Passive and active isolation of structural vibration transmission between two plates connected by a set of mounts

This paper introduces the theory of an impedance-mobility matrix model used to predict the structural vibration transmission between two plates, which are mechanically coupled via an active mounting system. With this model the active and passive isolation effectiveness of different types of mounting systems has been studied. In particular, the case of a three-mount isolator system with inertial or reactive actuators has been investigated in order to assess the influence of the mount stiffness and of the presence of rigid elements (block masses) at each end of the mounts. Three cost functions have been investigated: first, the minimization of the total structural power transmitted by the source to the receiver; second, the cancellation of out-of-plane input velocities to the receiver and third the cancellation of out-of-plane input forces to the receiver. The simulations carried out have shown that the best passive and active isolation are both achieved when soft mounts are used. The number of mounts and the presence of block masses at each end of the mounts significantly affect the passive isolation but have shown a smaller influence on the active isolation. The three control strategies studied have shown similar active control effectiveness in all cases examined and for both inertial or reactive control actuators. The validity of the model has also been assessed by comparing the predicted levels of vibration transmission with and without control with measured data taken from a laboratory experiment. (C) 2000 Academic Press.