Decoupling Control For Multi-axis Seismic Testing Table Based On The Dynamic Model

As a common used lab-facility,vibration simulation table is widely used in the industrial circle.For example,in the field of seismic simulation.Before the new designed building structure was put into use.Vibration testing is a fixed procedure to make sure the structure is safe when an earthquake occur.Also the vibration table is used in the simulation of the real working vibration environment of the civilian and the military products.However,due to its complex dynamic and other characteristics,the system has a strong coupling effect between the degrees of freedom.First of all,this paper introduced the working principle,function and all the components of the system briefly.The kinematics and the dynamics analysis of the system is carried out in order to study the reasons of coupling phenomenon.The coupling reasons are discussed in following aspects.Such as the elasticity of the hinge and foundation,the dynamic characteristics of payloads,the eccentricity between the control point and the center of gravity etc.In order to analyze the coupling phenomenon due to the dynamics of the hydraulic legs.The multi body dynamic model was introduced with the application of Cane method.With the Cane equation,the coupling force can be calculated in real time.And it is one of the preparations of the decoupling control.The gravity point of the platform and the control point could be misaligning.And the system could have heavy eccentric payload.Under these circumstances,the form of the mass matrices in the dynamic equations transformed from diagonal matrices into non-diagonal matrices.And the non-diagonal mass matrix can lead to system coupling phenomenon.Secondly,in order to analyze all these coupling phenomena and reasons of vibration table,the joint simulation model of Simulink and SimMechanics software was established.By solving the equivalent mass matrix and the equivalent stiffness matrix,the natural frequencies of the system for each degree of freedom are obtained.Through the classical three variable control strategy,the system bandwidth was expanded,the damping ratio of each degree of freedom was increased,and the stability of the system was improved.A decoupling control strategy based on dynamic model was proposed for the system.The system coupling can be compensated by the controller.At the same time,because of the redundant characteristics of the vibration table.Inner forces can influence the control performance of the system as while.This paper improved the traditional eight degree of freedom control strategy.By extend the application field to systems with eccentric loads.Finally,the decoupling control strategy based on the dynamic compensation was experimentally verified by comparing with the results of the experiment without the decoupling controller.