Modeling And Control Of Electromagnetic Suspension Vibration Isolator

Issue of the ship's vibration reduction has attracted people's attention for a long time. Passive vibration isolation technique has been traditionally used to reduce the ship's vibration. But its isolation performance in low frequency is not good enough. Active vibration isolation can overcome the inherent defect of passive vibration isolation in low frequency band, and has been deeply researched recently.This paper is dedicated to experiment study of self-designed Electromagnetic Suspension Vibration Isolator (ESVI)'s active control. It aims at improving the ESVI's vibration reduction performance in low frequency and not reducing it performance in high frequency.Force Transmissibility, Insertion Loss and Vibration Level Difference are three most popular methods to evaluate passive vibration isolation. For this ESVI, after giving the expressions of the three methods, its passive vibration isolation characteristic is studied by simulation and experiment. Result shows that it is true the passive vibration isolation performance of the ESVI in low-frequency is not good and active vibration isolation is needed.The designed ESVI's electromagnetic actuator which through upper and lower electromagnets attracting armature induces electromagnetic force is nonlinear. By controlling current in electromagnet coil strength of magnetic field can be controlled and then magnetic force can be controlled. MTS809 electro-fluid servo system is used to measure force the electromagnetic actuator induces, when it is passed different current under different gap, and then least squares method is used to get the functional relationship between them. After comparing Linear Power Amplifier with PWM Power Amplifier, PWM Power Amplifier is selected as control signal's power amplifier part. After considering that the other parts of the ESVI is linear, linear controller designing method can be used to get control variable which the electromagnetic actuator needs induce, and then through solving the functional relationship, the real control variable– current in the electromagnet coil can be got. Experimental result of optimal control shows that this controller design method is viable. Besides, software for active vibration isolation experiment has been programmed using VC++ programming language.Two ways to deal with the problem of reference signal extraction is given. And experiment study has been given for each of them, and their defects are also analyzed independently. After filtering the base's acceleration signal, Filtered-x Least Mean Square (Filtered-x LMS) algorithm is used in the ESVI's active vibration control. Experiment result shows that the active vibration isolation efficiency upon passive vibration isolation is more than 8dB, which meets the technical requirements of the ESVI.