Bandwidth of Linear Classically Damped Systems with Application to Experimental Model Aircraft

Bandwidth is a widely known concept and tool used in structural dynamics to measure an oscillator’s capacity to dissipate energy over time, for example, when used in half-power damping estimation of structural modes. RMS bandwidth is a generalization of bandwidth that overcomes some of the limitations encountered with conventional bandwidth, including the prerequisite of linearity, single-mode response, and light damping. However, its mathematical form does not reveal much about the physics behind it. In this study, the RMS bandwidth expression was extended to multiple degree-of-freedom, linear, time-invariant, classically damped systems by deriving an analytical RMS (ARMS) bandwidth in terms of a system’s modal parameters and initial modal energy distribution. ARMS bandwidth reliably and accurately computed a single measure for a practical structure’s dissipative capacity. In addition, a purely data-driven methodology for assessing the modal energy distribution was developed. ARMS bandwidth was applied to single and multiple degree-of-freedom systems and an experimental model aircraft to demonstrate its broad applicability. Future work will address the effects of nonclassical damping distribution, time-varying parameters, and nonlinearities.