Several design issues on the tunable electromagnetic vibration absorber

This paper addresses several design issues related to a newly developed electromagnetic vibration absorber (EMVA). The EMVA consists of a clamped-clamped aluminum beam and a permanent magnet that is embedded in the centre of the beam and placed between two poles of a C-shaped electromagnet. By varying the current of the electromagnet, stiffness of the EMVA can be adjusted instantaneously. The EMVA is capable of suppressing vibration of the primary system excited by a harmonic force with a variable frequency. First a simplified equation is proposed to compute the flux density distribution in the gap of the electromagnet. The approximation error caused by the simplification is investigated. Second, the effect of cross-sectional shapes of the permanent magnet on the variable magnetic stiffness and the constant magnetic stiffness is examined. Finally, the effect of the gap spaces of the electromagnet on the variable magnetic stiffness is studied.