> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On > Behalf Of Jon S. Berndt > Sent: Friday, March 23, 2007 10:29 PM > To: FlightGear developers discussions > Subject: Re: [Flightgear-devel] Phidot not zero.. And bank > angle constant... > > > Hi, > > > > I'm sorry but its sounding a little anomalous to me. > > > > >From the kinematic relationships; > > > > p = phidot - psidot sin(theta) > > > > q = thetadot cos(phi) + psidot cos(theta) sin(phi) > > > > r = psidot cos(theta) cos(phi) - thetadot sin(phi) > > > > now for a steady turn, theta can be approximated close to > zero and for > > the thetadot is also close to zero and negligible. So we are left > > with roughly; > > > > p = phidot > > > > q = psidot sin(phi) > > > > r = psidot cos(phi) > > > > If we p q and r were to be measured in the body axis, I guess they > > would be zero. But in the inertial frame; > > > > p = phidot = 0 since its in a level turn the bank angle would > > be constant > > > > q = psidot sin(phi) = non zero since phi has a value and in the > > inertial frame the heading is changing > > > > r = psidot cos(phi) = non zero again > > > > Therefore q and r should have values and so should psidot, but > > thetadot and phidot should be zero or close to zero. > > > > Am I missing something? Please do let me know. > > Sorry. I confused myself. I may have been thinking of body > accelerations, not rates. Or something. > > Your equations look good. > > I ran a test script with the JSBSim c172. In a constant turn > I saw this at steady state: > > P = ~0 > Q = ~3.5 deg/sec > R = ~6 deg/sec > > Pdot = ~0 > Qdot = ~0 > Rdot = ~0 > > phi = ~30 deg > theta = ~4 deg > psi = from 200 deg to 20 deg > > phidot = ~0.0 > thetadot = ~0.0 > psidot = ~6 deg/sec > > I think this works out about right. So, at least JSBSim is > working correctly. > > Jon >
Yeah, what he said.... ;-} Bill ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
