Extension of Phase-Locked Loop Experiment for Application to Ground Vibration Test

Phase-locked-loop (PLL) experiments have been successfully used in the recent years to obtain backbone and frequency response curves of nonlinear structures. However, applications to large-scale structures as for instance in a ground vibration test (GVT) have been scarcely addressed, mainly because of difficulties in the tuning of the controller and limitations to single-input single-output (SISO) control. To overcome these challenges, we propose a variation of the PLL that requires only one control parameter, thus importantly reducing the tuning effort. A method to systematically determine this parameter is presented, making the proposed design less heuristic. Extension to multi-input multi-output (MIMO) control is also highlighted, which expands its potential to identify complex structures such as aircrafts. Numerical and experimental studies validate the new design.