65 replies to this topic

[Dylan8660]

The Problem

 

For me, the one thing missing from Mini development either from the factory or aftermarket is the application of an anti-lock brake system. As a community we have been able to extract considerably more power from our cars than they were ever given in standard form, an 80+bhp engine can be bought off the shelf, the application of turbos, twice the valves or full engine swaps means we have classic cars that can keep up with or embarrass their modern counterparts, but they can’t stop like them. Our driving style has to be different to compensate for this and we have cars that can handle their way out of trouble. But this also means that when we need to stop quickly we REALLY need to stop quickly.

 

The brakes on our cars are generally quite good, the standard 2 pot disc brakes do a good job and the cars light weight means that job is done efficiently, but they can also be easily locked up giving a loss of control. Cadence braking has been the prescribed solution to this scenario but this takes presence of mind in a panic situation and if applied properly it can generally get you out of trouble at the cost of a slightly increased braking distance. The problem is having the presence of mind in a situation where the natural intuitive human reaction is to press down harder on the brake pedal. This can be compounded when the Mini is not the regular daily drive but rather a modern car with an ABS system is what the driver’s more used to. How many of us now automatically apply the clutch in a hard braking situation, regardless of the vehicle you’re in?

 

Anybody who has contemplated the retro-fitting of an ABS system to their Mini will be acutely aware of the complexity these systems employ, the expense required and the difficulty in mating the necessary parts to such an old design which is probably why it has never been done. The system I am proposing strips back the complexity down to the basic requirement of cadence braking as a result of the natural driver reaction to an emergency braking situation.

 

The Challenge

 

Is it possible that we can, as a forum or the wider Mini community develop an automated braking system that delivers safer emergency braking better than human effort? Is there the knowledge and experience amongst us to identify and specify the necessary components and to be able to design the control system? Can we collaboratively come up with a cost effective DIY solution that not only Mini owners can feel confident in but also give an option to all classic car drivers who feel they could benefit from such a system?

 

Design brief

 

To develop an automated cadence braking system that performs better than the equivalent human method. It must be triggered by natural intuitive operator input thus shortening or removing the current reaction time to a given emergency braking situation.

 

 

[Dylan8660]

Initial design suggestion

 

A system could be constructed from three specific parts, i) a pressure sensor, ii) a cadence pump/valve, iii) a control circuit.

The operation of this system is that from brake pedal operation a fluid pressure that would normally result in brake lock is sensed and a signal to operate the cadence/ABS pump is sent until such time the pressure is relieved. This simple system would allow full normal operation of braking function including lock up but take into consideration the natural instinctive reaction to push the pedal harder in a panic scenario, negating the reaction time to this type of situation resulting in a more efficient method of cadence braking.

 

Considerations

 

Has this been oversimplified?

What has been missed out?

Is the natural human reaction that’s been described correct?

Are there potential problems with not having wheel sensors? (This is not traction or stability control, I don’t want to ruin the Mini with drive by wire.)

With an ABS system pressure is sent back to the pedal from the pump, would these fluctuations cause sensing problems? How can this be overcome?

Are there any similar examples already in existence?

The braking system is split front and rear, should this system only affect the front wheels or all wheels?

What frequency should the cadence have?

Should the pressure setting be fixed or switchable for driver preference?

Does there need to be any legal or insurance considerations?

What testing regime should take place?

Will the system require some sort of approval?

Would this approval be universal?

What size would a system of this type be?

Where would it be located on the car?

 

Collaborators

 

This forum has enough users with interest and experience of mechanical repair and engineering disciplines. This combined knowledge is probably greater in the world outside of Minis but it’s my belief that this can be harnessed to deliver the best solution possible in a collaborative way.

Can I ask all contributors that if suggesting components to make sure they are robust and available. Also where possible please link the datasheet, application examples and cost. If submitting calculations please publish them in full including the formulas used so that verification can take place easily.

 

Thank you

Dylan.

[nicklouse]

The operation of this system is that from brake pedal operation a fluid pressure that would normally result in brake lock is sensed and a signal to operate the cadence/ABS pump is sent until such time the pressure is relieved.

and that is where it fails.

the pressure required to lock your brakes is external. so you need to monitor the external inputs. (Wheel sensors)

[Dylan8660]

Great first reply, cheers.

 

Can you go into more detail about what you feel are the external and internal inputs in both ABS systems and non-ABS systems.

 

Thanks.

[Spider]

It probably goes without saying that a computer will be involved with the set up and I would think it considerably easier to interface the computer with electric brakes than hydraulic. I know what you maybe thinking but a few years (yes, years) back I read of a system being developed by Siemens and VDO which outperforms Hydraulic systems and would be considerably simpler to get it to 'talk' to a computer. Here's a 'teaser' I found on the net about the system;-

 

http://horsepowerspo...orm-hydraulics/

 

And from what I recalled in the Engineering Newsletter that I read, we will be seeing this system being fitted to production cars soon (if not already).

 

I thought I'd post this here as it may simplify your approach to it.

 

<Edit: There's a bit more info here;-

 

http://www.autonews....ew-brake-system

 

and I note that article is dated 2006 >

Edited by Moke Spider, 23 October 2015 - 10:04 AM.

[Jono_h]

The pressure required to look the wheels will difffer depending on circumstance - tyre spec / wear, road surface, weather conditions - so you can't just use pressure applied as your measure of whether to operate the system.

Hence why, as Nick says, you need to measure the rotational speed of each wheel to sense a lock up situation.

[David128]

Hi I found this on You Tube It appears to show the system ideas.

f

Also made me think about how would this feel.

 

1. when you now brake using hydraulics or cable rod etc there is always a feed back to you foot. With an e brake there would be      normally be none.

2. The e brake would have to be a sliding resistor type or brakes would be full on or off.

3. If the brakes failed and failed safe how would that work ? No brakes or full brakes

4. back up battery and 2 controllers in case 1 fails.

 

Maybe it will all be sorted but looks like Siemens are still some way off as last post I have found was 2008

[nicklouse]

It probably goes without saying that a computer will be involved with the set up and I would think it considerably easier to interface the computer with electric brakes than hydraulic. I know what you maybe thinking but a few years (yes, years) back I read of a system being developed by Siemens and VDO which outperforms Hydraulic systems and would be considerably simpler to get it to 'talk' to a computer. Here's a 'teaser' I found on the net about the system;-
 
http://horsepowerspo...orm-hydraulics/
 
And from what I recalled in the Engineering Newsletter that I read, we will be seeing this system being fitted to production cars soon (if not already).
 
I thought I'd post this here as it may simplify your approach to it.
 
<Edit: There's a bit more info here;-
 
http://www.autonews....ew-brake-system
 
and I note that article is dated 2006 >

just had a look up to circa 2020 and there do not seem to be any plans for anything other than hydro brakes. not mentioning the electrically controlled hand brake.

just had a look at the specs for a 2022 car. still hydro. I guess they still have issues to overcome to convince the makers to put them into serial use.

[nicklouse]

Great first reply, cheers.
 
Can you go into more detail about what you feel are the external and internal inputs in both ABS systems and non-ABS systems.
 
Thanks.

ABS relative wheel speeds. and a means of applying and removing the pressure.

non ABS the a means of applying the presure and removing the pressure.

both require some form of controller. one has an ECU and the other a Human.

[smurfomatic]

Throwing some ideas in here, I'm from an IT background as a profession but picked up a bit from my Dad who was a mechanic for most of his working life.

 

From a control point of view, it would seem to be relatively simple - a project that could be done using a Raspberry Pi or similar, with sensors on each wheel. As said above, you can't rely on "brake pedal fully depressed = brakes locking". 

 

In fact, do you even need to attach a sensor to the brake pedal at all? A brake can lock if it's badly adjusted on only half pedal pressure and this is just as dangerous as a full-on ABS type situation.

 

So, sensor picks up wheel lock (sudden decrease in rotation speed, especially if compared to recent average from that wheel and others) and the cadence braking system kicks in.

 

It would be difficult to have a system which operates independently on front and rear, as you'd need two cadence pumps - or four if you want to go crazy and give independent wheel control. Unless, is there a way of tying it in directly to each wheel caliper and not have a central pump? A relatively simple device which can increase and decrease brake pressure, that's plumbed into the brake lines for each wheel - does something like this exist?

[Dylan8660]

Thanks,

 

It is the human control, and more importantly reaction that needs to be improved/complimented. A driver doesn't need sensors to know when lock up occurs. Pilots for whom ABS was originally designed are isolated from this sensation hence the need for wheel sensing.

Drivers without ABS just use cadence braking when lock up is sensed this is what I'm looking to replicate.

 

Jono_h

 

That's why in the list of questions "Should the pressure setting be fixed or switchable for driver preference?" was asked.

 

Thanks,

I don't feel a killer blow yet, keep it going.

[Dylan8660]

Smurfomatic,

 

What is the current setup and what is the current method of cadence braking and what is the result of cadence braking on that setup? This was my starting point in exploring this question and I cant think of a good reason to change this setup only add some form of automation that complements it.

 

Good to have someone with electronic knowledge thinking about this but raspberry pi or arduino would be overkill on something this simple.

[Ethel]

I'd also been considering this. My intention is to use a remote servo on the front brakes only in a front/rear split system. You could then use a bleed off valve on the servo vacuum to reduce the braking effort. You might need an additional vacuum reservoir (with a cross over valve) if you wanted a cadence effect The rear end already has a partial solution in the form of an inertia pressure limiting valve.

[limby2000]

A very interesting debate I thought i,d just throw in my tupence. I owned an escort cabriolet back in the day mk4 model 1986. It was the first escorts to have abs, it was a very basic system that had a seperate unit which run off each drive shaft by a small fan type drive belt.very compact and no electronics, other than the microswitch which told you if the belt broke.

[smurfomatic]

Sorry Dylan, I'll always think of an electronic solution to this kind of problem! Couldn't come up with a mechanical way of detecting when a wheel has locked, so the only logical method for me was a Raspberry Pi or similar, allowing you to adjust things as you go along.