Thrust vector control of upper stage with uncertainty of the centroid

During the orbit transfer of upper stage, the command direction of thrust vector determined by the guidance system should ideally pass through the centroid when the thruster is working. However, it is hard to realize in actual operation. Moreover, the low identification accuracy of position that leads to the uncertainty of centroid position makes the situation worse. This paper discusses the issue of the thrust vector control (TVC) problem of the upper stage to make sure the thrust vector of the GT passes through the centroid and aligns with the command direction under the uncertainty of centroid. First, a thrust vector control system consisting of the attitude control for the upper stage and the gimbal control of the GT ensures the thrust vector passes through the upper stage's centroid is proposed. Second, a modification procedure is designed to draw the thrust vector aligns with the command direction. The control and modification system can draw the thrust vector tracks the position of the centroid and aligns with the command direction. The validity of the algorithm proposed in this paper is verified by numerical simulations.