Frequency domain design for prespecified state and control constraints under persistent bounded disturbances

A frequency domain procedure for synthesizing controllers for single-input, single-output systems satisfying state and control constraints in the presence of persistent bounded input disturbances is presented. The input disturbance is modeled as an unknown but bounded process. The state and control constraints are treated explicitly. The primary objective is to construct a controller that: (1) uses only minimal allowable control effort, (2) does not violate the prespecified state constraints, and (3) maximizes the input disturbance bound. Constraints usually expressed in the time domain are mapped to the frequency domain, and this is followed by a transparent loop shaping procedure in the Nichols chart to complete the design. The effectiveness of the proposed method is illustrated by designing a controller for a third-order boiler-turbine set