Design of discrete-time H∞ optimal servo compensators

In this paper a new approach to the design of H_∞ optimal discrete-time servo compensators is presented. The design procedure for single-input single-output plants uses a frequency domain description and is based on the solution of a coupled system of diophantine and spectral factorization equations. An important feature of this approach is, that it leads to reduced-order controllers and therefore avoids singularity problems arising with standard H_∞ approaches. The proposed algorithm is simple to implement and easy to use, because the optimal H_∞ norm is a direct result of the algorithm and needs not to be prespecified.