Insensitivity properties of multirate feedback control systems

The design capabilities of a class of periodic systems, multirate systems with multiple input and fixed output (MIFO) rates, for application to the eigenstructure assignment robust design technique, are examined. A special feature of the MIFO multirate systems is the ability to introduce extra design freedom in the eigenproblem by a suitable choice of sample rates. The criteria for the selection of minimum sample rates to produce this extra design freedom and the implication of this choice for the eigenstructure procedure are outlined. The use of the extra freedom to produce perfectly decoupled closed-loop modal responses is examined. The improved insensitivity properties of these solutions are demonstrated with an example which compares the performance of multirate and corresponding single rate designs