Full-order Sliding Mode Based Attitude Synchoronization Control For Spacecraft Formation

Attitude synchronization control of spacecraft formation plays a significant role in many space missions,e.g.space-based interferometry,synthetic aperture imaging,etc.,and hence it has attracted great attentions in recent years.Spacecraft system is nonlinear,high coupling,and subjects to external disturbances from environment,which will affect the highprecision performance,even worse destroy the stability of the spacecraft control system.Facing more flexible and variable spacecraft missions,old control schemes have been challenged.Based on full-order sliding mode control method,multiple spacecraft system which subject to matched disturbances is studied in this thesis.The contents of this thesis are as follows:(a)The attitude tracking problem of single spacecraft with matched disturbances is studied.Attitude dynamics of rigid spacecraft is modeled by unit quaternion for global representation.Based on full-order nonsingular terminal sliding mode technique,a continuous finite-time control scheme for attitude control system is designed.The influence of control parameter for the control system is discussed with respect to control precision,response time,and chattering.Also the differences between the proposed scheme and other existing popular sliding mode methods are investigated.Some simulation cases are presented to illustrate the effectiveness of the proposed control scheme with respect to the different control parameter and different control laws.(b)In the fundamental of the aforementioned result on the single spacecraft,an attitude synchronization problem for spacecraft formation with undirected graph topology is studied.Attitude dynamics of rigid spacecraft is modeled by unit quaternion.First,an assumption that every follower spacecraft have direct access to the leader spacecraft is given.Based on recursive full-order sliding mode technique,a centralized finite-time attitude synchronization scenario is proposed.To release the aforementioned assumption,a novel high-order finitetime sliding mode estimator is proposed.Based on this estimator,a decentralized control scheme for attitude synchronization is designed.(c)To avoid the performance decline by inducing the auxiliary estimator,an actual decentralized attitude synchronization problem is studied.A directed graph topology is set for slight communication burden.Attitude dynamics of rigid spacecraft is modeled by Modified Rodrigues Parameters(MRP).Based on full-order terminal sliding mode technique,a finitetime decentralized attitude synchronization scheme is proposed.Some simulation cases are presented to show good performance on precision of the proposed control scheme.