ABS Based Traction Control System

fredsub · Post by **fredsub** » Sun Nov 20, 2005 9:25 pm

What I was thinking was measure the four wheels using interrupts over a set time period (100ms or 10hz).

either that, or sampling the digital inputs at 2xthe max freq is the right approach.
It will be interesting to see how much steering effect can be ignored....I guess we will find out....
Initially i'm planning on the traction control to be manual, ie 1 button for each wheel, at least until sorting out sensor issues etc..

Also, what shall we think of for failsafe ? ie you don't want it to brake a wheel by accident/fault when your going at 100kph either because of fault or forgeting to switch it off

I am thinking perhaps on a microswitch (or 2) on the gears 1st/2nd so it'll only be allowed to operate whilst in 1st/2nd. What do you think?

futurelec.com.au - yeah, discovered them just a few weeks ago,
ordered the ATMega Dev board and some other stuff.......

Seems we each have a different method for making PCB

I have been using the PRP positive resist/UV exposure method, but since running out of old batch of PRP, have had zero results with the new stuff

, so time to investigate the alternative of toner transfer, seen some good result of it on the web, and got me a laser printer lately too.

Hey, Ben, can you tell me exactly what paper you used for the toner transfer ?

Ultimately, after any prototype stage, we will need to have boards manufactured, just so at least this can be offered to anyone with barely any electrical knowledge.

take a look at http://www.sesame.com.au

hmm, need to find out where to get connectors for the ABS....

Ben · Post by **Ben** » Wed Nov 23, 2005 8:32 pm

fred-sub wrote:Also, what shall we think of for failsafe ? ie you don't want it to brake a wheel by accident/fault when your going at 100kph either because of fault or forgeting to switch it off

I am thinking perhaps on a microswitch (or 2) on the gears 1st/2nd so it'll only be allowed to operate whilst in 1st/2nd. What do you think?

I was thinking of allowing it to only operate up to 40km/h.

fred-sub wrote:Hey, Ben, can you tell me exactly what paper you used for the toner transfer?

I use Kodak Picture Paper, the double sided gloss stuff. Just buy a couple of sample packs to find which one works for you.

fred-sub wrote:hmm, need to find out where to get connectors for the ABS....

I am starting to think that wrecker's could be a good place to start for this stuff!!

Ben · Post by **Ben** » Wed Nov 23, 2005 8:40 pm

wagonist wrote:I hope you guys have remembered that when you go round a corner all 4 wheels are spinning at different revs & your programming will have to take that into account.
the tighter the turn, the greater the difference.

Yes, and the difference in wheel speed between a turn and a free spinning zero grip wheel is huge enough that it is easy to account for 'turns' and loss of grip easy enough.

wagonist wrote:How are you going to stop/slow the wheel that's spinning too fast?
retarding the timing of cutting fuel is really primitive & will just slow the whole car, not stop the wheel spinning.
If you're going to effort of fitting the ABS sensors, I'd be fitting the entire system & then using that to activate the brake on the spinning wheel. This is how the better modern 4wd systems work.

Have you been paying attention??? I and others have mentioned several times the installation of ABS units to actuate the braking of the wheels.

Engine power retardation has zero ability to increase grip in a zero grip situation.

wagonist · Post by **wagonist** » Wed Nov 23, 2005 10:04 pm

I've been trying to pay attention, but there's a lot of technical knowledge mixed up in there which is over my head. Hence the comments which raised the queries, which you have now confirmed.

From seeing the status of some of the projects it was unclear as to whether the full ABS system was going in, or just the sensors

fredsub · Post by **fredsub** » Sun Nov 27, 2005 10:05 am

Mechawagon wrote:I was thinking of allowing it to only operate up to 40km/h.

Got any suggestion of how to do that simply? got mechanical speed gauge here....I suppose there is like that speedo kit Jaycar has.......

Mechawagon wrote:wrecker's could be a good place to start for this stuff!!

well yes, but I expect I need to rewire the connector end....disassembling those sealed plugs is a real pain in the ###.
I've spent quite a bit of time web searching connectors...no luck yet.....some manufactures have such appaling web sites to search..

Alternative is use new different connector that is avail from digikey etc....but probably still need sealed type, and they are not cheap!

Peejay wrote:PWM on the main motor may be possible to adjust the overall force applied by the brakes so it's not just a matter of on or off.

The main motor simply maintains overall constant system presure, its the individual valves we should modulate I think....However initially I had in mind was how long the free wheel is braked for, not by how much (force) applied.....now whether this is the same thing.....or same result .... ? dunno..

PeeJay · Post by **PeeJay** » Sun Nov 27, 2005 12:29 pm

fred-sub wrote:The main motor simply maintains overall constant system presure, its the individual valves we should modulate I think....

So does the motor have to have any control curcuit to regulate the pressure or do you just apply power to it?

With the valves, are they a simple on/off thing or can they be adjusted somewhere inbetween?

Ben · Post by **Ben** » Sun Nov 27, 2005 6:50 pm

fred-sub wrote:
Mechawagon wrote:I was thinking of allowing it to only operate up to 40km/h.
Got any suggestion of how to do that simply? got mechanical speed gauge here....I suppose there is like that speedo kit Jaycar has.......

Hey,

With a 36 tooth gear wheel for the sensor a subie is doing 185hz or thereabouts at 40km/h with 27" tyres, the software will handle that easily.

fredsub · Post by **fredsub** » Mon Nov 28, 2005 10:50 am

of course use the same sensor info to give speed info too......what was I thinking?.........

Ben · Post by **Ben** » Sat Dec 31, 2005 5:53 pm

Ok, quiet times recently....

I had a bit of trouble acquiring an AVRISP unit, but now have one and it is all built up and ready to go.

The next month will see me spending a bit of time at home bored and when I am not fishing I am going to spend a bit of time trying to get some signals up and running from the wheels and display the speeds.

Then start on installing the abs!!!

PeeJay · Post by **PeeJay** » Tue Jan 10, 2006 9:04 pm

Did a bit of work on trying the abs sensors today. I think they will work - just!

At 4 KM/H with 14" wheels (0.5 rev/s) the sensor gives about 170mV AC p-p

I built a simple precision rectifier which amplifies the signal into a square wave (lots of clipping) and rectifies it as well. This can then be fed into the interrput pin on the microcontroler.

Spinning the wheel at 1 rev/s gives an output frequency of 120 Hz.

PeeJay · Post by **PeeJay** » Thu Jan 26, 2006 6:46 pm

There is a good article on making a speed pickup on P70 of the Feb06 Silicon Chip. It uses a Hall effect sensor and a wooden bearing that clips onto the driveshafts. I could scan it if anybody wants to look.

PeeJay · Post by **PeeJay** » Tue Apr 25, 2006 6:22 pm

It's been a bit quiet here lately so I thought I'd do an update on where I'm at:

I've just finished puting the lib brakes with the abs sensors on the front of my RX so I can at least have 2 wheel control for now.
I've designed a circuit to take the inputs from the sensors and feed them into the control unit
I've built a switch board with a bunch of push buttons and switches so I can manually operate the hydrolic unit while driving to see what happens.
I just finished testing a circuit that can read diagnostic info (speed, rpm, egine load etc.) from the EFI unit on the car. Don't know if I'd need it but it will make for a pretty display

As soon as I figure out how to operate the hydrolic unit I can put it all together!

MUDRAT · Post by **MUDRAT** » Tue Apr 25, 2006 9:30 pm

Keep us posted, I'm still interested, I just have nothing of value to contribute.

PeeJay · Post by **PeeJay** » Tue May 16, 2006 7:15 pm

Well, I got the hydrolic unit working.

But it dosen't work. All it will do is push back on the brake pedal.

I think I'll have to try a hydrolic unit from a model equipped with traction control.

fredsub · Post by **fredsub** » Wed May 17, 2006 8:07 am

I think fluid is finding path of least resistance back to brake pedal. Maybe via proportioning valve ? you still got that in the fluid circuit?

PeeJay · Post by **PeeJay** » Wed May 17, 2006 10:54 am

When I operate the pump nothing happens until I press the button for the valve, then the pedal comes back, and no amount of standing on it will stop it. It also seems to disengage the brake.

fredsub · Post by **fredsub** » Wed May 17, 2006 12:09 pm

I think you got the same abs unit i have, sounds like is generating enough fluid pressure tho,
the 2 pipes at the back that are at an angle, I'm not sure which may be an entry or return pipe....maybe the wrong way??
in anycase i don't think pressure should be pushing back up into the brake master?
can the pump on the abs run in either direction?

hmmm.i'm thinking now..i saw forestor at a wrecker some months ago...looking likes its a good idea to find out what it'll cost to strip the brake line system out...along with any valves/connectors and whatnot......I believe it uses the same ~5mm lines (very standard brake line size apparently)

Ben · Post by **Ben** » Wed May 17, 2006 8:07 pm

Well it certainly looks like I am gonna have to get my arse into gear and do something with this - boat stuff has taken priority lately though!!!

L needs some other work done before I can spend money on stuff like this...