Robust high-precision attitude control for flexible spacecraft with improved mixed H₂/H_∞ control strategy under poles assignment constraint

A novel improved mixed H₂/H_∞ control technique combined with poles assignment theory is presented to achieve attitude stabilization and vibration suppression simultaneously for flexible spacecraft in this paper. The flexible spacecraft dynamics system is described and transformed into corresponding state space form. Based on linear matrix inequalities (LMIs) scheme and poles assignment theory, the improved mixed H₂/H_∞ controller does not restrict the equivalence of the two Lyapunov variables involved in H₂ and H_∞ performance, which can reduce conservatives compared with traditional mixed H₂/H_∞ controller. Moreover, it can eliminate the coupling of Lyapunov matrix variables and system matrices by introducing slack variable that provides additional degree of freedom. Several simulations are performed to demonstrate the effectiveness and feasibility of the proposed method in this paper.