AHRS using MLKF filter.

Multiplicative Linearized Kalman Filter in quaternion formulation. Estimates the gyro bias and needs magnetometer to update all 3 axes. Not suitable for fixedwings! Suitable for rotorcraft. The magnetometer is used and needs to be well calibrated. Estimates attitude and heading. Does not use GPS.

Example for airframe file

Add to your firmware section: This example contains all possible configuration options, not all of them are mandatory!

 <module name="ahrs_float_mlkf">
   <define name="AHRS_MAG_UPDATE_ALL_AXES" value="FALSE|TRUE" />
   <define name="AHRS_MLKF_IMU_ID" value="ABI_BROADCAST" />
   <define name="AHRS_MLKF_MAG_ID" value="ABI_BROADCAST" />
   <configure name="AHRS_ALIGNER_LED" value="1" />
 </module>

Module configuration options

Configure Options

name: AHRS_ALIGNER_LED value: 1
Description: LED number to indicate AHRS alignment, none to disable (default is board dependent)

Define Options

name: AHRS_MAG_UPDATE_ALL_AXES value: FALSE|TRUE
Description: Use magnetometer to update all axes and not only yaw
name: AHRS_MLKF_IMU_ID value: ABI_BROADCAST
Description: ABI sender id of IMU to use
name: AHRS_MLKF_MAG_ID value: ABI_BROADCAST
Description: ABI sender id of magnetometer to use

Auto-loaded modules

The following modules are automatically loaded (just as if you had added them in the airframe file)

ahrs_sim module

Files

Header Files

The following headers are automatically included in modules.h

ahrs.h

Source Files

Raw ahrs_float_mlkf.xml file:

<!DOCTYPE module SYSTEM "module.dtd">
<module name="ahrs_float_mlkf" dir="ahrs">
  <doc>
    <description>
      AHRS using MLKF filter.
      Multiplicative Linearized Kalman Filter in quaternion formulation.
      Estimates the gyro bias and needs magnetometer to update all 3 axes.
      Not suitable for fixedwings!
      Suitable for rotorcraft. The magnetometer is used and needs to be well calibrated. Estimates attitude and heading. Does not use GPS.
    </description>
    <configure name="AHRS_ALIGNER_LED" value="1" description="LED number to indicate AHRS alignment, none to disable (default is board dependent)"/>
    <define name="AHRS_MAG_UPDATE_ALL_AXES" value="FALSE|TRUE" description="Use magnetometer to update all axes and not only yaw"/>
    <define name="AHRS_MLKF_IMU_ID" value="ABI_BROADCAST" description="ABI sender id of IMU to use"/>
    <define name="AHRS_MLKF_MAG_ID" value="ABI_BROADCAST" description="ABI sender id of magnetometer to use"/>
  </doc>
  <settings>
    <dl_settings>
      <dl_settings NAME="AHRS">
        <dl_setting var="ahrs_mlkf.mag_noise.x" min="0.0" step="0.02" max="1.0" module="subsystems/ahrs/ahrs_float_mlkf" shortname="mag_noise_x" param="AHRS_MAG_NOISE_X" type="float" persistent="true"/>
        <dl_setting var="ahrs_mlkf.mag_noise.y" min="0.0" step="0.02" max="1.0" module="subsystems/ahrs/ahrs_float_mlkf" shortname="mag_noise_y" param="AHRS_MAG_NOISE_Y" type="float" persistent="true"/>
        <dl_setting var="ahrs_mlkf.mag_noise.z" min="0.0" step="0.02" max="1.0" module="subsystems/ahrs/ahrs_float_mlkf" shortname="mag_noise_z" param="AHRS_MAG_NOISE_Z" type="float" persistent="true"/>
      </dl_settings>
    </dl_settings>
  </settings>
  <autoload name="ahrs_sim"/>
  <header>
    <file name="ahrs.h" dir="subsystems"/>
  </header>
  <makefile target="!sim|fbw">
    <configure name="USE_MAGNETOMETER" default="1"/>
    <define name="USE_MAGNETOMETER" cond="ifeq (,$(findstring $(USE_MAGNETOMETER),0 FALSE))"/>
    <define name="AHRS_ALIGNER_LED" value="$(AHRS_ALIGNER_LED)" cond="ifneq ($(AHRS_ALIGNER_LED),none)"/>
    <define name="USE_AHRS"/>
    <define name="USE_AHRS_ALIGNER"/>
    <file name="ahrs.c" dir="subsystems"/>
    <file name="ahrs_aligner.c" dir="subsystems/ahrs"/>
    <file name="ahrs_float_mlkf.c" dir="subsystems/ahrs"/>
    <file name="ahrs_float_mlkf_wrapper.c" dir="subsystems/ahrs"/>
    <raw>
ifdef SECONDARY_AHRS
ifneq (,$(findstring $(SECONDARY_AHRS), mlkf float_mlkf))
# this is the secondary AHRS
$(TARGET).CFLAGS += -DAHRS_SECONDARY_TYPE_H=\"subsystems/ahrs/ahrs_float_mlkf_wrapper.h\"
$(TARGET).CFLAGS += -DSECONDARY_AHRS=ahrs_mlkf
else
# this is the primary AHRS
$(TARGET).CFLAGS += -DAHRS_TYPE_H=\"subsystems/ahrs/ahrs_float_mlkf_wrapper.h\"
$(TARGET).CFLAGS += -DPRIMARY_AHRS=ahrs_mlkf
endif
else
# plain old single AHRS usage
$(TARGET).CFLAGS += -DAHRS_TYPE_H=\"subsystems/ahrs/ahrs_float_mlkf_wrapper.h\"
endif
    </raw>
  </makefile>
</module>