Study On Orbital Characteristics And Control Of Hovering Spacecraft

Hovering technology of spacecraft will become the important support for future on-orbit servicing, such as urgent rescue, on-orbit maintenance, on-orbit surveillance, module replacement, on-orbit injection, orbit clearing and operation on uncooperate target.The orbital characteristics of hovering spacecraft were analysed in this dissertation, and the control method for keeping spacecraft hovering formation was researched. The means of designing hovering orbit and the way to perform the hovering mission between the mission spacecraft and target spacecraft were discussed. Besides, a measure for keeping spacecraft hovering formation stable was given. The main work and achievements in this dissertation are summarized as follows:Firstly, the definition of spacecraft hovering was provided. The hovering distance, azimuth angle and pitching angle were chosen to describe the mission spacecraft's hovering location and direction in the relative motion coordinate.Then, the kinematic method for mission spacecraft hovering around a target spacecraft which operate on a circular or an elliptical orbit was studied. Through dynamics analysis, the formulas to calculate the standard control acceleration and speed increment for keeping hovering state wre presented. Furthermore, the way to carry out the hovering was proposed. Any simplification was not adopted when researched these formulas, so the equations were precise, and we called them"model one". By simulation, the hovering energy requirement for different mission was taken into contrast, and the conclusion proved that the hovering technology was feasible.Subsequently, a hovering method at any selected position on elliptical or circular orbit was presented in this thesis.This method was proposed based on orbit dynamics theory. By comparing this method with the model one, we got the conclusion that this calculation method was satisfied with our requirement.Finally, the control method for keeping hovering formation was studied in this thesis. Using T-H equation and LQR control, a controller was designed to eliminate the initial position and speed error. The simulation result proved that the control system was able to make the mission spacecraft adjusted to its correct position rapidly and accurately ,and keep the hovering formation stable.The spacecraft hovering orbit characteristics and control are the foundations for the overall hovering technology. And the work in this dissertation can be used for the further studies on the approach method before hovering and the security design for hovering orbit.