MIMO FRF Testing of License Plate

Extracting the natural frequencies, damping shapes, and mode shapes of a structure aids in improving the design of the unit under test. In this case, the modal characteristics of a license plate is acquired by performing a modal analysis.

A MIMO FRF test is carried out using a pair of modal shakers and 14 accelerometers to obtain the vibration characteristics. The shakers impart energy to the structure for a longer period, which ensures an increased data set. The higher quality of the measurements also aids in the better estimation of the modal parameters.

A roving response method is usually implemented with a modal shaker test, but this procedure induces a mass loading effect in the results. To avoid this, small uni-axial accelerometers are attached on all the measurement points to capture the response of the entire plate in one shot. To run the high-channel count test (14 response channels and 2 excitation channels), a pair of Crystal Instruments Spider-80X front-ends are used with a Spider-Hub. The latest 8.0 release of the EDM Modal software assists in executing the MIMO FRF test.

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Modal Space - In Our Own Little World

Could you explain the difference between time domain, frequency domain and modal space? I hear it all the time but I'm not sure what's the difference.

There's a lot to explain but let's start with something simple.

This question gets asked often. There's a lot of different aspects relating to this so let's start with a simple explanation without using too much math and explain all of this with a simple schematic. Let's use the figure to discuss all these different aspects of the time domain, frequency domain, modal space and physical space. Now there are a lot of parts to discuss in the figure, so let's take them in pieces - one at a time - and then summarize everything at the end. You might also want to remember the discussion we had before when you asked me about what modal analysis was all about ("Could you explain modal analysis for me?") to help with the discussion here.

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Poly-X, the Poly-reference LSCF Implementation and Experiment

A poly-reference least-square method for modal parameter identification of a system in frequency-domain is discussed and implemented. It can also be considered as a multi-reference frequency-domain implementation of the recognized time-domain based Least-Squares Complex Exponential (LSCE) estimator.  The main advantages of the Poly-reference Least-Squares Complex Frequency-domain estimator (p-LSCF) are its capabilities of handling high system orders and high modal density. The stability diagram is much cleaner which makes the selection of system poles easier. Other advantages are lower computational times and the ability to handle multiple references. The Poly-X is Crystal Instruments’ version of p-LSCF, which is included in the EDM Modal software package. A MIMO FRF experimental test is carried out to demonstrate these advantages.

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Announcing Crystal Instruments’ new distributor, Avenir Technologies FZE for the United Arab Emirates, Saudi Arabia and Kuwait region

Crystal Instruments (CI) is excited to announce Avenir Technologies FZE as our new distributor in the United Arab Emirates region. Avenir Technologies FZE is located in the UAE, with offices in Dubai and Abu Dhabi.

Avenir Technologies is a value adding technical distributor providing high performance test & measurement products along with advanced technological solutions for the vibration market. They have extensive experience in providing solutions for military organizations, research labs, engineering teams, manufacturing companies, and the oil & gas industries.

Avenir Technologies also offers installation, field service and calibration with their delivered test systems.

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EDM 8.0 Release

Crystal Instruments is pleased to announce the release of EDM 8.0, the most advanced featured version of Engineering Data Management software. This new release of EDM supports exciting new hardware systems, convenient new software features, and helpful online resources.  

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Variable Sampling Rate for Synchronized Data Acquisition

The Spider-80Xi platform gives users the immense flexibility to combine the Spider-80Xi, Spider-80SGi or Spider-80Ti devices into one system with synchronized data acquisition. The Spider-80SG and Spider-80SGi can work as general-purpose data acquisition systems that not only supports strain measurement but also supports several sensor types requiring precision excitation voltage, including MEMS and strain gage based sensors. The Spider-80Ti on the other hand can acquire temperature data along with any other type of measurement quantity by using it with any combination of Spider-80Xs and Spider-80SGs.

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Multiple VCS instances

The Ethernet connection interface is one of the most important features of the 4th generation Spider series vibration controller. It provides the flexibility of location, reduces noise and electrical interference, and uses one PC to monitor multiple controllers.

In a lab environment, multiple computers and controllers are set up and connected to the same LAN. The EDM VCS software on each computer detects all Spider controllers on the network and connects any controller not yet connected by EDM VCS to a computer. Users can conveniently connect any controller from one computer, one at a time. When using multiple controllers at the same time, the same number of computers are needed to run EDM VCS on each controller.

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