Robustness Evaluation of Theta-D Technique for Spacecraft Attitude Control Subject to Reaction Wheel Failures

Abstract

Satellite mission life, especially for commercial Geostationary Earth Orbit (GEO) missions, has recently been aimed at reaching its 18 years life of services. This goal, driven by customers’ demand and competitive market, has challenged Attitude Control Subsystem (ACS) engineers to develop adequate ACS algorithms to accommodate this extended life of services in the presence of limited and aging hardware components (i.e., ACS sensors and actuators). This paper evaluates the robustness of an attractive ACS scheme, which has recently been proposed using the  D  control design technique to maintain the satellite pointing accuracy subject to loss of one or two reaction wheels out of its four wheels assembly mounted in a pyramid configuration. The robust performances of the  D  controller are evaluated using the following two conditions: (1) Loss of Various Wheel Locations and Pair Combinations and (2) Initial Condition Uncertainties (i.e., “tolerant range” per axis that the proposed controller can still handle).