Research On Control Of Chaser Spacecraft With Proximity To Space Target

As the development demands for the missions of utilizing and occupying outerspace, it has been a research focus of aerospace technologies for proximity to atarget spacecraft and performing adjacent operation, which are widely applied tomany missions such as spacecraft formation flying, on-orbit service, space conflict,etc. It plays a key role in the above missions to make chaser spacecraft to approachtarget and perform relevant maneuvers effectively, especially for rapid andsuccessful proximity to uncooperative target spacecraft. For the above problem, thechaser relative orbit and attitude control with proximity to target are studied in thisdissertation, including the following contents:The proximity mission is divided into three phases, including short-rangeproximity and flyaround, final approach and attitude maneuver. In the short-rangeproximity and flyaround phase, the relative orbit multi-pulse control algorithm forproximity to target is proposed to meet the requirment that the proximity maneuvercan be performed from any direction and orbit plane. The different glideslope orbitis designed, and pulse selection method based on safety velocity is then proposed. Inthe flyaround phase, free flyaround is firstly studied, and then a bi-ellipse flyaroundalgorithm is presented to perform rapid maneuver, and then meet the requirments ofquick survey and some specific missions.Considering the uncooperative properities of target spacecraft and therequirement of rapid maneuver for space missions, the closed-loop feedback controlof relative orbit is studied for the final approach phase. Based on the Lyapunovmethod, the feedback controllers are proposed respectively in the absence andpresence of escape maneuver of the target. Furthermore, an adaptive controller isdesigned for the situation that parts of target spacecraft orbit information can not beobtained. We further considered the disturbances and modified the adaptivecontroller, which can increase the robustness of closed-loop system. Based on thefinite time control theory, a finite time controller for relative orbit maneuver isproposed, and a finite time observer is then designed to deal with the escapemaneuver of the target, which makes the chaser to successfully achieve the finalapproach.After the above two phases of proximity mission, it is necessary for thesubsequent operations to make the chaser to perform attitude maneuver, and then thespacecraft attitude robust control is investigated. The chaser spacecraft is firstlyassumed as a rigid body, and a sliding mode controller based on relative attitudeerrors is proposed to deal with attitude tracking problem. A generalized disturbance observer and a modified controller based on the observer are designed to deal withdisturbances and model uncertainties, and then improve control accuracy and makethe spacecraft platform stable. The convergence of the observer is studied. If theflexible appendages are further considered, an error-quaternion-based sliding modecontroller, which only requires attitude angle and angular velocity, is proposed in thepresence of disturbances and model uncertainties. The boundedness of modalvariables of flexible appendages is discussed by Lyapunov method.In order to achieve rapid attitude maneuver, the attitude control problem ofchaser is studied by the finite time control theory. The chaser is firstly considered asa rigid body, and the Lagrange attitude model is proposed. A finite time controller isthen designed to achieve attitude maneuver, and the globally rapid convergence isdiscussed. Furthermore, a quaternion based finite time controller is proposed toachieve attitude tracking, and the robustness to disturbances and model uncertaintiesis studied. A modified saturation function is further proposed to guarantee the globalfinite time property. If the disturbances and uncertainties can not be obtained due tothe complicated space environment, an adaptive finite time controller is presented toachieve attitude tracking. The chaser is finally considered as a flexible body, and thethe nonsingular controllers are presented to perform attitude maneuver. Numericalsimulations are finally provided to illustrate the performance of the proposedcontrollers.