On Wednesday 14 Oct 2009, Alan Teeder wrote: > > -----Original Message----- > > From: leee [mailto:l...@spatial.plus.com] > > > > > Did you try scheduling your autoplilot´s height-error to > > > pitch demand gain with 1/V (speed inverse) ? > > > > > > Alan > > > > Re-read the end of the paragraph after the one you quoted above > > ;-) > > > > LeeE > > Red Face (me that is)
Heh :-) I added the reciprocal filter type to specifically address this problem. It's still more of a work-around than a cure though. > > I can't help thinking that there must be another problem > somewhere. It should only be necessary to up the frame rate above > 20Hz if you need to simulate vibrations, not aircraft motion and > autopilot control loops. > > A possible cause is if the simulation is not ordered correctly > and some equations in the solution are receiving old inputs which > relate to a previous time frame. Errors due to this effect would > reduce as the frame rate is increased. > > Anything in the simulation which has a faster response that that > provided by a 20Hz frame rate can safely be ignored for > man-in-the-loop stuff as the man just won't be capable of seeing > or reacting to it. > > Alan It really depends on what you're trying to do with the autopilot. As I said, for aircraft that only need relatively slow responses you can get away with a 20Hz rate, but even then there's little margin of safety insofar as the controller will be working near its minimum stable rate. Where you need faster responses though, you really need higher rates and it's not just an issue of having a person in the loop. For example, one of the things I was playing with on the SU-37 and YF-23 updates was to intercept stick inputs and have a stick-mode where the stick set a target pitch & roll instead of controlling the elevator/elevons/ailerons directly. In this case I really needed to achieve a pitch/roll-change rate of 20-30 degrees/second, without overshoot, and you just can't do that with the controllers running at ~20Hz. There's also the added advantage that with a higher resource availability for the FDM and autopilot controllers you could make the controllers more predictive by using several samples to match a curve, instead of just reacting the the difference between consecutive samples. LeeE ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
