ROBUST SERVO DESIGN WITH APPLICATIONS

An optimal multivariable proportional-integral (PI) controller with pr eassigned eigen-spectrum is designed so that the system output would t rack constant reference inputs in spite of constant but unknown plant disturbances. A sequential strategy for modal servomechanism design is given for the above problem. In addition, since the proposed PI contr oller is of state feedback type, an observer capable of estimating the unmeasurable state variables in spite of the presence of unknown dist urbances is introduced, thus resulting in a suboptimal overall system. The separation property for the overall servo/observer system is illu strated. The design strategy is successfully used for position control of a brushless DC motor, and in a regulator mode for controlling a he adbox which is an integral part of the modern paper machines used in t he pulp and paper industry.