Re: [Flightgear-devel] autopilot u_min and u_max...
On Sat, 15 Mar 2008 20:51:08 -0700 SydSandy [EMAIL PROTECTED] 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 -- SydSandy [EMAIL PROTECTED] OK it seems the errors were caused by my autopilot config file, u_min and u_max work with prop and value as expected , but I need to test further , just in case ... Cheers -- SydSandy [EMAIL PROTECTED] - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] autopilot u_min and u_max...
On Sunday 16 March 2008 03:51, SydSandy 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/vse012070mrt/direct/01/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] autopilot u_min and u_max...
On Sun, 16 Mar 2008 21:59:18 + LeeE [EMAIL PROTECTED] wrote: On Sunday 16 March 2008 21:52, LeeE wrote: On Sunday 16 March 2008 03:51, SydSandy 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 Oops - that should have said u_max/u_min to +/- 40 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 and again above - u_max u_min to +/- 1.0 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 Sigh... u_max u_min to +/- 0.25 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 Doh! LeeE Hi LeeE, Thanks for the tips. Still I think it would be a good idea to make these two settings modifiable with a property , don't know if any one else agrees . It turns out that the problems I was having was my autopilot config file , it's been working fine so far it simply checks for value or prop like the recent Kp update, and uses the u_min and u_max value if no prop or value tag is present ... now, the fun part, to try to create an lnav /vnav flight profile :) Cheers -- SydSandy [EMAIL PROTECTED] - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] autopilot u_min and u_max...
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 -- SydSandy [EMAIL PROTECTED] - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse012070mrt/direct/01/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
