Design of H∞ Discrete-Time Controllers for Multivariable Systems via Given Engineering Performance Indices

For a linear MIMO control plant affected by unknown bounded external disturbances a design method of discrete output controllers that provide given or achievable performance indices such as control errors, settling time and stability margins radii for each control loop is proposed. The approach is based on the standard procedure of H
_∞
optimization formed in a special way. The robust properties of the designed system in terms of the Nyquist plot for the separate control loops broken at the plant input are studied, their connection with the absolute stability property of the system is found. A numerical example illustrates the effectiveness of the proposed approach.