APM:Plane 3.5.2 released

The ArduPilot development team is proud to announce the release of version 3.5.2 of APM:Plane. This is a minor release with small changes.

The main reason for this release over the recent 3.5.1 release is a fix for a bug where the px4io co-processor on a Pixhawk can run out of memory while booting. This causes the board to be unresponsive on boot. It only happens if you have a more complex servo setup and is caused by too much memory used by the IO failsafe mixer.

The second motivation for this release is to fix an issue where during a geofence altitude failsafe that happens at low speed an aircraft may dive much further than it should to gain speed. This only happened if the thrust line of the aircraft combined with low pitch integrator gain led to the aircraft not compensating sufficiently with elevator at full throttle in a TECS underspeed state. To fix this two changes have been made:

  • a minimum level of integrator in the pitch controller has been added. This level has a sufficiently small time constant to avoid the problem with the TECS controller in an underspeed state.
  • the underspeed state in TECS has been modified so that underspeed can end before the full target altitude has been reached, as long as the airspeed has risen sufficiently past the minimum airspeed for a sufficient period of time (by 15% above minimum airspeed for 3 seconds).

Many thanks to Marc Merlin for reporting this bug!

The default P gains for both roll and pitch have also been raised from 0.4 to 0.6. This is to help for users that fly with the default parameters. A value of 0.6 is safe for all aircraft that I have analysed logs for.

The default gains and filter frequencies of the QuadPlane code have also been adjusted to better reflect the types of aircraft users have been building.

Other changes include:

  • improved QuadPlane logging for better analysis and tuning (adding RATE and QTUN messages)
  • fixed a bug introduced in 3.5.1 in rangefinder landing
  • added TECS logging of speed_weight and flags
  • improvements to the lsm303d driver for Linux
  • improvements to the waf build system

Happy flying!