Numerical and experimental comparison of the energy transfer in a parametrically excited system

This study is based on experimental results obtained from a test rig for a 2-DOF vibrational system. The main feature of this test rig is an electromechanical actuator which enables the variation of a mechanical stiffness parameter. The vibrational system is excited by this device, resulting in a parametrically excited system. In this study, the test rig is operated such that an initial deflection is applied to the masses, but no external excitation acts on the system. The actuator coils are driven by a current following a harmonic function defined by amplitude and frequency. The latter defines the parametric excitation frequency (PEF). When the mechanical system performs free vibrations, the parametric excitation may initiate an energy transfer between the two vibrational modes of the system. This transfer depends primarily on the PEF. For certain values of the PEF only one of the vibrational modes is affected. At other frequencies both modes are influenced and a continuous intermodal energy transfer is observed. A numerical model for the test rig was established and allows a comparison of experimental and numerical results. The total system energy as well as the modal energies are calculated from the measured and from the simulated signals. Interesting experimental observations are reported concerning the transfer of energy, and are in good agreement with simulated results.