Abstract
To improve the vibration reduction performance of two-stage vibration isolation systems for marine engines under wide frequency band and multifrequency excitation, the magnetorheological (MR) damper is introduced into the vibration isolation system and an optimal controller is designed. Taking the test results of MR damper dynamic characteristics as sample data, the forward and inverse models of the MR damper are identified by the least square method and neural network (NN) method respectively, and the identification results are applied to semiactive control of the two-stage isolation system. Based on the analysis of vibration source, a six-degree-of-freedom mechanical model of two-stage system based on the MR damper is established. The optimal controller taking the minimum force transmitted from the engine to base as the control objective is designed. The system model and numerical simulation analysis are established using MATLAB. The results show that the isolation effect of optimal control is better than that of passive vibration isolation in the whole frequency band. In addition, good control effect is achieved in the low-frequency resonance region which is most concerned in engineering, which is of great significance to further improve the vibration reduction performance of marine engines.
Highlights
E semiactive control system can improve the vibration isolation performance and reduce the external energy supply [4, 5]. e semiactive control based on MR material has the advantages of low energy consumption, fast response, simple structure, and good reliability. e MR dampers and MR absorbers based on MR material have been developed as controllable isolation devices installed in the engines for vibration alleviation and mitigation [6]
At is to say, it is necessary to convert the required control force signal into current signal to adjust the output of MR damper. e conversion of force signal and current signal can be achieved by using the inverse model of MR damper or using the algorithm that can convert the control force into current signal. erefore, accurate inverse dynamic modeling is the premise of applying MR dampers to dynamic mechanical vibration control
Conclusions e MR damper is introduced into the two-stage vibration isolation system for marine engines, and its input current is controlled by the control module. e optimal control method is used to study the transmission characteristics of semiactive isolation systems
Summary
Based on the forward and reverse mechanical models of the MR damper, considering the current limitation of the MR damper, the control module is established and applied to the semiactive two-stage isolation system control. E neural network inverse mechanical model of the MR damper is used to calculate the required control current from the expected damping force. In order to ensure the effectiveness of the inverse mechanical model, it is necessary to obtain rich dynamic response information which can cover the working range of the MR damper as training samples.
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