Single GPS based Roll Angle Estimation of a Rolling Airframe

초록

In this paper, we propose the roll angle estimation method for a rolling airframe using only single GPS(Global Positioning System) unit. It is possible to know the direction of a GPS satellite relative to the local geographic position of an airframe because in-orbit GPS position of the satellite is one of the outputs of a GPS unit. If the angle of attack of the airframe is negligible, the pitch and yaw attitude angles can be easily calculated from the velocity vector which is also the output of the GPS unit. Now we assume that the airframe is slowly rotating along with the longitudinal axis of the airframe. Then intensity of the received signal of the GPS will be changed as airframe’s rolling motion. The intensity of the received GPS signal is theoretically maximized when the GPS antenna towards a GPS satellite. Using the geometry between the GPS unit and the GPS satellite, we can easily calculate the roll attitude angle of the rolling airframe when the GPS antenna towards the GPS satellite. Practically, however, the roll attitude angle measurements are very poor because peak points of the signal intensity are not clearly identified due to the irregular antenna patterns and the multi-path noises. By introducing the Extended Kalman filter algorithm, we greatly improve the roll angle estimation accuracy. We made a sophisticated ground test equipment to experimentally validate the proposed method.