H/sub /spl infin// control and parametric controllers for descriptor systems

In this paper, we study the existing problem of an H/sub /spl infin// controller for descriptor systems. One necessary and sufficient condition is presented by means of two generalized algebraic Riccati inequalities. Using the method of linear fractional transformation, the controller is parametrized by the admissible solutions to the Riccati inequalities with free parameter Q, a real-rational stable transfer matrix with an H/sub /spl infin// norm less than a specified number.