What’ll happen to a quadcopter when it’s hovering at same point in air in guided mode and suddenly GPS get disconnect ? Will it trigger a gps failsafe and land straight down safely? or can keep moving at any place while coming down after gps failsafe trigger ?
It will drift with the local wind conditions while it is either Landing or in AltHold depending on which of those you set. Land is default.
Yeah, thats what actually happened, but it doesn’t seem only like drifting, it kept going anywhere and kept changing directions, when I triggered land, it does reduced the altitude for some period but then started to climb again slowly, finally got crashed into a wired fence
Is this a normal behaviour, shouldn’t it try to land ignoring that its moving anywhere ?
also will using this command mode_guided.set_angle(Quaternion(0,0,0,0), -40, 0, 0) can help in bringing the quadcopter straight down in guided mode if GPS get disconnected in air ?
I see you have some other posts detailing a complex EKF height estimation problem. If this copter is one of the ones experiencing the EKF issue than this is likely related. When GPS is lost in a GPS mode the default failsafe is land mode. From the ArduCopter EKF failsafe wiki:
In autonomous modes that require GPS (i.e. Loiter, PosHold, RTL, Guided, Auto, etc) the FS_EKF_ACTION controls the behaviour. By default this is “1” meaning the vehicle will switch to Land mode. This is a “pilot controlled” land meaning the pilot will have control of the roll and pitch angle but the vehicle will descend at the LAND_SPEED. It will land and finally disarm its motors"
It is possible the copter correctly entered land mode and set a target decent speed. However, the problems with the altitude estimation caused the copter to behave erratically in the z-axis. The x and y axes would continue to coast with any velocity they had when the failsafe was triggered as well as respond to roll and pitch stick commands.
I think it would be better to get the copter to behave as expected and use the built in failsafe handling, rather than try to force a custom failsafe command. Do you have a log of the failsafe flight that can be shared?
thanks for looking into it, you are correct with everything, but there was no EKF/IMU related issue on this quadcopter, i think i would have taken the control from remote during that period when gps got disconnected in air, but i don’t have telemetry attached to quadcopter, so i didn’t get any hint what happened on that quadcopter when gps got disconnected
I switched to land before failsafe triggered, it was moving all around and slowly started descending before failsafe got triggered, but due to some intervention from remote end which i was carrying i put that quadcopter back to guided mode somehow after failsafe triggered, so i don’t think it was trying to land after that, and it was good that it got crashed otherwise anything could have happened.