characterisation of vibratory, pulsation and noise … · cav april 2017 0/20 characterisation of...

CAV April 2017 0/20

CHARACTERISATION OF VIBRATORY,PULSATION AND NOISE SOURCES

Goran PavićINSA Lyon, France

CAV April 2017 1/20

scope

Objectives: predict the transmission source → surroundings allow meaningful specs formulation troubleshoot the causes of excessive levelsDifficulty: source excitation depends on its environment !Challenge: independent source characterisation.Problem: no norms / standards !

Industrial techniques: sound power vibration level p-p pulsations

Academic techniques: holography inverse BEM beamforming

assemblerNVH design

supplier

supplier supplier

subsuppliersub

supplier

subsupplier

CAV April 2017 2/20

source needs a double descriptor

circuit current ic

open-loop voltage VS

load resistance RL

=

source resistance RS

+

Source → 2 descriptors: driving potential coupling capacity

Receiver → 1 descriptor: coupling capacity

Mechanical / acoustical:coupled velocity Vc

blocked excitation Eb

receiver impedance ZRsource impedance ZS

coupled impedance: RSc ZZZ +=

simplemultiple Vc = Eb

Zccoupling: -1

CAV April 2017 3/20

vibration

blocked excitation Fb ? source impedance ZS ?

Difficulties: forces and moments translations and rotations multiple coupling points.

=wrench

=screw

How to get Fb ? Vc FbZc-1= How to get ZS ? Zc ZS ZR= −–

To make this work: a convenient calibration receiver is needed !

The coupling (operational) forces transmitted to any surroundings of impedance Z will read: bSc FZZZF 1)( −+=

CAV April 2017 4/20

smart receiver

Fb = ZcVc ZS = Zc – ZR Solid block 6-DOF screw sensor 6-DOF wrench sensor

Fit 6 simple sensors !

Excitation by 6 external forcesMeasurement in running conditions

Source coupled

Source removedExcitation by 6 external forces:

The block measures both source descriptors in all DoF

coupling pointvibration characterisation:

smart receiver

soft mount source footsolid block

source

CAV April 2017 5/20

equivalent force approach

Example:4 connection points

=4 wrenches(24×1 vector)

impedance (24×24 matrix)

4 screws(24×1 vector)

eq. force(6×1 vector)

impedance (6×6 matrix)

eq. screw(6×1 vector)=

equivalent force: resultant of interface wrenches !equivalent screw: mean of interface screws!vibration characterisation:

equivalent force

CAV April 2017 6/20

measurement practice

water pumpcompressorhydromotor

CAV April 2017 7/20

equivalent force application: electro-pump

characterisation

prediction

vertical

lateral

CAV April 2017 8/20

equivalent force application: compressor

3D force sensor

Source characterisation

blocked charact.operat. measuredoperat. predicted

lateral

verticalblocked charact.operat. measuredoperat. predicted

CAV April 2017 9/20

insertion of resilient mounts

Blocked forces

boltedmounts

Operational forces:

lateral

vertical

CAV April 2017 10/20

pulsation

Difficulties: impedance measured with the source operating blocked pressure impossible to measure directly

blocked pressure impedance

1.1m1 2


multiple load technique

pulsation characterisation:multiple load

coupled pressure pc

SLS

Lc P

ZZZP+

=

blocked source pressure pS

≥2 different loads: ZL1, ZL2…


laboratory measurement: gear pump

measuredpredicted

5b, 600 rpm(gear meshing: 150 Hz)

10b, 1500 rpm(gear meshing: 375 Hz)


industrial measurement: vane pump

measuredpredicted

5b, 2000 rpm

3b, 1000 rpm

7b, 3000 rpm


airborne noise

blocked pressure impedance

Difficulties: source coupled to receiver through a surface physical surface of source extremely complex source power depends on the surroundings.

define an interface surface S. separate into source space and receiver space identify blocked pressure of running source Pb identify impedance of idle source space ZS

source space receiver space


dummy source: principle

1. build a simple dummy similar to original source2. fit the dummy with K small drivers3. measure source noise in N control points4. replace the source by the dummy5. establish TRF drivers / control points

P (N×1)

T (N×K)6. compute driver strengths Q out of P = T Q Q (K×1)

Source model: applicable to any receiver environment !

Q2

Q1

…Qk

QK

airborne noise characterisation:dummy source


dummy source: demonstration

200 Hz

1000 Hz


dummy source: vibrating box

Semi-anechoic spacetransfer functions →

analytical computation


dummy source: excavator


equivalent source approach

Ω0

Ω

vn

real source → set of monopoles reproduce normal boundary velocity diffraction disregarded (small

sources)

The normal vibration velocity can be measured by an accelerometer array.

airborne noise characterisation:equivalent source


Field computed using: equivalent source method mirror image principle

application to a loudspeaker cabinet

measuredpredicted


summary

source characterisation methods → industrial applications dual source descriptor → blocked excitation and impedance best way to characterise a source → measurement unified approach to vibration, pulsation and noise

vibration: smart receiver **** equivalent force method ***

pulsation: multi-load method **

noise: dummy source method *** equivalent source approach ** coupling surface method *****

* simple ***** difficult


how to define surface impedance ?

original field

expand into N eigenfunctions

….

discretize into N patchesIn either case:p, v : N×1 vector

Z : N×N matrix

p = Z v


coupling using patches: examples

62 patches 142 eigenfunctions62 patches

142 eigenfunctions

patch size < λ/3


steel block, 70 kgL 400mmW 280mH 80mm

calibration block impedance

characterisation of vibratory, pulsation and noise … · cav april 2017 0/20 characterisation of...

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