| Topic: |
Science > Physics |
| User: |
"Gernot Frisch" |
| Date: |
06 Apr 2006 10:00:49 AM |
| Object: |
Helicopter physics |
Hi,
I want to program a toy-helicopter simulation. Not totally
sophisticated, but just a bit of realism.
Assuming z-axis is up/down, x=front/back:
Here's my thoughts so far:
when you move the x-y lever, the rotor "surface" get's inclined
immediately. Resulting in a inclination of the rotor thrust force. Due
to the interia of mass, the helicopter will start to do a looping if
you pull backwards a lot (I think).
So, I have this forces:
^ F_up
|
-----o-----
|
--^--
| *+-------X
-----
\ | |
-------
|
V F_g
* = center of mass
F_up = rotor force in direction of rotor at top of heli
F_g = gravity force in direction down at center of mass
These 2 forces provide a torque moment on the chasis. In 3D that's ...
er... 2 torque moments. around X and around Y axis (local).
The up/down lever simply controls the F_up force, right? I should add
some delay in accelerating, I guess.
The back-propeller applies a 3rd torque moment around local z axis,
right?
How would I rotate the heli with the torque monents? Is any (most) of
my thoughts baloney?
Thank you in advice.
--
-Gernot
int main(int argc, char** argv) {printf
("%silto%c%cf%cgl%ssic%ccom%c", "ma", 58, 'g', 64, "ba", 46, 10);}
.
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| User: "CWatters" |
|
| Title: Re: Helicopter physics |
06 Apr 2006 11:34:42 AM |
|
|
"Gernot Frisch" <Me@Privacy.net> wrote in message
news:49kokrFp4mlpU1@individual.net...
The up/down lever simply controls the F_up force, right?
When the collective pitch is increased to go up (Z) the throttle has to be
opened to provide more power accelerate the helicopter vertically.... the
torque increases and the tail rotor has to be adjusted to compensate.
Obviously you could ignore this effect to make programming easier but less
realistic.
Lets say you are in the hover. If you want to move in any direction without
changing height you also have to increase power. That's because the rotor
disk has to be tilted so only a component is available to counter weight.
I should add
some delay in accelerating, I guess.
The back-propeller applies a 3rd torque moment around local z axis,
right?
The tail rotor is used to counter engine torque.
How would I rotate the heli with the torque monents?
Well you rotate the helicopter using the tail rotor to either under or over
compensate for the engine torque depending on which way you want it to turn.
Is any (most) of
my thoughts baloney?
No I just think it's going to be harder and more complicated than you think.
.
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|
| User: "Gernot Frisch" |
|
| Title: Re: Helicopter physics |
06 Apr 2006 07:07:44 PM |
|
|
The up/down lever simply controls the F_up force, right?
When the collective pitch is increased to go up (Z) the throttle has
to be
opened to provide more power accelerate the helicopter
vertically.... the
torque increases and the tail rotor has to be adjusted to
compensate.
Obviously you could ignore this effect to make programming easier
but less
realistic.
Lets say you are in the hover. If you want to move in any direction
without
changing height you also have to increase power. That's because the
rotor
disk has to be tilted so only a component is available to counter
weight.
Is this with real helicopters the case, or does some "software"
compensate this? When I have the throttle for the rotor power (=
F_up), this effect will show up in my program. The length of F_up
stays, the vertical component shrinks.
Is any (most) of
my thoughts baloney?
No I just think it's going to be harder and more complicated than
you think.
Do I have to take yaw/pitch torque into account, or can I simply leave
it and draw the heli inclined resulting from thrust direction and
flying direction?
.
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|
| User: "CWatters" |
|
| Title: Re: Helicopter physics |
07 Apr 2006 02:07:59 AM |
|
|
"Gernot Frisch" <Me@Privacy.net> wrote in message
news:49lom9Fp3n91U1@individual.net...
Lets say you are in the hover. If you want to move in any direction
without
changing height you also have to increase power. That's because the
rotor
disk has to be tilted so only a component is available to counter
weight.
Is this with real helicopters the case, or does some "software"
compensate this? When I have the throttle for the rotor power (=
F_up), this effect will show up in my program. The length of F_up
stays, the vertical component shrinks.
I don't think they have a system to compensate for this (the pilot does it).
Some model helicopters have a system to sense and maintain rotor rpm so that
if loaded up the throttle is automatically opened.
Is any (most) of
my thoughts baloney?
No I just think it's going to be harder and more complicated than
you think.
Do I have to take yaw/pitch torque into account, or can I simply leave
it and draw the heli inclined resulting from thrust direction and
flying direction?
Yes you can ignore it but a real helicopter pilot flying your simlator would
probably notice the effect was missing.
.
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