Minimum power spacecraft attitude control laws for small constant disturbance torques

Control logic for maintaining a spacecraft´s attitude with a minimum expenditure of energy in the absence of disturbance torques and in the presence of large constant disturbance torques has been discussed in aerospace literature. This paper presents the minimum energy control logic for the case of small constant disturbance torques. Reaction jets, with variable average specific impulses, are assumed to be the torquing devices, though the discussions can be easily extended to other devices. The possible types of attitude control system limit cycles are presented in phase-plane form and their relative propellant consumption rates are compared.