Parallel compensator for control systems with nonminimum phase plants

Following the Smith compensator the parallel compensator designed for nonminimum phase plants is introduced in the paper. The compensator connected in parallel to the plant changes its properties so that the replacement plant model becomes minimum phase and may be shaped dependently upon the goal of the control. In the case of regulation on a constant level a first order lag may be chosen for the replacement plant model. In the case of tracking or disturbance rejection of signals with frequencies belonging to some working frequency band, the replacement plant model should have its frequency response close to that of the plant, in the working frequency band. The proposed approach simplifies the design and improves accuracy of the control.