Robust gyro-free attitude estimation for a small fixed-wing unmanned aerial vehicle

This paper proposes a backup attitude estimation scheme for small fixed-wing unmanned aerial vehicles (UAVs) in the event of gyroscopic failure. The attitude is propagated in terms of 3 degrees-of-freedom (DoF) aircraft dynamics. The errors in attitude propagation are updated using indirect attitude information obtained from accelerations as sensed by onboard accelerometers and a global positioning system (GPS) receiver. In the event of gyroscopic failure, large uncertainties are introduced into the attitude propagation model. Such uncertainties in states and parameters are modeled as norm-bound uncertainties and a discrete-time robust extended Kalman filter (REKF) is implemented to estimate the attitude of the UAV.