Control Algorithm Research On Space Target Safe Proximity

On-orbit service technology has remarkable economic characteristics and it has become an important research direction in space mission development.During the process of on-orbit service,it is essential to ensure that servicing spacecraft could response to the target's state changes and avoid conflicts with other space objects,thus realizing safe proximity to target.This dissertation focusing on spacecraft on-orbit service,studies collision-free control algorithms for space target safe proximity.The main work in this dissertation includes:The deviation propagation model of relative orbit dynamics is investigated.Using the CADET method to conduct derivations on TH equations and getting a propagation model related to system states and their deviation statistics.By comparison with the result of Monte Carlo method,the effectiveness of the proposed model can be validated.Designing orthogonal experiments and conducting numerical simulations to analysis how different deviations influences the accuracy of rendezvous.The safe proximity control algorithm for avoiding obstacles with a spherical envelope is investigated.Introducing the basic theory of artificial potential function and building a workspace potential filed model.Simplifying the structure of space objects into the form sphere according to their shape features and then building the shortest distance model between two spheres to judge whether collision happens or not.Combining the finite-time sliding mode control and artificial potential function theory to design a collision-free control strategy and proving its stability.Through numerical simulation,the effectiveness of this proposed control methodology is validated.The safe proximity control algorithms for avoiding obstacles with non-spherical envelopes are investigated.Introducing Sigmoid potential function basic theory and building a unified workspace potential filed model.Describing the envelope of obstacles in the way of ellipsoid and establishing the shortest distance model between two ellipsoids to judge whether collision happens or not.Combing Lyapunov function method and Sigmoid potential function theory to design a collision-free control algorithm and making proof to its stability.Utilizing numerical simulations to prove the effectiveness of this proposed strategy.Translating the envelope of obstacles into a cuboid and establishing the shortest distance model between them.Combing optimal sliding mode control and Sigmoid potential function theory to design a collision-free control law.Conducting stability analysis and validating the effectiveness of the proposed method by numerical simulations.The collision-free cooperative control algorithm for relative orbit and attitude is investigated.Taking two coupling factors: the installation of actuators and the orbit controller's not overlapping with the center of mass into consideration and establishing the spacecraft relative orbit and attitude coupling mathematical model.Utilizing Terminal sliding mode control theory and APF theory to design the six degree of freedom tracking controller and the collision-free orbital controller respectively and analyzing its stability.Conducting numerical simulations to test the effectiveness of the proposed method.This dissertation conducts a deep research on the control problem of space target safe proximity: utilizing CADET method to analysis the influence caused by orbit derivations on the accuracy of rendezvous;utilizing potential function methods to study several control algorithms for avoiding obstacles with various surface envelopes;studying the orbit and attitude cooperative control algorithm under the situation of two coupling factors.The work of this paper provides an effective reference for spacecraft on-orbit safe flying.