On Samstag, 24. April 2004 21:31, Andy Ross wrote:
> It's a misfeature in the gear modelling.  YASim has pretty much the
> same behavior.  Both FDMs model gear force as a function of "skidding
> velocity", which is fine for dynamic solutions.  But a gear that is
> planted on the ground is capable of "holding" an aircraft at zero
> velocity, which doesn't work with the current FDMs -- zero velocity
> produces zero force.
>
> What's needed is code that, at low speeds, uses a spring model for
> gear force based on the distance in position from where the gear is
> "stopped".  Which sounds easy, but in practice is awfully hard.  I've
> gotten started on this several times, and never produced useful
> code.
Yep, kind of true.

Jon and I are working on a solution to this. At least for JSBSim.
It is not only the gear modelling which plays a role here, the time 
integration of the equations of motion play a role too.

There is code on a development branch in JSBSim's cvs which addresses this and 
also works well so far.

And Andy, If I remember right, I believe that it was a comment of you about 
the problem beeing stiff, that made me look into JSBSim's timestepping ...
;)

   Greetings

         Mathias

-- 
Mathias Fröhlich, email: [EMAIL PROTECTED]

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