Re: [Flightgear-devel] speed-with-pitch

2004-09-21 Thread Roy Vegard Ovesen
På Tue, 21 Sep 2004 12:00:09 +0200, skrev Roy Vegard Ovesen 
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I would suggest to use airspeed as input to a PID controller, your 
desired airspeed as reference and the elevator control surface as output. 
I haven't tried this, so good luck!
Works like a charm :-) I got it stable with: Kp=0.0125, Ti=30.0, Td=0.0 
with the Piper. You can start from there, and I'm sure that fine tuning 
will get better performance.

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Roy Vegard Ovesen
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Re: [Flightgear-devel] speed-with-pitch

2004-09-21 Thread David Culp
  I would suggest to use airspeed as input to a PID controller, your
  desired airspeed as reference and the elevator control surface as output.
  I haven't tried this, so good luck!

 Works like a charm :-) I got it stable with: Kp=0.0125, Ti=30.0, Td=0.0
 with the Piper. You can start from there, and I'm sure that fine tuning
 will get better performance.

Thanks Roy, it works better now, but still not enough to prevent crashing.  It 
looks like I'll still need an external monitor to clamp the pitch angle.  For 
instance, if I'm doing an idle descent at 250 kts and reset the speed to 300, 
I need to keep the airplane from going straight down.

Dave
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David Culp
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Re: [Flightgear-devel] speed-with-pitch

2004-09-21 Thread Roy Vegard Ovesen
På Tue, 21 Sep 2004 12:02:34 -0500, skrev David Culp 
[EMAIL PROTECTED]:

 I would suggest to use airspeed as input to a PID controller, your
 desired airspeed as reference and the elevator control surface as 
output.
 I haven't tried this, so good luck!

Works like a charm :-) I got it stable with: Kp=0.0125, Ti=30.0, Td=0.0
with the Piper. You can start from there, and I'm sure that fine tuning
will get better performance.
Thanks Roy, it works better now, but still not enough to prevent 
crashing.  It looks like I'll still need an external monitor to clamp the 
pitch angle.  For instance, if I'm doing an idle descent at 250 kts and 
reset the speed to 300, I need to keep the airplane from going straight 
down.
50 kts is quite a large change in reference, if you could change it 
gradually from 250 to 300, I'm sure that would be safer. It is not 
uncommon, in the process control world, to only let the reference change as 
a ramp. A gradual change at some appropriate rate, instead of a sudden 
change.

If you feel that you absolutely have to control the pitch angle, I would 
suggest that you go for a cascade configuration. One controller to control 
pitch angle using the elevator and one to control airspeed using the 
(controlled) pitch angle. Now you can easily limit the pitch angle.

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Roy Vegard Ovesen
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