Subsystem/ahrs
AHRS subsystem
The AHRS subsystem specifies which attitude estimation filter you are using.
Currently possible AHRS subsystems are
- int_cmpl_quat
- int_cmpl_euler
- float_dcm
e.g. for the latest complementary filter:
| File: conf/airframes/myplane.xml |
<firmware name="fixedwing or rotorcraft">
...
<subsystem name="ahrs" type="int_cmpl_quat"/>
</firmware>
|
There is a test program ( sw/airborne/test/ahrs/compare_ahrs.py ) to compare different AHRS implementations on simple test cases.
Complementary Euler (fixed point)
Not recommended for fixedwings, as this filter doesn't compensate for centrifugal force when flying turns.
| File: conf/airframes/myplane.xml |
<firmware name="fixedwing or rotorcraft">
...
<subsystem name="ahrs" type="int_cmpl_euler"/>
</firmware>
<section name="MISC">
<define name="FACE_REINJ_1" value="1024"/>
</section>
|
Complementary Quaternion (fixed point)
Currently not recommended for fixedwings, as this filter doesn't compensate for centrifugal force when flying turns. The capability for this is already there (with AHRS_GRAVITY_UPDATE_COORDINATED_TURN), but it isn't fed with the necessary data yet.
Other flags of interest are:
- AHRS_PROPAGATE_LOW_PASS_RATES : apply a low pass filter on rotational velocity
- AHRS_MAG_UPDATE_YAW_ONLY : use mag to update yaw only
For the latest integer complementary quaternion filter (int_cmpl_quat):
| File: conf/airframes/myplane.xml |
<firmware name="rotorcraft">
...
<subsystem name="ahrs" type="int_cmpl_quat"/>
</firmware>
<section name="AHRS" prefix="AHRS_">
<define name="H_X" value=" 0.51562740288882"/>
<define name="H_Y" value="-0.05707735220832"/>
<define name="H_Z" value=" 0.85490967783446"/>
</section>
|
To calculate the normalised local magnetic field insert the relevant location coordinates hereand calculate.
Screenshot of noaa page.
Copy the north(x),east(y),vertical(z) component values into scilab and execute "X/norm(X)".
Screenshot of scilab page.
