Operational Modal Analysis featuring GPS Time Stamping Technology

The rugged and intuitive CoCo-80X handheld system is now combined with Crystal Instruments’ patented GPS time synchronization technology (featuring a time accuracy of 100 ns) to further expand field measurement capabilities. Users are now able to execute Operational Modal Analysis using the handheld CoCo-80X to study the dynamic characteristics of large structures such as bridges and buildings.

Users can transfer testing plans and 3D model geometry created in EDM Modal into multiple CoCo devices to acquire ambient vibration responses. The GPS time stamp technology will  synchronize measurements carried out simultaneously on multiple devices. EDM Modal software will post-process and analyze the data to provide the modal parameters of the test structure. This robust workflow seamlessly integrates the operational modal analysis process.

The major steps in the process are briefly described below.

1. Create Geometry

  • The geometry model of the structure can be created or imported from EDM Modal using the simple and powerful Geometry Editor tab.

  • Users can graphically edit or modify default models included in the built-in component library or use the editor table to fine-tune and obtain the desired 3D geometric model of the test structure.

modal geometry model

2. Create Testing Plan

  • Testing Plan in EDM Modal is a powerful tool which provides users with the ability to create, customize and control the flow of the testing process.

  • Users can view acquisition status information and change (or modify) the parameters for each individual measurement entry.

modal analysis
modal test

         

3. Upload Testing Plan

  • The test plan is uploaded to multiple CoCo-80X devices.

modal test plan

4. Configure Analysis Parameters on CoCo-80X

  • Various analysis parameters are configured according to test requirements on the CoCo-80X devices.

modal test parameter
modal analysis parameter

5. Input channels and trigger parameters on CoCo-80X

  • The input channels and trigger parameters are set up according to the test requirements.

input channels
modal test triggers

6. Enable recording and GPS functionality on CoCo-80X

  • The raw time stream data for active channels on multiple CoCos is set up for recording.

  • The GPS functionality for multiple CoCos is enabled for time synchronization.

time stream recording
GPS time stamping

7. Execute measurements on CoCo-80X

  • Measurements are acquired by multiple CoCo-80X devices and the raw time stream data is recorded.

modal measurements
operational modal analysis
modal analysis measurement

8. Download recorded data to EDM Modal

  • The recorded measurements from multiple CoCo devices are downloaded to EDM Modal using the Testing Plan.

modal test data

9. Post-process measurements to calculate spectrum data

  • The raw time stream signals are processed to calculate GPS signals between all response channels.

modal measurements

10. Review complete data set in Modal Data Selection

  • The complete set of GPS signals obtained from processing the raw time data can be reviewed and compared.

  • The signals can be further smoothed to reduce noise.

smooth test signal

11. Use Mode Indicator Function to review spectrum data

  • The modes of the test structure can be identified using the various MIFs in EDM Modal.

  • This process assists in selecting a suitable band for the next stage of curve-fitting.

mode indicator function

12. Curve-fit data to obtain modal parameters

  • The complete set of CPS signals can be curve-fit using various estimation methods to obtain the natural frequencies, damping ratios, and operational deflection shapes of the test structure.

modal parameters

13. Results

  • The MAC Chart and Modal Parameters obtained from the OMA Test of the structure is displayed.

operational modal analysis
structural test
modal test
Modal Testing & AnalysisAakash Umesh Mange - Senior Application EngineerStructural Dynamics Testing