On Tuesday 03 February 2004 02:23, Jim Wilson wrote:
> "Curtis L. Olson" <[EMAIL PROTECTED]> said:
> > For everyone: I've integrated this into a larger document which attempts
> > to explain the basic ideas behind control theory and then describes the
> > specific PID algorithm we have implimented for FlightGear. This
> > information isn't strictly necessary for building aircraft specific
> > autopilot configurations, but it's such cool stuff it's worth mentioning.
> > :-)
>
> It is indeed! Is the altitude hold working for you? I'm finding that the
> first stage is outputing values that ocilate from max to min and back in
> probably 5 or 6 (not timed yet) cycles. Anyway, I haven't looked at the
> code or adjusted any of the parameters yet. I just wanted to know if maybe
> it's something unique to my setup before messing with numbers.
>
> Best,
>
> Jim
I started with putting the generic AP in the TSR2 and got similar behaviour.
I haven't had a chance to see the docs yet but I've got a reasonable alt hold
by reducing Kp & Ti, quite drastically.
<!-- Altitude hold. 2 stage cascade controller. -->
<!-- Stage #1 sets target rate of climb based on diff between current alt
-->
<!-- and target altitude. -->
<pid-controller>
<name>Altitude Hold (Altimeter based) Stage 1</name>
<debug>false</debug>
<enable>
<prop>/autopilot/locks/altitude</prop>
<value>altitude-hold</value>
</enable>
<input>
<prop>/instrumentation/altimeter/indicated-altitude-ft</prop>
</input>
<reference>
<prop>/autopilot/settings/target-altitude-ft</prop>
</reference>
<output>
<prop>/autopilot/internal/target-climb-rate-fps</prop>
</output>
<config>
<Kp>0.1</Kp> <!-- proportional gain -->
<beta>1.0</beta> <!-- input value weighing factor -->
<alpha>0.1</alpha> <!-- low pass filter weighing factor -->
<gamma>0.0</gamma> <!-- input value weighing factor for -->
<!-- unfiltered derivative error -->
<Ti>20.0</Ti> <!-- integrator time -->
<Td>0.00001</Td> <!-- derivator time -->
<u_min>-40.0</u_min> <!-- minimum output clamp -->
<u_max>40.0</u_max> <!-- maximum output clamp -->
</config>
</pid-controller>
Obviously, I've upped the u_min & u_max here too.
Heh! - I'll get the docs tomorrow...
LeeE
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