May 21, 2015
More about GPS failsafe here.
LOW BATTERY
When the battery reaches a low state (voltage under certain value), Erle-Copter will land with
a quick repeating tone. If Erle-Copter reaches the low battery limit during a mission, it will re-
turn to the launch point before landing.
This failsafe permits to you to minimize the risks of having a sudden death of Erle-Copter
and enables a better use of your LiPo batteries.
More about low failsafe battery here.
EKF CHECK & FAILSAFE
The EKF check runs on Erle-Brain and will trigger when the EKF’s compass and velocity “vari-
ance” are higher than 0.8 (configurable with EKF_CHECK_THRESH parameter) for one second.
This “variance” increases as the estimates become untrustworthy. 0 = very trustworthy, >1.0 =
very untrustworthy. If both variances climb above the EKF_CHECK_THRESH parameter (de-
fault is 0.8) the EKF/Inav failsafe triggers.
When the failsafe triggers, Erle-Brain’s tone-alarm will sound. If telemetry is attached
“EKF variance” will appear on the HUD. And EKF/DCM error will be written to the
dataflash logs.
If flying in a flight mode that does not require GPS nothing further will happen but
you will be unable to switch into an autopilot flight mode (Loiter, PosHold, RTL, Guided,
Auto) until the failure clears. If flying in a mode that requires GPS (Loiter, PosHold, RTL,
Guided, Auto) the vehicle will switch to “pilot controlled” LAND. Meaning the pilot will
have control of the roll and pitch angle but the vehicle will descend, land and finally
disarm it’s motors. The pilot can, like always switch into a manual flight mode including
Stabilize or AltHold to bring the vehicle home.
The EKF check and failsafe can be disabled by setting the EKF_CHECK_THRESH to “0” through
the Ground Control Station’s Config/Tuning » Full Parameter List. Alternatively it can be made
less sensitive by increasing this parameter from 0.8 to 0.9 or 1.0. The downside of increasing
this parameter’s value is that during a flyaway caused by a bad compass or GPS glitching, the
vehicle will fly further away before the vehicle is automatically switched to LAND mode.
More about EKF failsafe here.
Erle-Copter, a smart drone powered by Linux 8
