EP1964107B1 - Method and system for actively influencing noise, and use in a motor vehicle - Google Patents

Description

The present invention relates to a method for active noise control, in particular in a motor vehicle. Furthermore, the invention relates to a corresponding system and its use in a motor vehicle.

Systems for active noise control, which are also referred to as ANC systems (active noise control) serve, for example, in a passenger compartment of a motor vehicle to reduce by coupling controlled acoustic signals, the noise level of a source of interference, for example the motor. In this active compensation, the noise is reduced by superposition with additional vibrations, so-called anti-sound. The controlled coupling of secondary sound also any harmonics and / or the root of the primary noise can be amplified. As a rule, harmonious tone sequences, for example, are perceived as pleasant. By selectively suppressing individual frequencies of the engine noise and amplifying other frequencies, for example, a perceived engine noise can be designed specifically. One speaks then also of sound design.

In the following, compensation sound is understood as a secondary sound coupled in addition to the noise sound, which can act both amplifying and damping at specific sound frequencies.

The same principle results in the compensation of structure-borne noise, by means of actuators counter vibrations are coupled into a solid, which cause a noise reduction or noise change.

As a rule, the noise or vibration sources are essentially periodic sound sources. The resulting from the periodicity excitation frequency of the noise source is used as an input to an adaptive control of the noise reduction system. If this characteristic for the respective noise source As time changes, adaptive control of the noise mitigation system makes a corresponding adjustment in the compensation sound injection.

An adaptive control for active noise reduction, for example, from DE 196 32 230 C2 known. There, a reference signal generator is provided which detects an engine speed and generates an electronic reference signal having information about the engine speed. This may be, for example, a pulse signal, which is guided via signal lines to a sine generator provided in the noise reduction system. In the motor vehicle, a corresponding reference signal can also be derived from the ignition coil signal, which is directly related to the engine speed and thus the acoustic excitation frequency of the engine.

In active noise reduction systems, it is necessary to keep the corresponding excitation frequency or an equivalent reference signal for the actuation of the actuators or compensation loudspeakers as continuous as possible in time. In noise reduction systems according to the prior art, therefore, a measuring sensor usually used near the engine is provided, which supplies a corresponding reference signal to the actual control of the noise reduction system. The noise reduction system is usually located in the passenger compartment, so long signal paths and a corresponding wiring are required.

In the JP-06-109069 a noise reduction system for motor vehicles is described in which the actual processing unit for an LMS algorithm is operated at a lower clock rate than the analog-to-digital converters and digital-to-analog converters which detect a corresponding input signal or provide analog drive signals for compensation speakers. The implementation of the LMS algorithm for determining filter factors of adaptive digital filters of the arithmetic unit is carried out by the reduced clock rate with less effort. In this case, a derived from the engine speed reference signal is used in the algorithm.

Due to progressive automation and the integration of various control and regulating tasks in modern systems in a digital manner, analog continuous-time monitoring signals are hardly available any more. In modern motor vehicles, data communication takes place, for example, via digital bus systems, such as, for example, the CAN bus (Controller Area Network Bus). In such asynchronous serial bus systems, real-time data communication is no longer possible. For the indication of the engine speed in the fittings of a motor vehicle, e.g. a deployment rate of only 10 per second is sufficient.

Typically, several bus systems are kept in current motor vehicles. A first high-speed bus is provided in the engine compartment, which controls the engine network and having an engine speed provision period of the order of 10 to 20 milliseconds. A second slower data bus, coupled via a gateway to the high-speed bus, serves to connect control units for the comfort and interior functions of the motor vehicle, such as tachometers, tachometers, etc.

The motor speed reference variable, which is important for a system for active noise control, is thus only available at a lower provision rate of about 10 times per second, ie every 100 milliseconds on the slower data bus provided in the interior of the motor vehicle. In particular, when accelerating and braking the engine, the only very discretely present discrete reference variable, for example, the engine speed, the operation of the active system in the passenger compartment difficult.

It is therefore an object of the present invention to provide a reliable method for influencing noise. Furthermore, the invention has for its object to provide a system for active noise control.

This object is achieved by a method for influencing noise in accordance with claim 1 and by a system for active noise control having the features of patent claim 10.

Further embodiments of the invention will become apparent from the dependent claims.

The invention provides a method for influencing noise, preferably in the event that a reference variable characterizing the respective noise source exists only in time-spaced samples.

According to the present invention, the time-discrete characteristic reference variable is extrapolated starting from the respective readout times, wherein at least two temporally preceding readout values of the reference quantity are used in an extrapolation model or a readout value of the reference quantity and a change parameter of the reference quantity are used for an extrapolation. That in the inventive method generated reference signal is thus practically time-continuous, but at least with a sampling rate, with which a digital system is operated for noise control. This allows a reliable adaptation of the compensation sound injection by the device for active noise control to the time-varying excitation of the noise source.

In this case, it is essentially understood periodically that the excitation frequency can change during the operation of the noise source, as is the case, for example, with a motor during acceleration or deceleration.

In the method according to the invention and the system according to the invention for influencing noise, the current actual excitation, which is characterized by the reference variable, is always taken into account in the control of the compensation sound injection. The invention therefore enables irradiation of secondary sound or compensation sound with particularly high amplitude and phase accuracy.

The inventive method enables the coupling of a system for active noise control directly to a, for example, in-vehicle data bus, which has only a low repetition rate with respect to the characteristic reference variable. This eliminates the need for an additional measuring sensor for recording the reference size and the corresponding cabling.

The proposed method and system for influencing noise according to the invention is particularly suitable for use in a motor vehicle in which further data for the prediction of the engine speed between readings from the data bus can be taken into account for an improved extrapolation model. The invention can also be easily implemented in programmable digital control devices of the active system for noise control.

Advantageous embodiments and further developments of the invention are subject of the dependent claims and the description with reference to the accompanying figures.

• Fig. 1: eine schematische Darstellung eines erfindungsgemäßen Systems zur Geräuschbeeinflussung in einem Kraftfahrzeug;
• Fig. 2: ein Ablaufdiagramm des erfindungsgemäßen Verfahrens; und
• Fig. 3: ein Diagramm mit Schalldruckpegeln in Abhängigkeit von der Motordrehzahl.

The invention will be described in more detail below with reference to a preferred exemplary embodiment of an adaptive system for influencing noise in a motor vehicle. It shows:

• Fig. 1 : a schematic representation of a system according to the invention for influencing noise in a motor vehicle;
• Fig. 2 a flowchart of the method according to the invention; and
• Fig. 3 : a diagram with sound pressure levels as a function of the engine speed.

In the Fig. 1 an inventive system for influencing noise 1 is shown, which is coupled to a data bus 2 in a motor vehicle.

In the engine compartment M of the motor vehicle, a high-speed CAN-BUS 3 is provided, which serves for networking engine control devices 4, 5. One of the engine control devices, for example, a speed sensor 4, which provides information about the speed of the motor 16 to the high-speed bus 3. Another engine controller 5 reads the engine speed and other vehicle operating data from the high-speed bus 3 and sends corresponding control signals to the engine 16 to the high-speed data bus 3. The engine speed is typically 10 to 20 milliseconds on the high-speed data bus 3.

In the vehicle interior I, in the Fig. 1 is shown on the right side of the dotted line, a low-speed CAN bus 2 is provided, which is coupled via a gateway device 6 to the high-speed CAN bus 3. To the low-speed CAN bus 2, for example, display devices 7 are coupled for speed, speed, tank level or other common monitoring variables or positioners 8 for comfort functions of the vehicle.

On the low-speed CAN bus 2 is the speed information, which is a characteristic reference quantity for the noise source, for example the motor 16, only with a repetition rate of about 100 milliseconds. That is to say at 100 millisecond spaced deployment times are current speed information readable. Furthermore, the signal propagation times between the high-speed CAN bus 3, the gateway 6 and the low-speed CAN bus 2 can result in further delays. The delivery times can thus also be present irregularly spaced.

The system for influencing noise 1 has an extrapolation device 9, which is coupled via suitable data lines 10 to the low-speed CAN bus 2 provided in the vehicle interior. A device for active noise control 11 is also provided, which receives a reference signal 12 generated by the extrapolation device 9. The device for influencing noise 11 supplies control signals 13 to one or more actuators 14, which are shown here by way of example as a loudspeaker 14. Further, a noise sensor or a microphone 15 is coupled to the noise control device 11, which receives the noise or a noise sound emitted from the motor 16 as a noise source in the illustrated example, and the compensation signal outputted from the speaker 15 ,

The noise control device 11 controls the irradiation of the compensation noise by the loudspeaker 14 in response to the reference signal 12 associated with a reference variable characterizing the noise source, such as the engine speed, and the sound level recorded to the microphone, such that interference with the noise radiated secondary or compensation sound a noise change occurs. In this case, the example perceived by an occupant modified sound can be designed so that the sound is perceived as pleasant. In this case, derived from the excitation frequency of the noise source, ie the fundamental frequency, derived higher harmonics can be selectively damped or amplified by secondary noise, so that a desired noise color occurs. It is not only integer harmonic excitations by the secondary sound injection changeable, but any harmonics can be influenced to achieve a respective sound design.

If the engine speed changes as a reference variable, for example during acceleration or deceleration of the vehicle, the noise-influencing device 11 requires a corresponding actual reference signal 12 in real time in order to adapt the compensation sound injection to the changed excitation frequency of the motor 16. At the low-speed CAN bus 2, however, the reference size is only available at certain provision times. Therefore, the extrapolation device 9 according to the invention performs in the Fig. 2 by method steps described in more detail.

The extrapolation device 9 reads out the present engine speed N ₁ in a first step S1 at a first provision time t ₁ , and stores this in a second step S2. The read-out and storage takes place in each case at successive provision times t _i , which are predetermined by the state and the architecture of the respective data bus, for example the low-speed CAN bus 2.

Using an extrapolation model S4, the extrapolation device 9 extrapolates the values of the read-out and stored rotational speeds in step S3 and generates a corresponding reference signal 12, which is output in step S5. In this case, the reference signal 12 is generated in such a way that the respective values of the reference signal 12 approximate the current reference variable between the provision times t _i as well as possible.

A preferred extrapolation model provides for linear extrapolation by means of an excitation frequency / time or motor speed / time gradient. At the time of delivery t _i and t _i-1 , the engine speed values N _i and N _{i-1 are} read out. The time difference between the provision times t _i , t _i-1 is Δt = t _i -t _i-1 . Between these two times t _i , t _i-1 , the engine speed changes by ΔN = N _i -N _i-1 .

Für im Wesentlichen beliebige Zeitpunkte t>t_i lässt sich linear die Drehzahl extrapolieren: $$\mathrm{N}\left(\mathrm{t}>{\mathrm{t}}_{\mathrm{i}}\right)={\mathrm{N}}_{\mathrm{i}}+\stackrel{•}{\mathrm{N}}\left(\mathrm{t}-{\mathrm{t}}_{\mathrm{i}}\right)\mathrm{.}$$

The extrapolation device 9 determines this change in the reference variable or the engine speed and calculates the resulting rotational acceleration to: $\dot{\mathrm{N}}=\frac{\mathrm{.DELTA.N}}{\mathrm{.delta.t}}\mathrm{,}$

For substantially arbitrary times t> t _i , the rotational speed can be extrapolated linearly: $$\mathrm{N}\left(\mathrm{t}>{\mathrm{t}}_{\mathrm{i}}\right)={\mathrm{N}}_{\mathrm{i}}+\stackrel{•}{\mathrm{N}}\left(\mathrm{t}-{\mathrm{t}}_{\mathrm{i}}\right)\mathrm{,}$$

The extrapolation device 9 supplies this estimated engine speed N (t) as a reference signal 12 to the device for influencing noise. The extrapolation device 9 supplies this reference signal 12 with a reference signal rate that corresponds, for example, to the clock rate of the device for influencing noise 11. Usual rates are for example in the order of 1-5 kHz.

In addition to a linear extrapolation, further modified extrapolation methods are possible. For example, several values of the engine speed that have been read out in the past can be taken into account and extrapolation polynomials of higher orders can be used.

A refined modeling of the noise source, in the example of application of the engine described here, can also be done by considering other engine-related parameters, such as the actual load or changes in the engine behavior, which are given by a motor control. In this case, the pedal dynamics of accelerator and / or brake pedal, control signals of an anti-lock brake system or electronic stabilization system or other data can be done. The data required for such models is available through the digital data bus systems in the vehicle.

Further preferably used extrapolation models include self-learning models, ie models in which adjustments are made during operation in the respective extrapolation algorithm, for example by changing extrapolation parameters. During extrapolation, known properties can also be incorporated via the noise source or its control, for example a motor control. For example, motors are often automatically decelerated at certain particularly high speeds. Such knowledge is advantageously taken into account in the extrapolation.

In the prediction of the rotational speed data, the signal propagation time between, for example, the rotational speed sensor 4 via the high-speed CAN bus 3, the gateway 6 and the low-speed data bus 2 is preferably also taken into account. Thus can be achieve a further improvement of the extrapolated engine speed or the values of the reference signal 12 to the actually existing reference size.

In an alternative embodiment of the method according to the invention, the extrapolation of the actual values of the reference variable can also be performed by using a change parameter which characterizes the temporal change of the reference variable and a read value of the reference variable, provided a corresponding change parameter, such as the rotational acceleration Ṅ, on the data bus is readable. In principle, the invention requires only arbitrary time-readable parameters that allow to perform an extrapolation. Possibly, delivery times for a corresponding change parameter and delivery times for the values of the reference size are closer in time to each other than the delivery times for the values of the reference size among each other.

In the Fig. 3 are sound levels using the method and system according to the invention for active noise control and in dependence on an engine speed. The adaptive control in dependence on the generated reference signal is for example in DE 196 32 230 C2 explained in more detail and used in the example considered here, the noise reduction.

The solid line curve A represents the sound pressure level without an active system for influencing noise in a four-cylinder engine on a microphone in a vehicle interior for the ignition frequency, ie twice the engine speed. The engine speed was within 60 seconds from 1000 revolutions per minute to 6000 Raised revolutions per minute.

The dotted curve B represents the sound pressure using an ANC system in which the delivery times for an update of the engine speed are at a time interval of 100 milliseconds and no extrapolation according to the invention has been carried out. That is, the engine speed was assumed constant between the delivery times. Especially at speeds from about 2000 revolutions per minute This rough update, such as the provision rate of a low-speed CAN bus, is no longer sufficient to achieve noise reduction with an ANC system.

The dashed line shows the sound pressure level using the method according to the invention for influencing the noise, wherein a linear extrapolation of the engine speed was performed according to the equation I for generating the reference signal. In this case, the provision times t _i divide each 100 milliseconds. The inventive method or the use of a system according to the invention for noise control significantly improves the active noise reduction over the entire speed range.

The present invention therefore provides a method for reliably influencing noise, in which an active device for influencing noise is provided with accurate information about the actually present excitation frequency of a noise source. Due to the method according to the invention, the system according to the invention provides particularly efficient noise control, although a reference variable characterizing the respective noise source is present only on a random basis.

A particular advantage of the present invention is that no additional sensor must be provided, but that system can be coupled directly to a data bus.

Although the present invention has been explained in more detail with reference to a preferred embodiment, it is not limited thereto, but variously modifiable. The stated delivery rates and data bus protocols are only to be understood as examples. An irregular provision of the reference size is also possible. An irradiation of secondary sound can also take place outside the vehicle interior, for example through loudspeakers in the exhaust system or in the air intake filter.

The invention is not limited to use in a motor vehicle, but may preferably be used whenever there are periodic noise excitations.

This may also be the case, for example, with motor-driven fans, pumps, reciprocating compressors or other devices. Also switching frequencies at certain power electronics, which can be queried in a data bus, can be used as a possible reference size.

Furthermore, the method according to the invention or the extrapolation device and the device for influencing noise can be implemented completely computer-implemented. In this respect, for example, a programmable microcontroller device is conceivable which carries out the method according to the invention in the programmed state.

Although the invention has been described using the example of vibration in-couplings in air as a fluid medium, an application to change structure-borne noise is also possible.

LIST OF REFERENCE NUMBERS

1

System for active noise control

2

Niedriggeschwindigkeitsdatenbus

3

high speed data

4

Speed sensor

5

motor control

6

gateway

7

display

8th

Deputy controller

9

extrapolation

10

data line

11

Device for active noise control

12

reference signal

13

control signals

14

actuator

15

microphone

16

engine

Claims (19)

1. Method for influencing noise, wherein a noise source (16), in particular an engine in a motor vehicle, generates the noise by means of an essentially periodically changeable excitation, and wherein a reference variable that is characteristic of the noise source, in particular an engine rotational speed, is present at predetermined successive supply instants (t_i), said method having the following steps:

   - reading out at least one first value (N_i-1) of the reference variable at a first supply instant (t_i-1) and a second predetermined value at a second supply instant (t_i),

   characterised by means of

   - generating the reference signal (12) at at least one instant (t) between the second supply instant (t_i) and a third supply instant (t_i+1) in dependence upon the first and second values that are read out, and

   - supplying the reference signal (12) to a device for actively influencing noise (11) and said device generates control signals (13) for at least one actuator (14) in dependence upon the reference signal (12), wherein the at least one actuator (14) emits a compensating sound that interferes with the noise.
2. Method according to claim 1,
   characterised in that
   a change parameter (N) of the reference variable or a second value (N_i) of the reference variable is read out as the second predetermined value and the reference signal (12) is extrapolated in dependence upon the first value (N_i-1) of the reference variable and the second value.
3. Method according to claim 1,
   characterised in that
   the following step is provided as a further method step:

   determining the change (ΔN) of the reference variable between the first (t_i-1) and the second supply instant (t_i),

   wherein the reference signal (12) is extrapolated in dependence upon the value (N_i) of the reference variable that is read out at the second supply instant (t_i) and in dependence upon the change (ΔN) of the reference variable.
4. Method according to any one of the preceding claims,
   characterised in that
   linear extrapolation is performed.
5. Method according to any one of the preceding claims
   characterised in that
   in addition, the reference signal (12) is extrapolated in dependence upon further values of the reference variable at further supply instants.
6. Method according to any one of the preceding claims,
   characterised in that
   in addition, the reference signal (12) is extrapolated in dependence upon further characteristic variables for the noise source.
7. Method according to any one of the preceding claims,
   characterised in that
   the reference variable is an engine rotational speed or an excitation frequency, in particular of an engine.
8. Method according to any one of the preceding claims,
   characterised in that
   a delay time between an instant when the reference variable is changed and a respective supply instant, in particular as a result of signal propagation delays between a measuring sensor (4) and a data bus (2) that supplies the reference variable, is taken into account for the extrapolation.
9. Method according to any one of the preceding claims,
   characterised in that
   the compensating sound is emitted in such a manner that harmonics of the noise source (16) are at least in part amplified and/or attenuated, said harmonics being derived from the periodic excitation.
10. System for actively influencing noise (1), in particular in a motor vehicle, for changing noise that is generated by a noise source (16), in particular an engine, having an essentially periodically changeable excitation frequency, having a device (11) for actively influencing noise, said device generating control signals (13) for at least one actuator (14) in dependence upon a reference signal (12), wherein the at least one actuator (14) emits compensation noise that interferes with the noise,
    characterised by means of
    a data bus (2) at which a reference variable that characterises the respective excitation frequency of the noise source (16) can be read out at predetermined supply instants (t_i), and
    an extrapolating device (9) that is coupled to the data bus (2), said device generating at a reference signal rate the reference signal (12) that is allocated to the reference variable, wherein respective values of the reference signal (12) extrapolate the reference variable between the supply instants (t_i).
11. System (1) according to claim 10,
    characterised in that
    in addition, a change parameter (N) of the reference variable can be read out at the data bus (2), wherein the extrapolating device (9) extrapolates the reference variable in dependence upon at least one read out value (N_i) of the reference variable and the change parameter (N).
12. System (1) according to claim 10 or 11,
    characterised in that
    the extrapolating device (9) is configured in such a manner that said device implements a method according to at least one of the claims 1 - 9.
13. System (1) according to claims 10 to 12,
    characterised in that
    in addition, when generating the reference signal, signal propagation delays as a result of reading out the reference variable and/or a delay as a result of supplying the reference variable on the data bus (2) are taken into account.
14. System (1) according to any one of the claims 10 to 13, characterised in that
    the data bus (2) is embodied as a CAN bus in particular in a vehicle.
15. System (1) according to any one of the claims 10 to 14,
    characterised in that
    the extrapolating device (9) and/or the device for actively influencing noise (11) is/are embodied as a digital signal processing device or digital signal processing devices.
16. System (1) as claimed in any one of the claims 10 to 15,
    characterised in that
    the device for actively influencing noise (11) generates the control signals in such a manner that harmonics of the noise source (16) are at least in part amplified and/or attenuated by means of the compensating sound, said harmonics being derived from the periodic vibrating excitation.
17. Use of a system for actively influencing noise (1) according to any one of the claims 10 to 16 in a motor vehicle, wherein the noise source is an engine, the reference variable is an engine rotational speed, and the data bus (2, 3, 6) is embodied as a CAN bus for an engine control unit (5) and for monitoring an engine state.
18. Use as claimed in claim 17,
    characterised in that
    data for the engine control unit (5), in particular acceleration values, pedal positions, pedal movements and/or switching parameters are used as further variables that characterise the noise source.
19. Use as claimed in claim 17 or 18,
    characterised in that in the motor vehicle a first high speed CAN bus (3) that is provided in an engine compartment and a second low speed CAN bus (2) that is provided in a passenger compartment are provided, wherein the reference variable and/or the further variables that characterise the noise source are read out from the low speed CAN bus (2).

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