ガスジェットによるスピン安定衛星の最適姿勢制御

抄録

This paper deals with an attitude control scheme for an orientation maneuver of spinning spacecrafts with body-fixed gas-jet thrusters.
The spin axis control and the angular momentum vector control are the two controls proposed so far for small-angle maneuvers. The two control methods are extended to the large-angle maneuvers with which nonlinear dynamics must be taken into account. In the spin axis control, the spin axis and the angular momentum vector are simultaneously controlled by gas-jet thrusters to coincide with the desired orientation. The control time interval and the fuel-consumption are adopted as performance criteria. In the angular momentum vector control, only the angular momentum vector is positively controlled. After that, the passive nutation damper aligns the spin axis with the angular momentum vector. The adopted performance criteria is the fuel-consumption. These concepts are formulated as optimal control problems.
The necessary conditions for these problems are obtained via Pontryagin's Maximum Principle. They show that the optimal control is of an on-off or bang-bang type. This result is encouraging to the users of thrusters providing only constant torques, because they may hope to realize optimal controls by applying the thrusters.
Analytical solutions of the above mentioned problems are difficult to obtain because of their high dimensionality and nonlinearity. Minimum fuel problems are numerically solved by the method based upon the linear programming proposed by Wolshe et al. This method is also adopted with modifications to solve minimum time problems. Obtained results reveal that the angular momentum vector control is superior to the spin axis control from the viewpoint of reduction in the minimum fuel-consumption.