Active Vibration Isolator And Adaptive Vibration Control Methods

Vibration is a phenomenon that widely exists in engineering applications. The performance of passive vibration isolation is limited due to its inherent disadvantages. Compared with the passive vibration isolation,active vibration isolation (AVI) is more adaptive to the variation of vibration environment. Moreover, AVI system is more suitable to suppress low frequency vibration and broadband random vibration.A new passive-active isolator has been studied, using an electromagnetic actuator to output the active force and controlling the motion of the actuator by applying proper control algorithms. The isolator has the advantages of both the passive and active isolation. Main work is summarized as follows:(1) Design an electromagnetic actuator applied to AVI. The finite model of the actuator is first established and its physical parameters are worked out with modal analysis. The specially designed structure ensures that the first natural frequency of the actuator is kept below 20Hz and no resonance peak occurs in its working band, which is an expected performance and is beneficial to vibration control. The measured frequency response shows that the finite element model is accurate and the frequency response of the actuator output force has no resonance peak within 20-3000Hz exactly, fully meeting the performance requirement.(2) The mathematical model of an AVI system is established, and PID control of the system under stochastic force excitation is simulated. By using MATLAB and SIMULINK, the effects of velocity feedback, acceleration feedback and force feedback are verified.(3) The adaptive algorithms of Filtered-x LMS and FTF are simulated. By identifying the control channel and applying strategies of these two algorithms, the effects of the control strategies are compared.(4) The dynamic characteristics and performance of the active isolator as well as the Filtered-x LMS are experimented. The transfer function of the control channel is identified and the active control is completed by a real-time controller made by National Instruments.