16.1.2008 1

Engine Test

RotasPro Noise Analysis

16.1.2008 2

The company was founded in 1985. It is situated in Göttingen in the heart of Germany. Since 1989 the main product are measurement system for the acoustical quality analysis. There are 18 employees and more than 500 test systems deployed.

Base system are ROTAS and MESAM-4 (a joint development with DaimlerChrysler). Build on top of them are APAS for the cabin noise analysis, ROTAS-GP for the analysis of gearboxes, transmissions and engines, ROTAS-ZP for the single gear test, ROTAS-TMO for the test of tapered roller bearings.

MESAM 4

APAS-II

Base System Engines, Gearboxes and Components

Cabin noise

ROTAS-Mobil

Discom Industrial Measurement Inc.

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ZF DGear Testers 4 Systems

Volkswagen D, ES, SA,AR, China,B,SK,BR

Gearboxes, Transmissions, Gear Testers, Cabin Noise Production Database, 178 Systems

Tongil, Korea

Axles, Durability test Stand, 1 System

SFT, Magna Stey Powertrain

Axles and gearboxes 28 Systems

Skoda, Cz

Gearboxes, 7 Systems

SAIC Shanghai Automobile Internatiol Corp.

Gearboxes test systems, 5 Systems

SKF D, USA, India, Ukraine

Tapered Roller Bearings, 35 Systems

Robert Bosch Starters, injection pumps, production database 6 Systems

Renault, PeugeotTransmissions, Gear Testers 11 Systems

GM, USA, Opel D and AGearboxes and Axle Testers, Gear Testers 44 Systems

Jatco, Japan

CVT Transmissions

Discom: Customers and Applications

Fiat, Iveco, Tata, It, Brazil, India

Manual Transmissions 20 Systems

Getrag, USA Sc, Single Flank Gear Tester for Cummins Engine Gears with Tors. Acceleration

Graziano, Italy Gearboxes and Axles for Audi, Aston Martin, Ferrari, Lamborghini, Maserrati

Eaton, Br and India

Manual transmissions, mobil system

Ford, D

Gear Testers 4 Systems

First Automobile Works, China

Gearboxes 2 Systems

DaimlerChrysler D, US Cooperation MESAM4, gearboxes, transmissions and engines. 48 Systems

Borg-Warner, USA,UK Transmissions und Axles 11 Systems

Bentley, UK

Cabin Noise Analysis APAS, 2 Systems

American Axle, USA

Front and Rear Axles, 5 Systems

Hyundai, Korea

Gear tester 2 Systems

Cummins

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Rotas NVH Testing

End of line test with vehicle correlation and the ability to find production errors

Separation of noise components from shafts with synchronous averaging

Calibrated evaluation for comparison of the production process with car experiences

Simultaneous measurement and evaluation of all transmission order components

Recognition of nicks on gears and bearings

Trainable system in combination with fixed limits

Test results stored in central data base

Intranet evaluation of test results for groups of test benches

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Parameter- und Limit Database

Parameter- und Limit Database

RotasAnalysisProgram

RotasAnalysisProgram

Result DatabaseArchives, SQL-DBResult Database

Archives, SQL-DB

Web StatisticsWeb StatisticsPresentationPresentation

Test StandControl

Test StandControl

Sensors

ROTAS Test Stand Configuration

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Rotas Analyzers

19”-Industrial PC.TAS Frontend RAID systemDual Core and I7 CPUs

Panel with IPC and TASFrontend. AC and UPS buildinto panel

TAS USB Measurement frontend.10 analog channels, 4 speed inputs, D/A monitor outputs.Mobile system with USB power for 5 ICP sensors

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BKS03 Accelerometer

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 k Hz

-20.0

-15.0

-10.0

-5.0

0.0

dBg

TrnsFnc

The BKS03 has a linear frequency range of up to 10 kHz and can be used to pick up the NVH signal also from unfinished surfaces

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Input

One rev

Exact order analysis is accomplished by generating of the same amount of samples per revolution of a part, independent of its revolutionary speed.

Digital resampling allows for the processing of 3 to 5 shafts of a transmission.

From this resampled time domain signal, spectra evaluation produces order components. These are the amplitudes of sine components, which are cyclic with the revolution of the part

Order Analysis

Input

One rev

Input

One rev

Constant numberof samples perrevolution

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Revolution Synchronous Transmission Analysis

Input Shaft Interm. Shaft Output Shaft

The transmission noise is the sum of the noise originating from the individual mechanical components.

For the gear noise components, the individual sources can be isolated by the transmission ratio.

Synchronousorder analysis:The signals are acquired synchronousto the inner shafts.AcousticalStroboscope

Input Shaft

Interm. Shaft

Output Shaft

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Signal

Background

Average:Signal enhanced

For every shaft, averaging is performed synchronous to its revolution.

Signal components of the synchronous shaft are enhanced, other noise components are attenuated.

One shaft is shown. Rotas can do the processing for 3 to 5 shafts simultaneously.

Usually, only one sensor is needed.

The synchronization can be done for inner shafts, for which only the transmission ration is known.

Synchronous Averaging

Signal

Background

Signal

Background

+

+

+

+

+

Summe * 1/n =

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Synchronous Averaging

Noise peaks are shown in the synchronous channel that is synched with the respective shaft.A valuable nick detection is based on the Crest value:

Crest = Peak value/RMS value

100 200 300 400 500 600 700 800 900m Rev

-10.0

-5.0

0.0

5.0

10.0

g

Oran.SK1

1 2 3 4 5 6 7 8 9 10 11 12

12 Cylinder Engine, 700 UPM, 1 Rev Cam Shaft

Cylinder

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Evaluation of Order Spectra

10 20 30 40 50 60 70 80 90 Ord

45

60

75

90

105

dBgVGW

VGW-lim

The order spectra of the synchronous channels and of the mix channel are compared with alimit curve. Every order of the limit curvehas an underlying error code. This error codeis generated from transmission ratios in a semiautomatic fashion. If the limit curveis exceeded, the error code gives rise to anerror message in plain text.

The limit curves consist of portions, whichare generated by a learning process and ofportions which are set to fixed values.

The learn rnode is used for those spectralportions, where there are results from driving experiments available yet. Generally thisholds true for tooth spacing problems,ghost orders and bearing noise (in themix channel).Fixed limits are adopted from driving experiments,usually for the gear mesh and for the side bands.

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10 20 30 40 50 60 70 80 90 Ord

20

40

60

80

100

dBg

MaxBnd

MinBnd

StdDev

AW-avg

SK1-lim

10 20 30 40 50 60 70 80 90 Ord

20

40

60

80

100

dBg

MaxBnd

MinBnd

StdDev

AW-avg

SK1-lim

Spectral Limits

Limit curve from Average + Offset + n times standard deviation. Overridden by minimum and maximum polygons and by the fixed hats.

Hats for gear mesh orders and their side bands

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Learning

For all measurements, the following statisticalproperties are computed:

Average (AV) undStandard deviation (STD)

From these numbers, a limit L is generatedaccording to

L = AV + Offset + n* STD.

The offset and the multiplier of the standard deviation is selectable. For spectral measures,an offset of 5 dB and a std-factor of 3 is normally used. Maximum and minimum values set upper and lower bounds for the limit L.

A new learn consist of a base learn (usually 5 units), where all units are accepted that are below maximum polygons and below hats.

The base learn is followed by an additional learning (usually 100 units). Here every unit is evaluated against the already established limitcurves. Only error free units will be added to the learning sample.

Another available choice consists of a indefinite learn process with a selectable time constant.

During the whole learning process, the fixed limits apply. This assures, that all known data (like limits from car experiments) will be used as a guidance during the process.

What is learned Learning methods

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Order spectrograms

Order spectrograms are recorded for the engine vibration signal.

From these order tracks for arbitrary orders and order spectra for arbitrary speeds can be generated:

1) Ordnungs-Spektrogramm 4. Gang Zug

Order track for the 65. order

2) Order spectrum at 2241 RPM

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Order Tracking

The critical noise sources in a car are usually the gear mesh orders and their sidebands.

These noise sources are highly speed dependent. Detailed speed dependent evaluation uses the track of mesh orders and sidebands over speed.

The gear mesh H1 base order and its harmonics are tracked over speed and compared with speed dependet limit curves.

The track form depends on torque, drive/coast and on the resonances within the gearbox and the test stand.

Within speed bands, average and maximum amplitudes can be evaluated and compared to limits. The single values are ideal for statistical analysis over time. Speed band

Tracked Value Curve 1 Curve 2 H1 Max Bd1 79.1 dB 75.5 dBH1 Aver Bd1 76.2 dB 71.9 dB

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Synchronous Angular Spectrogram

0.05 g

0.35 g

0 45 90 135 180 225 270 3150

100

200

300

400

Rev

Short-time spectra are computed over the revolution of the engine. Several spectra are averaged and indicate spectral abnormalties at certain angles.

Nicks and Ticks of all kinds can be identified with this method

Grad NW

Ordnung

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Hydraulic Valve Defect

und PrüftechnikIndustrielle Meß-

0.05 g

0.45 g

0 45 90 135 180 225 270 3150

100

200

300

400

Rev

0 1 0 0 2 0 0 3 0 0 4 0 0 R e v0 . 0 5

0 . 1 00 . 1 5

0 . 2 0

0 . 2 5

0 . 3 00 . 3 5

0 . 4 0

g

0.05 g

0.45 g

0 45 90 135 180 225 270 3150

100

200

300

400

Rev

0 10 0 20 0 30 0 40 0 R ev0.0 5

0.1 00.1 5

0.2 0

0.2 5

0.3 00.3 5

0.4 0

g

0 2 4 6 8 10 12 14 16 Hz0.40.60.81.01.21.41.61.82.02.2g

A defective hydraulic valve is shown in the angular spectrum for twodifferent positions of accelerometers on the cylinder head

Modulation Spectrum

Rev Synchronous Spectrogram

Camshaft Degrees -> Camshaft Degrees ->

Ord

ers

->

Ord

ers

->

Rev Synchronous Spectrogram

Orders ->

Accel back right Accel front left

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Measurement Report

A protocol is generated for every unit. It holds information about unit type,serial number, time of measurementand defect report.

There are three kinds of report:

Short:: serial numbers only for goodunits, defect report for failing units.Normal: Report line for every unitLong: All measurement values in tabular form.

Around 300 measurement resultsare stored in a protocol database forstatistical evaluation. 5000 units useabout 20 Mbyte of disk space.

The test stand control system can request several protocol variantsfor own recording purposes.

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Management of Multiple Test Benches

Server

Parameter Setting and Statistical Evaluation

Test Benches

Intranet

DataParameter

PC withInternet Explorer

Central archive of test results Parameter setting and statistical evaluation from every PC with intranet access.

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RotasAnalyzerRotas

Analyzer

MeasurementDatabase

MeasurementDatabase

Measurement Archives

Measurement Archives

RotasPresentation

RotasPresentation

Intranet StatisticsIntranet Statistics

Rotas Data Flow

Server or Test Stand

Test Stand

Work Group PC

Work Group PC has presentation software installedCan use Intranet statistcis via Internet Explorer

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GM6R Silao Stand 2 Type 8CKA [80] Serial 618CKA20013288 29.Feb'2008,07:08:09 Transmission NOK ***--------------------------------------------------------------------------------code errortext gear value limit avg u O/Tp ch 16718 Transmission: Order loud in 6-Coast 6-sC 92.3/ 90.1/ 66.7 dBg 57.00 R116718 Transmission: Order loud in 6-Coast 6-sC 96.4/ 92.6/ 76.8 dBg 53.00 MixR16718 Transmission: Order loud in 6-Coast 6-sC 93.5/ 93.4/ 77.5 dBg 54.50 MixR16718 Transmission: Order loud in 6-Coast 6-sC 96.5/ 95.5/ 77.7 dBg 76.50 MixR16718 Transmission: Order loud in 6-Coast 6-sC 93.8/ 88.1/ 72.1 dBg 133.00 MixR16718 Transmission: Order loud in 6-Coast 6-sC 89.5/ 88.7/ 72.6 dBg 135.50 MixR16718 Transmission: Order loud in 6-Coast 6-sC 89.1/ 89.0/ 72.8 dBg 136.50 MixR16718 Transmission: Order loud in 6-Coast 6-sC 90.8/ 89.1/ 74.4 dBg 147.00 MixR16718 Transmission: Order loud in 6-Coast 6-sC 93.2/ 92.8/ 77.0 dBg 166.00 MixR16718 Transmission: Order loud in 6-Coast 6-sC 92.7/ 92.7/ 76.7 dBg 176.00 MixR16718 Transmission: Order loud in 6-Coast 6-sC 95.1/ 91.2/ 75.4 dBg 198.50 MixR16718 Transmission: Order loud in 6-Coast 6-sC 99.0/ 95.1/ 78.4 dBg 233.00 MixR16718 Transmission: Order loud in 6-Coast 6-sC 96.3/ 95.2/ 78.4 dBg 234.50 MixR

Order Spectra

618CKA20013288 29.Feb'2008,07:08:09

und Prüftechn ikIndustriel le Meß-

80 dBg

90 dBg

0 50 100 150 200 250 300 -0

50

100

150

200

250

300

350

400

450

Ord

0 50 100 150 200 250 300 350 400 450 500 Ord60

65

70

75

80

85

90

95

100

105

110

115

dBg

Unit x multiple runs in pink. First run highlighted in blue.

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Order spectra of production units can be displayed in Campbell or in 3-D graphs. Cuts in the order or in the unit direction show order amplitude versus units or the spectrum of one unit. The pictures show the order spectra of 300 production units. A ghost order of 118 is present in the first 40 units tested.

Spectral Statistics

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Order Tracks

During the ramps, spectral components are evaluated over the speed.

Usually, the main gear mesh orders and their harmonics are tracked.

In addition, energy in order bands may be tracked as well.

Track limits (shown in red) can be self learned or set manually.

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Complete Data Report of a single Unit

Macro controlled display of archived data.

The database is used for searching of serial numbers, test results etc.

Then the presentation software displays a full measurement report

Sensor Group 1

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Intranet Statistics

The information of the SQL measurement database can be retrieved via the intranet.

The production results and the measurements can be seen online.

An arbitrary time interval can be selected for the analysis.

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Statistical Evaulation for Types and Benches

Test results The evaluation can be done over gearbox types or over test benches.

Any time interval can be specified.

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Measurement Statistics and Bench Comparison

Over 300 individual measurement results can be evaluated.

The comparison of test benches makes it easy to administer large production facilities.

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Reject Analysis, Top n and Type Specific

The results are shown both in tabular and in graphical form