the engineering integrity society...prosig’sprotor provides a complete hardware and software...

• The Society focuses on the areas of Fatigue, Testing and Durability and is sponsored by industry.

• The aims are to support industry and newly qualified engineers.

• The Society consists of three groups.• Durability & Fatigue Group• Simulation, Test & Measurement Group• Sound, Vibration & Product Perception (NVH)

The Engineering Integrity Society

Activities

• Conferences, Seminars and Workshops

• Young Engineer Seminars

• Peter Watson Prize

• Formula Student Sponsorship (WLV Uni. 2018-2019)

• Task Groups (focus on new topics e.g Wind/Wave)

• Annual Exhibition

• Journal Publications

• Presentations & Technical Papers welcomed

Fundamentals of Data Capture & Analysis

Adrian LincolnPrincipal Analyst

Prosig Ltd

Supporting the EIS

Who are Prosig?

Prosig was established in 1977 by members of

the Institute of Sound & Vibration Research at

Southampton University. The existing UK

headquarters in Fareham UK were completed in

1982.

In 2014 Prosig became part of Condition

Monitoring Group (CMG) Limited. Together,

Prosig & CMG have numerous product and

technology synergies, which provide significant

advantages to its customers.

What does Prosig do?

Noise & Vibration MeasurementProsig’s mobile noise and vibrationmeasurement systems are built around theDATS-tetrad data acquisition system and DATSanalysis software.

Vibration Condition MonitoringProsig’s PROTOR provides a complete hardwareand software solution for vibration monitoringof large rotating plant. Acquisition subsystemsmonitor the machinery and are networked to acentral server.

EngineAnd Mounts(PE,IEPE,VC)

TransmissionAnd Mounts (PE,IEPE,VC)

EngineComponents(PE,IEPE)

InstrumentCluster (PE,IEPE)

Seat, Seat Rail, Head Rest,Floor Pan (IEPE,VC)

Suspension/Stabilisation(IEPE,VC)

Radiator/Fan/Shroud (PE,IEPE,VC)

Chassis (IEPE,VC)

Drive Line System (PE,IEPE)

Suspension/Stabilisation (IEPE,VC)

Body PanelsAnd Bumpers(IEPE,VC)

Exhaust Systemand mounts (PE)

Mirror Assemblies (PE,IEPE)

SteeringSystem (IEPE,VC)

Motors/Pumps(PE,IEPE)

BrakingSystem (PE,IEPE)

Technology KeyPE = PiezoelectricIEPE = Integrated Electronics PiezoelectricVC = Variable Capacitance Wheel Trim (PE,IEPE)

Wheel Acceleration (VC)

BrakingSystem(PE,IEPE)

Automotive Vibration and Acoustic Measurements

How do we measure vibration?

… Sample Motion Amplitudes (levels & times)

… Record Event Times (tachometer edge times & intervals)


SAMPLING

How accurately do we need to sample a vibration signal? (how small must the amplitude steps be between sampling

levels?)

… depends on the type of analysis to be used

… do we need to know true peaks in the time signal?


SAMPLING LEVELS

The number of levels is usually defined by the maximum numberof bits used in the digital representation of a signal’s amplitude.

For example, a range of 0 to 1023 (or -512 to +511) corresponds to0 to 1111111111 which is 10 bits.


SAMPLING LEVELS


Values stored are at the nearest amplitude and nearest time to the true analogue signal.

SAMPLING

Recording the amplitude of a vibration signal at specific times.

-2

-1

0

1

Dis

pla

cem

ent [m

m]

0.6 0.8 1.0 1.2 1.4

Time [Sec]

Analogue Data

-2

-1

0

1

Dis

pla

cem

ent [m

m]

0.6 0.8 1.0 1.2 1.4

Time [Sec]

Digitised Data


SAMPLING

Recording the amplitude of a vibration signal at specific times.

-2

-1

0

1

Dis

pla

cem

ent

[mm

]

0 .6 0.8 1.0 1.2 1.4

Time [Sec]

Digitised Data


SAMPLING

How fast do we need to sample a vibration signal?

… depends on the type of signal being captured



SAMPLING

How fast do we need to sample a vibration signal?

… depends on the type of signal being captured


… Sound is also a type of vibration


SAMPLING

Examples of automotive signals: (locations)

… Acceleration (Seat Track, Steering Wheel, Gearbox,

Exhaust…)

… Sound (near Driver’s Ear, Pass-By, Exhaust Emission…)

… Tachometers (Engine & Wheel Speeds, Gear Wheels…)

… Displacement (Crash-Test, Brake Disc Thickness, Roll Angle…)

… Strains (Suspension Components…)


SAMPLING

Types of automotive signals: (in terms of speed and size)

… Acceleration (large / small, low speed / high speed signals)

… Sound (loud / quiet, high speed signals)

… Tachometers (low or high speed signals)

… Displacement (large / small, low speed signals)

… Strains (small, slow speed signals)


How do we quantify speed? - Frequency, Time Intervals …

… related to Cycles and Periods (Simple Harmonic Motion)


What is Frequency?



What is Frequency?


Period T = 1/(frequency)also

Rev Period T = 1/(angular frequency)

P=1/f…

P=1/f…

-1.0

-0.5

0.0

0.5

1.0

Sin

e w

ave

[V]

0.0 0.5 1.0 1.5 2.0

Angle [radians]

-1.0

-0.5

0.0

0.5

1.0

Sin

e w

ave [

V]

0.0 0.5 1.0

Time [periods]

π 2π0 0 T/2 T


SAMPLING

Has this data been sampled adequately? … probably ok.

-2

-1

0

1

Dis

pla

cem

ent

[mm

]

0 .6 0.8 1.0 1.2 1.4

Time [Sec]

Digitised Data


SAMPLING

Has this data been sampled adequately? … probably not ok.

-2

-1

0

1

Dis

pla

cem

ent

[mm

]

0 .6 0.8 1.0 1.2 1.4

Time [Sec]

Digitised Data


SAMPLING

How do we quantify if data been sampled adequately?

-2

-1

0

1

Dis

pla

cem

ent

[mm

]

0.6 0.8 1.0 1.2 1.4

Time [Sec]

Digitised Data


SAMPLING

How do we quantify if data been sampled adequately?

Can we reconstruct the data to look the same?

Can we accurately estimate its statistical properties?

Can we accurately estimate its frequency properties?


-2

-1

0

1

Dis

pla

cem

ent

[mm

]

0.6 0.8 1.0 1.2 1.4

Time [Sec]

Digitised Data

SAMPLING

Data reconstruction – Shannon’s sampling theorem

Perfect reconstruction of a signal is guaranteed if you have measured it at

more than 2 points per cycle. In practice the sampling rate should typically be

at least 2.5 times faster than the highest frequency of interest.

-2

-1

0

1

Dis

plac

emen

t [m

m]

0.90 0.95 1.00 1.05 1.10

Time [Sec]

Digitised Data


Claude Shannon (1916 – 2001)

Mathematician, Electrical Engineer & Cryptographer

Proved that logical (Boolean) algebra can be implemented electrically

Founder of digital circuit design theory

Defined the term “bit” (binary digit) for storing information


SAMPLING - Aliasing

High Frequencies appear as low frequencies when sampled too slowly


SAMPLING - Aliasing

Aliasing also affects video sampling – causing the “wagon wheel” effect.


Data Analysis: Time Domain Statistics

Descriptors (Mean, Peak, RMS, Standard Deviation, Correlation)

Predictors (Probabilities, Trend Curves,…)


Frequency Analysis

… what’s Fourier got to do with it?


Frequency Analysis

… what’s Fourier got to do with it?

Mathematician and Physicist (1768-1830)

Claimed in his Theory of Heat Flow that any periodic function (signal) can be expanded as an infinite summation of sinewaves.


Frequency Analysis – Fourier Analysis

… Fourier analysis is a family of mathematical techniques, all based on decomposing signals into sinusoids.


Frequency Analysis – Fourier Analysis

… Visualisation of a summation


Frequency Analysis – Discrete Fourier Transform (half-range DFT)

Simple Sinewave Analysis

63.1Hz sinewave half-range DFTmodulus & phase of half-range DFT


Frequency Analysis – Properties of the Fast Fourier Transform (FFT)

Frequency Resolution

… is dependent on

a) Sampling Rate (samples/sec - not cycles/sec (Hz)!)

b) Number of Samples (binary block size)

Resolution = Sampling Rate Number of Samples


Frequency Analysis – Properties of the Fourier Transform(DFT/FFT)

Amplitudes are Linear

… in other words

FT{x} + FT{y} = FT{x+y}

+ =



Frequency Amplitudes are Averaged

… in this example

50% of signal has amplitude=1, the remaining 50% has amplitude=3

+ =



Frequency Amplitudes are Averaged

… for example

FT{Af0} + FT{3Af0} = FT{2Af0}

+ =


Frequency Analysis – Aliasing

Aliased frequencies are mirrored around the Nyquist frequency


Frequency Analysis – Aliasing

Aliased frequencies must be removed by analog filtering before sampling


Prosig Data Acquisition Systems: old and new

1990

2019


DATS – Analysis SoftwareRotating MachineryFatigue & DurabilityModal AnalysisStructural AnimationHammer TestingN.V.H.AcousticsSignal Source AnalysisHuman Response BiodynamicsHealth and Usage Monitoring (HUM)Time-Frequency AnalysisMulti-Plane BalancingSound Mapping



… any questions?

Supporting the EIS

• Tyre Road/Runway Interaction: Modelling, Simulation & Experimental Validation – 22 November, HORIBA-MIRA

• Instrumentation, Analysis and Testing Exhibition – 2 April 2019 Silverstone

• Fatigue 2020 – 29 June – 1 July 2020, Downing College, Cambridge• Additive Manufacturing – February 2019• Young Engineers Seminars – various dates

For further information please see our website.

Future Events

Contact

• Website: www.e-i-s.org.uk

• Tel: EIS Secretariat – Sara Atkin

+44 (0) 1623 884225

• Email: [email protected]

mailto:[email protected]

the engineering integrity society...prosig’sprotor provides a complete hardware and software...

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