Characterization of Force-Frequency Shifting dynamics for low frequency excitation

A novel approach know as Force Frequency Shifting (FFS) is under developed for low frequency (less that 1 Hz) vibration excitation for large structures (i.e., buildings, bridges, stadiums, ballroom floors, etc.). Initial implementation of the method applied a time variant force to the test structure in a spatially varying fashion. More recent work has demonstrated that low frequency excitation performance gains may be realized through the use of carefully placed stationary components with controllable time-variant damping. This work will present the modeling and subsequent analysis to describe the underlying dynamic phenomena. A system model is developed and numerically solved in Matlab-Simulink. The results show phasing between the stiffness and damping components contribute and inhibit to the desired low frequency excitation force. The damping force is shown to trend toward zero as the difference frequency approaches the natural frequency. A parametric study focusing on the relationship between the time-invariant and time-variant damping demonstrates their effects on the desired low frequency excitation.