Quoting Jon S Berndt <[EMAIL PROTECTED]>: > >Other topic: Are there any suggestions about how to build a d/d(t) of > >a property in fdm > > Markus: > > For JSBSim, you can use the flight control components. This is a > quick reply, so maybe I have not thought this all the way out, yet. > But, I suspect you can get a derivative control like this: > > In LaPlace space, a derivative is simply "s", right (it's been a long > time since I've worked in LaPlace space - someone correct me if I am > wrong, please). You can use the Tustin substitution to go from > LaPlace space to the time domain (z domain), as we do with all the > JSBSim flight control components (this is typical in industry, too). > Have you seen the "Automatic Flight in JSBSim" document at the JSBSim > web site? Go to www.jsbsim.org, select Documentation, then select that > title. You will see the Lead-Lag and Second order filters described. > Select the coefficients for these two filters to give you only an "s" > in the numerator. For the lead-lag filter you would selectC1 = 1, C4 > = 1, and C2 and C3 would be 0. For the second order filter, C2 and C6 > would be 1 and C1, C3, C4, and C5 would be 0. Using these filters > should give you the derivative of the input. Now, I have not used > these filters for that purpose, yet. Initialization would be very > important for them to work correctly. I'd have to test them out to see > if that worked correctly.
LaPlace has been long time ago, but I tried your hint and it works. I use a LEAD_LAG_FILTER to calc the d/dt thx a lot, that made FCS pitch controll possible w/o trigger malfunction causing unflyable attitudes ;) after a while. markus _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
