Attitude controller design for orbital target tracking of geostationary satellite under avoidance constraint

Abstract

The main object of this study was the coordinated attitude generation for a tracking satellite on geostationary under avoidance constraint and the attitude control for tracking. A coordinated attitude control problem is raised because a tracking satellite on geostationary always needs maintain communication with a ground station while tracking space objects simultaneously. The coordinated attitude control addressed in this study is related to the attitude maneuver of a tracking satellite and orbital motion of targets normally at lower Earth orbit. MRP (Modified Rodrigues Parameter), which is effective in large angle attitude maneuvers were employed. The initial attitude error was calculated based upon an arbitrary initial configuration for the target tracking, so that a sequential tracking from one to another target can be achieved easily. Additionally, avoidance maneuvers to protect sensitive onboard sensors from the Sun and the Moon were designed using a navigation function. When the avoidance areas are located on the transient path due to the coordinated attitude maneuver command, the maneuver is performed with no violation against the given constraint areas by adopting the navigation function. But after convergence, the acquired coordinated attitude produces a problem of non-maneuver against a new violation of constraint. Therefore, a penalty law was applied to solve the problem. The designed controller was derived to meet Lyapunov stability. In addition, a residual avoidance effect by the avoidance area was verified using a sandwich theorem. The stability of the designed controller was also investigated based on many simulations.