AbstractThe problem of unknown and ummeasurable disturbance rejection in linear discrete multivariable control systems is considered, at that problem decomposition into disturbance estimation and compensation is suggested. It has been shown, that control structure with disturbance observer and disturbance compensator used for ummeasurable disturbance estimation and compensation may be treated as an Inverse Model Control approach. Moreover, the connection between inverse model design problem and unknown input observer theory has been established in order to give a practical way to inverse model parameterization and design. The properties of closed-loop feedback/feedforward combined control system with inverse model-based controller have been also investigated for the purpose of attainable disturbance rejection accuracy assessment.