

rockin said:

Not at all sure about that - the role of ABS is not to apply the brakes but...

I think I may have worded that poorly; I'm not talking about ABS applying the brakes, of course, as that's not what it does – but at lower speeds, when the brakes bring the car almost to stop, a simple ABS set-up (if you had your foot on the pedal and unless interrupted) could sense the wheel 'stopping' incorrectly as it locking up, and promptly release the brakes.

I think the original Maxaret units in aircraft disconnect below 10 knots or so for this very reason, so that the aircraf could actually come to a complete halt – that was why it suddenly sprung into my mind. This would have been a trait of very early systems, mind, as we've myriad sensors telling ABS units exactly what's going on these days.

Edited by Lewis Kingston on Tuesday 23 January 11:59

[RacerMike]

Anyone interested in the basics (including an explanation of how Mechanical ABS works) should have a look here:

https://www.howacarworks.com/technology/how-abs-wo...

There's a more in depth article about the Lucas Mechanical system here:

https://books.google.co.uk/books?id=NUzwukoJzGIC&a...

To summarise, the inertia from the locking wheel causes a clutch to engage and open a relief valve, unlocking the relevant wheel. Incredibly rudimentary by modern standards, but it worked well enough at the time.

A 2017 system has some fairly significant processing power, lots of solenoids and some powerful hydraulic pumps able to build 300+bar/s of brake pressure.

[RacerMike]

Lewis Kingston said:

I think I may have worded that poorly; I'm not talking about ABS applying the brakes, of course, as that's not what it does – but at lower speeds, when the brakes bring the car almost to stop, a simple ABS set-up (if you had your foot on the pedal and unless interrupted) could sense the wheel 'stopping' incorrectly as it locking up, and promptly release the brakes.

Actually, a modern system does actively build pressure in many situations. Something like 70% of driver don't press the brakes hard enough to achieve ABS, so in all modern systems, EBA (Emergency Brake Assist) senses the intention to do an emergency stop and actively builds enough pressure to achieve ABS.

[Lewis Kingston]

RacerMike said:

Actually, a modern system does actively build pressure in many situations. Something like 70% of driver don't press the brakes hard enough to achieve ABS, so in all modern systems, EBA (Emergency Brake Assist) senses the intention to do an emergency stop and actively builds enough pressure to achieve ABS.

Indeed – but that application of emergency braking pressure is not a function of an anti-lock braking system.

[RacerMike]

Lewis Kingston said:

Indeed – but that application of emergency braking pressure is not a function of an anti-lock braking system.

In it's most basic no, but a modern ABS system isn't really just a simple anti locking system anymore. At it's very basic there is a wheel inertia calculation in the software that compares the vehicle reference speed (vFzRef) (which is calculated via the Ax sensor, wheel speed sensors through a number of plausibility checks on whether to trust the vFzRef) against the individual wheel speed and a physics model of the wheel. But this doesn't really ever work on it's own and it's not simply an 'anti lock' function. More of a slip target PID (Proportional Integral Derivative) controller.

An ABS stop is now effectively broken down into a number of stages, which in it's simplest form is pre-control, control, and an end ramp.

Pre control
The pre control is based off a number of constantly calculated factors. The easiest way to think about it is a number of AND/NOT/NAND etc functions that are all independently calculated and act as a form of state estimator that allows the system to estimate what friction level the car is on, whether it's on a friction split (one or more wheels on low friction and the others on high), whether the driver is attempting an emergency stop, whether the reference speed can be trusted etc etc.

Control
The meat of the stop and the point at which the system is trying to optimise deceleration. The suspicion levels are still monitored at this point, but on the whole, it's aiming to achieve a constant slip level. You'll actually find that on a consistent dry tarmac surface, with a multi piston pump (the bit of the ABS pump that generates the pressure) you'll leave '11's down the road as the pressure variation in control is tiny. The feedback through the pedal will also be much more subtle as the system is able to hold a constant %age of slip.

End Ramp
This is a series of controller that start to take over during the end of the stop to fade out control and avoid the situations some people have mentioned like ending up in an infinite control loop that never allows the car to stop. There are also some important factors in here for incredibly low friction surfaces to prevent the car from losing control of the wheels as it dips below the measurable wheel speed close to 0.

[Lewis Kingston]

RacerMike said:

An ABS stop is now effectively broken down into a number of stages, which in it's simplest form is pre-control, control, and an end ramp.

A very interesting and comprehensive breakdown – thanks!

[RacerMike]

Lewis Kingston said:

A very interesting and comprehensive breakdown – thanks!

It's an incredibly complicated bit of software these days. And with every year, it get's more comprehensive and more powerful. Some of the latest bits of software in the industry constantly run a model of what they believe the car is meant to be doing and compare it against what the car is doing. I think most drivers would be quite surprised to try driving a modern car with absolutely no stability control at all....it affects more than just limit driving now and get's better with every generation.