Subsystem/ins
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 (Attitude and Heading Reference System) filter for attitude. Currently, only the experimental invariant filter is a full INS.
Currently possible INS subsystem types are:
| Type | Point Type | Firmwares | Notes |
|---|---|---|---|
| alt_float | floating | fixedwing | |
| gps_passthrough | all | ||
| xsens | |||
| xsens700 | |||
| no_type | all | ||
| Horizontal Filter Float (hff) | floating | ||
| extended | floating? | all | |
| ardrone2 | floating | ||
| float_invariant | floating | fixedwing |
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 defined to 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 not defined, FALSE or 0:
- 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)
e.g. to use with barometer:
| File: conf/airframes/myplane.xml |
<firmware name="fixedwing">
...
<subsystem name="ins" type="alt_float">
<define name="USE_BAROMETER" value="TRUE"/>
<subsystem>
</firmware>
|
GPS passthrough (gps_passthrough)
"dummy" INS that does no filtering whatsoever. It directly passes GPS position and velocity through.
| File: conf/airframes/myplane.xml |
<firmware name="fixedwing or rotorcraft">
...
<subsystem name="ins" type="gps_passthrough"/>
</firmware>
|
xsens
XSens Mti-G
| File: conf/airframes/myplane.xml |
<subsystem name="ins" type="xsens">
<configure name="XSENS_UART_NR" value="0"/>
<configure name="XSENS_UART_BAUD" value="B115200"/>
</subsystem>
|
xsens700
XSens Mti-G
| File: conf/airframes/myplane.xml |
<load name="ins_xsens_MTiG_fixedwing.xml">
<configure name="XSENS_UART_NR" value="0"/>
</load>
|
no_type
Vertical filter (in float) estimating altitude, vertical velocity and accelerometer bias.
If USE_GPS, horizontal position and velocity is set directly by GPS.
| File: conf/airframes/myplane.xml |
<subsystem name="ins"/>
|
Horizontal Filter Float (hff)
simple with float vertical and horizontal filters for INS
| File: conf/airframes/myplane.xml |
<firmware name="fixedwing or rotorcraft">
...
<subsystem name="ins" type="hff"/>
</firmware>
|
extended
Extended vertical filter (in float).
A 4-state Kalman filter that estimates:
- vertical position
- vertical speed
- accelerometer bias
- barometric offse
| File: conf/airframes/myplane.xml |
<firmware name="fixedwing or rotorcraft">
...
<subsystem name="ins" type="extended"/>
</firmware>
|
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