this improves 4 things in the POSITION1 controller based on logs from
4.2.0beta2. The changes are designed to increase the tolerance to
an incorrect value for Q_TRANS_DECEL, reducing landing overshoot
1) we fix the initialisation of the acceleration. The
init_xy_controller() function assumes zero accel, so we need to
call set_accel_desired_xy_cmss() just after that init to get the
correct accel. Thanks to Leonard for this fix
2) if we decel more than expected due to too low Q_TRANS_DECEL we
need to reduce the target speed, rather than putting the nose down
3) lower the default Q_P_JERK_XY to a value more appropriate for most
quadplanes (Leonard suggested a value of 2)
4) fixed the pitch envelope from Q_BACKTRANS_MS to start after the
airbrake phase is complete
we need to setup last_fw_mode_ms and last_fw_nav_pitch_cd when we
enter POSITION1 mode so that the expanding envelope pitch limit from
Q_BACKTRANS_MS is applied correctly
if we are flying too far off the target vector then exit airbrake
state. This prevents flying for a long distance away from the landing
point in airbrake mode
avoid running the motors while tilted past the tilt max if we are in
AIRBRAKE state. This stops a large amount of forward thrust from the
tilted motors while trying to slow down, while still maintaining
attitude control
we need to reset the takeoff target position while disarmed so we
don't use spurious position information from before we get good GPS
lock.
also remove the "Resetting previous waypoint" message as it doesn't
provide useful information and is just a distraction (it would be
printed continuously while waiting for arming with this PR)
in some situations (such as when landing approach is disabled) the
vfwd integrator can wind up to extreme values. This can put a huge
load on an electric quadplane as it is running both forward and vtol
motors, and the downforce from being nose down can be extreme.
It should never need to go above the cruise throttle in any reasonable
situation, so limit it to cruise to ensure we don't apply too much
forward throttle
prevent very high target speeds when the target velocity profile is
above the initial speed in POSITION1. Always allow up to 2*Q_WP_SPEED,
but don't go above the initial speed