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Leader/Follower synchronization of satellite attitude without angular velocity measurements

In this paper we propose a Leader/Follower output feedback synchronization scheme for control of the attitude of two satellites when angular velocity measurements are not available. Nonlinear observers are used to estimate the angular velocities. The attitudes of the satellites are represented by unit quaternions, and the control design is based on vectorial observer backstepping. The analysis of the method shows that the rotation matrices representing the attitude errors between the follower and the leader, and between the leader and its reference attitude, converge to the identity matrix for any initial conditions. The control scheme is simulated to validate the results.