Control And Trajectory Safety Of Rendezvous And Docking

Rendezvous and docking is a necessary operational technology, which is required for assembly larger units in orbit, re-supply of orbital platforms, exchange of crew in orbital stations, repair of spacecraft in orbit, and deep space exploration. A rendezvous and docking mission can be divided into a number of major phases: far range guidance, close range guidance, final approach, docking and departure. During different phase, the chaser has different control objective, constraint and trajectory safety problem. This thesis focuses on the control strategy and trajectory safety problem during the rendezvous and docking. The control and approach strategy are studied, and the method for describing and calculating trajectory safety is developed by probability and dynamics analysis. The main work and achievements are summarized as follows:The safety strategy of rendezvous and docking is discussed, and the model and method of collision analysis are presented. (1) The source threatening mission safety is analyzed. The passive trajectory protection and active trajectory protection are discussed, and target control zone for rendezvous and docking are analyzed. (2) Based on probability theory, a method for describing and calculating the collision probability between rendezvous and docking vehicle and debris is presented, and the method involves quantitatively analyzing the collision probability using quasi maximum instantaneous collision probability and total collision probability. The method calculating the indexes is developed, and the input required to perform a calculation includes the respective state vectors, position error covariance matrices and physical sizes of objects involved. (3) Two methods to analyze relative trajectory safety between chaser and target are developed, which are 3-sigma ellipsoid based methodology and collision probability based methodology.The strategy calculating maneuver for special point maneuver in far range guidance phase is presented, and maneuver method avoiding collision with debris is built. (1) A method to calculating maneuver for special point maneuver strategy is developed based on the facts that are single objective of every maneuver and tiny correction for orbit inclination and right ascension of ascending node. The basic idea of the method is disassembling calculating for phasing and orbit plane correction, and the equation for calculating maneuver is derived. (2) A method for determining the optimal collision avoidance maneuver is developed, and the two phasing orbits strategy is developed to avoid collision with debris.The control and trajectory safety in close range guidance phase are investigated. (1)The targeting error induced by CW guidance is analyzed and partitioned into several error factors and the corresponding mathematical error models are established. A method to correct the CW guidance error is developed based on precision model, and the control strategy for normal orbit plane is derived. (2) Two methods analyzing approach trajectory safety are built, which are method based on CW equation and method based on high precision orbit model. (3) A method for determining the optimal collision avoidance maneuver for close range guidance phase is developed.The control and trajectory safety in close final approach phase are studied. (1) The sightline control strategy for bad measure precision is developed, and the control methods for vertical direction, approach direction and station keeping are presented. (2)The safe approach velocities are investigated for cuboid, sphere and cone keep out zone. (3)The design method for optimal trajectory under safety constraint is developed. The cone and cuboid keep out zone can be described using line constraint, and then optimal trajectory design can be translated to line programming problem under line constraint. (4) The design strategy of collision avoidance maneuver is discussed, and the collision avoidance scheme is analyzed for V-bar and R-bar approach.The control and trajectory safety in departure phase are investigated. (1) The control of V-bar and R-bar departure in rendezvous and docking under field of view constraint is studied using both analytic and numerical methods. The relationship between field of view and departure maneuver is developed. (2) The departure trajectory and safety characteristic are discussed for V-bar departure, R-bar departure and arbitrary direction departure.In conclusion, important developments have been achieved for the control strategy and trajectory safety analysis method of rendezvous and docking. The method and conclusions in this thesis would be available for rendezvous and docking experiment.