Research On Hovering And Tracking Control Of Space Debris Removal Spacecraft

With the development of space technology,people’s life has been changed greatly.But meanwhile,it produces a huge number of space debris which may threaten the safety of spacecrafts and the astronaut when impacts occur.The amount of space debris has been increased exponentially.Therefore,it is of great significant to carry out the research on the active elimination of space debris.The study considers the low cost and flexibility of the debris removal tasks and is aimed at the two key problems which are hovering at arbitrary position and tracking in 6 DOF.The study includes the following two aspects:Methods of hovering stably at any relative position of the space debris.First,the relative motion model and error equation are eatablished.The problem of hovering is transformed into an optimal control problem by defining the quadratic performance index function,and the optimal closed-loop control algorithm is proposed based on LQR method.The simulation results shows that the proposed mothod can realize high-precision hovering at arbitrary location to the target debris.Tracking control of 6 DOF coupled orbit and attitude with dual quaternion.In this dissertation,however,integrated controller is designed to meet relative position and attitude requirement.Firstly,backstepping controller is adopted in integrated orbit and attitude control algorithm.In order to achieve the tracking of relative position and attitude between leader and follower spacecraft,considering external disturbance and system uncertainties,integrated orbit and attitude backstepping controller and integrated orbit and attitude anti-windup-backstepping controller with limited input are designed respectively.Furthermore,finite-time controller is adopted in integrated orbit and attitude control algorithm.Considering external disturbance and system uncertainties,a terminal sliding-mode algorithm is proposed under the fact that the vector part of dual quaternion is treated as control variable.And the singularity phenomenon,produced by terminal sliding mode,is analyzed theoretically in details.In order to avoid the singularity and improve the rapidity of system,a fast terminal sliding mode controller based on switching function is put forward.Finally,simulations verifiy the vadility of the proposed control schemes.