Singular H∞ suboptimal control for a class of two-block interconnected nonlinear systems

In this paper singular H_∞ suboptimal control for a class of two-block interconnected nonlinear systems is addressed. Under the assumption that the regular H_∞ suboptimal control problem is solvable for one of the blocks, an auxiliary nonlinear system is defined. Then it is shown that a feedback solution to the singular H_∞ suboptimal control problem for the auxiliary system also applies to the original problem. An explicit feedback solution is given for a special case when the auxiliary system can be strongly input-output decoupled. Application to the special case when one of the system blocks is passive is considered