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Fault tolerant low cost IMUS for UAVs

In this paper a Fault Tolerant system for the attitude estimation of an Unmanned Aerial Vehicle (UAV) using low cost magnetometers, accelerometers, and gyroscopes, implemented in an Inertial Measurement Unit (IMU) is proposed. An approach based on the Unscented Kalman Filter (UKF) for Detection, Isolation and Reconfiguration is investigated in the presence of a Hardware Duplex IMU mounted on board for flight control purposes. A state automaton, with comparative logics, detects if anomalies occurr on one of the two IMUs; then based on a comparison between the measured variables and their UKF estimations, the fault is isolated and identified. The proposed approach is an alternative to standard Hardware Triplex IMU architectures based on triple physical redundancy. At the expense of a higher computational cost and a small delay in isolating faults, the UKF based approach allows to limit the number of IMUs to two, or to guarantee a fail safe behavior in the presence of a double fault, even if contemporary, with Triplex IMUs. Experimental results on the implementation of a multiple IMU platform on a quadrotor flight control board are finally presented.