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

[Marv De Beque]

I am going to chime in.

I may have missed some posts, but here are my observations from flying sail
planes:

1)  The force required to move the stick is related to speed.  It is
probably not linear, but I don't know.

2)  When you release the stick it will move to its neutral position (which
changes depending on what the aircraft is doing at the time).

3)  Point 2 is important.  As an example, when you are in a medium banked
turn, you apply stick toward the turn.  When you transition to a steep turn
the "over banking" forces try to roll the aircraft over.  Opposite stick is
required to neutralize this effect.  You must physically push the stick in
the opposite direction and there will be considerable force required to do
this at times.

4)  Turbulence will force the stick to change position, particularly when it
is on one side or the other of the aircraft.

5)  Uncoordinated flight (spins, stalls, and slips) change the nature of the
stick feel completely.  Remember, it is possible to stall an aircraft at a
relatively high air speed.  A high G turn is one example where the weight of
the aircraft (not the mass) increases with G loading and you can stall.

I liked the passive system described by one post with two cylinders
connected by an adjustable valve, but when I thought about it, that only
acts as a damper and does not replicate the forces felt on the stick as you
hold it in any one position.  Plus slow versus fast transitions of the stick
have completely different effects that are not at all like the real forces
you feel on the stick.

Therefore, it must be an active system and you can start with aircraft to
make it simple and add in the other dynamic functions as you go along on
your project.  I would opt for two pneumatic cylinders that you could
rapidly compress and decompress and start writing simple algorithms to
control that.  As you master function, move on to other conditions.  At
least the hardware will do anything you want it to.   All you need to do is
upgrade your software.

Interesting project!

Marv


On 2/8/03 9:01 PM, "Matt Bailey" <mattb@rtccom.net> wrote:

> The thing is, in real life, control pressure increases as the control device
> is moved further from center.
> 
> -Matt Bailey
> 
> On Saturday 08 February 2003 19:14, you wrote:
>> Ken,
>> 
>> What if you used a variable pressure regulator (sensing airspeed) to
>> supply the closed cylinder?  That way, the presure that you would have
>> to push against with the stick would only vary with airspeed, not stick
>> position.
>> 
>> Keenan
>> 
>> Ken Schlote 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.
>>> The cylinder will need to be big so the amount of movement won't
>>> increase the pressure much. 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. This system will also need
>>> two cylinders per axis.
>>> 
>>> 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?
>>> 
>>> Ken
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