On Fri, 2002-02-22 at 16:23, Andy Ross wrote: > Tony Peden writes: > > Just for the record, what's most likely happening here is that since > > JSBSim senses that the gear are underground on the first update(), the > > gear code calculate a reaction force based on how far underground they > > are. > > One thing you might try is clamping the gear force to that produced by > fully compressed gear. That way, you avoid the absurd forces produced > by springs compressed by 100x their real-world size. It doesn't fix > the underground problem, but it might help keep the results from > exploding.
True, it would help. But what do we do then? I'm not ready to do anything approaching real structural modeling. > > Curtis L. Olson wrote: > > I don't know the details of how it works know, but it seems like the > > FDM would need to find a suitable starting point for the CG given the > > information FlightGear can provide (which is the ground elevation.) > > What YASim does is just lift the plane up until the (fully extended) > gear are off the ground, and drop it. The plane bounces nicely to a > stable resting orientation. JSBSim starts out doing a similar thing, but then goes on to adjust height, pitch angle,and roll angle until the aircraft is in equilibrium. At the moment, I think it's just not doing it with the right number at CL77. I don't yet know why that is. > > One thing to consider would be exporting the tile geometry to the FDMs > in some way. Assuming a flat ground plane is fine for runway > environments, of course, but curved surfaces won't work that way. One > way to do it would be for the FDM to provide a line description > (direction of gear compression), which the scenery would convert into > an intersection point and a normal vector for the ground at that > point. > > In particular, ski jumps have curvature of the order of the inter-gear > distance, and can't be approximated with any plane at all. Of course, > these are very special purpose, and might best be handled with a > special case inside the gear code... > > Andy > > -- > Andrew J. Ross NextBus Information Systems > Senior Software Engineer Emeryville, CA > [EMAIL PROTECTED] http://www.nextbus.com > "Men go crazy in conflagrations. They only get better one by one." > - Sting (misquoted) > > > _______________________________________________ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
