On the frequency domain linear quadratic optimal systems design

In this paper, a synthesis methodology of single-input-single-output frequency-domain optimal control system is developed to ensure asymptotic stability for the closed-loop system and to minimize a linear quadratic cost function. Furthermore, the equivalent two-degree-of-freedom scheme is considered. These two-degree-of-freedom compensators are designed so that the optimal control for the overall system is achieved and the return difference equality of the feedback loop is also satisfied, i.e. this system possesses the system performance with the optimal control sense and the robustness properties as in time-domain LQR optimal systems. The F-4E flight control system is considered as the design example to illustrate the validity of the design method