ledinot
commented
7 years ago Yes, here again it was written too quickly.
For landing, the target, or preset operating point, or (final) reference value, is more complicated than for the other phases. For all phases except landing there is only one target: either a Speed value or an Altitude value. But for landing there are three of them…, control is more complicated (but still assumed to be solvable with gain-scheduled PIDs).
Why? Because the payload has to be delivered at a specified place, or the mission will be considered to have failed. The “specified place” (1D horizontal navigation …) is defined by Distance, i.e the constant that was loaded once for all in mission preparation phase, not Distance(t) the instantaneous range performed by the drone.
So end of landing has to be such that at tf (t final), the last instant of flight:
- Distance(tf)~Distance, i.e (Distance(tf) – Distance) =< DeliveryPrecisionUpperBound.
- Altitude(tf)=0
- Speed(tf)=0
Otherwise there is a problem:
- Altitude(tf)=0, Speed(tf)=0, (Distance(tf) – Distance) > DeliveryPrecisionUpperBound => payload was delivered at an unspecified place. Mission failure.
- Altitude(tf)=/=0, Speed(tf)=0, Distance(tf)~Distance, => crash of the drone. Speed is the drone’s horizontal speed (also called ground speed), so the drone finishes its flight by falling vertically like a stone.
- Altitude(tf)=0, Speed(tf)> 0, Distance(tf) ~ Distance => hazard or crash depending on the value of Speed(tf).
This third case will be rare, it can only be made possible by windshear (vertical wind). The drone slows down (horizontally) while losing altitude and having a range nearing Distance, but a downward gust of wind (windshear) ‘smashed’ it on ground just before touching smoothly, leaving it no time to lose its residual horizontal speed.
De : Anthony Leonardo Gracio [mailto:notifications@github.com] Envoyé : jeudi 6 juillet 2017 15:22 À : AdaCore/RESSAC_Use_Case Cc : Subscribed Objet : [AdaCore/RESSAC_Use_Case] Distance objective when landing (#29)
In 6.7.4 (Reference Trajectory Generation), it's said that "For landing, a distance objective is added to the zero-altitude objective". But this distance objective is never mentioned in the other parts of the F_FC behavioral specification: only the speed/altitude objectives are used.
Where does it come from?
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In 6.7.4 (Reference Trajectory Generation), it's said that "For landing, a distance objective is added to the zero-altitude objective". But this distance objective is never mentioned in the other parts of the F_FC behavioral specification: only the speed/altitude objectives are used.
Where does it come from?