Failsafes

Individual failsafes are triggered when a certain set of conditions are met. Failsafe actions can be configured individually for each failsafe trigger. When a failsafe is triggered, the cooresponding failsafe action is executed. Some failsafes have additional settings that allow you to adjust the trigger conditions, such as maximum acceptable pressure or temperature.

Failsafe actions are only executed once when a failsafe is triggered. The vehicle can be armed during an active failsafe condition if the arming checks are passing. The flight mode can be changed as long as the failsafe conditions do not prevent it. If an active failsafe is cleared, the failsafe action will be executed again if the failsafe re-triggers.

Triggers

Leak

Triggered immediately when a configured Leak Detector detects a leak. The failsafe is cleared if the leak detector reports no leaks for two seconds.

Internal Pressure

This is triggered when the internal pressure of the water tight enclosure (WTE) exceeds the threshold set by the FS_PRESS_MAX parameter for two seconds. The failsafe is cleared immediately when the internal pressure is less than the threshold value.

Internal Temperature

This is triggered when the internal temperature of the water tight enclosure (WTE) exceeds the threshold set by the FS_TEMP_MAX parameter. The failsafe is cleared immediately when the internal temperature is less than the treshold value.

Ground Control Station HEARTBEAT

Triggered when a HEARTBEAT from the ground control station matching SYSID_MYGCS hasn't been received for more than 2.5 seconds. The failsafe is cleared immediately when a HEARTBEAT is received.

Note If the system id of the companion computer is a match with SYSID_MYGCS , then the heartebeats originating from a process (ie MAVProxy) on the companion computer may prevent this failsafe from triggering when expected.

Pilot Input

Triggered when pilot manual control input has not been received since the amount of time specified by the FS_PILOT_TIMEOUT parameter.

Sensors

Triggered when a sensor failure prevents the current flight mode to proceed. This occurs if the depth sensor fails while in depth hold mode. The autopilot will switch into MANUAL mode when triggered. This failsafe is always enabled, and is not configurable.

Battery

Triggered when the battery voltage drops below the voltage specified by the FS_BATT_VOLTAGE parameter, or if the remaining capacity drops below the capacity specified by the FS_BATT_MAH parameter.

EKF

Triggered when the EKF compass or velocity variances exceed the threshold set by the FS_EKF_THRESH parameter.

Crash

Triggered when the angle error exceeds 30 degrees for more than 2 seconds. This is never triggered in Manual or Acro flight modes.

Actions

Disabled

The failsafe is disabled, and nothing (not even event logging) will happen.

Warn Only

A message will be sent to the ground control station indicating the failsafe conditions have been met. The warning is sent via STATUSTEXT messages, there is no mechanism to immediately re-send the message in the case that it was not received by the ground control station. The warning is sent repeatedly at 20~30 second intervals as long as the failsafe conditions are met.

These warnings are also sent if the failsafe action is set to anything other than Disabled.

Disarm

If the vehicle is armed, the vehicle will disarm immediately when the failsafe conditions are met. The vehicle can be re-armed after the failsafe triggers, even while the failsafe conditions are met, as long as the arming checks are passing. If the failsafe clears due to resolved conditions, the vehicle will disarm again if the failsafe is re-triggered.

Surface

If the vehicle is armed, the vehicle will enter Surface flight mode. The flight mode can be changed by the pilot, and the vehicle may be disarmed at any point.

Hold

If the vehicle is armed, the vehicle will enter Position Hold mode, or Depth Hold mode, if positioning is not possible.

Sponsored by Blue Robotics. Code released under the GPLv3 License. Documentation released under the CC-NC-SA 4.0.
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