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MODAL VIBRATION CONTROL IN PERIODIC TIME-VARYING STRUCTURES WITH FOCUS ON ROTOR-BLADE SYSTEMS

Abstract. In this paper an active controller for a periodic time-variant coupled rotor-blade system is designed. A periodic modal state feedback control scheme is designed based on a modal transformation of the system into a linear time-invariant formulation. The transformation makes it possible to design the controller using classical linear control techniques. Moreover, it provides the possibility to reduce the order of the system resulting in a simpler and more implementable controller. Non-measurable state variables are estimated using a periodic time-varying state observer designed by a similar procedure. The applicability of the controller design methodology is evaluated by numerical simulations on a coupled periodic time-variant rotor-blade system. A simulation model for such a system is formulated and three different control schemes are designed using the described methodology. The results obtained demonstrate that the designed controllers are capable to cope with the time periodicity of the system. Furthermore, the results show that specific vibration modes can be selected and controlled separately and very effectively.