Research On H-infinity Control For Real-time Hybrid Simulation

Real-time hybrid simulation (RTHS) is a powerful tool to obtain responses andthen to evaluate dynamic performance of structures in civil engineering, to whichlots of attentions have being paid by researchers around the world. Only the twoparts in real-time hybrid simulation, refer to numerical substructure (NS) andexperimental substructure (ES), are compatible on the boundary, can the RTHS besuccessful, which demand the servo-hydraulic actuators must accurately realize thecommand signal delivered from the numerical substructure. However, theservo-hydraulic actuator is inherently a very complex system with nonlinearities andmay introduce time delay into the RTHS, which will minify the equivalent dampingratios and decrease the accuracy and stability of RTHS, in the worst case may causeRTHS instability. Meanwhile, the experimental substructure will behave nonlinearly,which can lead to poor tracking performance of the servo-hydraulic actuators. Thus,superior actutor control strategies will contribute to success of the RTHS.Studies on robustness of real-time hybrid simulation, consideringmulti-uncertainties, have been done. The main work of this study is summarized asfollows:Firstly, some work on the standard H-infinity control theory, by solving twoAlgebraic Riccati Equations, is made and H-infinity integral control is brought in.How the weighting functions, used in the design of H-infinity controller, affect thedynamic performance and suppress the disturbances are probed. A numericalexample is given based on the H-infinity control theory.Secondly, the simulink model of sevro-hydraulic actuators, developed by Jung,is employed in the design of H-infinity controller, PID controller and internal modelcontroller, which are used in the robustness analysis of modeling error, changes ofES, disturb and measured noise. Subsequently, numerical simulations of linear andnonlinear substructures are fulfilled. All simulations demonstrate that when thecontrollers designed by the transfer-function model are used to the system withmulti-uncertainties, the H-infinity controller exhibits better robustness.Thirdly, to obtain the model of FTS, a real-time hybrid simulation system,theoretical analysis and system identification are carried out. Two differentcontrollers, H-infinity controller and PI controller, are designed using thetransfer-function model, and series of numerical simulations are discussed. Aswitching control method, aiming at the controller with integral property, isdeveloped and applied to the real-time hybrid simulation with a linear spring as the experimental substructure. The results of numerical simulations as well as real-timetests show that the tracking performance and robustness of H-infinity control arebetter than PI control.