Discrete-time domain two-degree-of-freedom control design for industrial stable processes with input time delay

In this paper a discrete-time domain 2DOF design method is proposed for industrial stable processes with input time delay, based on a recently developed two-degree-of-freedom (2DOF) control structure. The setpoint tracking controller is analytically designed based on the H2 optimal control principle, and another controller for load disturbance rejection is derived by proposing the desired closed-loop complementary sensitivity function. Both controllers can be tuned independently to realize control optimization. Analytical expression of the setpoint response is given for quantitatively tuning the single adjustable parameter in the setpoint tracking controller. At the meantime, the tuning constraints of another adjustable parameter in the controller for disturbance rejection are derived by establishing the sufficient and necessary conditions for holding robust stability of the closed-loop system. Illustrative examples from the literature are used to show the effectiveness and merit of the proposed control method.