On Sunday 16 March 2008 03:51, Syd&Sandy wrote: > Hi all , > I've been trying to change the xmlautopilot to use <prop> and > <value> for the u_min and u_max properties , and currently have > quite a mess on my hands right now :) The idea is to have a min > and max property to control bank-limit / pitch with a panel knob > ... setting the u_min and u_max from a property seems to be > working , but I get some strange things happening . The pi-simple > controller isnt clamped anymore (so i removed the clamp check > )... and the output goes immediately to the u_min > value...although u_min and u_max are checked every update... Has > anyone else attempted this , with good results ? Or , hopefully , > already implemented this ? Anyway , I'll keep plugging away at > it, the answer is probably staring me in the face and I can't see > it. Is this something that should be implemented anyway ? > Cheers
Hi Syd, one way you could do this with the current autopilot controllers is to feed the output from your controller through a gain filter to get the range you want. For example, if you've set u_min/u_max to +/- 40 in your controller but want to reduce it to +/- 20, you'd set the gain value on the gain filter to 0.5. If you don't mind re-tuning your controller, it would probably make more sense to set u_min & u_max to +/- 1.0, then the gain factor would be the required bank or pitch angle limit i.e. for +/- 30 limits you'd use a gain of 30. Changing the output clamps does change the overall behaviour of the controller, however. I found that I got more desirable behaviour from a pitch controller (output is a hstab deflection) when I set the u_min & u_max limits to +/- 0.25 and then passed it through a gain filter with a factor of 4 to restore the required +/- 1.0 range, as opposed to setting the clamps directly to +/- 1.0. Heh - I'm still not entirely sure why this is, actually having fiddled with the code myself, but it came about through an experiment where I was trying to increase the effective bandwidth through parallelism. I started off with four identical controllers running in parallel, the outputs of which were summed but then I realised that I could get the same effect with a single controller using the gain filter technique. LeeE ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
