[ODE] Implementing new friction models

[Ed Jones]

Have you looked into using the force dependent slip settings of the 
contact joint?
 From the ODE docs;

"This is useful for modeling some situations, in particular tires. For 
example consider a car at rest on a road. Pushing the car in its 
direction of travel will cause it to start moving (i.e. the tires will 
start rolling). Pushing the car in the perpendicular direction will have 
no effect, as the tires do not roll in that direction. However - if the 
car is moving at a velocity /v/, applying a force /f/ in the 
perpendicular direction will cause the tires to slip on the road with a 
velocity proportional to /f/*/v/ (Yes, this really happens).

To model this in ODE set the tire-road contact parameters as follows: 
set friction direction 1 in the direction that the tire is rolling in, 
and set the FDS slip coefficient in friction direction 2 to /k/*/v/, 
where /v/ is the tire rolling velocity and /k/ is a tire parameter that 
you can chose based on experimentation."

I've had reasonable results from this in the past.

Cheers,
Ed.


Amund Børsand wrote:

>I assure you that if I ever get to the bottom of this the way I hope
>(i.e. get Pajecka working and implemented with the current ODE collision
>system) I will surely submit the code for inclusion in ODE cvs. It's the
>least I can do to say thanks... (Unless the Pajecka formula itself is
>under some kind of copyright restriction, I've found frighteningly
>little info on it on the net)
>
>
>"Megan Fox" <shalinor at circustent.us> skreiv:
>
>  
>
>>If you get any off-list replies on this, I would appreciate a CC on anything
>>particularly useful.  I'm a little unhappy with the default friction model
>>(well, almost entire lack of friction model) as well, and I'd really rather
>>stick the code in a modified ODE than attempting to strap it on externally.
>>
>>Thanks,
>>
>>-Megan Fox
>>
>>    
>>
>>>Is there an easy way to do it, into ODE's internal structure? I'm
>>>thinking about Pajecka and the likes, for tyre friction. My best idea so
>>>far has been to set normal friction coefficients to 0 and let the ODE
>>>collision system/contact joints to carry the weight if the object, and
>>>then calculating what forces are pushing in different direction and
>>>applying these back to the objects in question. But this will get very
>>>dirty when my tires hit multiple objects at the same time, which they
>>>will, as I am trying to make an offroad biased vehicle simulator.
>>>
>>>How are the current friction models implemented, how do they "know" what
>>>angles the surfaces in question have and so on? I guess I should look
>>>into the ODE sources myself, could you point me in the right
>>>direction/right source file? I have very little knowledge of the ODE
>>>internals so far.
>>>
>>>--
>>>Amund Børsand <amund £ offroad . no>
>>>
>>>
>>>_______________________________________________
>>>ODE mailing list
>>>ODE at q12.org
>>>http://q12.org/mailman/listinfo/ode
>>>
>>>
>>>      
>>>
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