Study On Multi DOF Elastic Load Modeling Of Electro-hydraulic Servo Shaking Table

Vibration test is a kind of common technical means to inspect the reliability and service life of product structures under the condition of vibration.It is widely applied to industrial fields.As one of the important equipment used in vibration test,the electro-hydraulic shaking table can achieve vibration environment simulation and the representation of typical signals.The specimen in previous studies is simplified to inertial load,which cause acceleration amplitude beyond the range of the stability and make system unstable.The thesis put the specimen equivalent elastic load based on the physical of the model and studied the effect of elastic specimen on the system frequency characteristics.The interaction between elastic load and the shaking table is coupled into a resonant system.Within the working frequency width,there may be a number of resonance peaks and resonance valleys,which have a serious impact on the acceleration frequency characteristics of the system.Resonant frequency must also be avoided in the sweep frequency test.Supported by the National Natural Science Foundation of China,the thesis studied the coupling effects of the elastic load on the acceleration frequency characteristics of electro-hydraulic servo shaking table,and provided a theoretical basis for the following decoupling control.Firstly,the development of the shaking table and the related research were reviewed,the content and significance of the research were introduced.The thesis introduced the working principle of the electro-hydraulic shaking table,system composition and common three state control strategies.In order to study the mechanical properties and the inherent properties of the elastic specimens,the modal analysis theory of the vibration theory was introduced.Secondly,considering the elastic effect of the specimen,according to the hydraulic mechanism model of the shaking table,the mathematical models were established under the condition of no-load,single DOF load,two DOF load and three DOF load.The different order open-loop transfer functions of the system were obtained.Based on the relevant experimental study and model test,the different DOF and different elastic stiffness of the specimen were established.The simulation was carried in MATLAB and the frequency characteristics of different models were obtained.Thirdly,the controller was designed according to the Three-Variable Control strategy to improve the stability and working bandwidth of vibration system.The mechanical performance index and modal frequency were obtained using Ansys/Workbench for different model for modal analysis.Combined with the simulation results in MATLAB,the thesis obtained the relevant conclusions of the different elastic stiffness and the degree of freedom to the resonant peak and resonant valley.