Effect of Time-Varying Delay on Stability of Real-Time Hybrid Simulation with Multiple Experimental Substructures

In a real time hybrid simulation (RTHS), the actuator delay might deviate experimental results, or even destabilize the real-time test. Currently, research is very limited on stability of multiple-degree-of-freedom (MDOF) structures with multiple delays. Using the Lyapunov-Krasovskii (L-K) method, this study proposes stability criteria for MDOF systems with multiple time-varying/constant delays, and derives a more accurate result. Application of criteria shows that the stability of time-varying delay system is smaller than the corresponding constant delay system. With number of DOF and delay increasing, the criterion accuracy decreases slowly for constant delay system; meanwhile, the stability difference between constant- and time-varying- delay system increases gradually. Such difference is significant with small stiffness ratio of physical substructure.