Real-Time Hybrid Simulation Based On Vector Form Intrinsic Finite Element Method And Field Programmable Gate Array

Real-time hybrid simulation(RTHS)is a novel structural testing method by combining numerical simulation and experimental testing together.To obtain the dynamic response of the entire structure,the structure in RTHS is divided into two substructures:the complex part with nonlinear or time dependent behavior to be tested by experiments,and the simple part with well known and elastic behavior to be analyzed by numerical simulation.In RTHS,high-speed computation of the numerical substructures is required to match the real-time loading rate of the experimental substructures.Therefore,simplified numerical models are commomly used to cut down the computation burden in RTHS,which may cause significantly deviation between the numerical model and the real structure and heavily affect the reliability of the RTHS results.Moreover,the increased computation efficiency brought by simplified numerical model is limited when the testing structure is in large dimension and thus the numerical substructure requires large number of degrees of freedom to simulate.To enhance the computation capacity,a RTHS framework based on the vector form intrinsic finite element(VFIFE)method and field programmable gate array(FPGA)has been proposed in this study.The work conducted in this study is summarized as follows.(1)The computing procedure of the VFIFE method and the computational independence of the algorithm were elaborated,then a parallel computing method of the VFIFE based on FPGA and Lab VIEW was proposed.(2)A RTHS platform based on FPGA and LabVIEW was set up,including both hardware and software.(3)The numerical model and the dynamics of the servo hydraulic loading system were discussed.The influence of the loading error caused by the actuator dynamics to the RTHS result was demonstrated.A feed-forward and feedback compensator was used to reduce the loading error in time domain.(4)A RTHS with a shear building model containing three degrees of freedom and a virtual RTHS with a cable-damper system containing as many as 147 degrees of freedom were conducted for the experimental and numerical verification using the proposed parallel computing method and RTHS framework.The results show that the proposed VFIFE and FPGA-based RTHS platform can be efficiently used to conduct the experimental research of RTHS simultaneously with good computation efficiency which makes possible the RTHS with a large number of degrees of freedoms to calculate.