SAMPLED-DATA CONTROLLER REDUCTION PROCEDURE

The problem of controller order reduction aimed at preserving the clos ed-loop performance of a sampled-data closed-loop system is investigat ed. Fast sampling of the system at a multiple of the sampling frequenc y followed by lifting allows capturing of the system's intersample beh avior and yields a time-invariant single-rate system; this then permit s standard order-reduction ideas to be applied. Special weighting func tions aimed at preserving the closed-loop transfer function are obtain ed, and weighted balanced truncation is used to reduce the controller. An example shows that without the use of fast-sampling, an unstable c losed loop can result from the reduction.