IMU - Migrate to a better attitude calculation algorythm

[digitalentity]

NAV code is now very sensitive to direction of gravity and magnetic field vector in aircraft frame - for controlling accelerations and heading. Estimating attitude as fast and precise as possible is a must. Current complementary filter is doing well, but there are better algorythms available, i.e. Robert Mayhony's DCM filter or Sebastian Madgwick's IMU fusion.

[digitalentity]

current:
text data bss dec hex filename
118204 224 14156 132584 205e8 ./obj/main/cleanflight_NAZE.elf

with Madgwick AHRS
arm-none-eabi-size ./obj/main/cleanflight_NAZE.elf
text data bss dec hex filename
122212 220 14160 136592 21590 ./obj/main/cleanflight_NAZE.elf

Madgwick's AHRS took almost 4kb flash! I'll try see if it works better than complementary filter.

[digitalentity]

Bench tests show that with Madgwick's AHRS heading is much more locked in (when using a compass). I've noticed that after a series of fast pitch-roll rotations complementary filter showed arbitrary heading and took half a second to correct using a compass. Using very same settings and same test Madgwicks AHRS was totally locked in.
But nothing comes without a price - for this I'm paying with extra 4k flash and lots of CPU cycles. When using complementary I was able to get looptime=1000, using AHRS I got only as low as looptime=1400. CPU is spending alot of time calculating AHRS.
Need to try it in-flight and see if it's worth it.

[digitalentity]

Just tried to fly it - much worse than plain old complementary filter. HORIZON mode is very slow to react, copter feels mushy. That's probably due to incorrect beta used. Postponing this for now.

[bk79]

Have you tried slowing loop time? Probably it could help

Il giorno 00:18 mar 04/ago/2015 Konstantin Sharlaimov <
notifications@github.com> ha scritto:

Just tried to fly it - much worse than plain old complementary filter.
HORIZON mode is very slow to react, copter feels mushy. That's probably due
to incorrect beta used. Postponing this for now.

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[digitalentity]

I'm closing this as new NAV PID controllers seem to be doing their job pretty good with current IMU. Will re-open if still necessary.