Frequency/Period Estimation and Adaptive Rejection of Periodic Disturbances

摘要

For a wide variety of systems, including sighting devices, weapons, machine tool arms, etc., operation under conditions which involve significant oscillatory disturbances is necessary. Often it is desirable to dynamically decouple the system from the disturbances by means of the intervention of active control. In many cases this must be done without a prior knowledge of the period (equivalently, the frequency) of the incoming disturbance. This document discusses a method for suppressing the oscillations of a linear system subject to an external periodic disturbance of fixed, but unknown, period. The method entails augmentation of the original plant with a compensator and parameter identifier. The near equilibrium dynamics of the resulting system are analyzed and shown to be related to a linear delay equation with infinite delay and periodic coefficients. A corresponding Floquet theory is indicated. A FORTRAN program approximately realizing the period identifier is included and numerical results obtained with this program are graphically displayed and analyzed.