[simpits-tech] Motion cues - a start

Fri, 12 Apr 2002 11:36:20 -0500

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Off and on, I brainstorm the requirements for a motion based sim, and will
now perform a brain dump:

Assuming a simple platform with only pitch and roll capabilities and also
assuming a simple aircraft. By simple I mean, not rolling past +/-60
degrees, not pitching past +/- 45 degrees and not equiped with function
after burners (or JATO bottles :-). I realize that might cause all the
military guys to stop reading, but I'm thinking baby steps here.

As mentioned, having a pit follow the joystick is inaccurate. However, it
should possible to approximate the motion.

To start, a really simple algorithm could match the roll of the pit to the
Ball on the TC. The ball already determines the left / right direction of
the force vector on the aircraft.

The next stop would be to add the pitch information. Baring any other type
of acceleration, the pitch of the aircraft should match the front / back
component of the force vector.

Now throw in acceleration / deceleration. Most sim software should be able
to generate ground speed. A simple algorithm that compares the ground speed
every fraction of a second should be able to compute the linear
acceleration. Add the gravity vector and via some basic trig you have the
angle the pit needs to pitched to replicate the front / back component of
the force vector +/- the aircraft's current pitch.

Once again, this should be sufficient for civilian sims not lighting up the
after burners...

Once these are incorporated, it should be a matter of trial and error to
produce a 'wash out' algorithm that brings the pit back to centre ready for
the next 'cue'.

Adding roll cues probably is where things start getting messy, and without
heave capabilities on your sim, turbulance and rate of climb fluctuations
are probably out of the question.

Another thought regarding adding heaving capabilities (to the sim, not your
gut) to simulate some turbulance, ground roll vibrations and landing
contact, would be to take the pitch/roll only pit and mount it to another
frame via those automotive air ride shocks someone mentioned a few days ago.

I agree that we'd all love to get our hands on a 6 cylindar fullmotion
platform and download the motion driver for MSCFS, F4, etc. from Boeing,
etc., but that's not likely to happen. So why not start simple and build a
driver that generate the various force vectors that occur in the plane, and
let other build drivers that take that information and move their pit?

Just some thoughts...
Alex

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<TITLE>Motion cues - a start</TITLE>
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<P><FONT SIZE=3D2>Off and on, I brainstorm the requirements for a =
motion based sim, and will now perform a brain dump:</FONT>
</P>

Assuming a simple platform with only pitch and roll =
capabilities and also assuming a simple aircraft. By simple I mean, not =
rolling past +/-60 degrees, not pitching past +/- 45 degrees and not =
equiped with function after burners (or JATO bottles :-). I realize =
that might cause all the military guys to stop reading, but I'm =
thinking baby steps here.

As mentioned, having a pit follow the joystick is =
inaccurate. However, it should possible to approximate the =
motion.

To start, a really simple algorithm could match the =
roll of the pit to the Ball on the TC. The ball already determines the =
left / right direction of the force vector on the aircraft.

The next stop would be to add the pitch information. =
Baring any other type of acceleration, the pitch of the aircraft should =
match the front / back component of the force vector.

Now throw in acceleration / deceleration. Most sim =
software should be able to generate ground speed. A simple algorithm =
that compares the ground speed every fraction of a second should be =
able to compute the linear acceleration. Add the gravity vector and via =
some basic trig you have the angle the pit needs to pitched to =
replicate the front / back component of the force vector +/- the =
aircraft's current pitch.

<P><FONT SIZE=3D2>Once again, this should be sufficient for civilian =
sims not lighting up the after burners...</FONT>
</P>

<P><FONT SIZE=3D2>Once these are incorporated, it should be a matter of =
trial and error to produce a 'wash out' algorithm that brings the pit =
back to centre ready for the next 'cue'.</FONT></P>

<P><FONT SIZE=3D2>Adding roll cues probably is where things start =
getting messy, and without heave capabilities on your sim, turbulance =
and rate of climb fluctuations are probably out of the =
question.</FONT></P>

<P><FONT SIZE=3D2>Another thought regarding adding heaving capabilities =
(to the sim, not your gut) to simulate some turbulance, ground roll =
vibrations and landing contact, would be to take the pitch/roll only =
pit and mount it to another frame via those automotive air ride shocks =
someone mentioned a few days ago.</FONT></P>

I agree that we'd all love to get our hands on a 6 =
cylindar fullmotion platform and download the motion driver for MSCFS, =
F4, etc. from Boeing, etc., but that's not likely to happen. So why not =
start simple and build a driver that generate the various force vectors =
that occur in the plane, and let other build drivers that take that =
information and move their pit?

<P><FONT SIZE=3D2>Just some thoughts...</FONT>
<BR><FONT SIZE=3D2>Alex</FONT>
</P>

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