DE102015214134A1 - Method and control device for active sound suppression in a motor vehicle - Google Patents

Abstract

The invention relates to a method and a control device for active noise suppression (ANC) in a motor vehicle, in which an online modeling is carried out for determining a transmission path between a sounder and a sound pickup, wherein the useful signals of a system for active noise generation are used as test signals. In this case, synthetic signals which do not belong to the natural excitation spectrum of the primary signal source are preferably used as test signals for online modeling. Preferably, the invention in the exhaust system of a motor vehicle with internal combustion engine is used as a drive motor, wherein the respective useful signals used as test signals of the system for active noise generation are synthetic engine orders, each lying between the speed-dependent engine orders of the noise generated by the drive motor noise.

Description

The invention relates to a method and a control device for active sound suppression.

In the printed prior art as well as in today's production vehicles, methods and control devices for both active sound suppression and active noise generation are known.

For active noise generation, also referred to as "Active Sound Design" (ASD), is for example the DE 198 45 736 A1 called the applicant. In this case, starting from various vehicle parameters, such as speed, accelerator pedal position or engine speed, engine noise is synthesized both in the vehicle interior and in the exhaust system by loudspeakers, whereby, for example, a vehicle-specific sound staging can be displayed.

In contrast, Active Noise Cancellation or Active Noise Control (ANC) is an attempt to eliminate disturbing noise in the vehicle through artificially generated sounds by means of destructive interference. For this purpose, for example, the DE 43 34 943 A1 called the applicant. In this case, the generation of a (secondary) signal is sought, which exactly corresponds to that of the noise of opposite polarity (also called anti-noise). Based on a measured (acoustic or non-acoustic) reference signal (for example, a speed signal), which is strongly correlated with the primary signal to be reduced, a secondary signal 180 ° out of phase is generated, by which this disturbing sound is extinguished. Both phase and amplitude of the secondary signal must be permanently adjusted or readjusted in practice due to various disturbances by a control unit. For this purpose, the resulting superimposition (residual error) of primary and secondary signal is measured by a suitable sensor (error sensor) and made available to the control unit. The sound generated by the loudspeakers to cancel out the disturbing sound is referred to here as a secondary signal.

For example, an ANC function can be implemented by introducing corresponding actuators and sensors in an exhaust system or an intake air guide or in an interior of a vehicle.

For the active noise reduction to have sufficiently good stability, the transfer function (or at least the phase shift) between the loudspeaker and the microphone (secondary route) must be known.

Due to the transit time, the secondary signal to the measuring position of the error sensor, there is a phase shift between the generated secondary signal and the measured error signal. The phase shift corresponds to the phase response of the transfer function.

Without consideration of the transfer function between secondary source and fault sensor and can lead to instabilities of the control system. In order to solve this problem, a corresponding compensation of this phase shift must be provided in the control unit. For this purpose, for example, the reference signal is filtered or billed with an internal model of the physical transfer function. The quality of the internal model of the transfer function decisively determines the effectiveness and stability of the ANC system.

In order to determine these secondary routes, there are two different methods, namely offline modeling and online modeling:
In offline modeling, a test function is calibrated once (for example, before the vehicle leaves the factory and / or during vehicle development), whereby the transfer function is determined once and stored in the control unit.

The disadvantage of this method is (especially for use in an exhaust system) that varies with the temperature and the flow velocity of the propagation medium, the sound propagation time of the secondary signal and thus also the phase of the secondary signal. In addition, these environmental influences lead to shifts of native resonances. Furthermore, both the characteristics of the error sensors and the speakers (drift of components) change. As a result, the secondary path and the transfer function change continuously.

In online modeling, these problems are circumvented in that the transfer functions are calibrated regularly or continuously during operation of the system. The calibration process is performed by test signals (noise, sine sweep, ...), which are recorded during operation. Through this technique, the air temperature as well as the drift of the components such as microphones and loudspeakers are included again and again in the determination of the transfer function and the stability of the system can be significantly improved.

A transfer function is usually provided with broadband noise or a sine wave. Sweep certainly. This test signal must be sufficiently loud and can be evaluated except for the natural stimuli of the primary source.

In the online modeling, it comes to the passengers to irritation, as a beeping / noise (sound of the test function) is perceived while driving. Such test signals / test noises could be interpreted by the driver as a defect.

In offline modeling, the secondary route is determined only once, which leads to a poorer functionality of the ANC function with increasing age. Especially with ANC in the area of the exhaust system, there are violent fluctuations in the boundary conditions such as the medium temperature (eg from -20 ° to + 900 ° C) or the medium speed, which means that the offline modeling results in a poor efficiency of the ANC function. In addition, the efficiency or stability of the system decreases as soon as one or more system properties (temperature, etc.) are removed from the values which prevailed in the one-time determination of the transfer function.

It is an object of the invention to improve an ANC system with regard to a targeted level reduction.

This object is achieved by the subject matters of the independent claims. Dependent claims are advantageous developments of the invention.

The invention relates to a method and a control device for active noise suppression (ANC) in a motor vehicle, in which an online modeling is carried out for determining a transmission path between a sounder and a sound pickup, wherein the useful signals of a system for active noise generation are used as test signals. In this case, synthetic signals which do not belong to the natural excitation spectrum of the primary signal source are preferably used as test signals for online modeling. Preferably, the invention in the exhaust system of a motor vehicle with internal combustion engine is used as a drive motor, wherein the respective useful signals used as test signals of the system for active noise generation are synthetic engine orders, each lying between the speed-dependent engine orders of the noise generated by the drive motor noise.

The invention is based on the following considerations:
The essence of the invention is the realization of an online modeling of the secondary route determination without using disturbing noises as test functions. For this purpose, the fact should be exploited that already generated by the active noise generation (ASD) certain motor frequencies and / or amplified or added more frequency components. This artificially generated sound should simultaneously serve as a test function and help to continuously redefine the secondary route by means of online modeling and, if necessary, to adapt it to the changed parameters.

The values of the transfer function (eg amplitude and phase) determined in this way can be stored as a multi-dimensional characteristic field as a function of the respective frequency but also as a function of other system properties such as temperatures in the system or the flow velocities in the control unit (amplitude _{transfer function} = f (f, T, v), phase _{transfer function} = f (f, T, v)). The signals of the other system properties can be generated, for example, via corresponding sensors or models and made accessible to the control unit.

As a test function, a signal that is uncorrelated with the primary signal must be used so that it can be clearly identified as a secondary signal. For this purpose, synthetic motor orders that do not belong to the natural excitation spectrum of the primary signal source are preferably used.

By interpolating the measurement data between two artificially generated, uncorrelated frequencies, the transfer function of an intermediate frequency generated by the primary source can be determined. Similarly, interpolation may be performed over another system property (such as temperature). For this purpose, for example, the orders already used by the ASD can be used in an exhaust system.

In the interior, both the artificial engine noise of the ASD and multimedia signals from the audio interface (eg music) can be used. In the case of several secondary sources, a temporal or frequency-dependent separation of the test signals is additionally necessary in order to be able to unambiguously identify the transmission path.

• – eine kontinuierliche Neubestimmung und Anpassung der Sekundärstrecke oder Übertragungsfunktion des ANC, ohne auf störende Geräusche der Testfunktion zurückgreifen zu müssen,
• – eine verbesserte Gesamtstabilität des ANC durch Onlinemodellierung und kontinuierliche Adaption an die Gegebenheiten und
• – ein wartungsfreies System, da Veränderungen im Frequenz- und Phasengang des Aktors und Sensors in der Übertragungsfunktion mit abgebildet werden.

The invention achieves the following advantages:

• - a continuous redetermination and adaptation of the secondary line or transfer function of the ANC, without having to resort to disturbing noises of the test function,
• An improved overall stability of the ANC through online modeling and continuous adaptation to the conditions and
• - A maintenance-free system, as changes in the frequency and phase response of the actuator and sensor in the transfer function are mapped.

In the drawing, an embodiment of the invention is shown. It shows

1 possible components of a device according to the invention and

2 Test signals for interpolation of the transfer function based on artificially recorded frequencies or engine orders.

1 schematically shows a cavity H, here an exhaust system in which a sound pickup M and a sounder or loudspeaker L are arranged. In the exhaust system H naturally creates a noise x. The signal x contains, for example, a tonal, z. B. speed-proportional frequency component f1, which is produced for example by the change of charge of the engine and transmitted or emitted via body or air sound paths. The interference sound x produced by the tonal frequency component f1 of the oscillations should be suppressed or canceled out by the active acoustic sound compensation device according to the invention.

A sensor S1 detects the rotational speed n of a drive motor not shown here, the input signal of a signal generator 4 is. The signal generator 4 generates an expected noise x corresponding to the speed n with a certain current frequency f1 and provides this interference sound x (f1) as an input signal to an online modeling module 3 available electronically simulating the electro-acoustic transmission path G between the speaker L and the microphone M. In the online modeling module 3 the phase shift P produced by the transmission path G is corrected for each frequency f of the background noise x based on stored maps.

The simulated interference sound x (f1) provided with the phase correction Pkorrx (f1) for the current frequency f1 becomes, as an input signal x '(f1), an amplitude conversion module 2 supplied, which generates a relation to the noise x '(f1) converted correction signal k' (f1) to extinguish the noise x and outputs via the speaker L in the cavity H. The online modeling module 3 contains a model correction unit 5 , which is provided on the basis of test signals for correcting the stored maps in particular for the correct determination of the phase correction P _{korr_x} (f2), which will be discussed in more detail below.

The output (signal e) of the microphone M is with the amplitude conversion module 2 connected, the output side (signal k ') is in turn connected to the speaker L. The amplitude conversion module 2 generates the correction signal k ', which is emitted via the loudspeaker L as a compensation sound k and is superimposed in phase opposition with the current interference sound x in the cavity H.

A residual sound e, so the sum of the compensation sound k (f1) and the actual current noise x for the current frequency f1, for example, by temperature changes, flow rate changes or component deviations remain. Accordingly, since the electro-acoustic transmission path G may change, the on-line modeling module becomes 3 through an adaptive process (online modeling) in the model correction unit 5 continuously adapted to the changed conditions:
Essential to the invention is the connection of the basically hitherto known system for active sound suppression with an active noise generation system ASD. The features essential to the invention are in 1 marked in bold. In the online modeling module 3 if necessary, by means of the useful signals of the system ASD as test signals t 'an adaptive online modeling of the secondary route determination in the model correction unit 5 carried out. In this case, synthetic motor frequencies including motor orders that do not belong to the natural excitation spectrum of the primary signal source are preferably used as test signals t '. The natural excitation spectrum of the primary signal source (here the drive motor) results from the actual currently present speeds n. In the drawing or in the present embodiment, the frequency f1 as an example of the natural excitation spectrum of the primary signal source (background noise x) and the frequency f2 as an example synthetic motor frequencies of the system ASD used. Essential in the embodiment is therefore that differ f1 and f2.

As a test signal thus a with the current primary signal (noise x) uncorrelated signal t 'is used so that it can be unambiguously identified as a secondary signal to determine the transfer function G and thus in particular for determining the phase correction for all required noise frequencies.

Further examples are in 2 shown. By interpolation of the measurement data for the phase shift P and possibly for the amplitude correction A between each two artificially generated, uncorrelated frequencies f2.1, f2.2, f2.3, f2.4 for t 'can Thus, the transfer function G (with respect to amplitude A and phase shift P) of an intermediate frequency (see dotted lines in the upper image of 2 ). For this purpose, the arrangements already used by the ASD for generating a desired drive motor sound can preferably be used in an exhaust system H.

2 shows in the upper picture a straight line of artificially established orders (ASD orders, see solid lines). In the middle picture the amplitude is A and in the lower picture is the phase shift P of the current transfer function G for the online modeling in the model correction unit 5 shown. This online modeling in the model correction unit 5 is after the update of the stored transfer function G in the form of new maps in particular for a phase correction but also for an amplitude correction again basis for the amplitude conversion module 2 for the suppression of background noise x. The crosses in the middle picture and in the lower picture of the 2 indicate measurements by means of the artificial secondary signals t 'here for the different frequencies f2.1, f2.2, f2.3 and f2.4. The solid lines between the crosses indicate the interpolations.

With a measurement for redetermining the transfer function G, it is therefore always necessary to wait until the current frequency f1 of the disturbing sound x 'or x of the drive motor of the frequencies f2 or f2.1, f2.2, f2.3 and f2.4 of the artificial sound t 'of the ASD system. The characteristic data stored for the test frequencies can then be used to suppress the background noise x if a current frequency of the background noise x assumes the value for which a test frequency previously occurred. Thus, the more test frequencies for determining the transfer function G before the occurrence of a noise x at the same frequency of a test frequency for the measurements and determinations of the new map data for model correction unit 5 could be used. The test signals t 'can therefore be output to the loudspeaker L simultaneously with the correction signal k', without affecting the vehicle occupants.

In addition, the measured values for amplitude and phase of the transfer function ( 2 , middle and lower image) not only as a function of the frequency f but also in addition depending on other system variables, such as the gas temperature in the system, are stored as a multi-dimensional map.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19845736 A1 [0003]
• DE 4334943 A1 [0004]

Claims (5)

Method for active sound suppression in a motor vehicle, in which an online modeling for determining a transmission path between a sounder (L) and a sound pickup (M) is performed, wherein as test signals (t '; t) the useful signals of an active noise generation (ASD) system be used. Method according to Patent Claim 1, characterized in that synthetic signals which do not belong to the natural current excitation spectrum of the primary signal source are used as test signals (t '; t) for online modeling. Control device for carrying out the method according to one of the preceding claims with a sounder (L), with a sound receiver (M) and with an online modeling module ( 3 ), which is connected to an active noise generation (ASD) system and a model correction unit ( 5 ) such that an online modeling for adaptation of the transfer function (G) by means of using the useful signals of the system for active noise generation (ASD) as test signals (t '; t) is feasible. Control device according to the preceding claim, characterized in that synthetic signals which do not belong to the natural excitation spectrum of the primary signal source can be used as test signals (t '; t). Application of the method or the control device according to one of the preceding claims in the exhaust system ( 1 ) of a motor vehicle with an internal combustion engine as a drive motor, wherein the useful signals of the system for active noise generation (ASD) used as test signals (t '; t) are synthetic engine orders, each between the speed-dependent engine orders of the noise generated by the drive motor (x; x' ) lie.

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