"Traction control" thread in "Motorbike Chat"
Originally Posted by Weeksy Apparently it has the abilty to sense if the front wheel is on the ground or not and acts accordingly, therefore ...

Nor extreme high sides then... Not difficult to imagine a road scenario where the front is off the ground and the rear wheel hits something slippy...

Guessing their marketing suits already saw the problem I'd thought up, which brings it back to being a gimmic for 99% of road riders.

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If beer is so bad for brain cells, why does my brain allow me to drink so much of it?

the 1098R and 1198S use differing forms of TC as the 1098R version is indeed illegal as it allows unused fuel through and can only work with the race exhaust system not the road legal version...

It was the comments I'd read about it comparing the front and rear wheel speeds that made me think it'd get in the way of wheelies.

The crank speed detection sounds like a much more effective way of implementing TC to me, that would definitely allow wheelies as the rate of change of crank speed would be inside the accepted rate of acceleration, question being, what happens with 'super sticky' tyres?

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If beer is so bad for brain cells, why does my brain allow me to drink so much of it?

This sentence:

"It even allows the bike to wheelie, knowing from the mathematics that the front wheel is slowing because it's in the air."

Hints to me that it is looking for rates of divergence between the front and rear wheels rather than raw speeds. If the rear starts to spin pre-highside it's speed will rise rapidly away from the front's, but if the front runs down slowly it will ignore it. But this is just a hunch.

I guess the acid test is to pull a minger and tap the front brake - see if the TC has an eppy

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aka 6x6

I haven't ridden the duc, but my GS has TC, as does the 2008 ZX10R I had in Scotland in the summer (tho Kwack don't call it TC for fear of litigation when an owner get's it all wrong).

If the duc version is as unobtrusive as they both are* then I really can't see what the fuss is all about.




(*= the kwacks was way better than the BMW which you can't wheelie. If I hadn't have known it was there I wouldn't have noticed it at all tbh.
The GS TC has however only ever cut in the once, under severe provovation in the wet last weekend with Olly following)

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Yep.

The 1098 stopped the spark,the 1198 stops the fuel,thus saving the cat from harm.

*cough*

Edit - I think that's launch control gone awol which I believe (could be wrong) is a separate gizmo to TC on the GP bikes.

How do you get it as a screen in the actual post?? I'm a numpty!!

Wrong it stops wheelies over a given speed which I believe is around 100mph, it allows them below that as they are a by product of going faster especially on track. I had the choice of the new bike with TC and wouldn't have it for the road as 100mph is only just into 2nd gear on one wheel.

I would however love it for track use

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mmmmmmmmm

I didn't think it would be geared so low for an unfaired bike.
I imagine anything over 100mph will quickly become uncomfortable anyway, no?

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Problem child

I think people are assuming the TC system is much simpler than it really is. It won't just sit their quitely snoozing away until it suddenly realises something's happened, and then switch the engine off until that thing stops happening.

I.e., it won't simply think "ah...the front wheel is going XXX slower than the back wheel, the rear wheel must be spinning" and then switch off the spark plugs until the difference between the two is back within a certain limit.

Educate us then oh great enlightened one.

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The system is quite complex and includes wheel speed sensors along with a gyro in the tail unit to add lean angle and accleration into the equation, as to how they make all the info work I guess we'll never know that !

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mmmmmmmmm

It'd probably make more sense to give an idea of the problems faced with devloping a traction control system.

First off take a look at this chart. People always say "tyres generate most grip when they're slipping at 10%", this graph shows that. It's a plot of force generated at the contact patch vs. tyre slip. This chart shows a tyre being 'turned', but the plot is exactly the same shape when you're considering longitudinal slip.



It's clear from that graph that tyres must slip in order to generate any grip. I.e., the wheels will always be spinning faster than they 'need' to, whether you've 'lost' traction or not. I.e. the speed at the wheel rim is faster than the vehicle translational speed (its speed along the road) under all conditions, except very very low speed.

The front and rear wheels will both be slipping to a certain extent, and the amount they're slipping will be different. The shape of that plot will also change depending on teh bike's lean angle and the overall acceleration (because of weight transfer).

What the TC system aims to do it keep the slip somewhere in the linear region of that graph, which sounds simple enough.

How do you know what the tyre slip is? Simple answer is you don't. All you know is front and real wheel speeds at the hub, you have no way of knowing what the bike's translational speed is, hence you can't know the slip. You can infer it though, which is what the system does.

How do you know what the shape of that graph is? Again, you don't. It's generally the same for all tyres, but there are obviously differences between tyres and even between the same tyre on two different days.

How do you know that the vertical load on the tyre is? You know the bike's dry weight, but you don't know the rider/load weight. You can also infer weight tranfer from vehicle acceleration, but you don't know what the weight distribution on the bike is, or if you're riding up/down hill etc.

What do you do about sudden throttle application? If you suddenly open the throttle you could quickly find yourself going over the peak of that graph and suddenly loosing grip. You could cut the power and regain grip, then re-apply it, but you'll end up with lurchy power delivery.

If you do decide you want to reduce power, how do you do it? If you cut the spark you get fuel going down the exhaust. You also get unburned fuel present in the combustion chamber which is no good for emissions and can mess up the next power stroke. If you cut fuel you have to re-wet the inlet tract when you start putting fuel back in for example, so activating the TC system has a knock-on effect for the period afterwards.

You can use crank speed to infer wheel speed, you could get problems with vibrations in the chain. I.e. the wheel could be spinning and vibrating (torsional vibration around it's centre) at a different rate to the crank. Also, how do you decide if the clutch is slipping or the wheel is slipping?

Ultimately you'll come up with an algorithm that considers such things as wheel speeds/acceleration, engine speed/acceleration, throttle position/change, lean angle, vehicle acceleration/lean angle and then comes up with an engine torque output demand. It'll then work out how best to meet that demand and could change such things as spark timing, throttle position, injection timing etc. The hard part is developing the coefficients for that equation (e.g. the numbers that actually control it).

The simple answer is to play it safe, and work that equation so that TC kicks in way before grip is theoretically lost. The Ducati system will let you get closer and closer to the peak of that graph as you turn it 'down', but it'll also have less certainty about it's 'decision' with a greater likelyhood that you could actually break traction with TC on.

A really good TC system will cut the engine power just enough to get you back into the straight line area of the graph, and then get the engine back up to power with the minimum possible knock-on effect. The trouble is, you can't actually measure all the critical inputs, so you have to infer them from other data, which is what makes the calibration hard.
As you can probably tell, these days the ECU and the TC system (and ABS, ASR etc.) are thoroughly linked together. MOre and more ECUs are being replaced by 'VCUs'.

Or, you could do something as simple as compare the wheel speeds and cut the spark if the rear wheel spins faster than the front, but that creates the kind of obtrusive TC system of the past.

Will it be just as horrible as a car TC system when it lets go?

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No it wasn't bloody well posted in SA.

I had TC on my ST24..horrid thing....stutter and jerky when operating, I used to turn it off as a matter of course when I got in the car.
I also have TC on the Pathfinder..but thats linked to the ESP, the ABS, the tea making system and all
the upshot of it is, that unlike the older ST's traction this is very progressive and seems to limit power smoothly rather than chopping it in and out, on the Pathfinder I'm quite impressed with it TBH, not ridden it on a bike but if its like the older systems it'd be a nightmare and if more like the newer stuff then it'd be fine

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Too much is NEVER enough...till it hurts...