Modal Analysis and Modal Testing - ODS, MIMO, OMA

Effective and affordable modal analysis and modal testing solution for ODS, MIMO, and OMA testing methods. The modal test is an indispensable tool to determine natural frequencies and mode shapes of any structure. With our solution, you are able to excite the structure with an impact hammer or modal vibration shaker and easily measure the response. Import or draw your geometry rich visualization and animation of your structures.

Modal Analysis and Modal Testing - ODS, MIMO, OMA solution from Dewesoft
IEPE
IEPE
Charge
Charge
Voltage
Voltage
Strain / Stress
Strain / Stress
Acceleration
Acceleration
Velocity
Velocity
Displacement
Displacement
Video
Video
High-speed video
High-speed video

Main Features

  • IMPACT HAMMER OPERATION MODE: allows grouping, rejecting and repeating measurement points; multiple references and excitation points are supported. The ability to move excitation and response points is giving the user full flexibility when performing measurements.
  • SHAKER OPERATION MODE: in combination with the in-built function generator module, the system allows any type of excitation from fixed sine with 1 MHz resolution, sweep sine, random, step sine, chirp, burst and others.
  • ADVANCED MATH: Operating deflection shapes (ODS), mode indicator functions (MIF), COLA analysis are fully implemented in Dewesoft while operational modal analysis (OMA) and time-domain ODS are available with close integration with an external software package.
  • RICH VISUALIZATION: animation of structure in all three directions and with different projections is available also during the measurement providing a great tool to determine the quality of results, giving the user a chance to repeat measurement of any point. The modal circle tool determines exact resonance and calculates viscous or structural damping factor.
  • UNV IMPORT/EXPORT: Geometry can be either built via an in-built geometry editor or imported via the UNV file. All data, from the raw time domain to auto spectrums and FRFs can be exported using standard UNV file format.
  • LIFETIME FREE SOFTWARE UPGRADES AND SUPPORT: Our data acquisition systems come bundled with award-winning Dewesoft X data acquisition software. The software package is always evolving and new features are being added. We offer lifetime FREE software upgrades and technical support to all our users.

Multireference Modal Test

Multi-reference modal testing is required in cases where the structure has more modes with the same resonance frequency. This is often referred to as ‘repeated roots’, where ‘roots’ refer to the solutions to the characteristic equation giving the frequency and damping values of the structure. This is, for example, the case for certain symmetrical structures.

Add multiple excitations and multiple response channels at the same time (for example triaxial responses and excitation in all three directions in one data file).

Easy and Quick Setup

In the case of a high number of measured channels, adding and removing the excitation and response channels is a very simple process with autofill setup.

Autofill functionality is enabled for:

  • Autofill for uniaxial and triaxial sensors (response channels)
  • Start node index and index increment selection
  • Define the direction and sign of added channels
  • Group the sensors and define the number of groups

Auto-generated Visualisation Screens

For an easier start, Dewesoft X software offers auto-generated displays for modal analysis. The predefined displays already come with the most often used instruments and an arrangement that makes sense according to the modal testing. 

One screen is generated for the acquisition and measurement process and the second screen is defined for the post-analysis of the measured data.

Of course, the flexibility of Dewesoft X data acquisition software allows you to easily change and customise the default displays or define unlimited news ones.

Structure Geometry Animation and Projection

Inside Dewesoft X DAQ software, you can quickly draw simple 3D structures as well as import more complex ones using UNV file format. The cartesian and cylindrical coordinate system is supported, which is great for drawing circular objects.

The FRF animation is performed by putting sine functions with the amplitudes and phases from the measurement into the geometry model points. You can animate the structure for a single frequency, which can be chosen in the 2D graph visual display.  

Animations can be performed at a selected frequency in all three directions. During the measurement, the color of the points is changing, for easier identification of the excitation point and theresponse points.

The structure can be shown in different projections:

  • 3D perspective,
  • 3D orthographic and
  • several 2D projections.

 

Merge Multiple Data Files Together

Dewesoft X software makes it very easy to record one data file for each point or group in your subject under the modal test.

After the measurements are done you can easily merge separate data files into one to analyze and animate the structure and observe the behavior.

Each transfer function contains information about response node, response direction, reference node and reference direction.

 

Operating Deflection Shapes (ODS)

In ODS analysis the structure is only excited by the machine, like in real operation, whenever it is not possible to vary the excitation frequency. Operating Deflection Shape (ODS) is the simplest way to see how a machine or structure moves during its operation, at a specific frequency or moment in time. There are only accelerometers used.

Inside Dewesoft X software modal test module, one of the acceleration sensors has to be defined as excitation (this one is the reference, normalized to 1), the others as a response. Animation can be displayed as usual but only makes sense in areas with good coherence.

Exporting Data

After the measurement is done the data can be exported to a lot of different file formats, e.g. UNV/UFF, Diadem, Matlab, Excel, Text... The transfer function can be separately exported by Real, Imag, Ampl or Phase part.

The Universal File Format (also known as UFF or UNV format) is very common in modal analysis. Depending on the header, it can contain either transfer functions, coherence, geometry, ... or various other data. We modified the  UNV/UFF export, especially for the modal test.

See the complete list of supported export file formats.

OMA - Operational Modal Analysis

The operational modal analysis is used for large civil engineering structures, operating machinery or other structures, making use of their output response only. These structures are always loaded by natural loads that cannot easily be controlled and measured, for instance, wave load (offshore structures), the wind loads (buildings) or traffic loads (bridges).

It is very difficult to excite large structures by artificial means. So OMA is more economical and fast and endowed by nature with characteristics of multiple-input/multiple-output (MIMO). It could be used to distinguish closely coupled modes. Moreover, all the measured responses come under an operational state of structures, and their real dynamic characteristics in operation could be revealed, so OMA is very suitable for health monitoring and damage detection of large-scale structures.

Advanced Modal Analysis

With the direct export option of your measured data to ME’scope modal analysis, you can import or directly acquire multi-channel time or frequency data from a machine or structure, and post-process it.

Me'scope's industry-leading interactive 3D animation suite allows you to observe order-related operating deflection shapes (ODS) from running machinery, resonant vibration and mode shapes from real structures, acoustic shapes, and engineering shapes directly from acquired data. 

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