It is shown that the dynamic behaviour of a disk-type magnetorheological (MR) fluid damper developed on shear mode for rotational machinery can be controlled by application of an external DC magnetic field produced by a low voltage electromagnetic coil and that the disk-type MR fluid damper can effectively attenuate the rotor vibration. In this paper, the dynamic behaviour of the disk-type MR fluid damper for attenuating rotor vibration under AC sinusoidal magnetic field is experimentally studied on a flexible rotor. It is shown that as the frequency of applied AC sinusoidal magnetic field increases, the capability of the disk-type MR fluid damper to attenuate rotor vibration significantly reduces. There is a maximum frequency of AC sinusoidal magnetic field for a given applied magnetic field strength to realize the MR effect. When the frequency of AC sinusoidal magnetic field is over the maximum frequency, the MR activity almost completely disappears and the dynamic behaviour of the disk-type MR fluid dampers under a high frequency AC magnetic field is the same as that without magnetic field. For a given sinusoidal magnetic field frequency, there is also a minimum AC sinusoidal magnetic field to active the MR effect. In the rotor vibration control of view, it is not necessary to use the AC power supply for disk-type MR fluid dampers.
A disk-type MR fluid damper based on shear mode has been developed and the experimental results show that the dynamic characteristics of a disk-type MR fluid damper can be controlled by the application of an external magnetic field with a low voltage. In this paper, the effectiveness of on-off control based on feedback of rotational speed, proportional (P) control and proportional-integral (PI) control, both based on feedback of disk vibration eccentricity, on controlling the rotor vibration are experimentally studied. It is shown that the simple on-off control was the most effective method in attaining the required objective, but as expected requires pre-knowledge of the switching speeds and there is a transient response with large amplitude at switching speeds. P and PI control can control the rotor vibrations, but both exhibit significant chattering which can adversely affect the control performance and still require to properly choose the controller parameters.
A disk-type MR fluid damper based on shear operation mode is presented in this paper. The magnetic field of the disk-type MR fluid damper is analysed by the finite element method. The effect of excitation current in the coil on the magnetic flux density in the axial gaps filled with MR fluid is studied both theoretically and experimentally. Finally, the effectiveness of the disk-type MR fluid damper for attenuating vibration of rotor systems and of a simple open-loop on-off control based on the feedback of rotational speed on controlling vibration of rotor systems are experimentally studied. It is shown that the dynamic characteristics of the disk-type MR fluid damper can be controlled by a simple magnetic coil with a low voltage, and the disk-type MR fluid damper is very effective to attenuate vibration of rotor systems.
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