automated system test for car engine order cancellers · 2017. 9. 18. · 08-10 september2017| aes...

Victor Kalinichenko, ASK Industries GmbH

Automated system test for car engine order cancellers

EOC: Stability, Performance, Artefacts

08-10 September 2017| AES Conference on Automotive Audio Victor Kalinichenko, ASK Industries GmbH Automated system test for car engine order cancellers |

EOC is a feedback system. As most of feedback systems, it may become instable, the performance may degrade, transient effects as a reaction on interferences or highly non-stationary disturbances may become audible.



Instability of EOC may be the reason of driver’s having got scared and lead to accidents



Instability may occur due to many reasons. Among them change of cabin transfer path. It may be caused, for example, by:


Large number of occupants Trunk is loaded

Temperature factor Touching/closing the microphone



Fig. Influence of temperature to the frequency response of the speaker


Additional factor of instability or performance degradation is deviations in mounting speakers in the production line and possible leaks


Fig. Influence of wrong mounting of the front bass speaker and caused leaks on frequency response


Some other factors influencing stability:- Aging effect- Echoic external environments, e.g. tunnels, garages, etc.- Opening doors, windows, open roof, etc (unless protected from).- Mechanical changes in the cabin- Damages from the road accidents- Bad (e.g. too sensible) tuning, or using the wrong tuning (e.g. error in configuration)- Driving program change- Production line errors, e.g. unintentional change of the polarity of speakers/mics,

damaging them, mis-cabling, using wrong tuning, etc.- Software development and signal flow errors: e.g. using time-variant or non-linear

processing modules in EOC path



Unevenness of the road impacts EOC performance and may cause audible artefacts.There are many other factors that may cause artefacts: cylinder switch in the engine, external/internal noises, vibrations, other NVH-signals, e.g. RNC, ESS, entertainment, etc.



Performance can drop due to most of factors influencing the stability, but there may be other reasons, e.g.

Performance = 0, if EOC is off.

Why can EOC be off?

One reason : untested programming bugs Other reason : un- or badly specified featuresFor example, customer has specified that EOC must be off in case roof position is not

closed. But this signal may not be present for non-convertible cars.



Other reasons for EOC performance degradation:

- Internal and external sounds: road noises, vibrations, wind, rain, etc.

- Permanent quick changing of the CAN-parameters (RPM, torque), especially in case of bad tuning of EOC parameters, e.g. “forgetting factor”

- Using of too robust tuning

- Applying the same tuning for different type of car, e.g. using left-hand drive car tuning in the right-hand drive cars “as is”

- Different position of the occupant’s head in respect to EOC microphone

- Updates of the car done in the garage, e.g. changing the engine software


EOC: Automated test environment


PurposeBuild the model of the external environment for the sound amplifier, i.e. its inputs and

outputs and give EOC manufacturer the opportunity to set up automated tests covering different, including almost improbable or even non-realistic conditions previously exampled. For the sound amplifier it should be looking like a car with loudspeakers, microphones, CAN-signals. This kind of tests is known as Hardware-In-the-Loop (HIL) test. It is always better to automatize whatever can be automatized in the test system, thus minimizing human’s errors.

What shall be covered by the HIL-test?- Hardware of the sound amplifier- Software- Audio-flow- Tuning- Integration




Building the system: high abstraction level



Each functional unit in the Industrial Computer isfully configurable from Conventional PC, e.g. one can specify which car cabin impulse responses to use, apply disturbance, or not, if yes, load from file or generate; what kind of engine model (ESS) to use, e.g. load one from file, or specify parameters of each harmonic; which signals to use in Analysis unit and how to compare them, where to put analysis results etc.


Some general requirements:- Extremely low latency time of the model (1 msec or less)- Constant latency from analog inputs to analog outputs. It must be kept not only within

one running session, but from session to session- Real-time processing, e.g. using real-time OS- Electrical and diagnosis compatibility of the test environment with the inputs and outputs

of the amplifier, e.g. compatible impedance- ATE must include not only loudspeaker inputs and microphone outputs but also

loudspeaker outputs and microphone inputs for the Model Measurement and Verification(MMV) procedure used for finding coefficients of FIR filters of the car cabin impulse responses so that the resulting transfer paths involving hardware analog components would be exactly the same as the analog transfer paths from electrical car loudspeaker inputs to electrical car microphone output

- Must be moveable, i.e. size and weight of ATE must not be extremely high

Desirable features:- The software for Industrial PC shall be able to use the same DSP Framework, DSP

modules and communication protocol as used in the EOC sound amplifier.



Types of tests:- Basic tests. Goal: to detect whether EOC is active

- Stability tests. Goal: to test whether instabilities occur in the tested EOC sound amplifier and if yes, under which operational conditions

- Performance tests. Goal: to test whether the performance is as expected and how it drops under disturbances and other factors influencing EOC

- Tests for artifacts. Goal: to test whether artifacts are detected during transient periods in case disturbances, e.g. simulating the knocking, speech, etc.



Analysis. Stability, performance and artifacts: key idea



Analysis. Additional possibilities: using the Reference EOC. Reference EOC loop can be used for additional analysis on how stable or what would be the performance of EOC under better conditions than simulated in HIL-test. For example, one can apply disturbance (e.g. voices in the car cabin) to the HIL-path and exclude it from the reference path and compare the performance degradation in case of presence of disturbances



Test conditions:- Basic conditions (CondB). Standard cabin impulse responses, temperature conditions

etc. RPM signal is applied as a linear ramp, e.g. from min value to max value.- Temperature variations (CondTemp). In the basic conditions cabin impulse responses

are modified by temperature changes. Activating temperature behavior of the transfer paths is done in block (8). Temperature changes may substantially influence stability and performance of EOC. Temperature models of transfer paths can be obtained using special thermo-chambers (normally available at every car manufacturer).

- Noise-like external signals (CondNoise). Basic conditions + Activating in the disturbance generator (9) generation of random noises with the spectral characteristics close to the modeling conditions. For example, wide band noise for wind, or pre-recorded rain signals, or correlated with RPM colored noise simulating sounds of tires, etc.

- Competitive external signals (CondExt). Basic conditions + Activating in the disturbance generator (9) generation of the harmonic signals, whose frequencies are close to the frequencies of the cancelled harmonic orders. The character of the competitive signals can change during time, e.g. frequency and amplitude deviation type. For example, whistling or other car noises can be applied during this test.



Test conditions:- Internal sound amplifier signals (CondInt). Basic conditions + playing back in the

amplifier audio and/or activating ESS function. As these signals are not observable in ATE, reference EOC can be used for comparison the microphone outputs of ATE in HIL-path and in the reference EOC.

- Change of the cabin characteristics (CondCab). In the basic conditions cabin impulse responses are replaced by responses of different cars or noises are added to the reference cabin responses, or reference impulse responses are modified by passing them through filters; among them applying the different gain emulating badly calibrated microphone. These conditions can model errors in mounting speakers, or different load of the car trunk or different number of occupants, closing the loudspeakers and other changes of cabin responses that may happen in real exploitation.

- Non-linearities of speakers or/and microphones (CondNL). Basic conditions + activate unit for non-linear processing modeling of loudspeaker or microphone damages, or non-linear mechanical vibrations resulting in non-linearity in the cabin transfer paths.




Circumstances that may result problems for EOC + analysis of testability

Obtaining car cabin responses


Obtaining the cabin impulse responses for the HIL-cabin model


In order to perform these measurements one should be able to access the analog inputs/outputs of the car, i.e. break-out box is required.


Obtaining the cabin impulse responses for the reference EOC in ATE


Ideas for other applications of ATE


- Development of new algorithms. Often the developers have no opportunity to develop algorithms directly in the car or the number of cars to be tested is very limited. It can be not only active noise control but other sound algorithms. Then ATE environment can be used.

- Preparing off-line pre-tuning and investigations on improving EOC. EOC pre-tuning can be done off-line after having obtained car cabin responses and measurements of engine at different torques. Additionally problematic areas can be also investigated off-line. Advantage of this approach that every point in the car model is observable. It is not true for real car.

- Improved tuning using cabin impulse responses with dummy head in the model. ATE can be expanded by adding cabin impulse responses of dummy head(s) placed on the occupants positions. It is applicable not only for EOC but for other sound algorithms.

Ideas for other applications of ATE

THE END

automated system test for car engine order cancellers · 2017. 9. 18. · 08-10 september2017| aes...

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