Controlmethods Of Single-degree-of-freedom Real-time Hybrid Testing

Seismic tests play an essential role in structural engineering due to thecomplicacy of the seismic excitation and structures. Meanwhile, there are someshortcomings of traditional hybrid testing methods, e.g. pseudo-dynamic testingmethod, to assess seismic behaviour of a structure, especially when a rate-dependent control device is installed in the target structure. In order to solve thisproblem, Real-time Hybrid Testing (RHTing) method was proposed, which ischaracterized by testing a structure with a large-scale or even full-scale specimen inreal-time. With this method, the tested structure is divided into two parts, i.e.numerical substructure and experimental substructure, and the coordination of theboundary condition between them is achieved by loading with a transfer system(typically an actuator or a shaking table). One of the key problems of the method isthe dynamics of the transfer system which can affect the stability and accuracy ofthe results; hence it is of great importance to weaken or eliminate this effect.This dissertation focuses on control strategies in the RHTing. Main researchwork and findings are summarised as follows.1、The Sliding Mode Controller(SMC) is used as the outer controller in theEquivalent Force Control Method (EFCM) instead of a PID controller consideringthe possible nonlinearity in the RHTing. The design approach of SMC is studied forRHTing. Real-time hybrid tests and numerical simulations are carried out with alinear or nonlinear specimen. Good control effects of the EFCM together with theSMC are validated by test and simulation results.2、The SMC in the EFCM is designed considering the unmatched uncertainties aswell. The effects of key parameters on performance of the SMC are discussed. Thestability of the EFCM with this method is analysed according to Lyapunov theorem.Finally, the effectiveness of the SMC is verified by numerical simulations of aRHTing with a nonlinear specimen.3、Adaptive Forward Prediction algorithm(AFP) is utilized to compensate for thetime delay in the EFCM. The effects of the key parameters of AFP on performanceof compensation effects are discussed through numerical simulations. Numericalsimulation and test results with a linear stiffness specimen illustrate that RHTingwith AFP compensation exhibit better performance than the conventional EFCM. Results of real-time hybrid tests with a nonlinear specimen demonstrate that theproposed method exhibits better accuracy than the EFCM with fixed-delaycompensation.4、In order to attain better velocity and/or acceleration control performance inRHTing, the EFCM based on an explicit integration method is proposed. Thescheme is firstly formulated with Newmark explicit method, then stability analysisis carried out via spectral stability technique. The feasibility of the approach isverified by RHTing results with a MR damper specimen. The Rosenbrock-based L-Stable Real Time (LSRT) algorithms are also implemented with the similarframework in order to improve acceleration control performance. The feasibility ofthe EFCM based on LSRT is proved by numerical simulations with an inertiaspecimen.5、The acceleration control methods in Dynamical Real-time Substructure Testing(DRSTing) are investigated. Firstly, in order to suppress the high frequencyoscillation of the acceleration responses in DRSTing, a pre-filter combined with apost-filter is proposed. In addition, the pressure difference feedback control isapplied to further improve acceleration control performance. The performance ofthe proposed scheme is validated by the DRSTing with a pure inertia specimen. Theproposed scheme is finally applied to DRSTing of a circle tuned liquid damper andfavourable acceleration control effects of the damper to the structure in earthquakeare proved by test results.