Actuator dynamics compensation based on upper bound delay for real-time hybrid simulation

Real-time hybrid simulation represents a powerful technique capable of evaluating the structural dynamic performance by combining the physical simulation of a complex and rate-dependent portion of a structure with the numerical simulation of the remaining portion of the same structure. Initially, this paper shows how the stability of real-time hybrid simulation with time delay depends both on compensation techniques and on time integration methods. In particular, even when time delay is exactly known, some combinations of numerical integration and displacement prediction schemes may reduce the response stability with conventional compensation methods and lead to unconditional instability in the worst cases. Therefore, to deal with the inaccuracy of prediction and the uncertainty of delay estimation, a nearly exact compensation scheme is proposed, in which the displacement is compensated by means of an upper bound delay and the desired displacement is picked out by an optimal process. Finally, the advantages of the proposed scheme over conventional delay compensation techniques are shown through numerical simulation and actual tests.