A new approach for single antenna INS alignment in multirotors allows faster time-to-application

ABSTRACT

GNSS/INS integration systems are increasingly used in the navigation of Unmanned Aerial Vehicles. To decrease the size and weight, single antenna GNSS is usually favorable in many UAV applications. To reach optimal accuracy, the system should be initialized properly. However, a single antenna GNSS/INS system cannot directly measure the initial heading of the UAV, without additional sensors such as a magnetometer or gyrocompass. Course over ground computation is also not feasible for vehicles like multirotors where the direction of motion is not aligned to the vehicle body axis.This paper proposes a new real-time approach for initial attitude estimation of a multirotor using a single-antenna GNSS and a MEMS IMU. An array of strap down navigators with random initial headings are spread in the environment and after a short period with sufficient motion, the best-fit navigator is determined and its attitude states are used to initialize the GNSS/INS fusion filter. This approach provides accurate initial attitude angles in a few tens of seconds, which is important due to the limited operational time of small UAVs. In addition, the proposed approach does not require a complicated process to be performed by the user at the UAV start-up, i.e.,any dynamic motion during the alignment phase is sufficient to reach the proper heading accuracy. Since this is a purely algorithmic approach, it does not require any additional sensor.