Near-Source Error Sensor Strategies for Active Vibration Isolation of Machines

Due to lightweight construction of vehicles and ships, the reduction of structure borne interior noise problems with passive isolation of engine vibrations might be not sufficient. To improve the isolation, a combination of passive and active isolation techniques can be used (so-called hybrid isolation). This paper focusses on the influence of the sensor positions on the performance of the active isolation. In general two strategies can be distinguished: sensors located in the accommodation with a direct minimization of the sound field and sensors located near the source of vibration. In this paper attention will be paid to an effective weighting of the near-source sensors in such a way that the interior noise in the vehicle is reduced. Also the nearsource strategy of minimization of the injected power is considered. The latter strategy is theoretically very attractive, but is much more difficult to implement in practice. The techniques are explained and compared to each other with the help of numerical models.