Simply structured controllers for vibration suppression in long rotors

In this paper suppression of the transient fexural vibrational disturbances in long rotors, with fuid flm bearings, is investigated. The rotor is described by a series of distributed shafts connected by the lumped discs, and the system is mounted on lumped fuid flm bearings. Upon determination of the dynamic stifness matrix of the system, the best approximate transfer function matrix description of the rotor, is determined. Initially vibration suppression by simple diagonal Proportional+Integral (PI) controllers is studied and via direct search optimisation techniques the PI parameters which exhibit fast vibration suppression is found. The resulted high integration rate, and low proportional gain PI controller, theoretically provided fast suppression time. However, it is shown that due to the strong coupling efect in the rotor system, and high rate of integration, the closed loop relative stability is weak, and feasibility of controller is questionable. Therefore, an alternative simple frst order controller without integration action, that is named “attenuation flter “is suggested that can produce stronger stability and produces signifcant (not full) vibration suppression. The closed loop multivariable control of the rotor system comprising two vibration sensors and two magnetic actuators using such attenuation flter, is then simulated. The response to step disturbances, has provided 95% suppression with signifcantly fast response. It is concluded that although the attenuation flter may not provide 100% suppression, but it more reliable since the integration of the error, that results weak stability is avoided.