Re: [Jsbsim-devel] F-16 Stability problems

[Bruce C. <bcl...@gm...>]

Eric:
 We will be working this week to interface JSBSim to a Wittenstien control
stick and was wondering if you had any updates that we can try that will
overcome the pitch oscillation and random roll problems.

Bruce

On Fri, Oct 21, 2016 at 4:14 AM, Erik Hofman <er...@eh...> wrote:

>
> I did some work on the PID's and got it almost working but the problem
> is the final details: getting the error to zero.
>
> But the process of starting FlightGear every time to test the changes
> makes it unpleasantly time consuming.
>
> Erik
>
> On 10/20/2016 08:55 PM, David Culp wrote:
> > From your description of the problem it sounds like integrator wind-up
> > could be the issue.  The fix was added to the PID component a few years
> > ago, but I haven't used it yet.  IIRC,  it involves specifying an error
> > property that when very near zero causes the PID controller to reset the
> > integrator.
> >
> > Dave
> >
> >
> > On Oct 20, 2016 11:25 AM, "Bruce Clay" <bcl...@gm...
> > <mailto:bcl...@gm...>> wrote:
> >
> >     Erik:
> >
> >     I realized that my reply had not popped up on the forum yet.  It
> >     seems I replied from my work email and that email does not get
> >     posted for some odd reason.
> >
> >     ---- previous reply ----
> >
> >       In thinking through your response I guess I have I
> >     misunderstanding of  the way JSBsim works.  I would have expected
> >     the PIDs to be in the base code not in the aircraft dependent
> >     scripts.  If we take a simplistic view of a PID as a filtering
> >     mechanism how does altitude affect the roll?  The problem tends to
> >     show up more in the low altitudes say under 10,000 feet and around
> >     600 knots.  Neither of these values are near the limits for the
> >     aircraft.  I do not see the oscillations during extreme maneuvers
> >     rather just the opposite.  Doing extreme maneuvers seems to
> >     stabilize the aircraft (i.e stop the oscillations).
> >
> >     I am no expert in the math behind the flight dynamics so I may be
> >     overlooking something.
> >
> >     Thanks for your help
> >
> >     Bruce
>
>
> --
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