External AHRS Systems

Rather than using ArduPilot’s internal Attitude Heading Reference System (AHRS) for attitude, heading and position, it is possible to use several external systems.

Supported Systems

Currently, ArduPilot supports these systems:

Setup

VectorNav300 or MicroStrain

This will replace ArduPilot’s internally generated INS/AHRS subsystems with the external system

VN-300 Specific setup

When setting up the VN-300, it will be necessary to set GPS_TYPE = 21 and GPS_TYPE2 = 21.

VN-300 data is expected at two different update rates, 50Hz and 5Hz. This is autoconfigured. See the USER MANAUAL for more details.

VectorNav100

  • AHRS_EKF_TYPE = 3 (ArduPilot’s EKF3)

  • EAHRS_TYPE = 1 (VectorNAV)

  • EAHRS_OPTIONS bit 0 set to 1 (“1” value) to disable its compensation of the sensor biases, letting EKF3 do that (since there is no internal GPS to provide the best estimates)

  • for all of the above, set the SERIALx_PROTOCOL to “36” (AHRS) and SERIALx_BAUD to “115” (unless you have changed the external unit’s baud rate from its default value) for the port which is connected to the external AHRS unit.

This will replace ArduPilot’s internally generated INS/AHRS subsystems with the external system.

In addition, instead of replacing ArduPilot’s INS/AHRS systems, it is possible to use an external AHRS system’s sensors (IMU,GPS, Compass, and Barometer) as additional sensors for use with ArduPilot’s INS/AHRS systems. Simply do not change the AHRS_EKF_TYPE from “3” (EKF3), but setup the others parameters as discussed above.