Comparison of uncertainty in passive and active vibration isolation

In this contribution, the authors discuss a clear and comprehensive way to deepen the understanding about the comparison of parametric uncertainty for early passive and active vibration isolation design in an adequate probabilistic way. A simple mathematical one degree of freedom linear model of an automobile’s suspension leg, excited by harmonic base point stroke and subject to passive and active vibration isolation purpose is used as an example study for uncertainty comparison. The model’s parameters are chassis mass, suspensions leg’s damping and stiffness for passive vibration isolation, and an additional gain factor for velocity feedback control when active vibration isolation is assumed. Assuming the parameters to be normally distributed, they are non-deterministic input for Monte Carlo-Simulations to investigate the dynamic vibrational response due the deterministic excitation. The model parameters are assumed to vary according plausible assumptions from literature and own works. Taking into account three different damping levels for each passive and active vibration isolation approach, the authors investigate the numerically simulated varying dynamical output from the model’s dynamic transfer function in six case studies in frequency and time domain. The cases for the output in frequency domain are (i) varying maximum vibration amplitudes at damped resonance frequencies for different passive and active damping levels, (ii) varying vibration amplitudes at the undamped resonance frequency, (iii) varying isolation frequency, (iv) varying amplitudes at the excitation frequency beyond the passive system’s fixed isolation frequency, and (v) vibration amplitudes for −15 dB isolation attenuation. In time domain, case (vi) takes a closer look at the varying decaying time until steady state vibration is reached