On Wednesday 04 February 2004 21:39, Jim Wilson wrote: > 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
Ah - that's interesting - I wasn't sure how small some of the numbers could be. I tried reducing it, but not nearly enough, and not seeing much difference, reset it. Had a chance to look at the docs today - er... ;) Something new to play with:) LeeE _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
