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 enables MNT_* parameter control of the camera mount code. It also
fixes the conversion of calculated angles between degrees and
integers, and fixes stabilised mount control when yaw control is not
available.
this allows us to use the MS5611 barometer at its full 100Hz sample
rate (80Hz for pressure, 20Hz for temperature). The pressure and
temperature values are averaged between reads without adding any
latency. Previously the driver would throw away values between
readings
This also fixes a race condition in reading from the SPI bus that
could lead to bad values from the barometer
this fixes several problems with reading analog sources:
- we were getting poor values because we didn't wait long enough for
an analog source to settle
- we wasted a lot of CPU cycles waiting for conversions
- we were not taking averages over many samples, which we did with
the old AP_ADC driver on the APM1
this seems to have been the cause of the 'flips' seen by Marco and
others. Testing by Craig and Alan shows that the flips are gone when
the barometric acceleration is removed.
It looks like a 5 point average filter is not enough to keep the
vertical acceleteration noise low. With high noise in the z axes, the
x and y axes are scaled back when the ge vector is normalised.
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
the new AHRS code doesn't use calculate() and the compass.heading
attribute. Instead it works on the raw magnetometer vector. This
change removes the internal calculate state from the compass object
and instead adds calculate_heading() for use by older code that
doesn't go via AHRS.
This significantly reduces the calculation involved in compass updates
The null offsets enable/disable code is also removed, as it is not
needed now that compass offsets are not linked to the AHRS state.
this allows the barometer driver to calibrate and return altitude and
climb rate values. This will be used by the AHRS drift correction code
for vertical velocity
The climb rate uses a 5 point average filter
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
