Study On Active Vibration Isolation Of Marine Diesel Generator

Vibration and noise of marine power plant and various auxiliary equipments(pump, fan, compressor, generator etc.) will seriously deteriorate the loading conditions, reduce ship concealment. Traditional passive vibration isolation method in the low-frequency case is difficult to realize vibration isolation. For the rotating or reciprocating mechanical system, the vibration frequency characteristic is discrete line spectrum. Therefore this paper combined with the broadband isolation advantages of passive vibration isolation in high frequency and the line spectrum vibration isolation capability of active vibration isolation in low frequency to reduce the vibration of marine diesel electric set and to explore the required algorithms and techniques of the active and passive vibration isolation in actual control.Firstly, through the FRF’s synthesis method the substructure model of marine diesel generator based on frequency response function is established. It shows that the theory of simulation and modeling simulation comparison, the frequency response function synthesis method based on substructure can be accurate and effective description of frequency domain transfer characteristics of the vibration isolation platform of marine diesel electric generator.Secondly, starting from the concept of adaptive filtering, multi-channel active control algorithm for based on Fx LMS feedforward algorithm is established. The tracking filter based on frequency online estimation can accurately filter out the different frequency signal components in the interference signal to restore the reference signal of respective frequency. At the same time, adaptive system identification based on LMS algorithm is explored and applied to the error channel identification. In addition, Fx LMS feedforward algorithm is sensitive to the reference signal, so the interference response signal which can be restored by the error signal and the error channel identification is chosen as the reference control signal.Afterwards, based on the above work, further research about interchannel crosstalk problems in multichannel active vibration control and saturation problem of control output triggered by excessive external interference is conducted. It is one of innovation ideas of this paper that, to increase the coherence between the reference signal and the interference response signal, the decoupling filter is introduced to reduce the influence of interchannel crosstalk. At the same time, the simulation proves the problem that reference signal artificially generated leads to insufficient signal coherence. Even using the rotational speed signal as the reference signal, loss of semioctave frequencies also makes the control of these frequencies unable. In addition, the saturation function is introduced to solve the saturation suppression problem of control output, and applied to multi-channel control simulation.Finally, through verification experiment and diesel generator vibration isolation experiment platform respectively, vibration active control algorithms and techniques are verified. In the experiment based on diesel generator active vibration isolation platform, the actuator can only achieve control effect in several spectral line and fail in vibration control of semioctave spectral lines. Besides, vibration amplification phenomenon even exists in some spectral lines. So it is necessary to strengthen the actuator and the power amplifier output capacity, optimal control algorithm and improve the frequency domain characteristics of reference signal to enhance the control effect. Especially there is almost no control effect in low frequency because the base is near rigid and output of the actuator is lower than in high frequency.