Re: [Slipstream-devel] Rider upper body roll and translation

[Dimitris Papavasiliou]

Hello,

> I have just had a decent play on today's CVS, and with the suggested
> values there is still significant head-shaking going on. Mostly it is a
> wheelie/gear change coming out of a bend that turns into a ridiculous
> head-shake down a straight. I've got my rider yaw as 70nm/rad and
> 7nms/rad. I'm thinking I'll need to turn up that damping.

Yes that's a situation not addressed by these control systems.  I
think the problem is entirely gearbox-related unless you actually
wheelie while turning.  If you simply unload the front then the
systems seem to be effective at avoiding large sideslip angles.  You
can try that out by disabling both sytems (setting a negative value
for load thresholds and a very high value for sideslip thresholds) and
trying to stand the bike up under full throttle when exiiting a turn.
 Without the sideslip angle limiter I get very nasty headshakes that
way.

I would generally say that the damping/stiffness coefficients for the
rider should be considered ok.  The reason is that the bike seems to
be stable provided you don't allow very high sidesip angles to
develop.  If you do allow this then it will tankslap but it would in
real life also.  Of course if there's no other way and the game is
rendered unplayable we'll have to resort to fixing it via the driver
(and in that case it helps more to set the lateral translation
stiffness of the driver body ridiculously high, say at 100kn/m) but
perhaps it's worth exploring other areas of tuning.

One particular area I've been wanting to check out is the supension
setup.  As you can see in the diagrams in the previous email when you
shift up the acceleration is momentarily increased as an impulse is
transfered from the crankshaft to the rear wheel loading it and
unloading the front.  This is bad enough (and can perhaps be mitigated
by better modeling of the gearbox) but it's probably made worse by the
fact that it doesn't get damped enough by the suspension thus leading
to a short oscillation of fore-aft load.  Perhaps better
compression/rebound damping values can improve the situation.  Let me
know if you have any luck.

> Attached is setup, session recording and a screenshot of the thing going
> down again as I quit. I was on a really good run of it working properly,
> too.
> Resolution has been fine since.
> This is a real long recording, with a huge off track excursion, so it'll
> be a good test of the replay technology.

I'm having trouble compiling Techne here at home so I can't test these
right now.  I'll give them a go when I return.

Dimitris

> On Sat, 2011-12-24 at 22:09 +0200, Dimitris Papavasiliou wrote:
>> Hello,
>>
>> > I hope that you mean that the peak lateral force is at 0.025, or else
>> > your steering torque cut off will be occurring before peak lateral
>> > traction is reached.
>>
>> Uh yes, missed a zero there again.  The correct number is indeed 0.025.
>>
>> Dimitris
>