LeeE wrote: > On Wednesday 19 December 2007 12:56, Tiago Gusmão wrote: >> LeeE wrote: >>> On Tuesday 18 December 2007 22:52, Tiago Gusmão wrote: >>>> LeeE wrote: >>>>> Hi all, >>>>> >>>>> I've noticed recently that after re-loading an autopilot the >>>>> filters that are being used seem to be getting a bit >>>>> 'confused'. I spotted it when I was comparing the unfiltered >>>>> input with the filtered output and saw that the input was >>>>> stable to 2 decimal places but the filtered output seemed to >>>>> be oscillating very quickly up to the first decimal place. >>>>> >>>>> I don't know if this happens with all filter types - all the >>>>> ones I've been using are noise-spike types. >>>>> >>>>> LeeE >>>> Are you sure it's oscillating instead of just catching up with >>>> the current input? anyway, you can try to enable debug on that >>>> filter and show us some values. >>>> >>>> In the meantime i've had my own problem with the AP (now >>>> solved, don't use alpha=0 or you will get a NaN that will >>>> bring FG to a halt if tied to the controls) >>>> but i found some things that don't make much sense to me >>>> >>>> xmlauto.cxx, line 798, FGXMLAutopilot::reinit: >>>> >>>> -why is build() called there? it's already called inside >>>> init() >>>> >>>> -maybe my C++ is a little forgotten, but don't we need to >>>> delete the objects contained in components() ? >>>> >>>> Cheers, >>>> Tiago >>> Hi Tiago, >>> >>> I'm not absolutely sure it's oscillating - it's changing too >>> fast to actually see the numbers to be sure - but the visual >>> pattern - that is, the apparent 'shape' that you can see >>> suggests it is rapidly switching between two values, which >>> change more slowly, over time, as the input changes. >>> >>> Like I said, I compared the un-filtered input with the filtered >>> output and while the input could be stable to 2 decimal places >>> the filtered output could be changing at the first decimal >>> place i.e. the output was varying more than the input by a >>> factor of up to 100, so it's not a case of the filter trying to >>> catch up. >>> >>> The effect is that it is oscillating because it's vastly >>> overshooting it's target in both directions. >>> >>> LeeE >> I wasn't able to reproduce, i tried with >> >> <filter> >> <name>test filter</name> >> <debug>true</debug> >> <type>noise-spike</type> >> <input>/controls/flight/elevator</input> >> <output>/controls/flight/filtered-elevator</output> >> <max-rate-of-change>0.1</max-rate-of-change> >> </filter> >> >> >> Also my "paper simulations" seemed ok. >> >> Could you post your filter? >> >> Anyway, the current behavior of resetting the filtered output to >> zero doesn't seem very good, i think starting at the current >> input would be best. >> >> >> >> Cheers, >> Tiago > > Hi Tiago, > > have a look at the 'Target Pitch Filter' in the BAC-TSR2 autopilot - > I saw the problem with that filter. The filename is: > Aircraft/BAC-TSR2/Systems/BAC-TSR2-autopilot.xml > > LeeE
I've tested it and it seems the input oscillates and can even change sign very briefly, you need to pause right after reloading the AP to be able to spot it. Because the filtered output will restart at zero, it will be able to quickly go negative and then will take quite some time to return to normal values. So while this is AP's fault, it's not because of the filter. Anyway, AP reloading isn't something we expect users to mess with, so i wouldn't bother much with it. And from what i've seen in the code, reloading is reliable in the sense that it really creates new instances of the objects, so there are no stale values. BTW, it was really nice to see the TSR2 fly KSFO -> KSCK over those hills, good work :) Cheers, Tiago ------------------------------------------------------------------------- SF.Net email is sponsored by: Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
