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Wrong calculation of rolling resistance
07-28-2011, 06:14 PM,
#1
Wrong calculation of rolling resistance
I have noticed two problems with GetRollingResistance:

Firstly, calculation in cartyre.cpp does not include normal force Fz.
Rolling resistance is approximated by
Code:
Fr = - f * Fz
where Fz is normal force in Newtons and f is
Code:
f = fo + KV^2
where V is vehicle velocity in m/s.

GetRollingResistance function does not include Fz which makes it off by a factor of 4000-5000. E.g. with "rolling-resistance = 1.3e-2, 6.5e-6" at standstill the resistance returns 0.013 N which is 1 milligram * force. Multiplying it by 4500N we get more realistic 60N or 6 kg*f per tyre.

Secondly, it is called from cardynamics.cpp with a wrong argument:
Code:
btScalar rolling_resistance = - tire[i].GetRollingResistance(wheel[i].GetAngularVelocity(), ...);

this should be longitudinal velocity, not angular.

Thanks
Leo
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Messages In This Thread
Wrong calculation of rolling resistance - by LBodnar - 07-28-2011, 06:14 PM
[No subject] - by NaN - 07-28-2011, 06:30 PM
[No subject] - by LBodnar - 07-28-2011, 06:45 PM
[No subject] - by NaN - 07-29-2011, 04:45 AM
[No subject] - by NaN - 07-29-2011, 11:59 AM
[No subject] - by LBodnar - 07-29-2011, 12:25 PM
[No subject] - by NaN - 07-29-2011, 12:56 PM
[No subject] - by LBodnar - 07-29-2011, 01:14 PM
[No subject] - by NaN - 07-29-2011, 01:20 PM
[No subject] - by LBodnar - 07-29-2011, 02:21 PM
[No subject] - by NaN - 07-29-2011, 03:13 PM
[No subject] - by LBodnar - 07-29-2011, 03:26 PM
[No subject] - by NaN - 07-29-2011, 03:51 PM
[No subject] - by NaN - 07-29-2011, 03:58 PM
[No subject] - by LBodnar - 07-29-2011, 04:00 PM
[No subject] - by NaN - 07-29-2011, 04:07 PM
[No subject] - by LBodnar - 07-29-2011, 04:07 PM
[No subject] - by LBodnar - 07-29-2011, 04:10 PM
[No subject] - by NaN - 07-29-2011, 04:11 PM
[No subject] - by NaN - 07-29-2011, 04:15 PM
[No subject] - by NaN - 07-29-2011, 04:19 PM
[No subject] - by LBodnar - 07-29-2011, 04:28 PM
[No subject] - by NaN - 07-29-2011, 04:33 PM
[No subject] - by LBodnar - 07-29-2011, 04:46 PM
[No subject] - by NaN - 07-29-2011, 05:07 PM
[No subject] - by LBodnar - 07-29-2011, 05:41 PM
[No subject] - by NaN - 07-29-2011, 05:49 PM
[No subject] - by LBodnar - 07-29-2011, 05:54 PM
[No subject] - by joevenzon_phpbb2_import3 - 07-29-2011, 07:46 PM
[No subject] - by LBodnar - 07-30-2011, 04:03 AM
[No subject] - by NaN - 07-30-2011, 05:49 AM
[No subject] - by LBodnar - 07-30-2011, 06:27 AM
[No subject] - by NaN - 07-30-2011, 06:35 AM
[No subject] - by LBodnar - 07-30-2011, 07:22 AM
[No subject] - by NaN - 07-30-2011, 07:44 AM
[No subject] - by LBodnar - 07-30-2011, 09:15 AM

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