Based On Sgcmg Satellite Attitude To Guide And Control Method Of The Actuator

A modern satellite is typically composed of a central rigid body and flexible appendages in order to reduce its quality and prolong its service life. Moreover, a single gimbal control moment gyroscope (SGCMG) is widely used in a satellite attitude system. On the other hand, an orbiting satellite is affected by various uncertainties such as model parametric uncertainties, actuator friction uncertainties, external disturbances and so on. It has been well known that the attitude control system of flexible spacecraft is a MIMO and strongly coupled nonlinear system with uncertainties. And a spacecraft attitude system requires high pointing accuracy, high stability and rapidity, so that it is roubst to uncertainties and can suppress appendages’ vibration. Both attitude guidance scheme and control law for flexible satellite are studied in this paper, which is organized as follows.To escape the inherent singularities of a SGCMG system of pyramid configuration, a singularity robust inverse (SRI) steering law is presented. The SRI steering law can make sure that the SGCMG system can escape singularities voluntarily. In presence of mechanical friction in SGCMG system, an adaptive steering law which can compensate the mechanical friction is proposed.To decrease the impact of various uncertainties, a robust control law based on RBF network is presented. To avoid singularity, a control scheme integrated attitude control algorithm and steering law for satellite using SGCMG is proposed. In addition, considering that the coupling effect between rigid body and flexible appendages can excite the appendages’ vibration and will significantly affect the satellite attitude, we design a control law in which flexible dynamics are taken into account. For arbitrary initial states, in the case that the angular velocity may not parallel to the eigenaxis, a near eigenaxis rotation occurs.In some cases that the initial and target position are know, a scheme of attitude guidance is taken into account to reduce appendages’ vibration excited by maneuver. The attitude guidance scheme is based on quaternion which is without singularities. A kind of attitude guidance based on a parabolic angular acceleration profilis is proposed for a flexible satellite Rest-to-Rest maneuvers. For the case of nonzero initial angular velocity, a Move-to-Rest attitude maneuver path based on an asymmetric sine angular acceleration is designed. Simulation results show the effectiveness of both attitude guidance schemes proposed.