Best achievable low order decentralized performance

The fixed order decentralized performance problem is formulated as a quadratically constrained control problem in terms of a stable map and the degrees of freedom of the controller. This problem is of the same type as the decentralized and/or simultaneous performance problems that have been discussed in our earlier work (1993), thus the same truncation-based solution procedure can be employed. The proposed approach is demonstrated through an example where the optimal parameter setting for decentralized P and PI control are identified.