Whos building their own Traction Control System?

[Popee]

Hi, as the title really! Im an Electronic Engineer tasked with designing a Traction Control System for this years car.

I was wondering how many other teams are building their own, and how are they going about it?

Im looking at retarding the ignition to limit torque. It should give me better control that a simple ignition cut, but I fear im opening a can of worms with regards to have how far I can retard the ignition without getting the EGT too high and damaging the exhaust valves! Also how much torque will be lost by retarding the ignition.

We have just got our bike and its being run in. Hopefully get it on the dyno soon and play about with the timing.

Also what microproccesors are people using? Initially I was looking at a PIC18Fxx, but I dont think it will be fast enough for my control system.

regards,
Lee

[Popee]

Hi, as the title really! Im an Electronic Engineer tasked with designing a Traction Control System for this years car.

I was wondering how many other teams are building their own, and how are they going about it?

Im looking at retarding the ignition to limit torque. It should give me better control that a simple ignition cut, but I fear im opening a can of worms with regards to have how far I can retard the ignition without getting the EGT too high and damaging the exhaust valves! Also how much torque will be lost by retarding the ignition.

We have just got our bike and its being run in. Hopefully get it on the dyno soon and play about with the timing.

Also what microproccesors are people using? Initially I was looking at a PIC18Fxx, but I dont think it will be fast enough for my control system.

regards,
Lee

[formula_wally]

Yes you are, two main things to remember, method of application, and sense of when to apply and how much. It should almost be a two person project. You have to be able to complete the whole system, if not, stop right now.

Timing retardation will get you get you a little ways to you cut. Dropped spark, and dropped fuel are better. Air blown pass a checked venturi(vacuum) valve in the plenum is dope. Electronic throttle would be boss too.

I love the avr family, pretty much the same as Pic, they'll accomplish the same thing, and remain a black box for everyone else on the team.

Timing considerations, if you have some pins availible on interrupts, and use assembly well, you may only need ~ 4mhz. A 16mhz atmel will be more than enough to track wheel speeds up to 100kmh (12 ticks/rev). Remeber to have a better scheme than logic bit bang. Try a numerical PID for starters. It may cause you to have to code in GCC.

Goodluck, and don't give up.

[Preston Schipper]

I've used the PIC18F's for some previous projects and found them very easy to use. Their built in CAN support along with spi/i2c is really nice. This year I'm working with some hardware using a powerPC. This is really nice becuase it has several TPU's that can perform time intensive processes independent of the ECU. I can have these keep track of each wheel speed and then do the control seperately. I've used other ECU's that can hold the rev's of an engine to a set point by just retarding timing. This is with no load on the engine so seems retarding timing could be a possibility for traction control. Here are some simulations we've been working on to see how a traction control system might perform on one of the lovely raining days in detroit. Need to update our tire models and improve the engine torque model.

http://ucsub.colorado.edu/~schipper/SAE/TCSim/runSim.html (http://ucsub.colorado.edu/%7Eschipper/SAE/TCSim/runSim.html)

Hope that helps.

[Popee]

Quote by Wally

"Air blown pass a checked venturi(vacuum) valve in the plenum is dope. Electronic throttle would be boss too."

I dont understand what you mean by this. Do you mean a seperate butterfy?. I would be concerned about its response time, although its something I can look into.

We will be using a CAN network on the car (Another team member is doing a digital dash and the network) So that should save me proccessing time.

Im currently experimenting with fuzzy logic for the control system. To simulate the car dynamics im using a program called carsim, then exporting the wheel speed data out into simulink via an 'S function' and the throttle input is then exported back into carsim. This way I dont have to model the many car parameters.

Progress is going well, however its going to take time to get a finished product. So far I can pull just over a car ahead of a car that doesnt have TC and uses full throttle:

SIMULINK:

http://i28.photobucket.com/albums/c211/Popee/m-simulink.jpg

RULE SURFACE:

http://i28.photobucket.com/albums/c211/Popee/m_surface.jpg

ANIMATION:

http://i28.photobucket.com/albums/c211/Popee/m_car.jpg

[Popee]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by formula_wally:
Yes you are, two main things to remember, method of application, and sense of when to apply and how much. It should almost be a two person project. You have to be able to complete the whole system, if not, stop right now.

Timing retardation will get you get you a little ways to you cut. Dropped spark, and dropped fuel are better. Air blown pass a checked venturi(vacuum) valve in the plenum is dope. Electronic throttle would be boss too.

I love the avr family, pretty much the same as Pic, they'll accomplish the same thing, and remain a black box for everyone else on the team.

Timing considerations, if you have some pins availible on interrupts, and use assembly well, you may only need ~ 4mhz. A 16mhz atmel will be more than enough to track wheel speeds up to 100kmh (12 ticks/rev). Remeber to have a better scheme than logic bit bang. Try a numerical PID for starters. It may cause you to have to code in GCC.

Goodluck, and don't give up. </div></BLOCKQUOTE>

Preston thats some nice work there. Where did you get the data for ignition retard vs torque? Was this done on a dyno?

How do you plan to retard the ignition? Im looking to knock up a little microcontroller that delays the signal to the coil pack.

regards Lee

[Preston Schipper]

Lee,

The engine is controlled by the powerPC that will take care of the traction control so I can retard timing as a please through the ECU. Sim of hp loss per degree retard is a guess so far. Waiting to do some dyno testing for that information. Are you going to receive your wheelspeeds over CAN? If so I might consider the delay in data. Have you considered how you will sample/provide data to your controller?

Preston

[Kenny T Cornett]

Aside from the weight, what do you all think of altering a oem sedan/coupe ABS system to make a traction control?

(sorry to be a bit off topic)

[Jersey Tom]

ABS modulates braking.. and brake line pressure afaik has to be completely manually controlled.

[Buckingham]

I've thought about ABS and it is possible to do it within the rules if you think outside the box, the problem is that this method is probably the most destructive (excessive rotor wear, internally resolving forces rather than reducing generated power). Also, pulling an abs system off a junker is bound to lead to a lot of wasted time figuring out how someone else's system works and thinking about how you can junk-yard-wars-it to make it do what you want it to.

[Popee]

Preston, I havent looked at that issue yet. Im not too familiar with CAN networks but they can transmit data at speeds of 1Mbps so i think it should be adequate. We will just set the wheelspeed sensors to the highest priority.

As for timing Its not something I have thought about. Im not sure how im going to calculate Rate of Change to if the inputs are coming in when I get them. Maybe I need a timer that gates the wheelspeeds at the minimum resolution they can be picked up at. Say 5mph....

Preston are you using a PID controller?

[Popee]

Kenny, in road cars the basis of Traction Control is ABS. They brake the spinning wheel. However we are treting to reduce engine power. In my opinion its not worth trying to fit the ABS module to the car. They are quite bulky, and probably wouldnt run without loads of trickery.

[BryanH]

CRAP! current traction control is enabled via drive by wire throttle. ABS is used for driver assist

[Frank]

moot argument anyway

in reply to the initial post
either fuel or ignition cut is fine for naturually aspirated race cars

ignition retard is overkill. why would you want ignition retard? is it easier to impliment?

[Popee]

Frank, its not easier to implement, but it gives you finer control of the output torque, and it can be done every conbustion cycle.

If you look at the 3D graph above you will see the power output varys depending on slip and the rate of change of slip. Im not trying to kill the wheelspin, I want to control it at around 10-20%.

[formula_wally]

The venturi valve idea is along the more rediculous idea-line. I got the idea from our press shop, at my co-op spot.

Compressed air, through a venturi, nozzles to awesome fluid dynamic things, a vacuum is generated, and pulls the pressure down in the plenum = Load control method. The rise time for 100 psi of compressed air is 100psi of vacuum for 100mSec of application. Add a check valve so that air cannot enter into the plenumm. Still doubt anyone would run it, or even try to justify the weight.

As far as application, Fuzzy is pretty much the only way to go. And to get the Judges to actually believe its usefull, it has to do more the detect wheel spin....

[Preston Schipper]

Currently I just had a P controller on there. I think an integral or derivative term would not help. Too much signal noise for a D and integrator wind up before a shift would suck. I plan to look into fuzzy logic and other more advanced control schemes shortly.

[Koen]

Hello, I am the TC/LC guy from the Delft team.

We are also planning on using TC and LC on the car this year.

My idea was to start using ingnition retarding, and maybe cutting. I think things like control with the throttle is not so easy, delay in flows and stuff. With retarding the engine engineer also warned me about overheating the enigine .. or maybe i need to do and cutting and fuel flow control. i don't know yet.

I see you are going to program it yourself, why not use an ECU with TC?

and those slip ratios, they are important, but without tire info you can make TC only as an idiot proof system so

1. i get info on the tire (difficult)
2. i'll just try (30%, 20%, 10% until it works nice enough).

Preston, there is something you can do against intergrator windup. it's called anti-windup. but maybe you are right, maybe P can be enough.

[Popee]

Hi Koen.

It looks like we will be using an ECU that does not have TC or LC, also the ECU's I have looked at simply seem to cut the ignition or spark completley. Im wanting to get some finer control of the torque reduction.

The problem is with retarding the ignition is the gases flowing out of the exhaust get very hot. Hopefully this wont be too much of an issue as our engine has Titanium valves. Also people wont be using the TC alot, maybe once or twice a lap on the slower corners, so I dont think overheating will be an issue.

At the moment im using longitudinal tyre info from an F3 tyre.

[Preston Schipper]

Try retarding timing on the track or dyno. Things will get hot, but cool back down very quicly once you stop retarding timing. I think for the short bursts where TC is needed retarding timing should be ok. Maybe adding fuel during these periods would help as well to cool things a bit.

[bigwig]

Retarding the timing a couple of degrees can result in significant torque losses without crazy increases in EGTs. I wouldn't be concerned about the heat. There is a huge misconception on how much fuel actually reduces temps. Its really not that much at all. http://www.innovatemotorsports.com/resources/rich.php I haven't checked his math but if its remotely correct you can see the cooling capacity is not enough to make a huge difference. Plus with the increase of fuel and retarding of ignition timing you could get some nice combustion similiar to what occurs on ALS systems. I'm sure we all know what that does to internal components, especially valves. That type of heat would worry me far more than the heat increase with retardation of 5*.

[Koen]

usefull information http://fsae.com/groupee_common/emoticons/icon_smile.gif

i still don't know if we are going to use an ECU with LC/TC. I'll ask the guys about the working of the ECU. If you are right, then maybe i also should think about making one my self.

So but you guys think it is possible to keep the RPM constant only with retarding? I think so too but i just don't know how the engine, we are using the Yamaha wr450 1 cilinder, reacts on retarding as in can i keep the RPM constant by only, for example, playing around 5* or need i go to 10*. That is something i'll need to test.

Some guy told me about drowning the engine after you stop retarding, the famous bwwwooaaaap. You think reducing the fuel flow can speed up the pickup process, or is this not true? because it looks to me that that won't happen, it ran fine on it before retarding, why would it not run fine after?

[Exhausted]

Here's a link to some information regarding traction control and cheap standalone engine management...

Traction Control and Engine Management (http://www.fourstrokedesign.com/forums/viewforum.php?f=2&sid=8a3f7174ccf84dd331f7cd200b13f140)

[Popee]

Exhausted thanks for the info. We are using an Aprilia 550 V Twin and retaining the stock ECU, so I will need to make an aftermarket TC System for it.

This engine is amazing. Produces an unrestricted 66kW and weighs 32kg!

[Koen]

I have a question.

We could say we want retarding instead of cutting because the retarding will make the car run smoother when TC is active.

Lee, you said that retarding will give you a better control, i agree, but is it really necessary? How constant should the RPM be? Within 10 RPM, 100 RPM? And how accurate will retrading be?

I also know what ECU we will be using, the MoTec m4 pro, it as TC and LC. I only need to know how there TC works, cutting, retarding, fuel adjusting?

[Bill Kunst]

Koen,
are you talking about engine rpm? Ideally, in a race engine, large rpm spikes due to rev limiting will inevitably shorten the life of the engine. As for the drivers sake, I would think that you would want it to be as seemless as possible. In that case, it becomes a matter of what is "noticeable". This is different for every drivetrain layout.

If you are talking about wheel speed:
Maybe I am crazy, but don't you want to calulate the rpm difference(wheel speed) based off slip angle?
Stated differently, the tire has a maximum tractive effort at a given slip angle, with TC you should be aiming for this. Is this the right thought?

Bill

[Koen]

yes, but if you detect wheel spin you need to reduce the engines output, torque, by "limiting" the rpm output of the engine. so if you cut or retard the spark it will act as a kind of rev limiter until the wheel spin is back in accepteble range.

The seemlessness will be determined by the responce of the controller itself, if it detects if fast and has a fast and enough damped responce then it won't be a problem. But remember a good driver will have it only active for maybe a second orso. I don't think we can build a TC which will work as effective as possible. It just to help drivers with a heavy foot.

The biggest problem is the slip angle, or ratio. I don't know it. we don't have any of this info of the tire so it will either be an idiot proof TC or we need te test alot.

I also know that the engine itself wouldn't like it, but it is not like the TC is working all the time. Only when exiting corner prolly.

[BryanH]

Koen, Motec TC cuts fuel & spark, which is ideal.
The Racelogic one I've used cuts fuel only and is also very effective. Cutting ign only can lead to fuel loaded cylinders. Not sure exactly what was going on but I've had the knock detector going crazy when I've used ign only rpm limit on a few engines. Motec changed to fuel & ign cut a few years ago to eliminate probs.
You will find that retarding the timing on the WR450 leads to very high Ex temps, Muffler destroyed ASAP!
Motec TC is very effective/sophisticated. You just need learn how it works.
Motec & Racelogic cut cylinders progressivly depending on how far away the acc rate is from the target, don't know WTF it's going to think of 1 cyl to play with... RMIT may be World Champs, but lets face it, the engine sounds crap and traction control is gunna make it worse....winning isn't everything
Earlier on someone was talking about knocking up a box to retard the spark, Intercepting a constant charge ign event, calculating a delay in degrees and sending off it's replacement on a rapidly accelerating 14K engine involves serious manhours and a 32bit processor. The most effective method is to read and then mimic the trigger and sync events on their way into the ECU, even then your max retard is limited to the diff in degrees btwn each trigger event minus the time to calc.

[Koen]

but with only cutting you also will put unburned fuel into the exhaust and that will also ignite.

how do you know that with retarding the wr450 will lead to very high Ex temps?

[bigwig]

Cutting fuel will not cause problems. If it did, OEM systems wouldn't cut fuel. You are talking about a VERY small amount of fuel and its only sitting in the combustion chamber for a very short period of time due to the fact the valves are still opening so the air is just going to leave the combustion chamber. Fuel cut is extremely safe.

As for cutting fuel/ignition. I don't understand why anyone would go this route on a traction control system. Isn't the point just to decrease power? Cutting fuel/ignition I'd imagine would cause lots of bucking, hiccuping, and very inconsistent results. If I were designing the system I'd make a controller which monitored acceleration at the wheels and if it was abnormal, it would send a voltage signal to the ECU. When the ECU received this voltage signal it would trigger the ECU to remove X degrees of timing until the voltage signal went away. You could also possibly monitor engine rpm(wheel spin=less load on the engine=easier to make the engine accelerate=rpm to rise very quickly) and then this could all be done via the CPU as long as you have a nice company that will throw together the feature. This is one reason I think projects like megasquirt are great for FSAE teams. If you want to add an option you can as long as you know assembly language.

Lastly, do not worry about ignition retard of a couple degrees. EGTs will not increase a significant amount for a couple degrees of timing removed for a couple of seconds. If they went up 100* I'd be shocked. 50* I'd be surprised.

[Koen]

ok, does anyone have concrete data, book or what ever on the effects of retarding, cutting and injection cutting? we are all talking about "i think" and you don't score any points with that. i have been looking but it is not easy to find.

[BryanH]

WR450 isn't timing sensitive under 8500, 8 degrees out makes almost no diff to kw. 15 degrees less and egt will skyrocket. Nearby stuff will BBQ. In RO4 everything was nearby.


Torque control is achieved by PROGRESSIVLY cutting cyls, starting with 1 per cycle and increasing to half the cyls in a sequence to maintain engine smoothness. On a multicyl engine the result feels more like valve float than turning the ign off and on as you seemed to expect. I consider that the WR450 is always in traction control mode as the power strokes are so far apart compared to a 600/4, and in the case of RMIT's setup I used the stock single flywheel trigger so that fast acc rates would retard the ign event giving a defacto traction control. Seemed to work OK.

Cutting fuel only does work very well. Cutting ign only at high throttle positions results in unburnt fuel in chamber and exhaust system. Just remem that there is 50 fuel economy points up for grabs, and retarding the timing won't help that.
RMIT did prove that 400 points are possible.

Good solution is to design progressive throttle setup, TB &lt;34mm, good mapping, thin race boots. Seem to remember biggest issue is finding drivers who actually use 100% TP for long enough http://fsae.com/groupee_common/emoticons/icon_biggrin.gif
"Always tell your competitors the truth, they will never believe you"

[BryanH]

Koen, download Racelogic, Motec, Autronic software and play with it, read their help/installation files.

[B Lewis @ PE Engine Management]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by bigwig:
If I were designing the system I'd make a controller which monitored acceleration at the wheels and if it was abnormal, it would send a voltage signal to the ECU. When the ECU received this voltage signal it would trigger the ECU to remove X degrees of timing until the voltage signal went away. </div></BLOCKQUOTE>

For those of you using the PE system you can use one of the "user analog inputs" to pull an adjustable amount of timing out based on an analog voltage just as bigwig suggests. We have also experimented with "RPM only" based traction control and it can be successful with enough tuning.

[formula_wally]

Using direct device lines into an AI line in the ecu to trim spark seems very simple and intuative. On the control theory side, this is a nightmare due to the fact the feedback loop and actuation have little in common with lots of mechanical devices in between, and the drivability of the car.

This is very similar to the corporate world, having an irate manger of a huge car company telling the line workers all at once to either make more or less cars. A bashing control scheme as such will exhibit erractic output response, posibly making the car much less driveable, and increasing Torque load variation. You need to go through the right chain of fier, and use Proportional methods.

The Engineering approach should be the simplest solution, with the smallest footprint, and the maximun effect. I would be more embarrased than proud to show a design judge how we implemented TC ( if you used angalouge inputs to retard spark).

[bigwig]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Koen:
ok, does anyone have concrete data, book or what ever on the effects of retarding, cutting and injection cutting? we are all talking about "i think" and you don't score any points with that. i have been looking but it is not easy to find. </div></BLOCKQUOTE>

I've tuned a number of street cars. On these street cars we use fuel cut for rev limiter, full throttle launch(2-step), and full throttle shifting(shift without lift). According to the wideband the car at these points are running at free air. They make a number of passes at the track holding the full throttle launch for a number of seconds without an issue. There is a large misconception that cutting fuel is a lean condition. Its not a lean condition. It's a no fuel condition. No fuel = no combustion. If there is a small amount a risidual fuel in the combustion chamber the likely hood of it being enough to cause irregular combustion is highly unlikely. If combustion did occur, with a very small amount of fuel, even under irregular combustion, the peak cyclinder pressure is going to remain low. Again, it's safe.

As far as retarding timing, again, look in the manufacturing world and how things like knock sensors work. Knock sensors remove arbitrary amounts of timing to allude detonation. Are EGTs a concern? Sure. But when one is only talking about less than 10* and they figure the amount of time the timing is going to be removed, the end result is its safer to remove the timing and have higher EGTs than not. We are already talking about a car that is running less than optimal timing so they are retarding on an already conservative tune. Again, EGT spikes won't be that impressive to worry about. The idea isn't to kill power, it is to limit it. The idea is to implement an idea that is cost effective and works well. Retarding the timing will limit power thus decreasing traction issues. Its up to you to find the optimal value, but if you retarded the timing 5* or less and saw unsafe EGTs I'd be shocked.

[Koen]

hello there,

Well we are going to use the Motec m4 profor LC and TC. It can:

Ignition cut
Fuel cut
Retard only
Retard + ignition cut
Retard + fuel cut

building TC and LC our selfs is just too much work and we don't have the knowhow yet. It is up to me to see what works best.

[Popee]

Hi everyone. Sorry I havent posted in a while. I have decided to go for a fuel cut traction controller. The Ignition retard would be too hard to implement. We are using the new Aprilia V-twin and we are unsure how altering timing would affect output torque. (We still havent got it on our dyno yet)

Fuel cut enabled me to simulate the traction control system as the relationship between cutting fuel to a cylinder is easily to define.

As the Aprilia ECU is fully adjustable we plan on using that, therefore there is no provisions for implementing traction control on it.

Therefore I have designed my own. The TC unit will sit inbetween the injectors and ECU, reading wheelspeed and engine speed data from the CAN bus and adjust the injector pulses accordingly.

Koen, do you have any Electronic Engineers on your team? With the right drive something like this can be done.

Lee