Abstract Real-Time Hybrid Simulation (RTHS) is a modern an‎d precise method for eva‎luating the dynamic response of structural systems under experimental conditions. In this technique, a numerical model of the structure is coupled with a physical subsystem through a real-time closed-loop control framework. However, the presence of nonlinear behaviors in physical components—particularly hysteresis an‎d mechanical backlash—can significantly reduce simulation accuracy, introduce instability, an‎d lead to the emergence of limit cycles. This study investigates the influence of these two nonlinear phenomena on the performance an‎d stability of RTHS systems. The test system consists of a servo valve–controlled hydraulic actuator as the physical component an‎d a numerically simulated single-degree-of-freedom mass–spring–damper structure. To model the nonlinearities, the Describing Function (DF) method was employed, an‎d the effects of hysteresis an‎d backlash were analyzed both independently an‎d in combination. System stability was assessed based on the geometric intersection between the nonlinear describing functions an‎d the frequency response of the numerical model in the Nyquist domain. Numerical simulations an‎d graphical analyses revealed that both hysteresis an‎d backlash reduce the critical input amplitude required to trigger instability, thus accelerating the onset of limit cycles. Furthermore, parametric studies demonstrated that structural damping ratio significantly affects the location an‎d nature of equilibrium points; an increase in damping tends to shift the intersection points an‎d heighten the system’s sensitivity to low-level excitations. Overall, the findings underscore the importance of accurately modeling hysteresis an‎d backlash effects an‎d utilizing analytical tools such as the Describing Function method to improve the robustness an‎d reliability of RTHS control strategies.

مصطفي نصيري

مصطفي منيري , ايمان فخاري گلپايگاني