Traction Circle vs Seperate Forces

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36 comments, last by bmarci 7 years, 11 months ago

I am still confused.

I just wanna know - what is so far the best found method to calculate slip and friction force. This would help me.

I think we all want to know this (and none of us know) :)

Uh... That's for sure. However, I even don't know a working version... :|

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Now I see for sure that my problem is the slip definition. How to make it work good at low speeds without ruining the realism? Is there a good way?

>> I just wanna know - what is so far the best found method to calculate slip and friction force. This would help me.

i remember a problem in 2nd year physics like this. its about 2/3rds of the way though the book Physics, by Tipler.

all this stuff can be calculated. its appears as though you simply haven't learned enough physics and mechanics to do it correctly yet. which is of course, easily corrected with a little RTFM.

go to your local chevy dealer, go to the parts department, and buy a copy of the "chevrolet power manual". the last chapter is vehicle dynamics, with roll centers, ackerman angles, the whole nine yards. its the kind of info real race teams use.

Norm Barrows

Rockland Software Productions

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all this stuff can be calculated. its appears as though you simply haven't learned enough physics and mechanics to do it correctly yet. which is of course, easily corrected with a little RTFM.

Where is TFM? :D

go to your local chevy dealer, go to the parts department, and buy a copy of the "chevrolet power manual". the last chapter is vehicle dynamics, with roll centers, ackerman angles, the whole nine yards. its the kind of info real race teams use.

I live in deep countryside. AFAIK, closest Chevrolet dealer is around 200 km away in the capital of Latvia. 'buy' word is scaring me. I am 15 years old - where can I get money that I can use for non-school releated purposes(maybe you can get some work for me?). By the way - most of the physics is almost clear for me here. I've got only 3 problems at the monent - slip definitions, engine -> clutch -> gearbox -> differential -> wheels angular velocity and torque relations and camber angle change depending on spring stretching.

The prior problem at the moment is the 'slip definitions'.

I just came up with something that's being called 'slip speed'. It's another definition of slip. I just plugged it in the Pacejka formula instead of slip ratio and(at least at low speeds) it works incredibly well.

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The equation is:

Vslip=?r?Vlongitudal

? = wheel angular velocity

r = wheel radius

Vlongitudal = wheel longitudal tangential speed

OK! I decided to compare it at different cases and compiled a table:

[attachment=31866:CompilationTable.png]

It seems that the slip speed never ever becomes bigger than slip ratio(note that the pacejka takes in % slip ratio). This may mean that it works in all cases?

I must now look for 'lateral slip speed' :)

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And here I do a little test with constant torque applied for all the wheels. Works amazingly well:)

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The method isn't as good as I though. It's working well at freeroll and returns great resistance torque values. However, it doesn't work well for the longitudal friction in situation when I apply torque to it. Help would be appreciated.

OK! What if I use slip speed for reaction torque and slip ratio for the force applied? May that be a real solution or is it still fake?

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It's really not doing well.

I just got an info from one person about thing called 'relaxation length' which might be a good solution for tire-friction problems. However, I can't find exact explanatory on how it works. Maybe somebody can help? Thanks!:)

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