Monday  |  Salon 10  |  04:10 PM–04:30 PM

#12250, A Mixed Impact Shaker MIMO Test Technique (MIS-MIMO)

Modal testing involves collecting frequency response functions using either an impact or shaker excitation technique. Impact testing is often performed due to the ease of the test setup and simplicity of the measurement process. But larger structures may not be adequately excited with single impact excitation locations as the test progresses.

The use of shakers increases the level of complexity of the test and imposes additional considerations and complications when performing shaker testing. While shaker testing can provide a much better control force level and frequency spectrum, the attachment of the shaker and stinger and associated equipment can have an effect on the measured frequency response functions. This becomes more important as more shakers are added to improve the overall measurement system. A multiple input multiple output (MIMO) test is used to collect all the frequency response functions at the same time to minimize inconsistencies in the data collected. However, there are times when the location for the measurement desired cannot be accomplished with shaker attachment due to physical inaccessibility; this can be especially true with impedance modeling.

Due to the pros and cons of the impact and shaker testing techniques mentioned above, a unique Mixed Impact Shaker MIMO test technique was developed and is called MIS-MIMO. The test consists of a traditional MIMO shaker setup but with the addition of an impact at additional locations which are not easily accessible for shaker testing. In addition, the impacts are applied in a multiple burst strategy similar to the burst random excitation used for shakers. And the impacts can actually be performed with a handheld inertial shaker with a force gage and hammer tip for better signal input specification.

The results of the complete MIS-MIMO test are described in the paper with all associated measurements to show the use of the technique; the technique was successfully deployed on two separate measurement systems with different complexity.

Peter Avitabile   University of Massachusetts Lowell