Design Of Active Vibration Isolation Tabel Based On Voice Coil Motor

With the development of manufacturing and measuring technologies,instruments and devices are required to be more stable and precise.The reason which limits the stability and precision of instruments is vibration causing by environment,especially the vibration with low frequency.Aiming at this issue,a kind of active vibration isolation system(AVIS)based on voice coil motor is designed in this thesis.This AVIS can be utilized to make ultra-precision instruments and manufacturing devices perform excellently.Firstly,analytical formula used to calculate magnetic flux distribution in air gap is deduced by applying surface current method and method of images.By comparing with the result of finite element software ANSOFT,the accuracy of analytical formula is proved.The dimension parameters of voice coil motor,including the thickness of yoke,the thickness of air gap and the width of magnet,are designed through the analytical formula.The comparation between finite element result and analytical result show that the error of magnetic flus density in air gap was less than 5% in the whole calculation region,and the error of force constant was only 6.2%,so that the voice coil motor can be used in the design of AVIS.Secondly,by the means of analyzing the principle of passive and active vibration isolation,the characteristics of these two method are introduced.The influence of different kinds of feedback variable are simulated to gain best effect.Based on foresaid analysis,a single degree of freedom AVIS with voice coil motor is designed and simulations are carried out to prove the performance of this AVIS.Experiments are conducted on single DOF AVIS,and the AVIS works from low frequency at 1Hz.The velocity is reduced to more than-25 dB at resonant frequency.With the active control on,the real mean square(rms)value of velocity is reduced to 6.1794μm/s,which is 11.641μm/s under passive control mode.And the vibration level of AVIS is promoted to VC-D.Finally,a 6-DOF AVIS is designed.Spring which is served as passive isolator is calculated according to relative rules.Linear driver used to drive voice coil motor is designed and its performance is tested by experiments.The dynamic of 6-DOF AVIS is analyzed,and the kinetics of sensor and actuator are derived according to mechanical design.Modal space is proposed to decouple multiple input multiple output system into single input and single output system,simplifying the design of controller.Active control experiments is carried out to test the properties of this AVIS.Experimental results show that the rms value of velocity can be reduce from 6.9359μm/s to 1.3451μm/s,which means that the vibration level is promoted to VC-E,and the peak to peak value of velocity is reduced dramatically from 44.524um/s to 8.3718μm/s.