Optimal H∞ sampled-data control in continuous time systems

A direct solution for the standard H_∞ problem is derived in a setting where a digital (discrete-time) controller has to be designed for a continuous-time system. Our Riccati equation based results include feasibility criteria and parameterization of all compensators with a specified performance. They also feature a characterization of the lowest sampling frequency needed to assure a desired level of performance. We consider both cases where the A/D and D/A elements are pre specified and cases where either or both these components are left as part of the design problem.