Adaptive Output Servocontroller for MIMO System with Input Delay*

The paper deals with the problem of simultaneous adaptive compensation of external disturbances and asymptotic reference tracking in linear time-invariant multi-input multi-output square plants with input delay and unmeasurable state. The plant to be controlled can be unstable. The external signals — disturbance to be compensated and reference to be tracked — are modeled as multi-harmonic signals with unknown frequencies, phases and amplitudes. The solution is based on suitable external signals parameterization and prediction as well as on special tracking error augmentation allowing one to overcome the problem of input delay in adaptation algorithm. Two adaptation algorithms using special augmented error are proposed: gradient-based algorithm and an algorithm with improved parametric convergence based on application of Kreisselmeier’s scheme. No a priori assumptions about knowledge of external signal parameters as well as about persistent excitation (PE) condition are needed for asymptotic reference tracking and disturbance rejection in the closed-loop system.