DRIVING THE MOBILITY OF TOMORROW

Acoustic Analysis of an Active Noise ControlExhaust System on HiL Test bench

2015 GT-SUITE European Conference26-10-2015 , Frankfurt / Main

F. Buganza, D. Tajic, J. Krüger, T. Rose, M. Conrath

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1st Patent (Paul Lueg 1933)• “Active sound compensation by anti-noise”• Measurement of source-noise sound waves via

microphone.• Calculation Procedure.• Projection of anti-noise (anti-phase signals) through a

speaker

Historical Limitations:• Anti-noise calculation involves complex mathematical

algorithms.• High-quality electronics & calculation speed is

necessary to realize in any dynamic environment• First practical application in Headphone for pilots

Active Noise Control

noise

anti-noise

residual noise

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Eberspächer's ActiveSilence-technologyPrinciple Advantages for exhaust systems

Packaging: Very effective in reducing basic engine firing & sub-firing orders, replacing the primary drivers for larger muffler volume: => eliminate silencers.

Backpressure/Performance:No need for reflection, expansion chambers or other restrictive acoustic devices:=> more power and torque.

Sound Design Flexibility:Software control of engine orders allowing an adaptive sound design:=> easy sound customization.

System ModularityVersatile muffler construction leading to more carry-over-parts, simplified tooling and development procedures:=> reduced development time and cost.

Engine Firing Sound

Speaker Anti-noise

Controller

Engine Speed & Load Signal (CAN)

Actuator withLoudspeaker

Error Microphone

Tailpipe

Exhaust Pipe

Engine

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ActiveSound / ActiveSilenceTypical System Layout and results

Achieved results:� single active exhaust line� -33% weight and -54%volume� backpressure similar to series� free sound design:

acoustic comfort / sport sound

1000 2000 3000 4000 5000 6000Rotational Speed [1/min]

50

60

70

80

90

100[dB(A)] Sound Pressure Level 1,8m behind car

2nd EO

Passive MufflerANC offANC on

Passive exhaust system:• dual line, 4x mufflers• 27 kg• 50 Liters

OVL

-33% weight and -54%volume

free sound design

ActiveSilence system: • single line, 1x muffler• 18 kg• 23 Liters

Actuator

Error sensor

CAN-bus

ANC control unit

Engine control unit

4

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The aim of the silence-HIL is to simulate till a ce rtain grade of accuracy the real system and allow a very fast calibration as well as an easier continuous engine ering of the ANC software.

Expected advantages of the HiL-System:

• at least 80% of design verification can be done on HIL system�less tests on roller dyno or real engine necessary

• faster design of the passive muffler, including mic rophone placement

• fast prototyping (SW and HW)

• 100% repeatability of test-environment, easy simulation of all possible environmental condi tions

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ActiveSilence-HiL : what? why?

Acousticrequirements

target exhaust system

ECU Development

fast muffler design

fast acoustic design (SW calibration

validation of new SW/HW features

estimation of microphone best

positioning

exhaust systemsimulation

ANC control unit

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ActiveSilence-HiL : Simulation requirements

Exhaust sound pressure level (NOISE):

Amplitude of 2 most significant engine orders throug h GT-Realtime shall be the same as in GT-SuiteThe phase relationship between the 2 most significa nt engine orders through GT-Realtime shall remain the same as the simulation through GT-Suite Spectrum: the frequency range is [25..500] Hz

Actuator sound pressure (ANTI-NOISE):The actuator mechanics shall be modelled input of the model is the speaker membrane displacement

Error microphone: sound pressure and electrical conversion

System noise/ uncertainty

ANC control unit

CAN-bus

Sampling frequency:for a realistic simulationthe Exhaust model shall be simulated @5kHz rate

Engine:CAN-bus simulationExhaust gas mass flow simulation

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ActiveSilence-HiL: Architecture

HIL Software

[RPM, Torque]

HIL Hardware

[Mass flow]

cold-endmodel

exhaust sound pressure model

[Membranedisplacement]

microphonemodel

cold end temperature

model

batterymodel

actuatormechanical model

central CPU, I/O interfaces :sensors, speaker emulation, battery supply...

GT-Suite-RT

HIL Hardware

Simulink

[Exhaust temperature]

[CAN BUS]

actuator electricalmodel

[Acousticpressure]

Simulink: electrical

GT- Realtime:acoustics +mechanics

HiL Control

ANC control unit

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ActiveSilence-HiL – design of the GT-Suite-RT model

catalytic converter model

Mass flow & engine temperaturemodel

Mufflermodel

junctionactuator �coldend

outletjuction

x0+x(t)x0

Loudspeakermembrane

p(t)

actuator mechanics

this is the GT-Suite model used in numerical simulations

let´s make the Real-Time version to be integrated on HiL…

error sensor

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ActiveSilence-HiL – design of the GT-Suite-RT model

STEP I

Muffler-out mass flow and temperature from numerical simulation were introduced as “inputs” to the active system only.

STEP II

Modified discretization, time step-size to ensure RT convergence:internal 2x oversampling �

step-size = 100 µs

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ActiveSilence-HiL – design of the GT-Suite-RT model

HiL control-SW(Simulink model) Actuator

electric modelSTEP III

Integration in the Simulink Model

STEP IVCode Generation throughSimulink Realtime

STEP VHil can finally run!

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ActiveSilence-HiL: Numeric (“full system”) vs. realtime simulations

2nd E.O.

4th E.O.

6th E.O.

2nd E.O.

4th E.O.

6th E.O.

2nd E.O.

1000rpm 3000rpm 4500rpm

A deviation

φdeviation

A deviation

φdeviation

A deviation

φdeviation

2nd engine order

< 1dB 1° 1dB 4° < 1dB 1°

4ht engine order

< 1.5dB 11° <3dB 5° < 1dB 11°

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ANC calibration :

cancellation on 1st, 2nd, 4th and 6th engine order

ActiveSilence-HiL: realtime simulation results

ANC OFF ANC ON

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ActiveSilence-HiL: realtime simulation resultsSPL at error microphone

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� the development of HiL fulfills the expectations� Realtime simulation @ 5kHz is possible, CPU usage ~40%� accurate simulations results� easy workflow� For several duties, the HiL is a valid substitute of expensive acoustic test on

vehicle

�Use case� as usual for SW/HW development � for dimensioning of ANC exhaust systems

�Next improvements:

� muffler shall be modelled on GT-Suite RT� improvement of sensor-noise modelling � sound reflections to speaker membrane and muffler shall be modelled as well� aggressive usage of multicore CPUs / multithreading to allow even more complex

simulations

Conclusions

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Thank You very much for Your attention!