Modal Parameter Extraction Of a Heavy Structure Using Multi Input Multi Output (MIMO) Test

To estimate the modal parameters of Excavator Cab by conducting Multiple Input Multiple Output (MIMO) Modal Analysis test. MIMO testing is done to obtain Frequency response functions(FRF’s) either with two or more fixed inputs of forces and multiple outputs(called Input referencing) or with fixed multiple outputs and multiple inputs(called Output referencing). In the present testing, fixed inputs (via four shakers) and multiple outputs using five triaxial accelerometers were used to plot the FRF’s. After this the FRF’s were processed i.e. curve fitting was done using PolyMAX frequency domain method for estimating the modal parameters. After obtaining modal parameters synthesized FRFs were plotted by curve fitting. The synthesized FRF is not 100% correlated with the original FRF because it doesn’t consider the lower and upper residual terms. The MIMO modal test conducted on the Excavator cab shows the capabilities of Multi Input modal test that if the structure is quiet heavy and rigid the multi input test becomes necessary because exciting at only one DOF will not be able to transmit the energy to the whole structure which will not help us to characterize the whole structure. Further the MIMO test will reduce the nonlinearities in the test and reciprocity can be checked easily.