AHRS using complementary filter in floating point.

Propagation is done in quaternion representation. Estimates the gyro bias. By default uses magnetometer for heading for rotorcrafts. For fixedwing firmware AHRS_GRAVITY_UPDATE_COORDINATED_TURN is enabled by default.

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_cmpl_quat">
   <define name="AHRS_MAG_UPDATE_ALL_AXES" value="FALSE|TRUE" />
   <define name="AHRS_USE_GPS_HEADING" value="FALSE|TRUE" />
   <define name="AHRS_GRAVITY_UPDATE_COORDINATED_TURN" value="FALSE|TRUE" />
   <define name="AHRS_GPS_SPEED_IN_NEGATIVE_Z_DIRECTION" value="FALSE|TRUE" />
   <define name="AHRS_PROPAGATE_LOW_PASS_RATES" />
   <define name="AHRS_GRAVITY_HEURISTIC_FACTOR" value="30" />
   <define name="AHRS_FC_IMU_ID" value="ABI_BROADCAST" />
   <define name="AHRS_FC_MAG_ID" value="ABI_BROADCAST" />
   <define name="AHRS_FC_GPS_ID" value="GPS_MULTI_ID" />
   <configure name="USE_MAGNETOMETER" value="TRUE" />
   <configure name="AHRS_ALIGNER_LED" value="1" />
 </module>

Module configuration options

Configure Options

name: USE_MAGNETOMETER value: TRUE
Description: set to FALSE to disable magnetometer
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_USE_GPS_HEADING value: FALSE|TRUE
Description: Use GPS course to update heading
name: AHRS_GRAVITY_UPDATE_COORDINATED_TURN value: FALSE|TRUE
Description: Compensation of centrifugal force via GPS speed (to fly in circles with a fixedwing)
name: AHRS_GPS_SPEED_IN_NEGATIVE_Z_DIRECTION value: FALSE|TRUE
Description: AHRS_GRAVITY_UPDATE_COORDINATED_TURN assumes the GPS speed is in the X axis direction. Quadshot, DelftaCopter and other hybrids can have the GPS speed in the negative Z direction
name: AHRS_PROPAGATE_LOW_PASS_RATES value: None
Description: apply a low pass filter on rotational velocity
name: AHRS_GRAVITY_HEURISTIC_FACTOR value: 30
Description: Default is 30. Reduce accelerometer cut-off frequency when the vehicle is accelerating: norm(ax,ay,az) ~ 9,81 m/s2. WARNING: when the IMU is not well damped, the norm of accelerometers never equals to 9,81 m/s2. As a result, the GRAVITY_HEURISTIC_FACTOR will reduce the accelerometer bandwith even if the vehicle is not accelerating. Set to 0 in case of vibrations
name: AHRS_FC_IMU_ID value: ABI_BROADCAST
Description: ABI sender id of IMU to use
name: AHRS_FC_MAG_ID value: ABI_BROADCAST
Description: ABI sender id of magnetometer to use
name: AHRS_FC_GPS_ID value: GPS_MULTI_ID
Description: ABI sender id of GPS 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_cmpl_quat.xml file:

<!DOCTYPE module SYSTEM "module.dtd">
<module name="ahrs_float_cmpl_quat" dir="ahrs">
  <doc>
    <description>
      AHRS using complementary filter in floating point.
      Propagation is done in quaternion representation.
      Estimates the gyro bias.
      By default uses magnetometer for heading for rotorcrafts.
      For fixedwing firmware AHRS_GRAVITY_UPDATE_COORDINATED_TURN is enabled by default.
    </description>
    <configure name="USE_MAGNETOMETER" value="TRUE" description="set to FALSE to disable magnetometer"/>
    <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_USE_GPS_HEADING" value="FALSE|TRUE" description="Use GPS course to update heading"/>
    <define name="AHRS_GRAVITY_UPDATE_COORDINATED_TURN" value="FALSE|TRUE" description="Compensation of centrifugal force via GPS speed (to fly in circles with a fixedwing)"/>
    <define name="AHRS_GPS_SPEED_IN_NEGATIVE_Z_DIRECTION" value="FALSE|TRUE" description="AHRS_GRAVITY_UPDATE_COORDINATED_TURN assumes the GPS speed is in the X axis direction. Quadshot, DelftaCopter and other hybrids can have the GPS speed in the negative Z direction"/>
    <define name="AHRS_PROPAGATE_LOW_PASS_RATES" description="apply a low pass filter on rotational velocity"/>
    <define name="AHRS_GRAVITY_HEURISTIC_FACTOR" value="30" description="Default is 30. Reduce accelerometer cut-off frequency when the vehicle is accelerating: norm(ax,ay,az) ~ 9,81 m/s2. WARNING: when the IMU is not well damped, the norm of accelerometers never equals to 9,81 m/s2. As a result, the GRAVITY_HEURISTIC_FACTOR will reduce the accelerometer bandwith even if the vehicle is not accelerating. Set to 0 in case of vibrations"/>
    <define name="AHRS_FC_IMU_ID" value="ABI_BROADCAST" description="ABI sender id of IMU to use"/>
    <define name="AHRS_FC_MAG_ID" value="ABI_BROADCAST" description="ABI sender id of magnetometer to use"/>
    <define name="AHRS_FC_GPS_ID" value="GPS_MULTI_ID" description="ABI sender id of GPS to use"/>
  </doc>
  <settings>
    <dl_settings>
      <dl_settings NAME="AHRS">
        <dl_setting var="ahrs_fc.gravity_heuristic_factor" min="0" step="1" max="50" module="subsystems/ahrs/ahrs_float_cmpl" shortname="g_heuristic" param="AHRS_GRAVITY_HEURISTIC_FACTOR" type="uint8" persistent="true"/>
        <dl_setting var="ahrs_fc.accel_omega" min="0.02" step="0.02" max="0.2" module="subsystems/ahrs/ahrs_float_cmpl" shortname="acc_omega" param="AHRS_ACCEL_OMEGA" unit="rad/s" type="float" persistent="true"/>
        <dl_setting var="ahrs_fc.accel_zeta" min="0.7" step="0.05" max="1.5" module="subsystems/ahrs/ahrs_float_cmpl" shortname="acc_zeta" param="AHRS_ACCEL_ZETA" type="float" persistent="true"/>
        <dl_setting var="ahrs_fc.mag_omega" min="0.02" step="0.01" max="0.1" module="subsystems/ahrs/ahrs_float_cmpl" shortname="mag_omega" param="AHRS_MAG_OMEGA" unit="rad/s" type="float" persistent="true"/>
        <dl_setting var="ahrs_fc.mag_zeta" min="0.7" step="0.05" max="1.5" module="subsystems/ahrs/ahrs_float_cmpl" shortname="mag_zeta" param="AHRS_MAG_ZETA" 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" firmware="fixedwing">
    <configure name="USE_MAGNETOMETER" default="0"/>
    <define name="AHRS_USE_GPS_HEADING" cond="ifneq (,$(findstring $(USE_MAGNETOMETER),0 FALSE))"/>
    <define name="AHRS_GRAVITY_UPDATE_COORDINATED_TURN"/>
  </makefile>
  <makefile target="!sim|fbw">
    <configure name="USE_MAGNETOMETER" default="1"/>
    <define name="USE_MAGNETOMETER" cond="ifeq (,$(findstring $(USE_MAGNETOMETER),0 FALSE))"/>
    <define name="AHRS_ALIGNER_LED" value="$(AHRS_ALIGNER_LED)" cond="ifneq ($(AHRS_ALIGNER_LED),none)"/>
    <define name="USE_AHRS"/>
    <define name="USE_AHRS_ALIGNER"/>
    <define name="AHRS_PROPAGATE_QUAT"/>
    <file name="ahrs.c" dir="subsystems"/>
    <file name="ahrs_aligner.c" dir="subsystems/ahrs"/>
    <file name="ahrs_float_cmpl.c" dir="subsystems/ahrs"/>
    <file name="ahrs_float_cmpl_wrapper.c" dir="subsystems/ahrs"/>
    <raw>
ifdef SECONDARY_AHRS
ifneq (,$(findstring $(SECONDARY_AHRS), fcq float_cmpl_quat))
# this is the secondary AHRS
$(TARGET).CFLAGS += -DAHRS_SECONDARY_TYPE_H=\"subsystems/ahrs/ahrs_float_cmpl_wrapper.h\"
$(TARGET).CFLAGS += -DSECONDARY_AHRS=ahrs_fc
else
# this is the primary AHRS
$(TARGET).CFLAGS += -DAHRS_TYPE_H=\"subsystems/ahrs/ahrs_float_cmpl_wrapper.h\"
$(TARGET).CFLAGS += -DPRIMARY_AHRS=ahrs_fc
endif
else
# plain old single AHRS usage
$(TARGET).CFLAGS += -DAHRS_TYPE_H=\"subsystems/ahrs/ahrs_float_cmpl_wrapper.h\"
endif
    </raw>
  </makefile>
</module>