4-Degree-of-freedom anti-windup scheme for plants with actuator saturation

In this paper, a 4-degree-of-freedom (DoF) anti-windup scheme is developed for anti-windup compensation of plants with actuator saturation. Instead of LMIs (Linear Matrix Inequalities) in modern anti-windup technique, sufficient stability conditions of the proposed anti-windup scheme are derived under the framework of IQC (Integral Quadratic Constraint). The sufficient conditions are formulated as a checking on the positive definiteness of the related transfer function at all frequencies for MIMO systems (or positive sign for SISO systems), which provides a fairly straightforward tuning rule in the frequency domain. Moreover, by virtue of the proposed scheme, control design for disturbance response is decoupled from set-point response. The proposed scheme can be implemented without system states or state estimates. Compared with IMC-based, low-order or dynamic compensation anti-windup schemes, numerical example shows remarkable performance improvement of the proposed scheme for the saturated systems.