Active isolation of periodic machinery vibration from resonant substructures

Jenkins, M. D., Nelson, P. A. and Elliott, S. J. (1991) Active isolation of periodic machinery vibration from resonant substructures. Environmental Engineering, 4 (3), 6-11.

Record type: Article

Abstract

This article is based on a paper presented at Defence Oceanology International 91, held at Brighton on 6-8 March. A two-stage combined active and passive isolator is described in which the lower, passive, stage is an air mount designed to be highly compliant in shear to minimise the horizontal motion within the upper stage. The upper stage has a parallel arrangement of passive and electrodynamic active components designed to control the vertical motion only. The performance of a laboratory system using four of these mounts to isolate a raft from a resonant substructure is found to be good when the periodic excitation on the raft is primarily in either the vertical or the horizontal direction. A control system which drives the actuators to minimise the sum of the squared output of eight accelerometers on the substructure is found to perform somewhat better than one which minimises at only four accelerometers, at frequencies above about 60 Hz. Practical application of the isolators to controlling the vibration from a diesel installation is also discussed.

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