Research On The Long Time History Replication Time Domain Control Of Electro-hydraulic Vibration Testing System

The structural reliability of mechanical product shows its ability to endure the real environmental vibration in operation and transportation.As a versatile tool for examining structural reliability,long time history replication(LTHR) vibration testing have been paid more and more attention in automotive,ship and aeronautical engineering in recent years.LTHR vibration testing can be applied effectively to vibratory simulation of real environmental vibration with the electro-hydraulic shaker which implementing preprocessed target signal acquired from real one.In order to obtaining the target signal of LTHR testing control system,the long time history (LTH) preliminary processing techniques,including signal resampling and multiple segments signal smoothing algorithms will be presented in this dissertation.The former is used to acquire the low-pass filter coefficients in resampling process through proper transformation.With the transportation,the filter coefficients can be obtained from the corresponding matrix equation using by QR decomposition in high precision.The latter is used to minimize the effects of energy leakage in signal spectrum.The specially shaped windows are applied to the two signal segments after they are resampled and the two windowed time waveforms will be overlapped in some extent that the strong fluctuation and overshoot of shaker can be prevented effectively.After the acquisition of the target signal of LTHR vibration testing,the successive work is how to control the electro-hydraulic shaker in accordance with the given target signal for exact reproduction of real environmental vibration.In this dissertation,we find that the LTH control can be classified into two main categories,namely Gaussian and Non-Gaussian LTHR control, after systematical study on the statistical properties of real environmental vibration.Aimed at two different categories above,the adaptive inverse time domain replication control algorithms are proposed correspondingly with correlation analysis and high-order cumulants.The Gaussian one is used to achieve the real-time and high degree of accuracy control through the precise estimation of system inverse transfer behavior by correlation analysis.The Non-Gaussian one is used to improve the control accuracy and phase estimation under noise disturbance.And considering second-order statistical quantities are not appropriate to describe system behavior in Non-Gaussian circumstance,the system inverse transfer behavior is gained using by high-order cumulants.LTHR vibration testing is generally implemented using by the electro-hydraulic shaker with high load-bearing and pushing force.However,there is the existence of large waveform distortion and low frequency reponse.Considering these two drawbacks,the modeling method of electro-hydraulic shaker will be researched in this dissertation.After the model built,an adaptive three-variable control algorithm based on generalized predictive control(GPC) will be presented.Three-variable control scheme has been widely used in the vibration control of electro-hydraulic shaker.However,it is not appropriate for unknown time-lagged and time varying system by the reason of strong dependence on its own control parameters.In order to improve the flexibility of determining control parameters and minimize the effect of parameter time-variability in vibration control,the GPC will be applied to tune the control parameters and the recursive least square method will be used in system modeling in this dissertation. Numerical and experimental results indicate the proposed approach is efficient and versatile tool in minimizing the waveform distortion of eletro-hydraulic shaker.