Harmonic distortion from nonlinear systems with broadband inputs: applications to lung mechanics.

摘要: We present a simple index, extended harmonic distortion (k d ), to represent the degree of system nonlinearity under sparse pseudorandom noise inputs (SPRN). The frequencies in SPRN waveform are neither harmonics nor sums or differences other component frequencies. Expressed by percentage, thek is square root ratio output power at non-input total power. evoke three corrections recover truek imperfect inputs. Simulations on two block-structured nonlinear models (Wiener and Hammerstein) demonstrate necessity effectiveness these especially for Wiener-type nonlinearity. By applyingk pressure-flow data dog lungs, we found that interactions from lung arise primarily its tissues most likely processes governing tissue stiffness. This nonlinearity, assessed fromk , stronger higher tidal volumes enhanced (but lesser degree) during bronchoconstriction. conclude since approach avoids multiple-input measurements lengthy records, it may be useful tracking dynamic variations nonlinearities physiological system.