Design Of Feed-forward Controller For Active Vibration Isolation Based On Phase Compensation

Active vibration isolator(AVI)is an important guarantee for the normal operation of ultra-precision measurements,and attenuates the vibration from ground to make sure the stability of the worktable.The ground vibration attenuated by active vibration isolator has the characteristics of wide frequency band,small amplitude and complex vibration source.So,we hope that the active vibration isolator has a low starting isolation frequency and large attenuation capability of middle and high frequency.In the active vibration isolator,feed-forward and feedback hybrid control mode is generally used.The feedback control can inhibit the resonance peak and feed-forward control can reduce starting isolation frequency of the vibration isolation system,and increase the attenuation ability of middle and high frequency.Therefore,the purpose of this paper is to design a superior feed-forward controller to reduce the starting isolation frequency of the vibration isolation system,and to increase the attenuation ability of middle and high frequency.This paper takes the active vibration isolator of the air spring as research object,and set up the dynamic model of the primary channel and the secondary channel of the active vibration isolator.The open-loop identification experiment of active vibration isolator is carried out.By comparing the frequency response curve of the theoretical model and the frequency response curve of the identification model,it is found that the frequency response curve of the theoretical model coincides with the frequency response curve of the identification model,which verifies the correctness of the theoretical modeling and parameter identification.This paper deduced the structure of feed-forward controller on the basis of the established theoretical model and the work principle of isolator,and analyzed the influence of phase on feed-forward controller.Based on the above analysis,this paper analyzed the feed-forward channel phase and compensated for the presence of the phase offset.The controller parameters are the feature parameters of vibration isolation system and identification parameter error will affect the performance of the controller.Based on this practical problem,the filtered x-LMS control algorithm is used for designing feed-forward controller.Finally,the effectiveness of the proposed feed-forward controller is verified by simulation from time-domain and frequency-domain.After the completion of the feed-forward control channel phase compensation and feed-forward controller design,a comprehensive performance testing for study object is carried on,and test results show that he attenuation rate is close to-40 dB at the 10 Hz,and the maximum attenuation rate is close to-48 dB in this system after the feed-forward control channel phase compensation.The test results verified the effectiveness of the proposed feed-forward controller studied in this paper from time-domain and frequency-domain.