A stabilizing controller for multirate sampled-data systems

Designs a multirate controller for a given multirate sampled-data system which has a periodic output measurement scheme. A sufficient condition for maintaining observability in multirate sampled-data systems is given first. The design strategy for disturbance rejection is proposed. The proposed controller has IMC structure, and can be decomposed into a disturbance estimator and the inverse of the fast plant. The authors assume that the disturbance consists of a sum of finite number of sine waves with different frequencies and DC bias. Simple examples are presented for illustrations.