Attitude and earth velocity estimation - Part I: Globally exponentially stable observer

The main contribution of this paper is the development of a novel attitude observer based on a triaxial high-grade rate gyro and single body-fixed vector measurements of a constant inertial vector, in contrast with typical solutions that require two of these vectors. The proposed structure consists in a cascade observer, where the angular velocity of the Earth around its own axis is extracted in the first block and the attitude is estimated in the second. The stability of the system as a whole is analyzed and the error dynamics are shown to be globally exponentially stable (GES). Simulation results are presented that illustrate the achievable performance of this solution. In a companion paper an alternative observer is proposed on the special orthogonal group and both solutions are compared.