Fidelity assessment of Real-Time Hybrid Substructuring based on convergence and extrapolation

High quality of products and quick development cycles require reliable verification of the products. An applicable method for component testing is Real-Time Hybrid Substructuring (RTHS), which is a cyber-physical testing method combining numerical simulation and experimental testing. For the broad application of such testing methods, confidence in the test results must be gained. For this purpose, fidelity measures are required to indicate to the user how trustworthy the results are. The fidelity of an RTHS test does not only depend on the amount of errors in the loop, but also on the dynamics of the reference system and the interface locations. Current assessment measures do either not consider these dynamics/partitioning or require a reference solution or need knowledge about the dynamics of all involved components. This work proposes a novel strategy for fidelity assessment that circumvents these shortcomings: Fidelity Assessment based on Convergence and Extrapolation (FACE). The main idea is to deliberately vary the amount of error in the RTHS loop and monitor how this changes the RTHS result. From this relation, system understanding can be gained that is used in a further step to estimate the dynamics of the reference solution (i.e., if there was no error in the loop). The proposed method is applied to two application examples. In the first example, which is a virtual RTHS test of a linear system, the true reference solution is available and the prediction capability of the FACE method is verified. The second example uses data from a real RTHS test. Both examples reveal that the FACE method captures the dynamics influence of an error on the RTHS result and therefore helps the user to decide whether the conducted test was successful. This method can therefore be a valuable tool to assist users in the application of RTHS to a large variety of systems.