Design of smart machinery installations to reduce transmitted vibrations by adaptive modification of internal forces

Abstract

There is a requirement to isolate machinery from their surroundings to reduce the transmission of noise and vibration. Reducing the input disturbance of a system can reduce vibration levels, but this is not always a feasible option. One of the simplest ways to overcome these problems is to retrofit a vibration attenuation device. The method used for vibration isolation discussed in this paper is semi-active control and involves using tunable resonators at the mounting positions. These resonators operate by continually adjusting their characteristics such that a large force is generated, achieving vibration attenuation over a range of varying operating conditions. In this paper, the resonators are tuned such that the natural frequency of the resonator is equal to the excitation frequency. Open-loop control is used to roughly tune the resonator, with a precise algorithm changing the characteristics of the resonator such that the host structure and resonator are in quadrature. Using multiple resonators increases the complexity of the system as interaction is possible between the resonators. The interaction between well-coupled resonators is modelled and examined experimentally. A simple control algorithm is developed and implemented which demonstrates that the resonators can be tuned independently, irrespective of the dynamic coupling between them.