Start SDOFit by selecting Send to SDOFit from the AFPoly Tools menu while in the AFPoly Poles module. After the application is initialized, the SDOFit user interface appears and the Select Function task is selected.
Select the FRF from which the modal parameters will be estimated using References and Responses listboxes on the right side of GUI. Right clicking on the Responses listbox will provide additional options for selecting the function. The selected FRF are plotted in the magnitude and phase axes. More than one FRF can be plotted but you cannot proceed to the next task unless only one response is selected.
Select the frequency range by moving the cursors on the plot to either side of the mode (or modes) of interest. Simply click and drag the vertical line that runs between the horizontal arrows on the upper and lower edges of the plot. You can move the cursors in either the upper, phase axes or the lower, magnitude axes. The frequency range can also be selected in the Compute Poles task.
Proceed to the Compute Poles task by clicking on the radio button in the Task List on the upper left side of the GUI. Enter the number of modes to compute and the maximum residual order to evaluate. The frequency range can also be selected in this task.
Start computing poles by clicking START at the bottom right of the window. SDOFit switches to the Select Poles task when completed.
Enter Pick Pole mode by either selecting Pick Poles from the axes context menu or clicking the Pick Poles toolbar icon shown below.
Pick poles by clicking on the red-highlighted pole marker in the stability diagram. Selected poles will appear as filled-in markers and be listed in the Poles List on the left section of the window, as shown below. Selecting any pole for a residuals order selects all poles for that order and deselects the other orders. An FRF is synthesized for the selected order and plotted for comparison to the measured FRF to evaluate the estimated modal parameters.
Push the DONE button to close SDOFit and return the selected results to the AFPoly stability diagram.