[simpits-tech] May the Force Feedback be with you...

[Craig Rochester]

If you're using a servo controlled regulator to power the air cylinder, the pressure on the piston
is always the regulator pressure, regardless of the piston position.  That's the beauty of using the
regulator.  It relieves(exhausts) the excess air as the piston moves back and adds air as it moves
forward.

A spring loaded cylinder will eliminate the need for a second cylinder.  Or...you get a dual acting
cylinder and switch the air supply with solenoids change the direction of the force.

Craig R.



-----Original Message-----
From: simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org]On Behalf Of Matt Bailey
Sent: Saturday, February 08, 2003 9:27 PM
To: simpits-tech@simpits.org
Subject: Re: [simpits-tech] May the Force Feedback be with you...


On Saturday 08 February 2003 17:03, you wrote:
> Hi All,
> I woke up this morning and was thinking of some comments for this problem
> of trim and centering the stick. Matt has said it well. My comment for trim
> was going to be the same. As for the closed cylinder I'm not so sure. If
> the cylinder is closed the movement of the shaft will increase the pressure
> to a point were you can't move the shaft.

	Hmmmm, true. But you don't necessarily have to have full control deflection
occur at full cylinder compression. You would want to leave a few percent of
the cylinder available at full stick deflection, for the compressed air to
occupy. This way you could get full stick deflection.

> The cylinder will need to be big
> so the amount of movement won't increase the pressure much.

	You could just make the compressor component of the cylinder (the part
connected to the stick...sorry, I don't know the correct name for this
device, plunger?) smaller to decrease the rate at which pressure builds. You
DO want pressure to build fairly rapidly. Getting the distances, travel, etc
right would require experimentation. I picked this method because by its
nature it seems to fundamentally match what happens in the real world. A very
slightly sloppy center position, with naturally increasing pressure as the
control is moved further from center.

> If the cylinder
> is attached to a big chamber(and maybe this is what you are thinking Matt)
> then the movement of the cylinder won't be noticed.

	I don't quite follow this part. By cylinder, are you referring to what I was
trying to say earlier by "plunger"? The part that goes inside the chamber.

> This system will also
> need two cylinders per axis.

	Yep.

> My idea may work, use an innertube around a
> circular disk (attached to the stick) inside a retaining ring. The pressure
> would be controlled the same way but when you move the stick the disk would
> press on the innertube and you would feel the pressure. The air would
> simply move to the otherside of the tube and the pressure would remain the
> same. The stick would self center because the tube would go back the the
> orginal shape. This would be the same pressure in all directions.Trim would
> be just moving the tube assembly to a different center. Any thoughts or
> comments?

	Interesting. I don't really think just moving air around is sufficient, you
want some compression going on. But, you'd be compressing the air by reducing
the space inside the tube. The logistics of the system would be much simpler
than my idea.

	-Matt Bailey
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