Research On Ultra-low Frequency Sine Vibration Control Amplitude Identification Techniques

Ultra-low frequency vibration generally refers to the vibration of the frequency below 1Hz.Common in the ship bridge,aerospace,large-scale construction and other occasions.These vibrations will affect the normal operation of equipment,and even cause security incidents.Therefore,it is necessary to carry out the corresponding vibration environmental adaptability test.Electrodynamic shaker is the most widely used class of vibration test equipment.At present,the control frequency of the mainstream vibration controller of the electrodynamic shaker is generally above 5Hz,very few can reach 1~2Hz.This is because the ultra-low frequency range vibration level is very small,background noise is very large,and the real-time detection and recognition of the vibration signals become very difficult.Therefore,how to realize the vibration control of the ultra-low frequency range of the shaker is a difficult technology for the vibration control system of the electrodynamic shaker.In this paper,some key techniques in the ultra-low frequency sine sweep vibration control are studied from the viewpoint of signal processing.Based on the adaptive filtering of the ultra-low frequency sine sweep signal,a method of amplitude identification based on least square fitting is proposed.Furthermore,for the problem that the least squares fitting method decreases the accuracy of amplitude estimation with frequency reduction,an amplitude detection method of ultra-low frequency sine sweep signal based on variable sampling rate is proposed.At last,the simulation and experiment of the algorithm are carried out.The main contents and conclusions are as follows:1.Aiming at the problem of large background noise in ultra-low frequency,a signal denoising method based on adaptive notch filter is proposed.The LMS algorithm and RLS algorithm are used to filter the sine sweep signal.The algorithm is improved for the speed and convergence requirements.Finally,a finite impulse response(FIR)horizontal filter structure and a least mean square(LMS)algorithm are used to construct the system model and determining the adaptive noise reduction program.2.Based on the research of adaptive filtering mentioned above,the least squares fitting method is applied to the problem of amplitude identification of sine sweep signal for the characteristics of non-integer period.3.The influence of the time-varying characteristic of the sine sweep signal on the precision of the least-squares fitting is further studied.The order analysis technique of the rotating machinery fault diagnosis is introduced into the amplitude recognition.Based on the idea of equal angle sampling in order analysis,a signal resampling method based on variable sampling rate is proposed.The sine sweep signal is converted to a standard sinusoidal signal.Overcomes the problem that the accuracy of the amplitude recognition of the sine sweep signal decreases with the decrease of the frequency.4.The method of signal amplitude identification was tested and verified,including scheme design,test system setup and ultra-low frequency vibration control of the electrodynamic shaker.The experimental results show that the method proposed in this paper can effectively meet the requirements of signal amplitude detection for ultra-low frequency sine sweep vibration control.