Fixed gain controllers designed for nominal system, degrade in performance when system parameters are perturbed. By making the controller adaptive, ideal performance and granted stability of the closed loop system can be achieved for even a large change in system parameters. In the present study, adaptive controllers based on minimum variance, pole placement and linear quadratic techniques are investigated. The controller based on minimum variance is noise sensitive and actuator voltage changes sign after each sampling interval. Hence, it is detrimental to the life of piezoelectric actuators. Adaptive controller based on pole placement technique requires high control effort and gives poor performance at and near the nominal system. But, linear quadratic control based adaptive controllers are noise tolerant and are free from above mentioned limitations.
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