ACHIEVABLE CLOSED-LOOP PROPERTIES OF SYSTEMS UNDER DECENTRALIZED CONTROL - CONDITIONS INVOLVING THE STEADY-STATE GAIN

The question of the existence of decentralized controllers for open-loop stable multivariable systems which provide particular closed-loop properties is investigated. In particular, we study the existence of decentralized controllers which provide integral action (Type 1 closed-loop performance) and also demonstrate one or more of. unconditional stability, integrity with respect to actuator and sensor failure, and decentralized unconditional stability. Necessary, sufficient, and, in some cases, necessary and sufficient conditions on the open-loop steady-state gain are derived such that there exists a controller which provides these desired closed-loop characteristics. These results provide the basis for a systematic approach to control structure selection for decentralized controller design.