Traction feedback device?

[Squiggles]

I apologise if i have insulted anyone, it was not my intention. Though coming from the academic community i tend to expect an explanation when someone tells me im wrong

Give us the current ideas for the device, i.e. an update on the first post
Correct me, but it looks like you're aiming for an ABS-like system (without of course, the data being acted on by the device)... As a question, would you be confident in such a device then controlling braking efforts (technicalities aside)?

[Ecclesnz]

There should be no warning lights and bells until everything is cool some seconds later, at which point the unit should be giving the rider either a sweet smile or an angry glare - they can do the maths on those and figure out which means which.
Steve

Why is it I can picture some pocket rocket rider cocking it up in a corner, high siding it down the road, coming to a stop and then looking at their bike, which has a little grumpy face lit up on the dash saying "Bad Boy, Don't Do That Again".

Personally I wouldn't use something like this. But that's just my personal preference. As it has been explained it would be a "one size fits all" type gizmo. I ride a 22 year old 650 single cylinder cruiser. Where I sit on the bike is very different from those on most other style of bikes (personal choice), this can throw the physics way off as I understand. Cornering for me is very different and on a crotch rocket which will have infinitely more grip.

Perhaps if there were different profiles available as mentioned that would help. However what you are suggesting could in fact be more suited for the track as others have recommended. Simply because most of the bikes are fairly similar in set up and tyres used and such. Less variance in equipment being used, narrower range of results hopefully.

You say this device is targeted towards new riders to help them learn, but you are saying also that the rider will have to self evaluate a lot to compensate for diferent road conditions, tyres, weather etc. Slightly contradictory there.

Now I'm not knocking the device at all, if you want to build it, go build it. As long as you're not doing it in my garage I am not worried. However there has been some good info provided by those you might see as against your project. These people could in fact be some of your best resource if you can get them involved and get everyone communicating.

That's my thoughts anyway.

[BMWST?]

i dont see it as being of much use unless it can give an approximation of the actual traction available,rather than the ultimate traction available.If you have someone pushing hard and the back wheel is actually periodically stopping as the back wheel hops of the ground in braking,how could that be compensated for in comparing front and rear wheel speeds?

[LBD]

Why is it I can picture some pocket rocket rider cocking it up in a corner, high siding it down the road, coming to a stop and then looking at their bike, which has a little grumpy face lit up on the dash saying "Bad Boy, Don't Do That Again".

.

I am more worried about the scenario same as above but a little smiley face saying you only used 62% of available traction on that last corner...

[Ecclesnz]

I am more worried about the scenario same as above but a little smiley face saying you only used 62% of available traction on that last corner...

That's a very valid point.

In all honesty I don't want my bike making any faces at me.

[bogan]

Why is it I can picture some pocket rocket rider cocking it up in a corner, high siding it down the road, coming to a stop and then looking at their bike, which has a little grumpy face lit up on the dash saying "Bad Boy, Don't Do That Again".

Personally I wouldn't use something like this. But that's just my personal preference. As it has been explained it would be a "one size fits all" type gizmo. I ride a 22 year old 650 single cylinder cruiser. Where I sit on the bike is very different from those on most other style of bikes (personal choice), this can throw the physics way off as I understand. Cornering for me is very different and on a crotch rocket which will have infinitely more grip.

Perhaps if there were different profiles available as mentioned that would help. However what you are suggesting could in fact be more suited for the track as others have recommended. Simply because most of the bikes are fairly similar in set up and tyres used and such. Less variance in equipment being used, narrower range of results hopefully.

You say this device is targeted towards new riders to help them learn, but you are saying also that the rider will have to self evaluate a lot to compensate for diferent road conditions, tyres, weather etc. Slightly contradictory there.

Now I'm not knocking the device at all, if you want to build it, go build it. As long as you're not doing it in my garage I am not worried. However there has been some good info provided by those you might see as against your project. These people could in fact be some of your best resource if you can get them involved and get everyone communicating.

That's my thoughts anyway.

the plan is to have different tyre profiles stored in it, which would go a long way to customising it for different bikes, as physics wise (and as far as ideal traction is concerned) a bike is just a weight on two tyres (im probly gonna cop some flak for saying that, but as a simple model and in ideal road conditions its valid).

im a bit doubtful of its use on the track, cos expert track riders push hard enough to make the bike lose traction (just a little bit) then correct for it, so they already know the limits. Also im not even sure if it would be against the rules or not.

Yeh is mainly designed for new or casual riders who dont push to the limit, and have little idea on what the bike is actually capable of, so this would tell them how much mor grip they actually have available. For example, a new rider may go hard on the brakes and do an e-stop in 70m, but only use 50% of the traction available though he would think hes using almost all of it, now add the gizmo and he will use a lot more traction and stop in 55m, now in an emergency stop 15m could be a lot of difference. The flips side to that is of course when conditions are poor, and he thinks he can go harder and asses off, so far all ive come up with is that he has to look at the road surface and take it easy if it looks dubious. Though i have thought of the brake test for traction finding (will update the first post with details of this soon).

[bogan]

Give us the current ideas for the device, i.e. an update on the first post
Correct me, but it looks like you're aiming for an ABS-like system (without of course, the data being acted on by the device)... As a question, would you be confident in such a device then controlling braking efforts (technicalities aside)?

have updated the first post, and qouted here

Ive been toying with the idea of an electronic training device to help riders learn the limits by displaying the amount of traction being used in any given situation.

What it does is takes sensor data from the bike and works out all the net forces acting on the bike, it also calculates the weight distribution on each wheel. Using the cornering g-force, acceleration/decelleration forces, weight distributions, crest/dip forces, etc, it calculates the percentage of traction currently being used for each wheel and displays the highest one.

The value it uses for this maximum amount of traction is calculated using a number of constants which are programmed into the system, these are programed for each bike it is on. They include weight, rider and bike, tyre profile and friction co-efficient (can be found with two sets of scales).

What it cant do is sense the road conditions, potholes gravel, oil, wet, camber, the rider is responsible to back off if the road is slippery.

The display is currently under review, an LED bargraph is used in the current prototype, which shows the percentage scale in realtime, and records the max percentage used round a corner which it then displays after the corner for rider review. Other suggestions have been to use a beeper, beeps faster the more traction you use, and also to do datalogging in conjunction with GPS data.

The working idea of it is that it provides riders with a measure of the upper limit of traction they have available, (kind of like an intense track day would do, only without the practical experience obviously). For example, if a rider did a quick stop in 70m thinking he was using most of the traction, then put this gismo on the bike and found he could use a lot more, when he next did an emergency stop he could stop in 55m, thus being safer. There would be similar benifits while cornering and accelerating. The bit where this doesnt work is when the road conditions are poor, if he tried getting close to the gizmos idea of traction he would lock up, so the rider is still responsible for noticing porr road conditions and adjusting speeds and stopping force.

There is also the possiblity of a brak test to find the available traction, this would mean the rider rides along and locks up the rear wheel, the gizmo would then examine the deceleration needed and work out the force required to lock it up, and thus calculate the current road friction co-efficient, but again this would still not solve the problem of potholes, gravel spots, and oil slicks, though it would take care of different road quality and wet roads.

Your thoughts on this idea?

I would be confident in the system controlling the maximum amount of throttle applied (to stop skids, wheelstands, and high/low sides). However at this point im unsure whether it would be wise to control the brakes, as the stakes for a cock-up are a lot higher. Used in conjunction with a standard wheel speed differential abs system could improve braking though, as the ABS could be "warned" to look out for a lock up at a certain brake force, thus be quicker to respond to said lock up.

[2wheeldrifter]

Think it would easier just have a whole motogp pitcrew with at all times when riding.....

But really what do these guys test when testing... do they have one of these?????

[CookMySock]

If you have someone pushing hard and the back wheel is actually periodically stopping as the back wheel hops of the ground in braking,how could that be compensated for in comparing front and rear wheel speeds?

If you sampled and graphed this particular situation, and then did all sorts of other mathematics on it, it could be examined and classified as risky or not. Red light or green light.

the plan is to have different tyre profiles stored in it, which would go a long way to customising it for different bikes, as physics wise (and as far as ideal traction is concerned) a bike is just a weight on two tyres (im probly gonna cop some flak for saying that, but as a simple model and in ideal road conditions its valid).

Perhaps you would be better served to ignore that, and just watch for situations that you can diagnose as risky, for example, tail slides past point(x,y,z), nose slides past point(x,y,z) && dt/dv(tip in velocity) exceeds n. Alarm for these conditions, and then bump the systems tolerance up ever so slightly, so next time it doesn't alarm so readily, (ie it happened this time and we're still upright!)

It's a bit like checking fingerprints for known criminals.

im a bit doubtful of its use on the track, cos expert track riders push hard enough to make the bike lose traction (just a little bit) then correct for it, so they already know the limits.

Yes but that is exactly what DSP can analyze for you. Was that slide close to the limit or not?

I think for braking, you will be hard pressed to beat ABS. It's pretty clear when too much front brake was "too much" and really you need ABS to rectify it pronto. A red light on the dash is too late. I think many riders are more concerned with cornering rather than braking. Maybe it could scream at you if you were too hard on the brakes.

I would be confident in the system controlling the maximum amount of throttle applied (to stop skids, wheelstands, and high/low sides).

I don't think you should use it to wrap the rider in cotton wool. I think you you should use it to inform the rider if what they are doing is pushing the boundaries. A bike that won't do as it's asked because of some kid-glove electronics will just be irritating. Conversely, a bike that talks to you and either reassures or warns you, helps you grow as a rider.

However at this point im unsure whether it would be wise to control the brakes, as the stakes for a cock-up are a lot higher. Used in conjunction with a standard wheel speed differential abs system could improve braking though, as the ABS could be "warned" to look out for a lock up at a certain brake force, thus be quicker to respond to said lock up.

You could operate the system in tandem with ABS, independent of it or otherwise. It would not permit the rider to explore that territory with his brakes - is this what you want? Is this what he wants? Do you want to help the rider grow as a rider, or prevent it?

Steve

[Hoon]

There is also the possiblity of a brak test to find the available traction, this would mean the rider rides along and locks up the rear wheel, the gizmo would then examine the deceleration needed and work out the force required to lock it up, and thus calculate the current road friction co-efficient

Nice. One of the questions I had was how would you know how much grip the tyre has to start off with in the first place so this kind of answers that. The contact patch (and maximum available grip) also changes depending on how much weight/force is applied so if your model is clever enough you could use that sample and extrapolate the data to calculate the contact patch size across all forces and lean angles.

Telemetry mode in Forza Motorsport 2 is a great example of how grip changes and can be calculated and displayed realtime in a perfect world.

Forza Motorsport 2 telemetry(fast forward to 0:26s)

The green circle grows/shrinks as grip changes due to weight. The force acting on it is the line in the centre, when the line goes outside the circle then traction is exceeded.

[ManDownUnder]

It's a great idea but I can't see how it could be done...

That said - I don't understand a lot of stuff - doesn't mean it's going to fail.

I'm a fan of the simplest solution probably being the best... in this case training wheels or a stunt cage on a bike in a carpark.

[bogan]

If you sampled and graphed this particular situation, and then did all sorts of other mathematics on it, it could be examined and classified as risky or not. Red light or green light.

Perhaps you would be better served to ignore that, and just watch for situations that you can diagnose as risky, for example, tail slides past point(x,y,z), nose slides past point(x,y,z) && dt/dv(tip in velocity) exceeds n. Alarm for these conditions, and then bump the systems tolerance up ever so slightly, so next time it doesn't alarm so readily, (ie it happened this time and we're still upright!)

It's a bit like checking fingerprints for known criminals.

Yes but that is exactly what DSP can analyze for you. Was that slide close to the limit or not?

I think for braking, you will be hard pressed to beat ABS. It's pretty clear when too much front brake was "too much" and really you need ABS to rectify it pronto. A red light on the dash is too late. I think many riders are more concerned with cornering rather than braking. Maybe it could scream at you if you were too hard on the brakes.

I don't think you should use it to wrap the rider in cotton wool. I think you you should use it to inform the rider if what they are doing is pushing the boundaries. A bike that won't do as it's asked because of some kid-glove electronics will just be irritating. Conversely, a bike that talks to you and either reassures or warns you, helps you grow as a rider.

You could operate the system in tandem with ABS, independent of it or otherwise. It would not permit the rider to explore that territory with his brakes - is this what you want? Is this what he wants? Do you want to help the rider grow as a rider, or prevent it?

Steve

rear wheel hop could be easily identified, whether its something to worry about is another question, probably not in most cases, as long as its still contacting the ground periodically and the front has plenty of grip left i would say the bike is still stable.

hmmm yes it could also calculate how risky a slide was, and learn grip/handlng factors from that. The original idea was to prevent the rider getting that far, but i see no reaosn why it cant do both.

Yeh i definetely agree it wont beat abs, but how many bikes come with abs these days, it is getting more and more common in newer bikes, but older ones dont have it and these are what a lot of learners start on.

I wouldnt say controlling the throttle is wrapping the rider in cotton wool, as the system would only limit the throttle in order to prevent a crash, not in any other situation. And of course if youre a good enuf rider not to want it interfereing at all, it would be available without the cotton wool option.

Personally i dont think abs should be activated unless the wheel is actually skidding, the system could warn the abs that it is probly gonna skid soon so look for any hint of skidding, but im not sure whether that would be any benifit over the current abs systems, ive never rode one but i hear they are very fast acting.

Thanks Hoon, that forza 2 example is exactly what im trying to do, but for bikes.

[Malcolm]

I don't want to come in here like a jackass and tell you this isn't going to work...but I really don't think it's going to work.

I'm not sure if you've ever seen force & moment data for tyres (such as that generated from the Calspan TIRF facility), but each tyre varies hugely in the way it behaves. Even if you made some broad characterisations of tyres based on construction type, dimensions, inflation pressure, temperature, age etc, you still wouldn't be able to work out the effective coefficient of friction due to variations in the road surface. The most effective way I could see would be to use a slip angle sensor front and rear (look them up, currently these things cost so much that owning them is out of the range of all but the highest budget racing teams, although some experiments have been done on using optical sensors from mice). This is still not a lot of good if you don't know the slip angle limits of the tyre.

On another note, all the calculations that you're talking about, and logging from all the required sensors etc, is going to require immense computational power/speed - have you ever priced up a data-logging system such as a motec ADL2? You're looking at around $6k for a basic system before buying accelerometers or the other sensors it sounds like you'll need - and that doesn't even include the price of a processor to perform the VERY complex calculations you'll be needing to do hundreds of times a second.

It's a nice idea, I just think it's really financially impractical based on current technologies

[bogan]

I don't want to come in here like a jackass and tell you this isn't going to work...but I really don't think it's going to work.

I'm not sure if you've ever seen force & moment data for tyres (such as that generated from the Calspan TIRF facility), but each tyre varies hugely in the way it behaves. Even if you made some broad characterisations of tyres based on construction type, dimensions, inflation pressure, temperature, age etc, you still wouldn't be able to work out the effective coefficient of friction due to variations in the road surface. The most effective way I could see would be to use a slip angle sensor front and rear (look them up, currently these things cost so much that owning them is out of the range of all but the highest budget racing teams, although some experiments have been done on using optical sensors from mice). This is still not a lot of good if you don't know the slip angle limits of the tyre.

On another note, all the calculations that you're talking about, and logging from all the required sensors etc, is going to require immense computational power/speed - have you ever priced up a data-logging system such as a motec ADL2? You're looking at around $6k for a basic system before buying accelerometers or the other sensors it sounds like you'll need - and that doesn't even include the price of a processor to perform the VERY complex calculations you'll be needing to do hundreds of times a second.

It's a nice idea, I just think it's really financially impractical based on current technologies

Just had a google for the Calspan TIRF data but cant find any, would be a useful to look at by the sounds of it, anyone got a link? All the variations in the tyre behavious was why i wasnt planning on using it for racing, by measuring slips etc it may be able to learn rnough to be effective, but thats still not where i plan to focus. The basci theory was if a human can sense how fast it is possible to go round corners (without knowing all the finer points of tyre wall flex, and tyre temperature etc) then a computer system should be able to do it as well. Its not sposed to know the exact limits to 0.01%, just to give newbies an idea of how much traction is still available to them.

The computing stuff can easily be done by a single board computer, the new intel atom will be quite sufficient, with the increase in computer speed you dont have to buy the hardware specially made for the job anymore, generally any pc will do!

[Malcolm]

noone really publishes tyre data, it's extremely expensive to create - there are some generalised plots in vehicle dynamics books (such as Race Car Vehicle Dynamics by Milliken and Milliken) - I've never seen anything on motorbike tyres to know how they behave.

I think you're underestimating just how awesome humans are in terms of sensing stuff. The human is an extremely complex system of accelerometers, gyros, force and pressure transducers, optical and audio sensors all interlinked with powerful and precise actuators that create complex feedback based on actions.

I'm going to step back on the computing power side of it, because it's not an area I know a lot about. I am however currently playing with lap simulation software and have found it to process something like 10 times faster than real time - but that's without having to take readings from analogue sensors hundreds of times a second.

I was going to post a list of all the assumptions that you're going to have to make in order to create a model. I can't decide if it's a cunty thing to do, so I'm just going to start with a few.

So, you want to estimate coefficient of friction of a tyre based on a brake test, you'll either need to know or assume:
Mass of bike
Mass of rider
Centre of gravity position of bike
Centre of gravity position of rider (and assume he doesn't move.....)
Friction coefficient load sensitivity of tyres (and assume a curve shape for it, because it's not even close to linear)
Ellipse ratio of tyres - that is the ratio of max lateral force to max longitudinal force (this and the load sensitivity will give you the most crude tyre model that would allow you to estimate available force within 5%)
Wheel rate of front and rear suspension (to allow you to estimate forces in the highly dynamic scenario of braking), this could be calculated if you have suspension displacement pots
Damping ratios, front and rear, along with the force/velocity curves (I don't know how you'd get these without a shock dyno)
The values of anti-dive/lift that the suspension has designed into it

So, with the above you could potentially work out a coefficient of friction correction factor for the front tyre for the surface the test is performed on. We still have no idea about the rear tyre so we'll have to guess that I suppose. Let's try and apply it to going around a corner

First we'll need to correct the coefficient of friction for temperature, if the rider did the brake test on colder tyres the grip levels will have changed. You could assume it's negligible or characterise a temp vs friction curve and measure temp with an IR tyre pyrometer (solidstateracing.com has them for around $300NZ)
Next, we need to know what NORMAL load is on the tyre. We're going to have to assume the rider hasn't changed his CoG since the brake test, then we can use an accelerometer to work out loads. This gives us an estimate of lateral/longtudinal force that the tyre can currently supply
Then, we need to know how much longitudinal force the tyres are generating. This is going to be hard - we can assume a split based on mass distribution for lateral, but not for longitudinal. We can use an accelerometer to work out the total longtidunal acceleration, but unless it's a positive value (accelerating rather than braking), we can't easily tell which wheel is causing the deceleration. This is where stuff gets tricky - we could look at brake pressures, but that wont help is the bike is engine braking, or getting some drive from the idle. Not sure how you'll solve this one, but it needs to be solved because you can't ignore the effects of combined braking/cornering on the force a tyre can produce.

Let's say you've got the above sorted - it's all very nice but we've still got some big assumptions to cover.
Road camber - We could ignore this, but I think that would be a bad idea because I'll bet off-camber corners are to blame for numerous crashes. We can get road camber using 2 optical proximity sensors on the bottom of the bike, spaced a known distance apart, provided we also know the lean angle of the bike relative to horizontal.
Surface irregularities - you've stated earlier that suspension is supposed to maintain constant force on the tyres, and therefore you can neglect this. Hmmm. When you hit a bump there is an increase in normal force on the tyre - this force accelerates the unsprung mass and compresses springs and pushes fluid around in the dampers. It also accelerates the sprung mass by some amount. The amount the force increases by is not particularly easy to work out, infact it's damn hard. The amount it decreases by on the other side of the bump, as the wheel is returning to normal position - that's the real problem, and that's where you're going to lose grip. The force variation is dependant on: sprung mass, unsprung mass, spring rates (and motion ratio), damping force/velocity curves, tyre spring rate, tyre damping, and any hysterisys in the system due to friction (and probably more stuff I don't know). To give you an idea of the magnitude of these forces, you'll probably see a peak force on a good bump that's around 2 to 3 times greater than the force riding over smooth surfaces

There's more assumptions that are going to introduce error into your system, but I'm not here to berate you.

Now, as a final note -have you been tallying up the costs of the sensors listed above, and the time to install and calibrate them correctly onto the bike?