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A state estimation scheme that does not depend on the statistical distribution of bounded measurement noise is presented. This scheme is used to provide state estimates for feedback in an attitude tracking control scheme that exhibits almost global asymptotically stable tracking of a desired attitude trajectory with perfect state measurements. The control and estimation schemes use the global, unique representation of rigid body attitude provided by rotation matrices. Attitude and angular velocity state estimate updates are obtained from discrete multi-rate measurements using a deterministic filtering scheme. Propagation of discrete state estimates is carried out with a Lie group variational integrator, which preserves the orthogonality of rotation matrices during numerical propagation without reprojection. This integrator is also used to numerically simulate the feedback system. The performance of this attitude tracking control scheme is then compared with that of a recently reported quaternion observer-based continuous feedback attitude tracking scheme. This quaternion-based attitude tracking scheme is shown to exhibit unstable, unwinding behavior. Numerical

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This paper presents an estimator-based attitude tracking control scheme that uses feedback of attitude and angular velocity estimates constructed by an optimal state estimation scheme. The tracking control scheme gives almost global convergence to a desired attitude and angular velocity profile with perfect state feedback. The estimation scheme consists of measurement, filtering and state propagation stages, and the measurements are assumed to have deterministic error bounds. These error bounds are ellipsoidal and are referred to as uncertainty ellipsoids. Each measurement is followed by a filtering stage, which obtains the minimum-volume ellipsoid that contains the intersection of uncertainty ellipsoids corresponding to the estimated states and the measured states. The state estimates are propagated between measurements using a variational integrator that discretizes the equations of motion. This estimator-based tracking control scheme is applied to the model of a satellite in circular Earth orbit. Numerical simulation results with realistic error bounds on attitude and angular velocity measurements show the good performance of this estimator-based control scheme.