EDM Modal Multiple-Input Multiple-Output (MIMO) FRF Testing

MIMO FRF Testing is a dedicated module inside the EDM Modal software suite for acquiring FRF signals with several shakers driven simultaneously. It provides a purpose-built setup and operating process flow, and when combined with a large channel-count acquisition system such as the Spider-80X or Spider-80Xi, the multi-shaker excitation method delivers substantially higher efficiency and accuracy for FRF measurements while minimizing local stresses on the test article. In the multiple-shaker random excitation mode, the driving source signals are guaranteed to be uncorrelated with one another. The source output type supports pure random (white noise), burst random, chirp/burst chirp, pseudo random and periodic random. For the periodic random types, the delay block and cyclic block numbers can be set so that the structure reaches steady-state response before each acquisition, enabling precise window-free analysis. Multiple shaker excitation is valuable for separating and clearly identifying repeated roots and frequency-proximate modes. With more than one reference shaker, several columns of the frequency response matrix can be measured at the same time, and the poly-reference curve-fitting algorithm uses modal participation factors to isolate repeated and highly coupled modes. The modal analysis process is seamlessly integrated with MIMO FRF testing, so measurement and parameter identification run in one flow. Software features include an ease-of-use testing process, point/direction auto or manual increment, synchronized outputs, one or more excitation (reference) channels, a source trigger mode for synchronized acquisition and excitation, random/burst random/pseudo random/periodic random/chirp output types, delay and cyclic block number settings, a Scope tab to inspect channel data before measuring, and H1, H2, H3 and Hv estimation.