Switching Angular Velocity Observer for Rigid-Body Attitude Stabilization and Tracking Control

Abstract

This paper provides a new switching angular velocity observer formulation to the classical problem of rigid-body attitude tracking control in the absence of angular rate measurements. Exponential convergence of the angular velocity state estimation errors is proven using a novel error signal definition through the use of this switching-type observer. The observer synthesis and convergence properties are independent of controller design. The switching ensures continuity for all the estimated states. Further, the maximum number of switches required by the observer is shown to be finite and that zeno-type behavior cannot occur. A “separation-property” type result for the attitude tracking problem is established, wherein a proportional-derivative controller uses angular velocity estimates from the proposed switching observer in the absence of actual angular rate measurements, while ensuring almost global asymptotic stability for the overall closed-loop tracking error dynamics. The separation property is also proven to hold when a gyroscopic nonlinear compensation term is added to the proportional-derivative controller.