Numerical Study On Real-time Hybrid Testing Method Using Actuator-shaking Table

Shaking table real-time hybrid test is an effective method to overcome the shortcomings of full-structure shaking table test.The structure is divided into experiment substructures and numerical substructures.According to needs,the experiment substructures are physically loaded with actuators and shaking tables,and numerical substructures are numerically calculated.It fully combines the fast and efficient features of numerical simulation and the accuracy and reliability features of physical experiments,which has prominent advantages and broad application prospects.When a shaking table real-time hybrid test is carried out with lower parts of the prototype structure as a experiment substructures,the force balance condition at the boundary between the numerical substructure and the experiment substructures needs to be realized by an actuator with a force control mode,while the dynamic force loading control has a natural velocity feedback phenomenon,which means the force component corresponding to the frequency of the specimen is difficult to be loaded.High precision reproduction of boundary conditions is the guarantee of accurate and reliable hybrid test data,and is also the challenge of real-time hybrid test.In order to better complete the real-time hybrid test using actuator-shaking table with lower parts of the prototype structure as the experiment substructures,this paper proposes a new dynamic force loading strategy and a new real-time hybrid test method using actuator-shaking table,and the influence of time delay is studied.The main research contents and conclusions are as follows:(1)Based on the natural velocity feedback phenomenon,a dynamic force loading strategy based on linear velocity feedback compensation and minimum control synthesis algorithm is proposed for the real-time hybrid test using actuator-shaking table with the lower parts of the prototype structure as the experiment substructures.The principle of on-line identification of linear feedback compensation gain based on gradient descent method is described.The numerical simulation of five compensation methods,namely,no-compensation/Linear/Nonlinear/MCS/The proposed method,and the hybrid experiment of actuator and shaking table,are carried out.The results show that the proposed method has better control accuracy and robustness than other methods,and is easy to implement,cost-effective and has broad application prospects.(2)A new real-time hybrid testing method using actuator-shaking table is proposed for the real-time hybrid testing of actuator-shaking table with the lower partsof the prototype structure as the experiment substructures.A new substructure partition method is used in the new method,and an actuator with displacement control mode is used to load the substructure.The new test method formula was deduced,and the three-layer Shear Structure Model was simulated to verify the accuracy of the new method principle.Two commonly used time-delay compensation methods are used to simulate the actuator-shaking table hybrid test,and the results are compared with the exact response of the whole structure.The results show that the new real-time hybrid test method is easy to load and has high control precision,and the better test precision can be obtained by using the existing time delay compensation method.(3)Based on Taylor series expansion,the influence of time delay on real-time hybrid test is studied,and the influence of time delay on real-time hybrid test of stiffness experiment substructures,damping experiment substructures,mass experiment substructures and dynamic system experiment substructures is theoretically deduced and verified by numerical simulation.The results show that for real-time hybrid tests of stiffness,damping and mass specimens,time delay brings negative damping,negative mass and positive damping effects respectively.For hybrid test of dynamic system,time delay brings negative damping to numerical substructure and positive damping to experiment substructures.