Magnetic Mass Actuator (MMA)

Kiran SAHU
VTT Technical Research Centre of Finland

In VTT from quite a sometime now, research has been carried out to develop an elastic mass actuator (EMA) to reduce the sound radiation by suppressing the first radiation mode, which is themost efficient sound radiatingmode in low frequency region. Unlike the active damping device (ADD), which works only on resonance ; EMA is working quite well in a frequency band. In EMA, a mass plate is driven in between two electromechanical film (EMFi) layers. Electric interaction forces, which have been generated by supplying electric current to the EMFi layers, are controlled in such a way that the mass element tends to absorb vibrational energy, and thus, decrease the sound radiation of the panel on which it is attached. However, the amplitude of movement of the mass plate is quite low. Therefore, we were searching for a new solution which would improve the amplitude of vibration of the middle mass. In this study, a magnetic mass actuator (MMA) has been proposed in which a permanent magnet would be driven in between two electromagnets by changing the polarity of the supply current. By taking a feedforward/feedback signal from the plate vibration, the movement amplitude of the permanent magnet will be adjusted by adjusting the supplied current. In principle, both the electric and magnetic fields develop the Maxwell stress tensor to develop the interaction forces. Therefore, we expect the MMA would work exactly like the EMA but with improve performance.

Laboratoire de Mécanique des Structures et des Systèmes Couplés - LMSSC