Actual Off-Road Testing: climbing & descending (@ Hollister Hill RSVA - 10/23/23)

[GuyV]

So tell me then how to make traction control not "reactionary"?

There are physical limits, and "theoretical limits". Then there are theoretical limits based on false authority.

Lots of theoretical limits fail when they meet physical limits.

First up you would have to tell me about how a motor inverter controls rpm and torque, then we could discuss "how to fix it", because then we are talking about the same limitations.

Take a look at how "tesla" does it:



It's pretty decent for the conditions, but it has slip before the brakes engage, and that is with two wheels worth of perfect grip, not four with alternating levels of grip. You would think that after decades in the field and in the age of OTA they would know how to "fix it" by now?

So this is exactly what a DM setup will do in the CT that only has the ability to use the hydraulic brakes and traction control to control wheel slip. The only way to improve it is for a DM is to have better brakes that can be dosed so fast and accurately that they can simulate a locker....or simply have a locker.

Now a tri motor CT will be able to control the rear two wheels better, because it has a motor each, meaning it can modulate power for each rear, and a QM even better again with the front, but all will have a "delay" between when the wheel traction changes the torque that can applied to the contact patch of the tyre, and that the motor can respond in kind.

You can see how the wheels all produce varying levels of rotation here, where only one or two wheels are propelling it and then breaking traction. There is never a case it has 4 wheels turning at the same time with traction. Each time one wheel breaks traction it forces more load on the next until that breaks and so on. The cascade creates less effective traction, because one wheel is working against the other, instead of all together.



In comparison a locker act like a "tank track" in that all the tracks move at the same speed and the same torque, even if half of the same track is on ice (no friction) and the other half on solid ground (friction).

So if you want to discuss how, then please first define which motor version you would like to discuss the theoretical limits of, and what constraints or tests you wish to perform to recreate a simple diff lock.

I didn't say I was the one who could do it, I said you fail your own quote by insisting no one, and especially Elon can't. If he felt he needed to do it we know he would approach it from first principles, not be limited by how the experts have always done things in the past.

There are a couple of things even I can think to consider. One is that computers are fast enough to calculate projections on the fly rather than be totally reactive. Someone mentioned a thousand times a second, which to the computing power in a new Tesla is incredibly SLOW. Another is that a Cybertruck could read the terrain and evaluate it at that speed. It could be able to see and feel whether it is on mud, sand or whatever, and know what to do about that with AI training to anticipate the optimum application of forces for what will be under each wheel as it moves forward.

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[JBee]

I didn't say I was the one who could do it, I said you fail your own quote by insisting no one, and especially Elon can't. If he felt he needed to do it we know he would approach it from first principles, not be limited by how the experts have always done things in the past.

That is exactly what I meant with false authority.

There is no reason to believe that all things can be changed by Tesla or EM himself.

There is also no reason to believe that they can "change physics".

First principles is "knowing the physics" because that is the underlying principle that forms the foundation to engineer a solution from.

Hence my question how do you get something to not be "reactionary", being simply something that must respond after an event. To which you replied:

There are a couple of things even I can think to consider. One is that computers are fast enough to calculate projections on the fly rather than be totally reactive. Someone mentioned a thousand times a second, which to the computing power in a new Tesla is incredibly SLOW. Another is that a Cybertruck could read the terrain and evaluate it at that speed. It could be able to see and feel whether it is on mud, sand or whatever, and know what to do about that with AI training to anticipate the optimum application of forces for what will be under each wheel as it moves forward.

To which I can agree that is a possibility, but we must be careful here to define our argument within the framework of the conditions and machinery we are using, which is why I described all the motor variations from dual to quad.

We must also identify what surface we are traversing, hence my comment regarding NOT wanting to have traction control, when I am driving on soft sand, simply because I need wheel slip to move sand from the front of the tyre to the rear of it, to make progress.

Once we can define those then we can make some predictions and come up with ways how to solve them.

But I'm afraid simply saying EM/Tesla can do it is not enough. Whereas, Land Rover/Mercedes/BMW/VW/Rivian etc have all been working on this problem for multiple decades, and yet still have a hard time trying to achieve it with brakes alone, which is exactly what the situation is for current Tesla SEXY models and will be for the dual motor CT as well as can be clearly seen in the CT videos so far already.

 

[Crissa]

I didn’t say motors can’t be controlled sub-full rotation. I said that in order to detect one wheel has less traction, it will have to slip. Whereas with a locked axle it won’t. That’s why you can’t simulate a locked axle with independent motors on each wheel.

That’s what JBee and I have been trying to explain.

Well, he (and you by extension) is wrong.

I don't know why you think that. The power consumed by the motor will fluctuate based upon the load. The axle rotation can be controlled and detected at a very fine level. There are a bunch of ways to sense this.

Do they want to do that? I don't know. But I know it can be done.

Heck, I could do it on a robotic animation rig from the 80s. And it just used photocells, dots, and an 8088.

The superiority of a locked axle is irrelevant, since the Cybertruck will not have this capability. Software-based traction control must suffice.

To be perfectly honest, I didn't think they'd put the clutch into the Semi. So I don't know they won't have this feature in the Cybertruck.

I do know, though, that these proclamations that locked axles don't have wheel slip are wrong.

-Crissa

 

[JBee]

Well, he (and you by extension) is wrong.

I don't know why you think that. The power consumed by the motor will fluctuate based upon the load. The axle rotation can be controlled and detected at a very fine level. There are a bunch of ways to sense this.

Do they want to do that? I don't know. But I know it can be done.

Heck, I could do it on a robotic animation rig from the 80s. And it just used photocells, dots, and an 8088.


To be perfectly honest, I didn't think they'd put the clutch into the Semi. So I don't know they won't have this feature in the Cybertruck.

I do know, though, that these proclamations that locked axles don't have wheel slip are wrong.

-Crissa

Ok makes sense now. You missed the point, or didn't read the posts.

It is not about wheel slip, it's about asymmetric traction and unsynchronized propulsion.

In soft sand you WANT the wheels to slip, in a certain way.

Also which one are you talking about, a DM/TM/QM? All three have completely different control methods.

And so....sensing is "NOT" the problem, it is the method of RPM/torque control. It already has ABS sensors and needs to know the position of the rotor to a fraction of a degree in a brushless motor to switch the magnetic fields to run it. Try hooking up a battery to a brushless motor and see how far it spins. It won't.

Remember, with both wheels off the ground and the motor stationary, if you rotate one wheel, the diff will make the other wheel spin in the opposite direction. Therefore with a DM you can only use the brakes to distribute torque with a open diff.

 

[GuyV]

That is exactly what I meant with false authority.

There is no reason to believe that all things can be changed by Tesla or EM himself.

There is also no reason to believe that they can "change physics".

First principles is "knowing the physics" because that is the underlying principle that forms the foundation to engineer a solution from.

Hence my question how do you get something to not be "reactionary", being simply something that must respond after an event. To which you replied:



To which I can agree that is a possibility, but we must be careful here to define our argument within the framework of the conditions and machinery we are using, which is why I described all the motor variations from dual to quad.

We must also identify what surface we are traversing, hence my comment regarding NOT wanting to have traction control, when I am driving on soft sand, simply because I need wheel slip to move sand from the front of the tyre to the rear of it, to make progress.

Once we can define those then we can make some predictions and come up with ways how to solve them.

But I'm afraid simply saying EM/Tesla can do it is not enough. Whereas, Land Rover/Mercedes/BMW/VW/Rivian etc have all been working on this problem for multiple decades, and yet still have a hard time trying to achieve it with brakes alone, which is exactly what the situation is for current Tesla SEXY models and will be for the dual motor CT as well as can be clearly seen in the CT videos so far already.

Progress is an endless stream of problems that can't be solved until they are. Musk stands out as one of the master problem solvers of our time. One thing I am sure of is that with sufficient incentive someone could solve this one. Passive terrain that just sits there is a much simpler challenge than FSD in a world of crazy human drivers.

A much more important issue is whether an off-road vehicle where you just point the direction and it does everything is desirable. How rewarding would it be for drivers without the challenge, control, adventure and excitement?

 

[JBee]

Progress is an endless stream of problems that can't be solved until they are. Musk stands out as one of the master problem solvers of our time. One thing I am sure of is that with sufficient incentive someone could solve this one. Passive terrain that just sits there is a much simpler challenge than FSD in a world of crazy human drivers.

A much more important issue is whether an off-road vehicle where you just point the direction and it does everything is desirable. How rewarding would it be for drivers without the challenge, control, adventure and excitement?

Um I do off-roading for fun.

Getting stuck is just as much a part of it as using a shovel to get unstuck. Many people have other things they do for fun.

I don't want to take away from EM, but he also has accumulated a lot of good engineers that do the mediocre work, so he can concentrate on the bigger things.

In this case I don't think he'll bother much with finding a solution for traction control himself, and just hand this problem to a minion to solve, if it can be solved.

If I were him I'd do the same, and go straight back to SpaceX and work on my "little" Mars project. In the end Tesla is a means to an end for him.

 

[VR Driving]

I have a feeling that a very robust software 4x4 profile will appear when there is a quad motor. But for the launch cars, it's not going to be very good.

 

[GuyV]

Um I do off-roading for fun.

Getting stuck is just as much a part of it as using a shovel to get unstuck. Many people have other things they do for fun.

I don't want to take away from EM, but he also has accumulated a lot of good engineers that do the mediocre work, so he can concentrate on the bigger things.

In this case I don't think he'll bother much with finding a solution for traction control himself, and just hand this problem to a minion to solve, if it can be solved.

If I were him I'd do the same, and go straight back to SpaceX and work on my "little" Mars project. In the end Tesla is a means to an end for him.

Where Elon chooses to focus his attention and effort at any given time is about as unpredictable as things get. You are likely correct about him handing off much of the work of such a project, mostly software I imagine, to someone on his amazing team, which is what it is built for.

I'm not much concerned about Cybertruck off-roading personally, but narrow-thinking self-styled experts who contemptuously declare other folks endeavors impossible always attract my disdain. I see them as road-blocks to progress. I've spent seven decades watching impossible things being accomplished quite regularly.

 

[JBee]

Where Elon chooses to focus his attention and effort at any given time is about as unpredictable as things get. You are likely correct about him handing off much of the work of such a project, mostly software I imagine, to someone on his amazing team, which is what it is built for.

I'm not much concerned about Cybertruck off-roading personally, but narrow-thinking self-styled experts who contemptuously declare other folks endeavors impossible always attract my disdain. I see them as road-blocks to progress. I've spent seven decades watching impossible things being accomplished quite regularly.

You do realise that your argument that "you think" it is possible comes from a very weak position if you can't even describe how the physics works, or that you have experience on the subject matter, let alone an interest in it?

So if you want to shoot down my theories then please do so, but classifying me as a "narrow-thinking self-styled expert" is just an attack on myself, based on your poorly reseached opinion, and does not in any way discredit any of the arguments I brought to the table in detail. As I do on nearly every subject I engage on.

You're new here so I get that you don't know me, but after 4 years of discussing CT on the forum, I think I have learnt a few things or two, that at least gives me the right to question how they work?

Conversely, it would seem that you have no interest in debating the actual subject anyway, and are more interested in declaring yourself superior by association under a false appeal to authority, because you yourself have nothing at all to offer to the arguement.

That level of fanboism is quite concerning to be honest, and not rational at all, where nothing can be questioned anymore "just because".

Get back to me when you have something to discuss, about why and how it works, on the subject of off-roading, and not your wild fantasies about how there's two sets of metaphysics that make the world turn round, because EM is the center of the known universe.

 

[Trekboy]

Everything JBee is saying about mechanical lockers in dead-on. Imagine you're duck hunting and the only "roads" are the 45 degree slopes on the side of a levee. Of course, the downhill side of this levee is not where you want to go, but as you're moving, you feel your rear-end sliding downwards. Give it some gas and you slide even more. With a locking differential, when you give it that life-saving acceleration, your rear-end immediately straightens out and you are no longer sliding to your doom.

 

[GuyV]

You do realise that your argument that "you think" it is possible comes from a very weak position if you can't even describe how the physics works, or that you have experience on the subject matter, let alone an interest in it?

So if you want to shoot down my theories then please do so, but classifying me as a "narrow-thinking self-styled expert" is just an attack on myself, based on your poorly reseached opinion, and does not in any way discredit any of the arguments I brought to the table in detail. As I do on nearly every subject I engage on.

You're new here so I get that you don't know me, but after 4 years of discussing CT on the forum, I think I have learnt a few things or two, that at least gives me the right to question how they work?

Conversely, it would seem that you have no interest in debating the actual subject anyway, and are more interested in declaring yourself superior by association under a false appeal to authority, because you yourself have nothing at all to offer to the arguement.

That level of fanboism is quite concerning to be honest, and not rational at all, where nothing can be questioned anymore "just because".

Get back to me when you have something to discuss, about why and how it works, on the subject of off-roading, and not your wild fantasies about how there's two sets of metaphysics that make the world turn round, because EM is the center of the known universe.

LOL, I haven't declared myself superior, not being one of those who have declared the work of others to be impossible, with limited knowledge and presumption there are no factors they haven't fully considered. It's sad they don't apply their ingenuity to exploring how things might be made to work rather than obstruction. No need to get back to you, naysayers fall by the wayside on their own as technology marches on.

 

[Crissa]

Everything JBee is saying about mechanical lockers in dead-on. Imagine you're duck hunting and the only "roads" are the 45 degree slopes on the side of a levee. Of course, the downhill side of this levee is not where you want to go, but as you're moving, you feel your rear-end sliding downwards. Give it some gas and you slide even more. With a locking differential, when you give it that life-saving acceleration, your rear-end immediately straightens out and you are no longer sliding to your doom.

...Or you could assign all the power to the front axle and drag the rear onto the road.

There's just more than one way to take down a duck.

-Crissa

 

[JBee]

LOL, I haven't declared myself superior, not being one of those who have declared the work of others to be impossible, with limited knowledge and presumption there are no factors they haven't fully considered. It's sad they don't apply their ingenuity to exploring how things might be made to work rather than obstruction. No need to get back to you, naysayers fall by the wayside on their own as technology marches on.

I'm not a naysayer in any way, just a realist asking questions, driven by a curiosity to understand more about the world around me.

Some people just don't have the faculties to discuss or reason why they even care.
Progress is not made by faith alone.

 

[JBee]

...Or you could assign all the power to the front axle and drag the rear onto the road.

There's just more than one way to take down a duck.

-Crissa

Better duck! Logic incoming...

In that case you could just drive a FWD and never have a issue?
You could also pull it out with a winch, drive it backwards?

The argument is irrelevant, because it has nothing to do with the traction of the rear axle, or traction control, or wheel slip on that axle, or how that compares to a locker/no locker situation.

 

[SolarWizard]

I agree with Bill837 ... 'Lockers' are NOT common on most full size trucks and you generally have to find one optioned for a run of the mill LSD which need regular maintenance they never get (so most are roasted after 20-30Kmiles). Also, part time (air or electric) lockers are only useful when doing something that is clearly sketchy to begin with ... how many people are really going to be putting there 9000# $90K rig into such a predicament .... uh.... never mind.

The Humvee has Torsen 'lockers' which are actually a 'part time' traction control differential which is also known as a 'Detroit Locker' ... like the kind I've had on my Jeeps for the last 20+ years. Look on YouT for torsen differential and you can find some really interesting engineering vids about how it works.

Personally, I don't think the CT needs factory lockers. Based on what I've seen my wife's M-Y do on black ice, it works better than my JK or JT dealing with really poor traction (and no I'm not going to take the MY off road to prove anything).

Lockers on half ton trucks are exceedingly common . Go walk around a dealership lot.
They are also now extremely common on midsize trucks. All of them except for the lower cost version on GMs are electric locking.

Neither your JK nor your JT are full time 4x4 and a locker engaged on black ice is a recipe for disaster.


Anybody thats ever been around boat ramps knows the advantage of a selectable locker.

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