filter_1euro_imu module

Prefiltering for IMU data using 1euro filter.

The 1 Euro filter is an first order low pass filter with an adaptive cutoff frequency. It is able to efficiently remove high frequency noise when the average signal is stable with very small lag by increasing the bandwith to capture faster movements.

Only two parameters are required to tune the filter:

• mincutoff that defines the minimum bandwith: reduce it if noise at low speed is a problem
• beta that is the adaptation coefficient: increase it if lag at high speed is a problem

In order to use this filter for your IMU (on Gyro and Acell data, Mag passthrough), you only need to redefine the source of data in the ABI bindings of the AHRS/INS filter being used. For instance, if the 'ahrs_int_cmpl_quat' AHRS is used, this module should be loaded with the following options: define name="AHRS_ICQ_IMU_ID" value="IMU_F1E_ID" define name="AHRS_ALIGNER_IMU_ID" value="IMU_F1E_ID"

Example for airframe file

Add to your firmware section:

<module name="filter_1euro_imu"/>

Module configuration options

Airframe file section

• section name: FILTER_1EURO prefix: FILTER_1EURO_
  • name ENABLED value: FALSE|TRUE
    Description: activate or not the filter by default
  • name GYRO_MINCUTOFF value: 10.
    Description: minimum cutoff freq for gyro signal
  • name GYRO_BETA value: 0.1
    Description: adaptation coefficient for gyro signal
  • name ACCEL_MINCUTOFF value: 0.1
    Description: minimum cutoff freq for accel signal
  • name ACCEL_BETA value: 0.01
    Description: adaptation coefficient for accel signal
  • name FREQ value: 512
    Description: set fixed frequency, if not defined but INS/AHRS_PROPAGATE_FREQUENCY is defined it is used, otherwise autofreq is used

Module functions

Init Functions

These initialization functions are called once on startup.

• filter_1euro_imu_init()

Files

Header Files

The following headers are automatically included in modules.h

• filter_1euro_imu.h

Source Files

• modules/imu/filter_1euro_imu.c

Raw filter_1euro_imu.xml file:

<!DOCTYPE module SYSTEM "module.dtd">

<module name="filter_1euro_imu" dir="imu">
  <doc>
    <description>
      Prefiltering for IMU data using 1euro filter.

      The 1 Euro filter is an first order low pass filter with an adaptive cutoff frequency.
      It is able to efficiently remove high frequency noise when the average signal is stable
      with very small lag by increasing the bandwith to capture faster movements.

      Only two parameters are required to tune the filter:
      - mincutoff that defines the minimum bandwith: reduce it if noise at low speed is a problem
      - beta that is the adaptation coefficient: increase it if lag at high speed is a problem

      In order to use this filter for your IMU (on Gyro and Acell data, Mag passthrough), you only
      need to redefine the source of data in the ABI bindings of the AHRS/INS filter being used.
      For instance, if the 'ahrs_int_cmpl_quat' AHRS is used, this module should be loaded with
      the following options:
        define name="AHRS_ICQ_IMU_ID" value="IMU_F1E_ID"     
        define name="AHRS_ALIGNER_IMU_ID" value="IMU_F1E_ID"     
    </description>
    <section name="FILTER_1EURO" prefix="FILTER_1EURO_">
      <define name="ENABLED" value="FALSE|TRUE" description="activate or not the filter by default"/>
      <define name="GYRO_MINCUTOFF" value="10." description="minimum cutoff freq for gyro signal"/>
      <define name="GYRO_BETA" value="0.1" description="adaptation coefficient for gyro signal"/>
      <define name="ACCEL_MINCUTOFF" value="0.1" description="minimum cutoff freq for accel signal"/>
      <define name="ACCEL_BETA" value="0.01" description="adaptation coefficient for accel signal"/>
      <define name="FREQ" value="512" description="set fixed frequency, if not defined but INS/AHRS_PROPAGATE_FREQUENCY is defined it is used, otherwise autofreq is used"/>
    </section>
  </doc>
  <settings>
    <dl_settings>
      <dl_settings name="1e_imu">
        <dl_setting min="0" max="1" step="1" var="filter_1e_imu.enabled" module="imu/filter_1euro_imu" shortname="enable" values="DISABLED|ENABLED" handler="reset"/>
        <dl_setting min="0.1" max="50." step="0.1" var="filter_1e_imu.gyro_mincutoff" module="imu/filter_1euro_imu" shortname="gyro mincutoff" handler="update_gyro_mincutoff"/>
        <dl_setting min="0.0001" max="1." step="0.001" var="filter_1e_imu.gyro_beta" module="imu/filter_1euro_imu" shortname="gyro beta" handler="update_gyro_beta"/>
        <dl_setting min="0.01" max="10." step="0.001" var="filter_1e_imu.accel_mincutoff" module="imu/filter_1euro_imu" shortname="accel mincutoff" handler="update_accel_mincutoff"/>
        <dl_setting min="0.0001" max=".1" step="0.001" var="filter_1e_imu.accel_beta" module="imu/filter_1euro_imu" shortname="accel beta" handler="update_accel_beta"/>
      </dl_settings>
    </dl_settings>
  </settings>
  <header>
    <file name="filter_1euro_imu.h"/>
  </header>
  <init fun="filter_1euro_imu_init()"/>
  <makefile>
    <file name="filter_1euro_imu.c"/>
  </makefile>
</module>