happens). I was thinking that the suspension x,y,z were dynamic
variables influenced by the wheels (so the wheels were passing their
effects back to the body through the suspension). Instead, the
suspension position is a static variable used purely as a modifier for
the dynamic tire forces. Should have been obvious in retrospect!
Thanks!
Aaron
: On Sun, 14 Jul 2002 22:34:08 GMT, Aaron Liebling
: (emailed separately)
: Hi Aaron,
: Glad to see the source is actually of help. Might be cluttering at
: times. :)
:> In RBody::ApplyRotations, you do the following:
:>
:> for(i=0;i<car->GetWheels();i++) {
:> w=car->GetWheel(i);
:> forceCar=*w->GetForceBodyCC();
:>
:> torque.y+=forceCar.x*w->GetSuspension()->GetZ();
:> torque.y+=-forceCar.z*w->GetSuspension()->GetX();
:> ...
:> }
:>
:> I must be missing something, but this seems to imply that you're
:> going to apply a torque on the y axis of the body based on forward
:> or lateral movement.
: Not movement, but force. As a lateral force builds up at a tire, it is
: applied to the body as a rotational torque. As T=F*r, the above code
: converts the lateral force (forceCar.x) as a torque around the body's
: CG. The arm ('r') is taken as the suspension Z location.
: Same for longitudinal forces (Fx in Pacejka/SAE, forceCar.z in Racer,
: which uses the OpenGL axis system). This time the arm is the
: horizontal position:
: forceCar.z
: |
: V
: O-----O
: | |
: | |
: | x | x=CG
: | |
: | |
: O-----O
: <-->
: susp.x
:> Looking through your code, though, I could find no where that the
:> suspension positions are set (used here via the GetZ() and GetX()).
: It probably is in rsusp.cpp: RSuspension::Load().
:> I
:> assume this suspension position is supposed to reflect rotation of the
:> attached wheel, or is the effect of the wheels turning accounted in to
:> the body's torque elsewhere?
: It is just the wheel position; no wheel turning itself. Wheel turning
: is only used in determining slip angle. If the wheel is turned because
: of the steering wheel, lateral (Fy) forces will be generated, which
: are used in the above code in the same way. After all, the forces are
: transmitted to the body through the suspension; doesn't matter if the
: wheel is being turned or not.
: Cheers,
: Ruud van Gaal
: Free car sim: http://www.racesimcentral.net/
: Pencil art : http://www.racesimcentral.net/
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