Andy Ross writes: > Curtis L. Olson wrote: > > it seems to be more than a simple coordinate system difference, > > unless JSBSim/YASim swap X/Y axes or something strange like that. > > Could be a bug, too. What exactly is the behavior you're seeing? The > way the code in steam works is to look at the Y and Z "pilot > acceleration" vectors and compute a "down" direction. Is it the > direction that's wrong? > > * Not the same as coordinate acceleration, for the reasons discussed > before. And it shouldn't use X, which is the longitudinal axis. The > ball is constrained by its housing to the YZ plane. > > The steam.cxx code is the only place that uses these numbers, so a bug > could easily have gone unnoticed. I haven't looked at the ball in a > while, honestly, but I don't remember being surprised by anything > looking wrong.
I haven't looked at YAsim closely, but FlightGear and this other fdm I'm working on both use nearly the same formula to calculate the ball position. The steam code uses A_Y_pilot / -A_Z_pilot to calculate turn coordinator ball position. This other fdm code bases it's calculation on forces, but also in the Y and Z directions. I'm guessing that Ay / Az is roughly proportional to Fy / Fz so these two methods won't be exactly the same, but should be similar enough. However, I'm not using the TC ball output, but instead passing this FDM's Ay and Az to the steam code so it get's processed the same as JSBsim. The results from both are good and apparently correct, but off by an order of magnitude in scaling. I guess I'll have to try to find some time to dump out the values and see if I can figure out what's going on. Perhaps someplace in one of the pipelines, a units conversion was screwed up (maybe meters vs. ft or something?) Regards, Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities [EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
