Design of Observers and Servomechanisms for a Discrete-Time Linear System with Periodic Disturbances.

A state observer which rejects periodic disturbances is proposed for a discrete-time linear system. An observer-type compensator based on the above theory is newly developed, which rejects the influence of periodic disturbances from the output of a controlled system. This compensator cancels the periodic disturbance with the aid of asymptotic estimation of the periodic disturbance itself. Although this compensator does not estimate the real state, it is verified that this compensator can be used in system control as well as observers, and hence realizes an input/output performance characteristic equivalent to that of a servomechanism designed for the no- disturbance condition.