Synchrophasing Vibration Control For A Floating Raft Vibration Isolation System

As a noise and vibration control method,synchrophasing has been well developed in the area of propeller-induced noise control for aircraft cabins.It is realized that synchrophasing may be a simple and effective way to decrease vibration transmission by only adjusting relative phases between machines on a floating raft vibration isolation system.This method become a supplement to passive,semi-active and active vibration isolation approach to some extent.So far,the research work in synchrophasing vibration control is mainly about a relatively simple model,simple excitations and lacking of online control strategy.Thus,a complex floating raft vibration isolation system with multiple excitation sources based on a flexible foundation is developed in this thesis.Simulation and experimental investigations on influence factors,adaptive phase online optimization algorithm for synchrophasing vibration control are made comprehensively to promote the method more practicable.The following work has been done.First of all,an analytical model of a floating raft vibration isolation system with multiple excitation sources and flexible foundation is built by combining the FEM frequency response function synthetic method and the substructure impedance/mobility method.Meanwhile,an experiment rig is also designed and constructed,of which the dynamic behavior is acquired by the modal analysis.The results show that the model is accurate enough for the following simulation work.Then,the influence factors of the synchrophasing vibration control are simulated on the basis of the model.After choosing the proper cost function,simulation results are given to demonstrate the relationship of the optimum value of the cost function and the corresponding phase angle with the parameters of the excitations,such as the number,locations,and directions of the excitations,the magnitude ratio of different sources.An adaptive phase-adjusting algorithm based on conventional Filter-x LMS algorithm is proposed to purchase the optimum phase combination online for synchrophasing control.Another finite impulse response filter called phase-adjusting filter is introduced,of which the weight vector is adjusted according to the phase angle between the output signal of the original control FIR filter and the reference signal.So,the output signal of the phase-adjusting filter can be the reference signal with a particular lagging angle by this way.The output signals of the phase-adjusting as well as the control filter are introduced into the error signal after passing through the secondary path filter,in order to avoid the output signal of the control filter being divergent.The simulation investigation on multi-motor case and experimental one for a two-motor test rig verify the effectiveness and practicability of the adaptive phase-adjusting algorithm.At last,a floating raft vibration isolation synchrophasing online control system is constructed,in which electromagnetic inertial actuators are used to simulate equipment and a TMS320C6748 DSP board is used as the controller.The proposed adaptive phase-adjusting algorithm is applied to carry out the experimental study on synchrophasing vibration control under different working conditions.The results show that the proposed phase-adjusting algorithm is effective for synchrophasing online control.Up to 23.4dB attenuation is achieved for the vibration of the flexible foundation.The simulation analysis,the practicability of the adaptive phase-adjusting algorithm are verified.