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Torsional Vibration

 

As a top notch torsional vibration solution, LMS Test.Lab Torsional Vibration Analysis provides highly accurate torsional vibration analysis of rotating machinery with single or multiple shafts. The order sections can be extracted from fixed sampled frequency spectra as well as from data sampled synchronously with rpm, giving leakage-free, razor-sharp order cuts.

 

Torsional Vibration Analysis LR 01.jpgLMS offers a complete solution for accurate measurements of the torsional variations of one or multiple shafts.
 
The LMS SCADAS Mobile torsional vibration module (SCM-RV4) acquires, offline or in real-time, up to 4 tacho pulse streams at a high pulse rate. These pulses are translated into accurate angular velocity and displacement time histories at high aliasing-free bandwidth. Both TTL as well as analogue, unconditioned pulse streams are supported. Alternatively, the RV4 module is able to capture up to two incremental encoder signals.
 
The LMS Test.Lab Torsional Vibration Analysis software lets engineers analyze the torsional vibrations of rotating machinery with single or multiple shafts. RPM order sections can be extracted from fixed sampled frequency spectra as well as from data sampled synchronously with RPM, giving leakage-free, razor-sharp order cuts. The software is able to perform and process real-time observations of shaft angular displacements, speed or acceleration, torsion over shafts, belt transmission errors or other specific metrics.   
 
Acquired tacho-data can be corrected for missing or double pulses, or for unevenly spread pulses (pitch correction). Results can be viewed alternatively in RMS or peak format in order to match the legacy data. To correlate torsional vibration phenomena with other NVH-related problems, the LMS solution simultaneously records tacho channels signals with other quantities such as acceleration, pressure or strain.   

A correct test set-up is crucial to accurately measure torsional vibrations. Faster and simpler set-ups are made possible with the LMS Test.Lab zebra-tape correction algorithm. Using tacho-pulse streams from a zebra-tape wrapped around the rotating shaft, the LMS Test.Lab algorithm is able to correct the error generated by the butt-joint (the point where the two sides of the zebra-tape come together
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Features

  • High precision and high bandwidth torsional vibration measurements.
  • Simultaneous calculation of leakage-free, synchronously sampled order sections and generic noise and vibration signals.
  • Convenient calculation of angular velocity, shaft torsion and other typical parameters.
  • Accurate pulse correction for missing and non-equidistant teeth.
  • Butt-joint correction for measurements based on zebra-tape.
  • Online monitoring of angular velocity irregularities, spectra, waterfalls and color maps, octave displays and order sections.

Benefits 

  • Provides high precision torsional vibration analysis based on synchronous order data while acquiring narrowband waterfall data.
  • Effective test setup for noise, vibration and torsional signal measurements in a single system.
  • Provides wide range of spectral and time domain analysis tools.
  • Support of non-LMS proprietary data.



Covering a range of industries, LMS application cases let you discover how LMS solutions help our customers solve their real-life engineering challenges.

Avoiding Judder by Means of an Effective Transmission Design

Fuel economy has become a vital issue for the brand image of vehicles these days. In response to this challenge, engine developers use downsizing as well as higher torques at lower engine speeds. This development effects also transmissions. Here, new engine trends are to be implemented as efficiently as possible at a minimum of losses. Therefore, LMS analysed the usage of the torque converter and the lock-up clutch at an early stage to optimise performance and losses.

vehicle vibration test quality 1.jpgFord Front-End Accessory Drives Group reduces testing cycles by half with LMS Test.Lab

Reinforcing its commitment to make quality, fuel-efficient, safe and technologically advanced vehicles, the Ford Motor Company has radically improved vehicle quality and is working hard to rank number one in quality performance. This turnaround strategy hinges on focused efforts throughout the Ford organization, including the FEAD group where LMS Test.Lab helps double the number of torsional and other vibroacoustic tests to ensure high quality standards on all the automaker’s US front-end accessory drive designs.

Virtual wind turbine design acoustic radiation 1LMS helps Moventas increase testing efficiency in developing wind turbine gearboxes

Business is booming at Moventas, a leading tier-one supplier of gearboxes for wind turbines. Company sales increased 40% last year, reflecting tremendous growth of this alternative resource in the face of sky-high energy prices. According to the World Wind Energy Association, global installed wind turbine capacity has grown ten-fold in the last ten years and has increased 25% just in the past year. Predictions from the association indicate that the 74 gigawatts of current worldwide wind-powered electrical generation will more than double by 2010, when levels are expected to reach 160 gigawatts.

Torsional Vibration Measurement and Analysis

With eco-engineering comes a new range of issues to solve. New powertrain designs like start-stop systems, downsized engines, advanced torque lock-up strategies or the generic trend for weight reduction of the powertrain raise the importance of an in-depth understanding of torsional vibrations as they negatively impact comfort and ultimately engine and driveline efficiency. It is in general a concern in case of power transmission systems using rotating shafts and couplings, and thus equally important e.g. Turbo machinery manufacturers and integrators or for the marine drivelines.





Images

Torsional Vibration Analysis LR 02.jpg Torsional Vibration Analysis LR 03.jpg Torsional Vibration Analysis LR 04.jpg
Fixed and synchronous sampling on torsional vibration signals support analysis in the time/frequency or in the angular/order domain. Pulse trains from shaft encoders or gear toothpicks are converted to rotational speed variations and processed with other vibration channels. Use the time signal calculator for removing average rpm or derive shaft torsion.


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