Multi‐rate real‐time hybrid simulation with adaptive discrete feedforward controller‐based compensation strategy

Abstract Real‐time hybrid simulation (RTHS) is an innovative experimental testing technique that tests only some structural components for which accurate numerical models do not exist (i.e., experimental substructure), while modeling the rest of the structure numerically (i.e., numerical substructure). Conventionally, the two substructures in RTHS are executed at the same rate and interact in real time. Multi‐rate real‐time hybrid simulation (mrRTHS) is a modification of RTHS where different time step sizes are applied to the numerical substructure computation and the actuator control. This configuration provides a larger allowance for real‐time execution, thereby enabling the use of higher‐fidelity numerical models in RTHS. However, it complicates the data transmission between the substructures and introduces an additional time delay. The increased delay consists of communication and computational delays, which are independent of actuator dynamics. This study compares the data transmission within RTHS and mrRTHS configurations and confirms that mrRTHS experiences a larger delay error. To improve the accuracy of mrRTHS, a time‐varying interpolation built with Chebyshev polynomials is used. Additionally, a compensation strategy based on an adaptive discrete feedforward controller is introduced to compensate for actuator‐induced tracking errors and the increased time delay in mrRTHS. A demonstrative experimental study is conducted to investigate the seismic behavior of a large‐scale base‐isolated structure equipped with gyromass dampers. The results indicate that the proposed mrRTHS compensation strategy facilitates a more realistic assessment of the dynamic performance of structural systems by employing higher‐fidelity numerical substructures in mrRTHS.