> ..ok, time for another of my stupid questions:  Mathias, does your
> new model code include tire creep?  And tire sidewall flex?

There are a lot of tire effects that might be modeled.  The question faced
in deciding what to model is: given the purpose of this FDM, what should be
included to achieve the desired effect? There are some great technical
papers hosted in the NASA Langley (and perhaps NASA Dryden) technical report
servers. Several years ago when I was doing some initial R&D for the JSBSim
gear model I had some discussions with Bob Daugherty of NASA Langley about
gear modeling (where they do a lot of very serious gear modeling and
analysis), and he also referred me to some papers.  The range of
characteristics that might be modeled include tire slip, tire "wind-up",
spin up, and complex strut interactions, to name only a few of the more
difficult ones.  These problems are difficult even for detailed engineering
sims, and in the case of trying to model any generic vehicle, these problems
are compounded. There are some things I'd like for us to model, but JSBSim
also hopes to remain comprehensive and comprehensible at the same time, so
modeling some of the more subtle effects probably is not worth the effort.
In any case, Mathias and I in particular are working on some sweeping
changes for JSBSim that ought to make the gear modeling much more stable.
After that, there are many other improvements to make - one of which is
looking at the gear model to discern where improvements can (and _should_)
be made.  In the meantime, we are discussing some changes that might be made
and doing some limited research into the matter, including reviewing the
approaches used by other simulators such as racing sims.

Jon


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