Rejection of harmonic sensor disturbances in passive systems, and applications to attitude control

We consider the problem of asymptotic stabilization of nonlinear systems by output feedback, in the case in which the measured output is corrupted by additive harmonic noise. We restrict our attention to systems which are passive with respect to the measured output, and the sensor disturbance has a finite discrete spectrum. A simple condition for zero-state detectability of passive partially linear systems is derived, and the result is employed to analyze the loop interconnection resulting from the application of internal model-based controllers to the perturbed plant. The analysis applies directly to the problem of stabilizing the angular velocity and/ or regulating the attitude of a rigid body using noisy angular rate measurements. The proposed controllers have a simple structure that exploit the passivity property of both the internal model and the plant. Simulation results show the effectiveness of the design