Rotational and Torsional Vibration Manual v1.0

8/12/2019 Rotational and Torsional Vibration Manual v1.0

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Rotational andTorsional Vibration

Users Manual

Version: 1.0

Thank you!

Thank you very much for your investment in our unique data acquisition systems. These are top-qualityinstruments which are designed to provide you years of reliable service. This guide has been prepared tohelp you get the most from your investment, starting from the day you take it out of the box, and extending

for years into the future.

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Table f !ontents

Table Of Contents

" #otice.................................................................................................................................""." $afety instructions......................................................................................................%".% &bout this document...................................................................................................'".' (egend........................................................................................................................'

% )ntroduction........................................................................................................................*%." $ystem verview........................................................................................................*%.% +nabling TV includes RV module.............................................................................%.' /asic operating concept.............................................................................................0%.1 2eneral setup.............................................................................................................3%.* !ounter $ensor +ditor.............................................................................................."4

' Rotational Vibration..........................................................................................................""'." RV )ntroduction.........................................................................................................""'.% RV $etup...................................................................................................................""

'.%." )nput filter..........................................................................................................."%'.%.% Rotational 5! filter............................................................................................"%'.%.' utput channels................................................................................................"%

'.' RV 6easurement......................................................................................................"'1 Torsional vibration............................................................................................................"*

1." TV )ntroduction.........................................................................................................."*1.% TV $etup..................................................................................................................."*

1.%." 2earbox ratio....................................................................................................."1.%.% utput channels................................................................................................"1.%.' &ngle offset........................................................................................................"01.%.1 Reference curve................................................................................................"0

1.' TV 6easurement......................................................................................................"3* &dvanced analysis and export........................................................................................."7

*." rder extraction........................................................................................................"7*.% 88T peak calculation................................................................................................%%*.' &ngle-based data export...........................................................................................%1

6easurement accuracy....................................................................................................%0." +rror sources............................................................................................................%0.% !ounter accuracy......................................................................................................%0

.%." !ounter architecture..........................................................................................%0.%.% &ngle resolution.................................................................................................%3.%.' &ngle accuracy..................................................................................................%7

.%.1 8requency accuracy..........................................................................................%7.' $ensor accuracy.......................................................................................................'4

.'." #on centered mounting.....................................................................................'4.'.% Resolution error.................................................................................................'4

0 5ocumentation version history.........................................................................................''

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#otice

1 Notice

The information contained in this document is sub:ect to change without notice.

CAUTION5ewesoft 2mb;. shall not be liable for any errors contained in this document.5ewesoft 6& 5)$!(&)6$ T;+ )69()+5 =&RRT)+$ 86+R!;T&/)()T> 8)T#+$$ 8R & 9&RT)!?(&R 9?R9$+.5ewesoft shall not be liable for any direct, indirect, special, incidental, orconsequential damages, whether based on contract, tort, or any other legal theory, inconnection with the furnishing of this document or the use of the information in thisdocument.

=arranty )nformationA

& copy of the specific warranty terms applicable to your 5ewesoft product and replacement parts can beobtained from your local sales and service office.

To find a local dealer for your country, please visit this linkA httpABBwww.dewesoft.comBsupport and select Finddealerson the left navigation bar.

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5ewesoft has a team of people ready to assist you if you have any questions or any technical difficultiesregarding the system. 8or any support please contact your local distributor first or 5ewesoft directly.

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Rotational and Torsional Vibration

9rinting ;istoryA

Version Revision "00Released %4"'(ast changedA '. 5ecember %4"' "1A**

!opyright

!opyright E %4""-%4"' 5ewesoft 2mb;

This document contains information which is protected by copyright. &ll rights are reserved. Reproduction,adaptation, or translation without prior written permission is prohibited, except as allowed under the copyrightlaws.

&ll trademarks and registered trademarks are acknowledged to be the property of their owners.

1.1 Safety instructions

Your safety is our primary concern! Please be safe!

$afety symbols in the manual

WARNING

!alls attention to a procedure, practice, or condition that could cause body in:ury ordeath.

CAUTION

!alls attention to a procedure, practice, or condition that could possibly causedamage to equipment or permanent loss of data.

2eneral $afety )nstructions

WARNING The following general safety precautions must be observed during all phases ofoperation, service, and repair of this product. 8ailure to comply with theseprecautions or with specific warnings elsewhere in this manual violates safetystandards of design, manufacture, and intended use of the product. 5ewesoft 2mb;assumes no liability for the customerFs failure to comply with these requirements.

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#otice

1. About tis document

This is the ?sers 6anual for Rotational and Torsional Vibration Version ".4.

1." #e$end

The following symbols and formats will be used throughout the document.

IMPORTANT

2ives you an important information about a sub:ect.9lease read carefullyG

HINT

2ives you a hint or provides additional information about a sub:ect.

EXAMPLE

2ives you an example to a specific sub:ect.

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)ntroduction

%ntroduction

The HTorsional VibrationI software option of 5+=+$oftJ is used to obtain - or enhance an existing 5ewesoftsystem to - a rotationalBtorsional vibration monitoring and analyCing solution, for research, development andoptimiCation. =ith the small form factor of the 5ewesoft instruments e.g. $)R)?$, 5+=+-1', K the perfectmobile solution for test engineers and consultants is born.Torsional and Rotational vibration are calculated, as well as the corresponding velocities, the software cancompensate uncentered mounting of the sensor and can also take care about the gearbox ratio. 8urthermorethe possibilities of 5+=+$oftJ allow angle-domain visualisation and export.

=ith 5+=+$oftJ also data from other sourcesA e.g. Video, !, +thernet, K are perfectly synchroniCed inone datafile.

)f the powerful integrated post processing features of 5+=+$oftJ are not enough, you can even export thedata to several different file formats.

)n addition to Torsional Vibration, the system can be expanded with the rdertracking option to complete thepicture of the measurement situation.

.1 System Overview&s the torsional vibration measurements are very critical in terms of accuracy, only precise counter sensorsare supported. &t least one Rotational vibration, but usually two Torsional vibration encoders arenecessary.

+ither an encoder or a special R)+ sensor can be used. The R)+ sensor has less resolution, but is much lesssensitive to vibrations which could damage standard encoders over time.

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. &nablin$ T' (includes )'* module

(ike many additional mathematics modules also Torsional Vibration is an option to the standard5+=+$oftJ package and needs to be enabled in the ;ardware setupA +nter L$ettingsM L;ardware $etupMand then L6athM.

?sually this must not be done manually, since the license is already stored on your 5ewesoft instrument.

Nust click on the H&uto 5etectI button and all options will be detected and enabled automatically.

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)ntroduction

." +asic operatin$ concept

The Torsional vibration module inside 5+=+$oftJ is :ust one out of several other application modules whichoffers dedicated mathematics and dedicated visual controls like angle based @>-diagram.

EXAMPLE

>ou can use the output channels of the Torsional vibration module as an input for therdertracking module, and also apply additional mathematics on it.

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., -eneral setup

)n the first step we add one module with the D buttonA

The input mask of the TV module is split into following sectionsA

inputA define the counter channels for input e.g. !#T", !#T%

counter setupA define type of angle sensor e.g. +nc-*"%, !56-'4, and select ratio, if gearing used

filter setupA specify glitch filter and rotational filter

output channelsA select which calculations to be done, e.g. rotational velocity, torsional angle...

correctionA compensate constant angle offset, uncentered mounting, sensor errors

outputA preview of output channels B switch through with the arrow buttons

previewA preview of torsional angle

HINTThere is no need to configure the !ounter inputs separately in the !ounter setup, allthe settings are done out of the Torsional vibration module.The setup of the !ounters is done out of the Torsional vibration module.?sed !ounters will be locked greyed out in !ounter setup.

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)ntroduction

$witch to HView !hannel (istI on the right upper corner to see a list of the calculated output channels.

)t is important to know that we actually have two different parameters that can be measured with the torsionalvibration moduleA rotational vibrationand torsional vibration.

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. Counter Sensor &ditor

There are some typical sensors predefined. ;owever, if your type is not listed, you can define your ownsensor in the !ounter $ensor +ditor. #ote, that for Torsional Vibration module the sensor has to be either+ncoder or !56 type.

2o to $ettings O !ounter $ensor +ditor...

K and click on H&dd sensorI first, then enter a name, and set all other parameters. 5epending on the sensordifferent parameters are available. =hen finished, click H$aveP+xitI.

#ow the sensor can be accessed from the dropdown menu of the Torsional vibration module.

HINT

>ou can press L8"M in any menu in 5+=+$oft and the help for the specific topic willopen.

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"..1 %nput filter

The input filtercan be used to prevent glitches and spikes in the digital encoder pulse signal. )t can be setfrom "44ns to *us, the optimal setting is derived from following equationA

".. )otational /C filter

The )otational /C filterneeds to be set to cut the 5! component of the R96s. =e need to set the filter toinclude all wanted frequencies, but not too low, else we will have static 5! deviations on the output signal. )tcan be set from 4." to "4 ;C. >ou have to ensure that your lowest R96 is not filtered outG

& "4 ;C filter for example would mean, frequencies below 44 R96 would be suppressed.

".." Output cannels

The output channels are

Rotational angle filtered angle value of vibration

Rotational velocity filtered velocity vibration value

@ axis reference angle the reference angle, which is always from 4 to '4 and can be used as a

reference in angle based xy diagrams

8requency, in R96 unit

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Rotational Vibration

"." )' 0easurement

=hen you switch to measure mode, the calculated channels of the TV module are shown in the channelselector on the right side. 8irst idea would be to select the TV8requency channel and display inanalogBdigital meter or a recorder.

The $ensor"angle is the reference angle and can be used for an$lebased displayof @> recorder.&dd a@> recorder and click on $ensor"angle first Sx axis, then on Rot&ngle" Sy axis. Then set the recorderto H&ngle based x-yI in the properties on the left side. $elect e.g. % periods to be displayed. This xy recordernow displays the rotational angle of the current revolution. )t is like a scope, but with an angle reference

instead of a time reference.

Vary the R96 and when you come close to the resonance frequency, the amplitude reaches its maximum.

)n the next graph also the rotational velocity is added first derivation on the angle, according to theory it isshifted 74 degrees.

The last channel out of the module is called HRev. countI, a revolution counterA

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Torsional vibration

, Torsional vibration

,.1 T' %ntroductionTorsional vibration is an oscillation of angular motions twist which occur along rotating parts, such as gear

trains, crank shafts or clutches. =e need two encoders to measure the torsional vibration, so the torsionalvibration is actually a difference between angles of the two encoders. The torsional vibration also measuresthe static twist of the shaft with higher R96s.

The graph below shows the run up and coast down where we can nicely see the static twist of the shaft, andwhen passing through the natural frequency, the angular vibration of the shaft reaches its maximum.

,. T' Setup

=e extend the setup from the Rotational Vibrations6easurement by also connecting now the secondencoder.

n the left side is an encoder with fix coupledconnection to the motor first red box, on the rightside is another encoder second red box. $o wemeasure the torsion vibrations of the metal springbetween.

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&dd a Torsional vibration module with the D button.

$elect !#T4 as first and !#T" as second sensor input. Then further define the encoders by selecting thecorrect type from the dropdowns on the right side in our case +ncoder-*"% and +ncoder-"344.

&s already explained in the rotational vibration section, you can use the input filter for cleaning the signalfrom eventual glitches, and the rotational filter removes the 5! offset from the difference signal.

,..1 -earbo2 ratio

-earbo2 ratiostays "B" in our case. This is used for measuring the torsion angle across a gearbox.

,.. Output cannels

Torsional angle (dynamic torsional angle that is the angle difference from sensor 1 to sensor 2)

Torsional velocity difference in angular velocity from sensor " to sensor %

$ensor " Rotational angle

$ensor % Rotational angle

$ensor " Rotational velocity

$ensor % Rotational velocity

@ axis reference angle the reference angle, which is always from 4 to '4 and can be used as a

reference in angle based xy diagrams

8requency, in R96 unit

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Torsional vibration

,.." An$le offset

)n the section H&ngle offsetI you see the angular difference between the two sensors -"'0. !lick on H 3eroIto remove tis static offset. The current average value of the signal will be subtracted. Then click on the yaxis to auto-scale the signal. )t is now approximately 4.

,.., )eference curve

#ow there is also an option how to compensate uncentered mountin$and unsteady pulses fromencoder.

!entered mounting is very important. n the first picture " there is no problem, the disk is mountedperfectly. ;owever in real life, uncentered mounting like in picture % will appear. (etQs draw on the disk a redline on 4 degree and a blue line on 74 degree position. =hen the disk is turned, the sensor black box willcount the pulses and after a certain number detect the 74 degree position. /ut if you look at the disk now, itis far from 74 degreesG

Think of it rotating, then a constant sine wave will be generated additionally to the rotational vibrations. Thiscan be compensated in 5+=+$oft using the reference curve.

;owever, therefore it is required that the load must be removed from the engineG )t must be free-run.therwise you would also cancel out vibrations you want to analyCe. =hen the the machine is running, pressthe H$etI button.

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The current curve is now recorded over one revolution as a reference. &fter that the line is much more flat.

,." T' 0easurement

/elow you see an example setup screen with some typical instruments. $imilar to the rotational vibration

setup we can use the @> recorder to display the result angle-based. &fter the runup B coastdown you seetypical resonances and can analyCe the data further.

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&dvanced analysis and export

Advanced analysis and e2port

.1 Order e2traction

(et us look a little bit further and extend the functions by adding the rder Tracking option.

?sually it is included in the 5$& package, we can use it to extract the orders of the torsional B rotationalvibrations.

&dd an rdertracking module. 8or the frequency source we need to define the Torsional vibration moduleand the module created before. 5efine the ?pper and (ower R96 limit. This is used to reserve the memoryfor waterfall 88T. The waterfall will be drawn from the lower to the upper limit in the 5elta R96 step . )n thiscase, we will have '444-4 B *4 S 4 steps of waterfall. =e choose to extract the first three orders byentering H"U%U'I in the ;armonics field. The yellow field indicates that you have to press enter to overtake thevalues.

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=ith the '5 waterfall plot we can get a better picture of the situation. 9lot frequency against R96, or rders

against R96. n the left picture one can easily seperate into frequencies related and not-related to R96.

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8urthermore the amplitudes B phases or even real and imaginary part of the rders can be plot against thefrequency.

&gain, take the @> recorder, but now set graph type to H$ingle x axisI to get a /ode plot.

;ere you see the first harmonic green line with its maximum around %144 R96, matching nicely to theprevious measurements. Turning of the phase also indicates resonance.

HINT

$ettings can also be added B modified HofflineI Safter measurement on the datafile.

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. 44T pea5 calculation

ne of the standard measurements is, to do e.g. the run up of the machine, and then calculate the maxamplitude over the 88T.

&dd a 88T function from the H$pectral analysisI section in math.

Then select the input channel, here for example Torsionangle. $et to amplitude, verall, and averaging typepeak.

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;ere is an example, done offline on a datafile of course you also can do it online, during measurement. &section has been selected in the recorder instrument below green line to only analyCe the runup of themachine.

Then a %5 graph was added see instrument bar, red box and the &mpl88T math channel assigned.

> axis type can be set to logarithmic in the %5 graph properties left side for convenience.

>ou can do the standard export, or :ust click on the %5 instrument, and use H+ditI O H!opy data to clipboardI.

9asting, e.g. into +xcel gives following resultA

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." An$lebased data e2port

The angle-based display of measurement data is often very useful. )n the @> recorder you assign thereference angle H$ensor"angleI to the x axisU then set the view either to

An$lebased 2yA working like a scope, see the current cycle

Sin$le 2 a2isA see all cycles layed over each other Hpersistence modeI, easy to see minBmax overall cyclesU persistence can be ad:usted with the 9retime limit in the properties

#ow, how is it possible to export this cycle-based data 2o to 6ath and add a HReference scope arrayI.

=ith this great tool 5+=+$oft arranges the input data, e.g. HTorsionangleI over the H$ensor"angleI in amatrix by resampling the values to the angle-base, you also can select resolution, in this example we :ustuse " degree. The output data is 6)#, 6&@ and &V2 over all cycles.





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8or displaying the matrix data you have to use a different visual instrument, the %5 graph. Then you canassign the &V+, 6)# and 6&@ channels from the 6ath function.

$tore a datafile, afterwards in the +xport section only select the ' matrix channels in order that data has thesame formatA

;ere we have done the export to +xcel, instead of the time axis, we have angle-based data.

)f you copy the data, then use the Hpaste special...I function in +xcel, you can HTransposeI columns and rowsautomatically and get the angle from top down instead of left to right.

Selective e2port6

?se the recorder instrument to Coom into a section of your datafile in 5+=+$oft position both white cursors) and )) and click between them,then the calculation and export is only done over the selected data.

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6easurement accuracy

7 0easurement accuracy

7.1 &rror sources

The overall error of the measurement has to be split up into errors from the sensor and the counter

measurement uncertainty. ?sually the sensor errors make the ma:or amount.

7. Counter accuracy

7..1 Counter arcitecture

To understand how the angle resolution is determined, it is at first important to understand the internalarchitecture of the 5ewesoft !ounters. & combination of main and sub counter is used internally for gettinghigher precision at the frequency measurement. The main counter is running on event counting or encodermode. The sub counter is used for time measurement, it measures exactly the time of the input event with aresolution of 7,00 nsec S " B "4%,1 6;C relative to the sample clock.&t every rising edge on the !ounter$ource the counter value of the sub counter is stored in a register. &t every $ample !lock the values of both

counters are read out.

=ith these both measurement results not only the frequency can be calculated in a precise way. &lso the

event counter result can be shown in fractions because the exact time when the event occurs at the input isknown. The event counting result is recalculated with interpolation to the sample point like shown in thediagram below.

;ere the improvement of the measurement result is shown. =hile a standard counter input shows the valueup to one sample delayed, the counter input of the 5ewesoft instrument calculates the exact counter result atthe sample point.

IMPORTANT

The Counter value in the software is updated with the sample rate!

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7.. An$le resolution

The counter result is read out with the sample rate, therefore the same update rate applies for the calculatedangle.

8urthermore the angle resolution depends on the rotation speed R96.

/elow there are two angle-based %5 graphs showing the $ensor angle on the x axis at the same R96. Theoption Hdraw sample pointsI was enabled. n the left side the sample rate was set to *44 ;C, on the right to%*44 ;CA

$ince rotational and torsional calculations are all based on the sample rate, the angle resolution is the same.





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7.." An$le accuracy

&s the !ounter is working on an internal timebase of "4%.1 6;C, the angle accuracy is only depending onthe rotation speed R96.

The following formula shows how to calculate the angle accuracyA

res=

rpm

60360

102.4106

K "4%,1 6;C is the !ounter Timebase

The numerator shows the angle which is passing by in one second, this is then divided by the timebase ofthe counter, in one second we will get "4%.1 million samples.

7.., 4re8uency accuracy

&ny digital frequency measurement is based on period time measurement. The time between two edges ofthe input signal is HsampledI with the counter time base of "4%.16hC. =ith this simple measurement methodthe accuracy of the measured frequency is given by ratio between the input signal frequency and the countertime base frequencyA

ferror= fin

102.4106

=e can see, the error increases with input frequency. 8or example at "46;C the accuracy goes down to"4WG

(ike explained above, the advanced counter structure of 5ewesoft are using two counters internal countersand the output rate is synchronous with the the acquisition rate. =ith this technology we can limit themaximum error to the used acquisition rate.

The illustration below shows the accuracy at different input signals between % k$Bsec to "444 k$Bsec takingalso the typical counter time base accuracy of * ppm in account.

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7." Sensor accuracy

7.".1 Non centered mountin$

!an be corrected under certain conditions, see page "0chapter1.%.1 Reference curvein this document.

7.". )esolution error

&n additional error occurs due to mechanical tolerances of the used encoder. 5epending on the encodermode setting used @", @%, @1, they have influcence on the measurement.

91 mode6 8or this mode only the rising edge is important. )f the sensor marks are not preciselyrepeating at constant delta angles have a constant H:itterI, this also can be compensated with the referencecurve option

2oodA /adA

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9 mode6 8or @% mode both the rising and falling edge of the first encoder track are used, whichdoubles the resolution. /ut if the duty cycle is not exactly *4W, another error is introduced.

2oodA /adA

9, mode6 /oth falling and rising edges of both encoder tracks are used in @1 mode to get 1 times theprecision. The phase shift between the two tracks must be exactly 74 and the duty cycle *4W.

2oodA /adA

Therefore, the higher the mode used e.g. @1 compared to @", the more noise will be in the measurementdue to the discussed mechanical tolerances, because all effects appear together. )n a manner of speaking anencoder with a high resolution e.g. '44 pulses, is difficult to manufacture precisely, and therefore will havemore noise in @1 mode than one with lower resolution e.g. '4 pulses in @1 mode.

f course, if using two encoders as in torsional vibration, the errors are doubled.

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5ocumentation version history

: /ocumentation version istory

Revision numberA "00(ast modifiedA Tue 4' 5ec %4"', "1A**

'ersion

/ate;dd.mm.yy

yy< Notes

1.0 28.11.13 initial revision


Rotational and Torsional Vibration Manual v1.0

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