Nick wrote: > I just remembered another trick about zero-speed rolling models. > Below a threshold speed (say 1 m/s) you make the force proportional to > the velocity. That way you'll get zero force at zero speed. The > other thing that can happen if you don't is that you'll oscillate > about the zero speed point. This will stop that oscillation.
The FDMs do this already. It doesn't really stop the oscillation, but it does damp it somewhat. The problem is that if your slope of the force curve is too shallow, you get a "drift" problem. If you push a little on a real aircraft (or car, or whatever) it doesn't move, because the force is *not* proportional to velocity. But the aircraft as modelled above has some non-zero speed where the gear force is equal to the push force. So it wanders around, which isn't physical either. But this is only one problem of many. FWIW, I think most of the YASim planes sit quite well. Except the harrier -- it has a bounce/jitter problem for different reasons: the aircraft naturally sits on four gear points. The outriggers end up fighting with each other and the aircraft oscillates around its roll axis. This has nothing to do with gear friction at all, even though the symptom is the same. I made the existing model sit still by shortening the outriggers such that the aircraft comes to rest on just one, with the other one sitting just off the ground. Andy _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
