Using MoTeC Traction Control

[Wilko]

I'm part of the Cardiff Racing formula student team and am currently looking into the application of traction control. As in previous years we will be using the MoTeC M400 ECU. However, in the past we have not implemented the traction control functionality available with this component and there is a general lack of knowledge about determining the correct settings to use.

I was hoping that someone out there may have successfully used MoTeC traction control in the past and be able to give me some guidance. In particular I am currently uncertain regarding the following points:

1. What kind of method of reducing power to the engine is likely to be best? To me cutting the fuel seems like the most obvious thing to do. Cutting ignition would lead to unburnt fuel and I've heard that retarding can lead to high exhaust gas temperatures.

2. What is the best way of determining the optimum RPM Limit for any given ground speed during launch control? Can this kind of data only be collected by testing the car?

3. Is there a way of catering for different track/weather conditions without an onerous amount of testing being required?

4. Has anyone successfully implemented an on-board driver control(s) to tailor the exact performance of the traction control? The MoTeC software seems to provide the capability to do this using aim slip or gain compensation tables.

Any advice on these topics would be really helpful.

Cheers

Wilko

[Wilko]

I'm part of the Cardiff Racing formula student team and am currently looking into the application of traction control. As in previous years we will be using the MoTeC M400 ECU. However, in the past we have not implemented the traction control functionality available with this component and there is a general lack of knowledge about determining the correct settings to use.

I was hoping that someone out there may have successfully used MoTeC traction control in the past and be able to give me some guidance. In particular I am currently uncertain regarding the following points:

1. What kind of method of reducing power to the engine is likely to be best? To me cutting the fuel seems like the most obvious thing to do. Cutting ignition would lead to unburnt fuel and I've heard that retarding can lead to high exhaust gas temperatures.

2. What is the best way of determining the optimum RPM Limit for any given ground speed during launch control? Can this kind of data only be collected by testing the car?

3. Is there a way of catering for different track/weather conditions without an onerous amount of testing being required?

4. Has anyone successfully implemented an on-board driver control(s) to tailor the exact performance of the traction control? The MoTeC software seems to provide the capability to do this using aim slip or gain compensation tables.

Any advice on these topics would be really helpful.

Cheers

Wilko

[Pete M]

1) Ignition cut and ignition retard are instantaneous, while fuel cut has a slight lag, both in taking out power and putting it back in. Fuel cut is obviously the more fuel economic version. Ignition cut can lead to banging if you let it cut so much that it loads the exhaust up with fuel. Ignition retard can melt things if you don't know what you're doing.

2) Pretty much, although a bit of tyre data or even general guesses as to optimum slip and a good gearing calculator will help you. Basically, for the gear you're launching in, what engine rpm will result in the drive speed corresponding to optimum slip at each ground speed? In practice, this has to be weighed against keeping the engine rpm high enough to avoid it bogging down.

3) Not that i know of... just test on a few different surfaces and get a feel for how it changes things.

4) We haven't as yet, although it is relatively easy to do.

[Mike Claffey]

1. If you are limited in time, setup a fuel cut traction control map, since that will potentailly earn you alot of points in enduro/fuel. With more time, setup an ignition cut TC map for other events. I remember the drivers liking the ignition cut map more than the fuel one.

4. Yeah, can be done. If you can find a picture of our steering wheel & dash online, you'll see a picture of a rotary switch on the dash which is used to TC settings.

Goodluck

[C.Zinke]

I'm still in progress of testing and learning. We use the TC as IgnCut and Retard. We never testet the fuel cut. Some cool parameters are:

CutType: IgnCut
10km/h slip aim
10 Proportional
1 Derivative
0 Integral

If you use this settings the TC works, but in a way thats not correct. Why i'm posting this setting is, that these settings make the car sound amazing! Rapapapapaaaaahm! So if like to hear everybody that you use TC than use it ;o), BTW this setting is not that bad, still works ok. But from my expirence the values are 3-10 times lower for a good traction control


I still wonder, if a TC really makes the car faster?

I am the opinion that km/h as slip value should be better then percent as slip value. What do you think?

[blister]

I took us one Day to make TC adjustable and switch on/off. The Launch RPM is also easy adjustable.

What you need is lots of testing time.

Despite of this gimmicks, traction control was not used by one driver, and the other only used very small amount.

[js10coastr]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by C.Zinke:

I still wonder, if a TC really makes the car faster?
</div></BLOCKQUOTE>

Nope, just makes it easier to drive at the limit all of the time (assuming the TC is setup right).

[mtg]

And wouldn't making the car easier to drive at the limit make it faster?

[ben]

My only experience of the effect of TC is looking at data from our MotoGP bikes. It often becomes apparent that when you plot force vs. slip ratio you don't see a full peak and if the system is setup very aggressively you're always slightly sub limit in terms of outright grip.

This is often the case early in a race weekend, and as track condition and confidence improve you start to see something more like a traditional Fx vs. slip curve with a peak and drop off.

The best riders I've worked with use some TC, but a lot less than poorer riders. I've always put this down to the inherent lag in the control system and the rider responding to what the TC system's doing.

I know for sure that one team (not ours) is using strain gauges on the wheel rim and in-wheel telemetry to measure the lag in torque at the rear wheel following a TC intervention.

Ben

[js10coastr]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by mtg:
And wouldn't making the car easier to drive at the limit make it faster? </div></BLOCKQUOTE>

If we're defining it that way, absolutely! But I just want to clarify that it does not extend the traction circle. Tuning the suspension (and tires) will extend the envelope, while at the same time TC may limit the car/hide any handling issues.

[Poe]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">while at the same time TC may limit the car/hide any handling issues. </div></BLOCKQUOTE>
Or if the driver is steering the car with the throttle to mask an understeering condition, traction control will highlight that handling issue.

[murpia]

A lot depends on the sophistication of your TC alorithm, but here are some of the issues you could face. I'll leave it up to you to decide what's good and bad...

Ignition cut TC using more fuel than 'normal' driving.
Retarded ignition TC increasing exhaust gas temperatures.
Fuel cut TC responding poorly to re-introduction of torque.
Tyres operating more closely to their peak traction slip ratio for more of the lap and heating up / wearing out.
TC keeps the traction below peak slip ratio giving more lateral rear grip on exit.
TC keeps the traction precisely on peak slip ratio giving maximum acceleration on exit.
TC keeps the traction exceeding the peak slip ratio giving less acceleration & lateral grip on exit.
TC allows the driver to 'get away with' mashing the throttle flat on exit.
TC 'catches' minor rear breakaways, leading to smoother steering inputs.
TC 'catches' inside wheelspin for a loose or open differential.
Driving over a bump or kerb activates TC and holds car back.

Whatever you choose to implement, you really need to test it thoroughly. Have some mapping options available in case of significantly more or less grip and / or tyre wear at the competition venue vs. your test venue.

Regards, Ian

[murpia]

One more:

Large oscillations in rear wheel torque if the TC control loop is badly tuned...

Regards, Ian

[Wilko]

Thanks for all of the advice. It sounds like spending a decent amount of time testing is the key to getting things right. Also I can see some serious advantages to the driver being able to 'tweak' the system manually using an on-board control.

As far as power cutting goes the pros and cons seem to recommend ignition cut for better performance but fuel cut for economy. I don't see any major advantages to justify the additional amount of consideration that implementing retard would involve.

[ben]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
One more:

Large oscillations in rear wheel torque if the TC control loop is badly tuned...

Regards, Ian </div></BLOCKQUOTE>

Would this be an example of a positive feedback loop where the driver's modulating the throttle in response to the TC changing the torque delivered to the wheels?

I'd always wondered if such a situation could occur.

Ben

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ben:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by murpia:
One more:

Large oscillations in rear wheel torque if the TC control loop is badly tuned...

Regards, Ian </div></BLOCKQUOTE>

Would this be an example of a positive feedback loop where the driver's modulating the throttle in response to the TC changing the torque delivered to the wheels?

I'd always wondered if such a situation could occur.

Ben </div></BLOCKQUOTE>
I suppose such a 'pilot induced oscillation' could occur, but I never came across it. I was think more of the sort of torque oscillations you might get if the ignition cut pattern used by the TC was too coarse, like a hard rev limiter. It just means the slip ratio control is poor.

I have come across what we called a 'TC tankslapper' caused by the driver mashing the throttle flat on corner exit in the wet. As the tyre slip came up, the yaw angle of the car increased dramatically before the TC could catch the slide. Then the car would recover and the cycle would repeat. The car had a yaw angle oscillation of about 7 or 10 degrees amplitude at about 1Hz all round the corner...

Regards, Ian