Evaluating the Effect of Modelling Errors in Load Identification Using Classical Identification Methods

Figure 12

The loading is applied at DOF 5. Natural frequencies, damping ratios, and mode shapes are introduced as stochastic variables. The figure consequently shows the time history of the identified load using Method 1 and Method 2. Each time series shown has a 10 sec duration. The solid lines are the mean values of the estimated force (N), and the dashed line is the mean value of the estimated moment (Nm). The hatched green area indicates uncertainty on the force, while the hatched orange area is the uncertainty of the moment. Both are shown using the upper and lower 98% quantiles. Three selected points in time show the error probability density (in percent) for the estimated load in DOF 5. Note that the probability density is scaled differently between Method 1 and Method 2.