APX4 2.7.12


Please use the following Auterion Mission Control or newer with this version of APX4:

pageAMC 1.18.3

What's new

Compassless Flight Mode

What is it?

"Compassless" is a mode of operation of the navigation filter where no magnetometer data is used after initial heading alignment and the filter continues to estimate the true North through GNSS fusion. This is especially useful when the magnetic measurements cannot be used in flight because of external magnetic distortions (e.g. flying near a large metallic structure) or generated by the drone itself (e.g. high current flowing through the power cables).

How to use?

To enable, set EKF2_MAG_TYPE to "init" (6).

During the takeoff phase, the aircraft might exhibit some horizontal displacement, commonly known as "toilet bowling" while the initial alignment is still adjusting; those movements (usually less than 1 meter) allow the estimator to retrieve the correct heading.

In a situation where there is a magnetic interference that is preventing the aircraft to determine its heading before takeoff, the following options exist:

  • [Recommended] Move away from any sources of magnetic interference. In most cases, moving the drone a few meters away will allow it to get a better magnetic reading to figure out the heading and position mode will become available for takeoff.

  • Take off in altitude mode. Shortly after flying in altitude mode, GNSS heading will be locked and switching to position controlled modes is now possible.

Additional updates

  • Introduce optional failsafe actions for breaching the maximum wind limit via a new parameter, COM_WIND_MAX_ACT. Options include: warning only, RTL (default), and land.

  • Introduce hysteresis for disarm gesture while in air. Hysteresis time is set via COM_RC_DARM_A_H parameter.

  • Expose parameter, EKF2_BARO_B_EN, to optionally disable barometric pressure bias estimation. When enabled (default and recommended), the estimator will use GNSS height data to estimate the drift of the barometric height. Disable in case GNSS altitude should not be relied on.

What improved

  • Prevent the ADS1115 ADC driver from accidentally recognizing another device with the same address on the bus. For example, the SE050 chip on FMUv5X can have the same basic address of 0x48. Further prevent spamming the console when the device is lost.

  • Fixed bug declaring airspeed data invalid after VTOL transition in GNSS denied environments.

  • Fixed bug that, when attempting to start a mission that has been cleared, led to a state where the vehicle gets stuck in mission mode with motors at idle on the ground.

  • Fixed bug that reset an altered fixed-wing airspeed setpoint to cruise when switching to orbit flight mode. Flight speed is now only reset when switching flight modes (e.g. from Mission to Orbit or RTL).

  • Fixed a sign convention check on a component of tilt-rotor control allocation which led to faulty actuator desaturation behavior. Note this bug was only present when MC_AIRMODE was disabled (only typical during initial tuning/bring up of platforms).

  • Fixed occasional timing issue causing a VTOL pusher/puller thrust to drop to 0 momentarily after the front transition is completed. Only present on some ESCs which switch off completely on zero commands.

  • Improved logic which previously caused fixed-wing aircraft to climb again to RTL altitude when an RTL command is sent while already in the orbit down phase of a mission landing. The aircraft now continues on with the mission landing when RTL is commanded.

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