Lee Elliott <[EMAIL PROTECTED]> said: > 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... >
Hi Lee, Curt fixed that today. It even works pretty well with the 747. With the one he commited, the gain is higher than what you have (Kp=1.0), a little longer intergration period (Ti=25.0) and the derivator is way down to almost 0 (Td=0.000000001). Best, Jim _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
