ABSTRACT
This chapter provides an adaptive nonlinear compensation scheme, on the basis of a linear feedback control, to further improve the rejection of low-frequency disturbances such as nonlinear disturbances arising from friction torque or bias or other unknown disturbances, to cancel their effects through a proper estimation of the disturbances. It discusses a non-model based compensation, which is an adaptive and a more flexible scheme, applied to compensate the nonlinear or unknown vibrations in low frequency range. Nonlinearities such as friction in the actuator pivot are known to limit the low frequency gain of a control loop. A nonlinear controller is augmented with the KYP Lemma-based linear feedback controller, which remarkably improves the system disturbance rejection capability in low frequency range without sacrificing performance at other frequencies. To further improve the disturbance rejection in low frequency range, the linear control is combined with an adaptive nonlinear compensation.
