INS aiding with GNSS and magnetometer for unmanned helicopter using electric motor

GNSS and ARS are the most common sensors in low-end U AV. However, these sensors are vulnerable to built-in errors and cannot measure the body heading independently. Even the GNSS/INS cannot fully compensate the IMU errors in the initial alignment process and rectilinear flights. For an unmanned helicopter, which typically flies at low speed or hover, a magnetometer can be more useful than any other sensors when heading information is needed. The heading data can be easily calculated with a magnetometer. Its value is further upgraded by sensor fusion technologies which improve accuracy of the system dramatically. However, the electric motor which drives small helicopter U AV keeps the magnetometer from reading pure magnetotelluric vector. This paper shows the effects of electric motor on the magnetometer readings, and presents a method to compensate the effects. The results are verified with flight test data. The simulation and experimental results in this paper proves that aiding GNSS/INS with magnetometer increases observability and improves accuracy.