<!-- 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...
Some notes on tuning cascade controllers:
When tuning cascade controllers it is common practice to first tune the inner loop or the secondary controller in Lee's example that would be the vertical speed controller, and then tune the outer loop or the primary controller.
-- Roy Vegard Ovesen
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