PX4 - Safety Configuration
Introduction
Access documentation
Failsafes specify areas and conditions in which it is safe to fly. It also indicates actions to be performed if failsafe is triggered.
Most important failsafe settings are configured in QGroundControl Safety Setup page. Others are through parameters.
In remote, can use safety switches to immediately stop motors or return vehicle.
Failsafe Actions
| Action | Description |
|---|---|
| None/Disabled | No action. Failsafe will be ignored. |
| Warning | Warning message will be sent. |
| Hold | Will enter hold mode, and hover or circle. |
| Return | Enters return mode. Behavior is configurable. |
| Land | Will enter land mode. |
| Disarm | Stops motors immediately. |
| Termination | Turns off all controllers and sets PWM to failsafe values. Can be used to deploy a parachute, landing gear, etc. |
Safety Setup
through QGroundControl
Note: This only includes most important failsafe settings.
Low Battery
Triggered when battery capacity drops below one or more warning levels. You have Warn > Failsafe > Emergency trigger levels in battery percent.
Only options are to Warn, Return or Land. Either triggered when bat level falls below failsafe, or can distribute it according to the different trigger levels.
Manual Control Loss
Triggered if connection to RC transmitter or joystick is loss without fallback. In QGC, you can set RC Loss timeout and failsafe action.
Data Link Loss
Triggered if telemetry link to groundstation is lost. Can set a timeout and failsafe action.
Geofence
Triggered when drone breaches virtual perimeter. Can specify max radius and altitude or provide more complex geofences through alternate means. Also includes failsafe action on breach.
Configure Return Mode
This failsafe action can be configured here. Can set land/loiter behaviour after returning.
Configure Land Mode
Can specify descent rate in metres-per-second and also configure if the system should be disarmed (after a provided duration).
through Parameters or Other Means
Position (GPS) Loss
Triggered if quality of PX4 position estimate falls below acceptable levels (can be cause by GPS loss)
When triggered, it will either Hold or enter Land mode depending on nature of available information.
Can set the duration before failsafe trigger through parameter server.
Offboard Loss
Triggered if offboard link is lost while under offboard control mode. Refer to this section to understand what the offboard control signal rate signifies.
Traffic Avoidance
Allows PX4 to respond to transponder data during missions. Can set failsafe actions through parameters.
Failure Detector
Allows a vehicle to take protective action if it unexpectedly flips or if notified by external failure detection system.
Failure detector during flight is deactivated by default. Enable by setting CBRK_FLIGHTTERM=0
Failure detective is active on all vehicle types and modes, except for those expected to do flips.
Attitude Trigger
Can be configured to trigger if vehicle attitude exceeds predefined pitch and roll for longer than specific time period.
During takeoff, it invokes disarm if vehicle flips. Always active on takeoff irrespective of CBRK_FLIGHTTERM
External Automatic Trigger System (ATS)
External ATS must be connected to flight controller port AUX5 (or MAIN5) and configured using the assigned parameters.