Attitude Tracking Control of Gravity Gradient Microsatellite in Maneuvering for Space Exploration

The problem of the finite-time tracking control strategy is studied for a gravity gradient microsatellite BUAA-SAT in maneuvering. The contributions of the work are mainly shown in two aspects: 1) the analysis of the combined forcing action of the gravity and the constant thrust; 2) a method of the adaptive finite-time sliding mode tracking control. In orbital maneuvering, the gravity gradient microsatellite under a constant thrust shows complicated dynamics. The stability and pendular motion of the gravity gradient microsatellite are determined by the combined action of the gravity and the constant thrust. The dynamics characteristics revealed in this paper are conducive to derive an expected attitude trajectory for the attitude tracking control, which not only ensures the flight safety but also reduces the energy consumption of the controller. In order to avoid the vibration and the structure deformation of the coilable mast, the microsatellite is required to track the expected attitude trajectory in a finite time. Compared with existing finite-time sliding mode control methods, a desired tracking error function with a simple polynomial form is designed to eliminate the reaching phase problem and to enable the tracking error to converge to zero in a finite time; besides, an adaptive law is presented to solve the problem of the boundary of uncertainty. The Lyapunov stability analysis is performed to show the global finite-time convergence of tracking errors. A numerical case of the gravity gradient microsatellite is studied to demonstrate the effectiveness of the proposed controller.