Effect of time delays and sampling in force actuated real-time hybrid testing; A case study

This paper presents a study where real-time hybrid testing is applied on a double mass-damper-spring system. Simulations show how delays and sampling terms affect the system both when it is subjected to excitations forces and in free decay. In particular, it is shown how the stiffness of the actuator combined with time delays can have a profound effect on the real-time hybrid test case. Further, using the test case, first order Taylor expansions are used to show how linear stiffnesses combined with delays can be approximated as linear damping terms, while linear damping terms can be approximated as added mass terms. These approximations are useful in providing intuitive insight into how delays will affect the real-time hybrid test system.