On Thu, 8 Jan 2004 20:41:00 +0100 "Hof Markus" <[EMAIL PROTECTED]> wrote:
Other topic: Are there any suggestions about how to build a d/d(t) of a property in fdm
markus
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.
Jon
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