Subsystem/ins

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Revision as of 09:42, 6 March 2014 by AndrewChambers (talk | contribs) (extended)

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INS subsystem

The INS (Inertial Navigation System) subsystem specifies which position and velocity estimation algorithm you are using.

Most of the INS filters are only providing position and speed, and they need to be used together with an AHRS filter for attitude. Currently, only the experimental invariant filter is a full INS.

Currently possible AHRS subsystem types are

  • alt_float
  • gps_passthrough
  • xsens
  • xsens700
  • no_type
  • hff
  • extended
  • ardrone2
  • float_invariant

e.g. for the extended filter:

File: conf/airframes/myplane.xml
  <firmware name="fixedwing or rotorcraft">
     ...
    <subsystem name="ins" type="extended"/>
  </firmware>

Implementations

alt_float

Filters altitude and climb rate for fixedwings.

A 2-state Kalman filter that estimates vertical position and vertical velocity from GPS and barometric data.

When USE_BAROMETER is true:

  • GPS horizontal position and horizontal velocity is directly passed through
  • GPS vertical position sets the altitude for the barometric reference pressure (QFE)
  • Vertical position and velocity is a filtered based on barometric pressure with respect to the reference pressure and GPS vertical velocity readings.

When USE_BAROMETER is false or undefined:

  • GPS velocity is directly passed through to the vehicle's state.
  • GPS horizontal position is directly passed through.
  • Altitude is filtered based on GPS height and vertical velocity data.

Parameters

USE_BAROMETER - Enables the use of barometric data

DEBUG_ALT_KALMAN - Enables debug messages from the subsystem (Default: not defined)

GPS passthrough (gps_passthrough)

xsens

XSens Mti-G

    <subsystem name="ins" type="xsens">
      <configure name="XSENS_UART_NR" value="0"/>
      <configure name="XSENS_UART_BAUD" value="B115200"/>
    </subsystem>

xsend700

XSens Mti-G

    <load name="ins_xsens_MTiG_fixedwing.xml">
      <configure name="XSENS_UART_NR" value="0"/>
    </load>

no_type

simple INS with float vertical filter

  <subsystem name="ins"/>

Horizontal Filter Float (hff)

simple with float vertical and horizontal filters for INS

extended

Extended vertical filter (in float).

A 4-state Kalman filter that estimates:

  • vertical position
  • vertical speed
  • accelerometer bias
  • barometric offset

Parameters

INS_PROPAGATE_FREQUENCY - Defines the frequency (Hz) of the propagation model (Default: PERIODIC_FREQUENCY)

ardrone2

simple INS with float vertical filter for use with ardrone2_sdk

float_invariant

attitude and speed estimation for fixedwings via invariant filter