Robust H infinity suboptimal and guaranteed cost state feedbacks as solutions to linear-quadratic dynamic games under uncertainty

For linear-quadratic dynamic games in which norm-bounded time-varying uncertainty enters in all matrices of the system equation without assuming the matching conditions, the notions of robust minimax and maximin strategies are introduced. It is shown how to construct two auxiliary dynamic games with completely known equations in such a way that a minimax strategy for one of them and a maximin strategy for the other turn out to be the robust minimax and maximin strategies, respectively, for the original dynamic game. By assuming 'control' as the first player and 'disturbance' as the second player, we show that the robust minimax strategy in the appropriate dynamic game provides the uncertain system with a robust H infinity suboptimal control, which guarantees quadratic stability of the unforced uncertain system. The results presented in this paper generalize those obtained in previous works.