The main motivation for the release is a problem with flying without a compass enabled. If you fly 3.5.2 with MAG_ENABLE=0 or no compass attached then there is a risk that the EKF2 attitude estimator may become unstable before takeoff. This can cause the aircraft to crash.
The other changes in the 3.5.2 release are more minor:
- fixed loiter radius for counter-clockwise loiter
- fixed the loiter radius when doing a RTL at the end of a mission
- provide reasons to the GCS when a uBlox GPS fails to properly configure
- support a wider variety of NMEA GPS receivers
- use EKF1 by default if no compass is enabled
For those of you feeling a bit more adventurous you might like to try the 3.6.0beta1 release. There is still a fair bit more to do before 3.6.0 is out, but it already has a lot of new features and I have been flying it for a while now.
The biggest single change in 3.6.0beta1 is the update of PX4Firmware. This brings with it a lot of changes, including much better support for the Pixracer flight board.
There has also been a lot more work on QuadPlane support, which a new QRTL flight mode, plus support for using the forward motor in VTOL flight and active weathervaning support. If you are flying a QuadPlane you'll find the names of the copter rate control parameters have changed (just like they have in copter). You should be able to find the new parameters OK, but if not then please ask. I'll provide more detailed documentation with the final 3.6.0 release.
Detailed changes in 3.6.0beta1 include:
- merge upstream PX4Firmware changes
- new AC_AttitudeControl library from copter for quadplane
- modified default gains for quadplanes
- new velocity controller for initial quadplane landing
- smooth out final descent for VTOL landing
- changed default loop rate for quadplanes to 300Hz
- support up to 16 output channels (two via SBUS output only)
- fixed bug with landing flare for high values of LAND_FLARE_SEC
- improved crash detection logic
- added in-flight transmitter tuning
- fix handling of SET_HOME_POSITION
- added Q_VFWD_GAIN for forward motor in VTOL modes
- added Q_WVANE_GAIN for active weathervaning
- log the number of lost log messages
- Move position update to 50hz loop rather then the 10hz
- Suppress throttle when parachute release initiated, not after release.
- support Y6 frame class in quadplane
- log L1 xtrack error integrator and remove extra yaw logging
- limit roll before calculating load factor
- simplify landing flare logic
- smooth-out the end of takeoff pitch by reducing takeoff pitch min via TKOFF_PLIM_SEC
- added support for DO_VTOL_TRANSITION as a mission item
- fixed is_flying() for VTOL flight
- added Q_ENABLE=2 for starting AUTO in VTOL
- reload airspeed after VTOL landing
- lower default VTOL ANGLE_MAX to 30 degrees
- Change mode to RTL on end of mission rather then staying in auto
- implemented QRTL for quadplane RTL
- added Q_RTL_MODE parameter for QRTL after RTL approach
- reduced the rate of EKF and attitude logging to 25Hz
- added CHUTE_DELAY_MS parameter
- allow remapping of any input channel to any output channel
- numerous waf build improvements
- support fast timer capture for camera trigger feedback
- numerous improvements for Pixracer support
- added more general tiltrotor support to SITL
I flew both 3.5.3 and 3.6.0beta1 today and both are really flying nicely. I hope you all enjoy flying it as much as the dev team enjoy working on it!