this uses a new formulation of the GPS based drift correction from
Bill Premerlani that rotates the error vector to avoid relying on
accurate yaw. This means we should get accurate roll/pitch correction
even with lots of magnetometer interference
It also makes it possible to fly a multicopter with no compass. It can
even navigate and correct yaw (slowly!)
this follows the method that Bill developed in his fastRotations
paper. We've demonstrated that this is indeed needed in APM, as we
were able to produce the 'dizzy' effects in both the ArduPlane and
ArduCopter simulator
omega_I applied continuously. _ki larger. Stop integrating when _omega.length()>20
The key change was the scaling of ge to ensure the error is not
quadratic
This makes 3 major changes:
1) fixes the scaling of the yaw drift correction term to fix the time
constant
2) don't integrate the mag vector over multiple readings
3) accumulate omega_I changes over 15 seconds before applying, to try
to prevent omega_I picking up short term responses
this buffers up _omega_I changes in _omega_I_sum over a period of 10
seconds, applying the slope limit only when _omega_I_sum is
transferred to _omega_I.
The result is a huge improvement in the ability of _omega_I to track
gyro drift over the long term.
when a user first connects with USB, and later switches to the
telemetry port without restarting we were getting zero for error_yaw
in the logs, as AHRS.get_error_yaw() was being called twice.
This ensures we give the last value after the counter is reset
Andrew Tridgell
Jonathan Challinger
rmackay9