Frequency-domain assessment for tracking Servo-hydraulic actuator displacement in real-time hybrid simulations

Real-time hybrid simulation is a novel and effective technique for seismic tests. Servo-hydraulic actuators play an important role in a real-time hybrid simulation, where they serve to maintain the boundary conditions between the experimental and analytical substructures. Accurate actuator tracking directly affects the reliability of hybrid simulation results. Existing methods for actuator tracking assessment are often based on time-domain analysis. This paper proposes a frequency-domain actuator tracking method, based on use of the Fourier transform, which only requires the input and the output of the actuator and can simultaneously evaluate the phase delay and the amplitude error. To minimize the effect of the fast Fourier transform (FFT) and spectrum leakage on the analysis results, a Hann window is used to improve the accuracy of the method. The effectiveness of the proposed method is validated experimentally using a real-time hybrid simulation system which subjects the actuator to predefined sinusoidal and random signals.