12 A. Bartl et al. Fig. 2.4 Arrangement of the lumped mass system used for numerical studies Table 2.1 System parameters used in the numerical case study Virtual component (V) Stiffness (N/m) Mass (kg) kV,1 25,000,000 mV,1 10 kV,12 10,000,000 mV,2 3 kV,13 10,000,000 mV,3 3 kV,24 10,000,000 mV,4 3 kV,35 10,000,000 mV,5 3 kV,45 10,000,000 mV,6 2 kV,58 500,000 mV,7 2 kV,46 20,000,000 mV,8 4 kV,67 20,000,000 Test specimen (EXP) Stiffness (N/m) Mass (kg) kEXP,13 2,500,000 mEXP,1 2 kEXP,23 2,000,000 mEXP,2 4 kEXP,34 10,000,000 mEXP,3 8 kEXP,4 10,000,000 mEXP,4 5 2.5 Conclusion In this paper we propose an adaptive feedforward technique with harmonic regressor for interface synchronization in Real Time Hybrid Testing. The approach makes use of the assumption of harmonic excitation and steady state. It addresses stability and accuracy issues in cases where the simulated overall system is a structural system with low damping. Multiple DoF interfaces are necessary in many applications. As the choice of adaption gain parameters is getting a complex task for tests with multiple DoF interfaces, we propose the use of a recursive least square algorithm for the adaption of the harmonic parameters with only a single parameter for the controller design. Future work will include the experimental validation on a test rig with a multiple DoF interface as well as the comparison with other interface synchronization techniques for Real Time Hybrid Testing.
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