Research On Electromagnetic Semi-active Vibration Absorber

Semi-active vibration absorber is a research focus in current vibration control field, whose natural frequency can be changed along with the parameters changing. It can achieve certain operating frequency band by tracking external excitation frequency. The paper presents an electromagnetic semi-active vibration absorber, which is non-contact and whose stiffness can be changed instantly and tuned on-line. By varying the current of the electromagnet, the stiffness of the absorber can be adjusted instantaneously such that the absorber frequency can be tuned, thus it is capable of suppressing vibration of the primary system characterized by continuous frequency variation.Numerical methods were employed to compute the distribution of magnetic field around the gap area, the variable magnetic stiffness due to the interaction between electromagnet and permanent magnet and the constant magnetic stiffness due to interaction between electromagnet core and permanent magnet based on electromagnetism theory. The deducing processes were simulated by using MATLAB language. The inherent characteristics of system were investigated, Effects of different cross-sectional shapes of the permanent magnets on both magnetic stiffnesses referred above were studied. The influence of gap of electromagnets on the inherent characteristics of system was analyzed. The mathematics model of absorber was established by impedance analysis method. In order to investigate more about the intrinsic property, the relationship of frequency response function curves and the influence of damping on frequency response curves were analyzed.Based on the simulation, the experiment setup was designed and processed, and then the suppressing vibration performance of the electromagnetic semi-active vibration absorber was tested through experiments. The experiment and analytical values were compared. The results indicate that, natural frequency of this absorber can be changed continuously and linearly along with the current of electromagnet changing and it is capable of suppressing vibration of the primary system excited by a harmonic force with a variable frequency. For instance, the amplitude decreased by 11dB at 7 hertz.