Continuous, discrete and sampled data H∞ control-a unified framework

We present a unified and general framework for H_∞-control in both continuous time, discrete time and combinations of these. The general result is a hybrid continuous-/discrete-time H_∞ controller. Using a compact hybrid notation, the work shows a close relationship between the continuous and discrete-time solutions. In fact, the pure continuous and discrete time equations may be obtained as two similar interpretations of the general result. There are no assumptions made on certain system matrices being zero or normalised, e.g. D₁₁=0. The method is Riccati equation (RE) based, and it is shown how the continuous REs can be “lifted” into discrete ones reflecting the system behaviour during the period