rec.autos.simulators

I've got the basics of my engine in and every thing seems happy except
(and this is a big except) if steering inputs are applied while the
car is stopped, it rotates in place (more or less around its own
center).

Once the car has some speed, this behaviour seems to go away (but
steering inputs seem VERY sluggish, especially at high speeds where it
is almost impossible to turn...could these problems be related)?

I realise that this is pretty vague, but can anyone point me in the
right direction?

Aaron

Without knowing what forces you have simulated it would be
hard to suggest where to look.

If you have a kinematic simulation (modeling the trajectory)
then the vehicle should "turn" slower at higher speeds,
if by turning you mean the rate of rotation of the velocity
assuming you have implemented limits on lateral acceleration.
(With the same lateral acceleration, the turning rate will
be 2 times lower when twice as fast.)
- Matt

On Tue, 20 Aug 2002 04:08:53 GMT, "Matthew V. Jessick"

And how, indeed.
If you're using forces at all check why it's generating lateral
forces. You might use slip angles, which become non-zero when you
rotate the steering wheel. In that case, you need to keep the
slipangle low at low speeds, or do some other low-speed trick (there
are lots and that is a long discussion, but search RAS on 'SAE 950311'
on you'll get into the game).

Ruud van Gaal
Free car sim: http://www.racer.nl/
Pencil art  : http://www.marketgraph.nl/gallery/

That looks like the problem.  I have some low speed checking to make
sure that the slip angle == 0 at very low speeds, but it seems that I'm
still getting too much "shaking" in my model when I'm sitting still, so
the low speed check always fails.  I guess I'll have to try and figure
out where the error is coming from and get the car calmed down (at which
point the low speed checking should kick in and prevent rotation).

To confirm that this was the problem, I bumped up the threshold of what
was considered a low speed (and therefore slip angle should be 0) and
the rotating in place went away.

Aaron

: If you're using forces at all check why it's generating lateral
: forces. You might use slip angles, which become non-zero when you
: rotate the steering wheel. In that case, you need to keep the
: slipangle low at low speeds, or do some other low-speed trick (there
: are lots and that is a long discussion, but search RAS on 'SAE 950311'
: on you'll get into the game).