Two-degree-of-freedom design method of LQI servo systems:performance deterioration by the introduction of an observer and optimalobserver design

摘要

This paper studies a two-degree-of-freedom design method of robustservo systems for step references and disturbances in the setting ofoutput feedback. Specifically, we consider the introduction of a stateobserver, and show that the fundamental desirable properties (i.e.,two-degree-of-freedom nature) attained in the state feedback case areinherited, qualitatively speaking, to the output feedback case. On theother hand, we quantitatively clarify the performance deterioration ofdisturbance rejection caused by the introduction of an observer.Furthermore, a design method of the optimal observers for such servosystems that minimize this deterioration is given. Separation propertyis shown to hold also in the two-degree-of-freedom servo problem, andconnections of the optimal observers with the technique of loop transferrecovery and with perfect control of disturbances are discussed