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!
