A discrete time H∞ observer-based controller and its application to an aero-engine

Explicit state-space formulae for an H_∞-based two degrees-of-freedom robust controller are derived in discrete time. The controller provides robust stability against co-prime factor uncertainty, and a degree of robust performance in the sense of making the closed-loop system match a pre-specified reference model. It is shown that the controller consists of a plant state observer, the chosen reference model, and a generalised state feedback law associated with the plant and model states. A design for a high performance aero-engine is presented as an illustrative example. An efficient implementation strategy is developed. The controller structure is shown to be utilized to yield considerable savings in the number of real time computations required