@RogerR wrote:
I launch my XUAV Clouds via catapult. It’s always been successful with a headwind, but it’s marginal w/o one.
At least part of the reason is that the target pitch is sub-optimal as the plane exits the ramp. The following graph shows that the planes’s actual pitch while resting on the catapult ramp is 8 to 9% while the pitch target prior to launch is 4-5%. This discrepancy makes the P term for the pitch control -10 prior to launch.
When the catapult is triggered, the plane bounces a tiny bit (the three squiggles on the green line of actual pitch). At the end of the catapult ramp the pitch controller is nosing the plane down when the pitch target suddenly changes to 20% (which is the takeoff pitch set for the takeoff waypoint).
The problem appears to be that the pitch controller is trying to make the plane’s pitch less than the pitch of the ramp. Hence the PID controller drives the nose down to correct the error as it leaves the ramp. While the desired pitch from the takeoff waypoint also shows up at this point in time, the PID controller can’t react quickly enough and the actual pitch drops to zero before it starts to recover.
I’m considering raising the base of my catapult to reduce the launch angle from 9% down to 5%. But it would be much easier if I could change the desired pitch parameter for the moment prior to launch. Does “nudging” work for pitch during automatic takeoff?
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