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List:       flightgear-devel
Subject:    Re: [Flightgear-devel] [Flightgear-commitlogs] [FlightGear] 02/02: YASim gear: Clamping of _frac rep
From:       Julian Smith <jules () op59 ! net>
Date:       2023-07-23 9:30:36
Message-ID: 20230723103036.74e0e33d.jules () op59 ! net
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On Sat, 22 Jul 2023 22:24:41 +0100
Julian Smith <jules@op59.net> wrote:

> On Fri, 21 Jul 2023 19:36:48 +0100
> Julian Smith <jules@op59.net> wrote:
> 
> > On Fri, 21 Jul 2023 14:04:25 +0100
> > James Turner <james@flightgear.org> wrote:  
> 
> > > > Maybe we could simply add a quadratic term scaled by a new
> > > > dimensionless constant `spring2` in the XML:
> > > > 
> > > > force = _spring * compression * (_frac + spring2 * _frac**2)
> > > > 
> > > > [One could view `spring2` has modifying the maximum force of the
> > > > spring at full compression, 
> > > > 
> > > > force_max -> force_max * (1 + spring2).
> > > > 
> > > > For example `spring2=10` would result in 11x the force at maximum
> > > > compression compared to the default `spring2=0`.]
> > > > 
> > > > I'm hopeful that this could address the original problem without the
> > > > danger of pathological behaviour. I think it would be pretty easy to
> > > > implement too.      
> > > 
> > > Definitely worth a shot, as far as I'm concerned. Again I'd be    
> > 
> > Ok, i might have a look at this, unless someone else gets there first.  
> 
> I've just pushed a commit to next that implements this.

As the change is experimental, i haven't documented it on the wiki.

However it would be great if someone could try it out, perhaps on the
TF-G2 aircraft which was mentioned in the original bug report,
https://sourceforge.net/p/flightgear/codetickets/1509/.

See the above quoted text for how the new `spring2` term works.

Here's an example XML gear specification that uses the new term to
increase the maximum force by a factor of 11, while still
largely preserving the original behaviour at small compression values:

<gear x="-8.90" y="3.24"  z="-1.41" compression="0.25" spring="0.3" castering="1" \
damp="1.0" stiction="1" spring2="10">

- Jules

-- 
http://op59.net


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