Transmissions, Gearboxes and Axles RotasPro Noise Analysis

The company was founded in 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 20 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 and transmissions, ROTAS-ZP for the gear test, ROTAS-TMO for the test of tapered roller bearings. MESAM 4 APAS-II Base SystemGearboxes and ComponentsCabin noise ROTAS-Mobil Discom Industrial Measurement Inc.

ZF D Gear 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, Peugeot Transmissions, Gear Testers 11 Systems GM, USA, Opel D and A Gearboxes 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 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

Rotas NVH Testing End of line test with vehicle correlation and the ability to find production errors Separation of noise components from inner wheels of transmissions 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

Parameter- und Limit Database Parameter- und Limit Database Rotas Analysis Program Rotas Analysis Program Result Database Archives, SQL-DB Result Database Archives, SQL-DB Web Statistics Presentation Test Stand Control Test Stand Control Sensors ROTAS Test Stand Configuration

Rotas Analyzers 19”-Industrial PC. TAS Frontend RAID system Dual Core and I7 CPUs Panel with IPC and TAS Frontend. AC and UPS build into panel TAS USB Measurement frontend. 10 analog channels, 4 speed inputs, D/A monitor outputs. Mobile system with USB power for 5 ICP sensors

BKS03 Accelerometer 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

RotasPro separates the noise into the different sources inside the transmission like input, intermediate and output shaft. I addition, the the total noise is evaluated. A prominent method is the calculation of the spectral components of the noise. The spectrum shows the characteristic of the noise in form of a curve. For transmissions, spectral components exist for tooth mesh and its harmonics. The spectra are compared with limit curves. If the limit curve is exceeded, a defect can be assumed. In addition, temporal measurement give Crest, Peak and RMS values, which are used for the identification of nicks on the transmission parts. Noise sources A main noise source is the tooth mesh of the gears. Analysis of transmission noise

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 number of samples per revolution

Revolution Synchronous Transmission Analysis Input ShaftInterm. ShaftOutput 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. Synchronous order analysis: The signals are acquired synchronous to the inner shafts. Acoustical Stroboscope Input Shaft Interm. Shaft Output Shaft

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 I Signal Background Signal Background Summe * 1/n =

Synchronous Averaging II Nicks are shown in the synchronous channel that is synched with the offending shaft. The nick detection is based on the Crest value Crest = Peak value/RMS value AG4 V4.0 Typ 39 Unit Jun'2000,17:10: Code Description Gear Is Lim Av Unit Kx 448 NICK 3.-Gear / Up 3-Z 16.8/ 12.0/ 9.5 Crest ZwAn AG4 V4.0 Typ 39 Unit Jun'2000,17:10: Code Description Gear Is Lim Av Unit Kx 448 NICK 3.-Gear / Up 3-Z 16.8/ 12.0/ 9.5 Crest ZwAn

Time Domain Measurements Peak: The maximum amplitude in a time domain signal. In the example to the right the Peak value is about 15 g RMS: The average energy in a time domain signal. In the example to the right the RMS value is about 0.9 g. The exact formula is Sqrt(Sum((x i ) 2 ) for all measurement values x i Crest: The ratio of the peak value divided by the RMS value: Crest = Peak value/RMS value In the example to the right the Crest value is about It has no unit The Crest value is a good indication of the ‘Peakiness’ in a signal. Good gears have a Crest value of 3-8, bad gears have a Crest value from 10 to 30. Tickeval: The Tickeval value indicates the maximum difference of short-time spectra taken over the revolution from the average short-time spectrum for the revolution. Good gears have values of 6, bad gears have values above 12. AG4 V4.0 Typ 39 Unit Jun'2000,17:10: Code Description Gear Is Lim Av Unit Kx 448 NICK 3.-Gear / Up 3-Z 16.8/ 12.0/ 9.5 Crest ZwAn AG4 V4.0 Typ 39 Unit Jun'2000,17:10: Code Description Gear Is Lim Av Unit Kx 448 NICK 3.-Gear / Up 3-Z 16.8/ 12.0/ 9.5 Crest ZwAn Peak RMS

Separation of Gear Errors The acoustical signal holds the components of both gears. Knowing the transmission ratio, the periodicity of each gear can be found. Gear mesh components only depend on the pairing of the gears. Eccentricities and surface errors can be separated because they have a cycle that corresponds to the originating gear. The following errors can contributed individually: Eccentricities, Deviation from circular shape Tooth spacing Surface waves (Ghost Orders) Nicks The gear mesh component depends on the pairing Eccentricities and surface errors can be contributed individually

Fourier transform: Order spectrum Time Domain Versus Order Domain I Sine smooth gear contact Order at number of teeht: 5 Base order H1 Triang harsher gear mesh Harmonics at odd multiples of nr of teeth (5) H1, H3, H5,.. Sawtooth harsh gear mesh Strong harmonics of number of teeth (5) H1, H2, H3,.. Gear with 5 teeth, 4 revolutions

Fouriertransformation: Ordnungsspektrum Time Domain Versus Order Domain II, Modulations Sine with modulating sine Smooth gear mesh with eccentricity Order at nr of teeth H1 with side bands +/- 1 order Triang with modulating sine harsher gear mesh with eccentricity Harmonics H1,.. with side bands +/- 1 order Triang with modulating triang harsher gear mesh with several eccentricities Harmonics H1,.. with side bands +/- n.Order Gear with 5 teeth, 4 revolutions

Ord dBV Mix Antrieb Revolution synchronous averaging gives periodic (cyclic) signals. This corresponds to the cyclic nature of the gear sets. These signals can be transformed into the spectral domain without any time domain leakage windows. This allows for high spectral resolution. Eccentricities can be easily distinguished from the gear mesh orders. The noise components can be attributed to their origins. Blue: Conventional order spectrum with Kaiser Bessel Window Green: Revolution synchronous order spectrum without window function Synchronous Averaging III GM 2 *GM Ecc.. Ghost Orders

Order spectra of a lay shaft transmission Input VGW HW Mix Input H1Input H2 VZ1 H1VZ1 H2VZ5 H1VZ5 H2 5. Gg H15. Gg H2OW 5. Gg -10 dB-12 dB Limits: red O-Spectra: black Input: 26 Z VZ1: 35 Z VZ 4: 43 Z 5. Gear 27 Z i =

Evaluation of Order Spectra Ord dBg VGW VGW-lim The order spectra of the synchronous channels and of the mix channel are compared with a limit curve. Every order of the limit curve has an underlying error code. This error code is generated from transmission ratios in a semiautomatic fashion. If the limit curve is exceeded, the error code gives rise to an error message in plain text. The limit curves consist of portions, which are generated by a learning process and of portions which are set to fixed values. The learn rnode is used for those spectral portions, where there are results from driving experiments available yet. Generally this holds true for tooth spacing problems, ghost orders and bearing noise (in the mix channel). Fixed limits are adopted from driving experiments, usually for the gear mesh and for the side bands.

Measurement Report A protocol is generated for every unit. It holds information about unit type, serial number, time of measurement and defect report. There are three kinds of report: Short:: serial numbers only for good units, defect report for failing units. Normal: Report line for every unit Long: All measurement values in tabular form. Around 300 measurement results are stored in a protocol database for statistical evaluation units use about 20 Mbyte of disk space. The test stand control system can request several protocol variants for own recording purposes.

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

Learning For all measurements, the following statistical properties are computed: Average (AV) und Standard deviation (STD) From these numbers, a limit L is generated according 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 limit curves. 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

Cabin noise components Noise sources There are many different transfer paths for the sound and the vibration from the gearset to the drivers ear. Each path has its own frequency dependent transfer function Noise from the motor, wind and tires may mask certain frequency bands from the gears. These effects induce the speed, torque and vehicle dependent noise perception of the gear sets. Transfer paths

Averaging over microphone postions M2M1M3M4AccelSpeed Order Resamp FFT + Average Spectro- gramm Order- tracks To compensate for the cabin resonance's, four microphones are positioned within the cabin: Front left, middle and right position, one in the rear. The energy of the microphone signals is averaged in the spectral order domain. One sensor is mounted on the transmission to allow for the simultaneous analysis of the gearbox vibration data.

Order spectrograms Order spectrograms are recorded for the gearbox vibration signal and for the cabin sound field. 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

Vibration and Cabin Noise, Spectral Cuts Spectral Cut Cabin Noise: 12 db higher than background at 2640 RPM/110 Km/h 12 dB Spectral Cut Vibration: 50th order of 100 dBg at 2700 RPM

Vibration and Cabin Noise, Order Cuts

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 ValueCurve 1Curve 2 H1 Max Bd dB75.5 dB H1 Aver Bd dB71.9 dB

Shown are measurements with the GSW shift roboter, which measures forces and displacement directly at the transmission shift mechanism. Shifting effort is shown versus displacement Positive forces: Shift into a gear Negative forces: Shifting out of gear A: Synchronisation work when shifting into a gear. Good repeatability B: Shifting through after synchronisation. Varying force. C: Shifting out. Small forces for good transmissions D: Synchron ring missing Shift force evaluation AB C AB C AB C AB C AB C AB C D D

Evaluation of shifting effort versus lever displacement. The synchronization is evaluated via the work that is needed (F*s). Therefore, the area of the curve above a window A is computed (work = force * displacement). D: a transmission without a synchron ring. The maximum force during shifting into a gear are limited with the polygon B The maximum forces when shifting out are limited with a polygon C. End position: a settable end position must be reached when shifting is finished. Evaluation of Shifting Effort A B C D Schaltkraft über Weg für 150 Seriengetriebe. Bewertungsfenster erkennen fehlende Synchronringe und Schwergängigkeiten.

Management of Multiple Test Benches Parameter Setting and Statistical Evaluation Test Benches Intranet Data Parameter PC with Internet Explorer Central archive of test resultsParameter setting and statistical evaluation from every PC with intranet access.

Rotas Analyzer Rotas Analyzer Measurement Database Measurement Database Measurement Archives Measurement Archives Rotas Presentation Rotas Presentation Intranet Statistics Rotas Data Flow Server or Test Stand Test Stand Work Group PC Work Group PC has presentation software installed Can use Intranet statistcis via Internet Explorer

ROTAS Analyzer Measurement System Server Measurement Database SQL Server 2000 Measurement Database SQL Server 2000 Archive Files: One Test Run \outbox:\inbox: Collector Service Parameter Database Parameter Database Local Copy Measurement Transfer over Network

Order Spectra  Spectra are stored for the individual rotors in the transmission  An additonial Mix spectrum represents the order amplitudes of all parts combined  The spectra are either peak hold amplitudes or averaged amplitudes over a ramp  Limits can be self learned or manually set. The amplitude of gear mesh orders can be set individually by a database

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

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.

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

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.

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.

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.

Reject Analysis, Top n and Type Specific The results are shown both in tabular and in graphical form