JP3517886B2 - Active noise control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise control device for reducing noise by causing a control sound generated from a control sound source to interfere with noise transmitted from a noise source,
In particular, an active type that convolves a reference signal representing a noise generation state and an adaptive digital filter to generate a drive signal for a control sound source and updates the filter coefficient of the adaptive digital filter in a direction to reduce noise in space The noise control device is capable of performing stable control even in a situation where the acoustic transfer characteristics in the space have changed from the initial state.

[0002]

2. Description of the Related Art Conventional active noise control devices include those described in British Patent No. 2149614 and Japanese Patent Publication No. 1-501344. These conventional devices are noise reduction devices applied to aircraft cabins and similar closed spaces, and a single noise source such as an engine located outside the closed space has a fundamental frequency f ₀ and its harmonics. It operates under the condition that noise including the waves f _{1 to} f _n is generated.

[0003] More specifically, includes a microphone for detecting a plurality of the installed sound pressure to a location within the closed space, and a plurality of loudspeakers for generating a control sound to the closed space, the frequency f ₀ of the noise source - Based on the f _n component, those frequencies f ₀ ~
The loudspeaker is driven by a signal having a phase opposite to that of the f _n component,
Therefore, a control sound having a phase opposite to that of the noise transmitted to the closed space is generated from the loudspeaker to cancel the noise.

Then, as a method of generating the control sound emitted from the loudspeaker, PROCEEDINGS OF THE IEEE, VOL.
63 PAGE 1692,1975, “ADAPTIVE NOISE CANSELLATION:
PRINCIPLES AND APPLICATIONS ”
An algorithm that applies the DROW LMS 'algorithm to multiple channels is applied. The content of the paper is "A MULTIPLE ERROR LMS ALGORITHM AND
ITS APPLICATION TOTHE ACTIVE CONTROL OF SOUND AND
VIBRATION ”, IEEE TRANS.ACOUST., SPEECH, SIGNAL PRO
CESSING, VOL.ASSP −35, PP. 1423−1434, 1987.

That is, the LMS algorithm is one of the algorithms suitable for updating the filter coefficient of the adaptive digital filter, and is, for example, a so-called Filter.
In the ed-X LMS algorithm, a transfer function filter that models the transfer function from the loudspeaker to the microphone is set for all combinations of the loudspeaker and the microphone, and a reference signal representing the noise generation state of the noise source is set. The filter coefficient of the variable filter digital filter provided for each loudspeaker is updated so that the value of the predetermined evaluation function based on the value processed by the filter and the residual noise detected by each microphone is reduced. ing.

[0006]

However, in the above-mentioned conventional apparatus, for example, the environment of the control space such as temperature and atmospheric pressure, the deterioration of the acoustic equipment such as the loudspeaker and the microphone, etc. If the acoustic transfer characteristics fluctuate from the initial state, the accuracy of the transfer function filter that represents the transfer function from the loudspeaker to the microphone will be relatively reduced. If the filter coefficient of is updated, control may diverge in some cases. In addition, such a problem may occur when an unnecessary DC component is included in the reference signal indicating the noise generation state, the residual noise detected by the microphone, or the like.

As a measure to deal with such a defect,
A plurality of transfer function filters are set in advance in accordance with conditions such as the temperature of the control space, atmospheric pressure, the number of people in the space,
A method of switching the transfer function filter to be used according to changes in those conditions, or a method of performing noise reduction control while sequentially identifying the transfer function filters is also conceivable. Since it is practically impossible to set the transfer function filter in view of the storage capacity and the like, the effect is naturally limited. Further, in the latter method, the control content becomes complicated and the cost is increased. Further, there is a possibility that the control cannot be completed in a space where the situation changes relatively frequently, such as a vehicle passenger compartment.

The present invention has been made by paying attention to the unsolved problem of such a conventional device, and active noise capable of stable control without causing a large complication of control. The purpose is to provide a control device.

[0009]

In order to achieve the above object, the invention according to claim 1 is a control sound source capable of generating a control sound in a space where noise is transmitted from the noise source, and noise of the noise source. Reference signal generating means for generating a reference signal representing the generation state, residual noise detecting means for detecting residual noise at a predetermined position in the space, adaptive digital filter with variable filter coefficient, and a direction for reducing the residual noise. An adaptive processing means for updating the filter coefficient of the adaptive digital filter; and a drive signal generating means for convolving the value of the adaptive digital filter and the reference signal to generate a signal for driving the control sound source, In the adaptive processing means, the value of the filter coefficient to be updated is the value of another filter coefficient.
The filter to update if it stands out compared to
The value of the coefficient changes so as to approach the values of other filter coefficients.
The that stabilization control factor, is multiplied by the filter coefficient before updating
The filter coefficient is updated based on the update formula captured in the form .

In order to achieve the above object, the invention according to claim 2 provides a control sound from a noise source to a space where the noise is transmitted.
The control sound source that can be generated and the noise generation state of the noise source are displayed.
A reference signal generating means for generating a reference signal, and
Noise detection hand that detects residual noise at a predetermined position
Stage, an adaptive digital filter with variable filter coefficient,
In order to reduce the residual noise, the adaptive digital filter is used.
An adaptive processing means for updating the filter coefficient of the
Convolution of the value of the adaptive digital filter and the reference signal
Drive signal generation for generating a signal for driving the control sound source
Means for updating the adaptive processing means,
The value of the filter coefficient is
If the value of the filter coefficient to be updated is
Control stabilization coefficient that changes toward the value of the
To the value of the product of the signal driving the control source and the reference signal
The filter based on the update formula captured in the twisted form
To update the coefficients.

[0011] Then, the invention of claim 3, wherein, in the invention described in claim 1 or claim 2 wherein the reference signal generation hands
The stage uses a reference signal consisting of an impulse train with the same period as noise.
You generate.

Further, in the invention described in claim 4, in the invention described in any one of claims 1 to 3 , the control stabilization coefficient is an absolute value of a filter coefficient value to be updated and a filter coefficient included in the adaptive digital filter. It changes according to the ratio with the sum of the values.

[0013]

According to the present invention, the drive signal generating means generates a signal for driving the control sound source by convolving the adaptive digital filter and the reference signal. Therefore, the control sound source produces noise generated by the noise source. A control sound with a correlation is generated,
Immediately after the start of control, the filter coefficient of the adaptive digital filter does not always converge to the optimum value, so it cannot be said that noise in the space is necessarily reduced.

However, since the adaptive processing means updates the filter coefficient of the adaptive digital filter so as to reduce the residual noise, the filter coefficient gradually converges to the optimum value, and the noise is canceled by the control sound emitted from the control sound source. Noise in the space is reduced. Since the control coefficient that is variable according to the value of the filter coefficient to be updated is incorporated in the update equation of the filter coefficient of the adaptive digital filter in the adaptive processing means, the value of the filter coefficient is used for its own update calculation. Since it is fed back, it is possible to suppress it when the value of the filter coefficient behaves so that the control diverges by appropriately selecting the way to incorporate the control stabilization coefficient into the update formula. become.

[0015]

For example , in the invention according to claim 1 ,
Since the filter coefficient before updating is multiplied by the control stabilizing coefficient, the value of the filter coefficient before updating is adjusted by the control stabilizing coefficient and then taken into the update formula. On the other hand, in the invention of claim 2 , since the value of the product of the signal for driving the control sound source and the reference signal is multiplied by the control stabilization coefficient, the value of the signal for actually driving the control sound source is the control stability. It will be adjusted by the conversion factor and then incorporated into the update formula.

Here, it can be determined that the control is likely to diverge when the value of one of the filter coefficients of the adaptive digital filter is larger than the values of the other filter coefficients. Therefore, as in the invention of claim 1, wherein, when the value of the updated filter coefficient is projected as compared to the value of another filter coefficient value of the filter coefficients to the update of other filter coefficients When the control stabilization coefficient changes in the direction of approaching the value, the situation where the value of the updated filter coefficient is more prominent than other filter coefficients is mitigated, and the divergence of control is suppressed.

According to the invention of claim 3, the standard
Since the signal is an impulse train with the same period as noise,
An adaptive signal for the individual impulses that form the reference signal.
Since the response of the digital filter is an impulse response,
Matches the filter coefficient of the adaptive digital filter of.
Therefore, the drive signal generation means does not perform integration.
However, convolution operation can be performed. In the invention according to claim 4 , the ratio of the value of the filter coefficient to be updated and the sum of the absolute values of the filter coefficients included in the adaptive digital filter is such that the value of the updated filter coefficient is another filter coefficient. The value of the filter coefficient to be updated is more prominent than other filter coefficients when the control stabilization coefficient changes according to the ratio because it represents the size compared to the value of Is alleviated and the divergence of control is suppressed.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a first embodiment of the present invention, which is an active system for reducing muffled noise transmitted from an engine 4 as a noise source into a vehicle interior 6 as a space. The present invention is applied to the mold noise control device 1.

First, the structure will be described. The vehicle body 3 is supported by front wheels 2a, 2b, rear wheels 2c, 2d and suspensions interposed between the wheels 2a to 2d and the vehicle body 3. The vehicle shown in FIG. 1 is a so-called front-mounted engine front-wheel drive vehicle in which the front wheels 2a and 2b are rotationally driven by an engine 4 arranged in the front part of the vehicle body 3. A crank angle sensor 5 as a reference signal generating means is attached to the engine 4, and the crank angle sensor 5 is
A reference signal x representing the rotation of the crank of the engine 4 is supplied to the controller 10.

Loudspeakers 7a, 7b, 7c and 7d as control sound sources are provided in the vehicle interior 6 of the vehicle body 3.
The front seats S ₁ and S ₂ and the rear seats S ₃ and S ₄ are arranged at door portions facing each other. Furthermore, each seat S
₁ head restraint position of the to S ₄ is a microphone 8a~8h as residual noise detecting means, have been respectively disposed two by two, the residual noise signal e ₁ to e these microphones 8a~8h was measured as a sound pressure ₈ is supplied to the controller 10.

Then, the controller 10 executes the arithmetic processing described later based on the reference signal x supplied from the crank angle sensor 5 and the residual noise signals e _{1 to} e ₈ supplied from the microphones 8a to 8h. The drive signals y _{1 to} y ₄ are output to the loudspeakers 7a to 7d so that the loudspeakers 7a to 7d generate a control sound for canceling the muffled sound transmitted to the vehicle interior 6.

The controller 10, as shown in FIG.
An A / D converter 11 for converting the reference signal x supplied from the crank angle sensor 5 into a digital value, and a digital filter 12 to which the reference signal x converted into a digital value by the A / D converter 11 is input. , An adaptive digital filter 1 with a variable filter coefficient to which the reference signal x is also input
3 and the residual noise signal e ₁ supplied from the microphones 8a to 8h and amplified by the amplifiers 14a to 14h.
A / D converter for converting a to e ₈ into a digital value 15a~
15h and the processed signal r _lm filtered by the digital filter 12 and the residual noise signals e _{1 to} e ₈ converted into digital values by the A / D converters 15a to 15h are subjected to predetermined arithmetic processing. a microprocessor 16 for updating a filter coefficient of the adaptive digital filter 13, a drive signal y ₁ ~y ₄ output from the adaptive digital filter 13 to the amplifier 18a~18d driving the loudspeaker 7a~7d to an analog value And D / A converters 17a to 17d for supplying the power.

Here, the digital filter 12 is a digital filter C _lm (l = 1, 2, ...) Which models the transfer function between the loudspeakers 7a-7d and the microphones 8a-8h in the form of a finite impulse response function. , L, m
= 1, 2, ..., M), M (in this embodiment, M = 4)
Loudspeakers 7a to 7d and L (in this embodiment,
L = 8) have for all combinations of microphones 8a~8h of (L × M), the reference signal x and generates a value r _lm obtained by filtering with their digital filter C _lm output.

On the other hand, the adaptive digital filter 13 has M adaptive filter filters W _m having variable filter coefficients corresponding to the number of loudspeakers 7a to 7d, and the reference signal x is adapted to the adaptive digital filter W _m. The drive signals y _{1 to} y ₄ are generated and output by performing the filtering process with. Then, the microprocessor 16 receives the processed signal r _lm supplied from the digital filter 12,
According to the residual noise signals e _{1 to} e ₈ supplied from the microphones 8a to 8h, the filter coefficient of each adaptive digital filter W _m of the adaptive digital filter 13 is set to LM.
Update based on S algorithm.

Here, the LMS algorithm is one of the algorithms suitable for updating the filter coefficient of the adaptive digital filter, and is the l-th (l = 1, 2, ...,).
L: L = 8) the residual noise signal detected by the microphone is e _l (n), the residual noise signal detected by the l-th microphone when no control sound is generated from the loudspeaker is e _l (n), m-th (m = 1, 2, ..., M: M =
J-th digital filter C _lm of the transfer function between the loudspeaker and the l-th microphone modeled in the form of a finite impulse response function 4) (j = 0,1,2,
, I _C −1: I _C is a constant), and the filter coefficient is C _lmj ,
X (n) is the reference signal, and m is the reference signal x (n)
The i-th (i = 0, 1, 2, ..., I _K −1: I _{K of} the adaptive digital filter W _m for driving the th loudspeaker
Is a constant) and the filter coefficient is W _mi , Is established.

The terms with (n) are all sumps.
Represents the sampled value at ring time n, and I_CIs
Filter C_lmNumber of taps (filter order), I_KIs adapted
Digital filter W_mBy the number of taps (filter order)
is there. In the above formula (1), “ΣW” on the right side_mix (n-j-
i) ”is the reference signal x to the adaptive digital filter.
Output y when (n) is input_m(N) is represented by “ΣC
_lmj{ΣW_mix (n-j-i)} ”is the m-th Lau
Signal y input to the speaker _m(N) controls from there
Transfer function C is output to the space as sound_lmThrough the l-th
It shows the signal when it reaches the icrophone, and
ΣC_lmj{ΣW_mix (n−j−i)} ”is the l-th term
Is the signal reaching the microphone added up?
The sum of control sounds reaching the l-th microphone
It represents.

Then, the evaluation function Je is And

The LMS algorithm finds the filter coefficient W _mi that minimizes the evaluation function Je. Specifically, the filter coefficient W _{mi is} a value obtained by partially differentiating the evaluation function Je with respect to each filter coefficient W _mi. To update. Therefore, from equation (2) above, From equation (1) above, Therefore, if the right side of the equation (4) is set to r _lm (n−i), the filter coefficient is updated by the following equation (5).

[0030] Here, α is a coefficient called a convergence coefficient, and is a coefficient related to the speed at which the filter converges optimally and its stability.

In the present embodiment, the above (5)
Instead of using the equation as it is, based on the following equation (6) in which the control stabilizing coefficient γ _mi is incorporated into this equation (5),
The filter coefficient W _mi of the adaptive digital filter W _m is updated. That is, the control stabilization coefficient γ _mi is a coefficient set within the range of 0 ≦ γ _mi ≦ 1, and is set to a relatively small value when control is unstable and divergence is likely to occur. Is
While functioning to pull back the filter coefficient W _mi in the direction of the origin, it is set to a value close to 1 so that the convergence of the filter coefficient W _mi is not hindered when the control is stable.

In this embodiment, the control stabilization coefficient γ
_mi is set according to the following equation (7). That is, the control stabilization coefficient γ _mi is the value of the filter coefficient to be updated “| W _mi |” and its adaptive digital filter W _m.
Sum of absolute values of each filter coefficient W _mi included in
_mi | ratio of the "" _{| W mi | / Σ | W} mi | "is set on the basis of.

Here, in this embodiment, the digital filter 12, the microprocessor 16 and step 0 described later are used.
Adaptive processing means is configured by the processing of 01 to 004,
The drive signal generating means is configured by the processing of step 005 described later. Next, the operation of this embodiment will be described. Figure 3
3 is a flowchart showing an outline of processing executed in the controller 10.

First, in step 001, the reference signal x
And the residual noise signals e _{1 to} e ₈ are read, and then the process proceeds to step 002, where the reference signal x and the digital filter C are read.
_The processed signal r _lm is calculated by _convolving with _lm . Then, the process proceeds to step 003, and the control stabilization coefficient γ _mi is calculated for each filter coefficient W _mi according to the above equation (7).

Then, the process proceeds to step 004, and the filter coefficient W _mi of the adaptive digital filter W _m is updated according to the above equation (6). When the processing of steps 001 to 004 is completed, the process proceeds to step 005, and the reference signal x and the adaptive digital filter W _m are convoluted to generate the drive signal y ₁
.About.y ₄ are calculated, and these drive signals y _{1 to} y ₄ are output to the loudspeakers 7a to 7d in step 006.

[0036] Then, the control sound into the passenger compartment 6 from loudspeakers 7a~7d occurs immediately after start of control is not necessarily the filter coefficient W _mi of the adaptive digital filter W _m is converged to an optimum value Therefore, it cannot be said that the muffled sound transmitted to the vehicle interior 6 is necessarily reduced. However, as a result of repeatedly executing the processing of steps 001 to 006, each filter coefficient W _mi converges toward the optimum value, and the muffled sound transmitted into the vehicle interior 6 is transmitted to the loudspeaker 7.
It is canceled by the control sounds emitted from a to 7d, and the noise in the vehicle interior 6 is reduced.

Further, in the present embodiment, the control stabilization coefficient γ _mi calculated in step 003 is multiplied by the filter coefficient W _mi before updating, as shown in the above equation (6). Although it is incorporated in the update formula, (7) above
The control stabilization coefficient γ _mi calculated according to the formula is the value of the filter coefficient to be updated when the value of the filter coefficient to be updated is more prominent than the value of the other filter coefficient. Since it changes so as to approach, it is possible to prevent the filter coefficient from protruding, and it is possible to stabilize the control.

More specifically, for example, the filter coefficients W _m0 and W _m of the adaptive digital filter W _m having four taps, for example.
_m1 , W _m2 and W _m3 are W _m0 = 0.1, W _m1 = 0.5, W _m2 = 9 and W _m3 = 0.4 respectively, and as shown in FIG. Coefficient W _m2
It is assumed that the value of is much more prominent than the values of the other filter coefficients and tends to diverge.

Then, each filter coefficient W _m0 , W _m1 , W _m2
And the values of and W _m3, absolute value sum sigma of their filter coefficients W _m0 ~W _m3 | W _mi | ratio of, _{respectively, | W m0 | / Σ |} W mi | = 0.01 | W m1 | / Σ | W _mi | = 0.05 | W _m2 | / Σ | W _mi | = 0.9 | W _m3 | / Σ | W _mi | = 0.04 Therefore, in this case, the coefficient ζ = 0 if .1, each filter coefficient W _m0, W _m1, W _m2 and W _m3 the per (7) stabilization control is set in accordance with equation coefficients γ _m0, γ _m1, γ _m2 and gamma _m3 is, gamma _m0 = 0.999, γ _m1 = 0.995, γ _m2 = 0.
91, γ _m3 = 0.996, and the control stabilization coefficient γ _{m2 of the} third diverging filter coefficient W _m2 takes a small value.

Then, these control stabilization coefficients γ _m0 ,
γ _m1 , γ _m2 and γ _m3 are filter coefficients W _m0 and W, respectively.
_{If m1} , W _m2, and W _m3 are multiplied and taken into the updating equation (6), the third filter coefficient W _m2 is set to a small value. In other words, with the configuration of the present embodiment, it is possible to prevent the filter coefficient W _mi , which tends to diverge, from becoming extremely protruding and becoming large. Therefore, for example, the loudspeakers 7a to 7d and the microphone 8a
Even if the accuracy of the digital filter C _lm built in the controller 10 is relatively lowered due to a change in the acoustic transfer characteristic between 8 h and 8 h, stable control can be performed.

Moreover, since the control stabilization coefficient γ _mi is set according to each filter coefficient W _mi , the value of the filter coefficient is remarkably large as described above with respect to the filter coefficient tending to diverge. On the other hand, for the normal filter coefficient that does not tend to diverge, the control stabilization coefficient γ _mi becomes a value close to 1, so that it does not hinder the convergence of the filter coefficient to be updated, resulting in good noise reduction. You can control.

FIG. 5 is a diagram showing a second embodiment of the present invention, and like the first embodiment, the present invention is applied to an active noise control device for reducing the muffled noise transmitted to the passenger compartment. It is applied. The basic configuration and processing contents are the same as those in the first embodiment. That is, in the second embodiment, the output of the crank angle sensor 5 is not used as it is as the reference signal, but the output of the crank angle sensor 5 is passed through the A / D converter 11 in the controller 10 to the impulse generator 20. Then, the impulse generator 20 becomes an impulse having the same period as the muffled noise generated in the engine 4 (for example, in the case of a reciprocating four-cylinder engine, one impulse is generated every half rotation of the crank). The impulse train is generated and output as the reference signal x.

That is, the reference signal x is And the drive signal y _m (n) is Becomes Note that N is the number of points in the sampling cycle included in one cycle of noise. And the function δ (n)
Is δ (n) = 0; n ≠ 0 δ (0) = 1, so that the convolution operation of the above equation (9) does not substantially require integration, and if I _K = N , No addition is required, so that y _m (n) = W _mk (10) in the end, and the filter coefficient W _mi of the adaptive digital filter W _m is output as a drive signal in order in synchronization with the sampling clock. It will be done.

Similarly, the processed signal r obtained by convolving the digital filter C _lm and the reference signal x.
_lm also And the filter coefficient C of each digital filter C _lm
The convolution operation can be performed simply by adding _lmj as needed.

That is, assuming that the reference signal x is an impulse train having the same period as noise as in the present embodiment, the convolution operation of the reference signal x and the adaptive digital filter W _m and the convolution of the reference signal x and the digital filter C _lm are performed. There are advantages that the calculation is simplified and the processing speed is increased. Further, even in this embodiment, as in the first embodiment,
The control stabilization coefficient γ _mi is set for each filter coefficient W _mi , and the filter coefficient W _mi is updated in accordance with the update equation shown in the above equation (6) that incorporates the control stabilization coefficient γ _mi . However, the control stabilization coefficient γ _mi is set according to the process shown in FIG. 6 instead of the setting method of the first embodiment shown by the equation (7).

That is, the process shown in FIG. 6 corresponds to step 003 of FIG. 3 showing the outline of the process of the entire controller 10. First, at step 101, all control stabilizing coefficients γ _mi are initialized. Set the value to 0. Then, the process proceeds to step 102 and the residual noise signals e _{1 to} e
_It is determined whether the total sum of ₈ is smaller than a threshold value e _TH that can predict the divergence from the sound pressure of the residual noise.
In the case of “ES”, it can be determined that the residual noise in the vehicle compartment does not tend to diverge, and therefore the processes of steps 103 to 108 are executed.

That is, first, at step 103, the variable i is cleared, then the routine proceeds to step 104, where a predetermined update amount Δγ is added to the current control stabilization coefficient γ _mi to add a new control stabilization coefficient γ _mi. Is calculated. Then, in order to suppress the maximum value of the control stabilization coefficient gamma _mi to 1, when the stabilization control coefficient gamma _mi is determined to exceed 1 in step 105, the control stabilization coefficient gamma _mi in step 106 Is set to 1.

When the control stabilization coefficient γ _mi is set in step 104 or 106, the variable i is incremented in step 107, and the variable i reaches the tap number I _k of the adaptive digital filter W _{m in} step 108. Until the determination is made, the processes of steps 104 to 106 are executed. That is, the processing of steps 104 to 106 is i = 0 to
If sequentially executed within the range of I _K -1, all control stabilizing coefficients γ _mi will be updated.

Since the processes in steps 103 to 108 are repeatedly executed unless the residual noise has a diverging tendency, each control stabilizing coefficient γ _mi settles at 1 or a value close to it. On the other hand, if the determination in step 102 is “NO”, it can be determined from the residual noise that the control tends to diverge, and therefore the processes in steps 109 to 114 are executed.

That is, after the variable i is cleared in step 109, the process proceeds to step 110, and it is determined whether or not the update amount ΔW _mi of the filter coefficient W _mi is larger than the threshold value ΔW _TH. Is “NO”, it is determined that the filter coefficient W _mi does not particularly tend to diverge, and step 11
Move to 3. However, if the determination in step 110 is “YES”, it is determined that the filter coefficient W _mi tends to diverge, and the process proceeds to step 111, where the current control stabilization coefficient γ _{mi is changed} to the predetermined update amount. A new control stabilizing coefficient γ _mi is calculated by subtracting Δγ. Then, the process proceeds to step 112, and it is determined whether or not the new control stabilization coefficient γ _mi is smaller than 0. If this determination is “NO”, the process proceeds to step 113.

In step 113, the variable i is incremented, and the processes of steps 110 to 112 are executed until it is determined in step 114 that the number of taps I _k of the adaptive digital filter W _m has been reached. That is, the processing of steps 110 to 112 is performed with i = 0 to I _K −1.
If sequentially executed within the range of, the processing of steps 110 to 112 is executed for all the control stabilization coefficients γ _mi ,
Only the control stabilization coefficient γ _mi corresponding to the filter coefficient W _mi whose update amount ΔW _mi is determined to be larger than the threshold value ΔW _{TH in} step 110 is updated in step 111, and the processing of steps 110 to 112 is performed. Is step 10
Since the second determination is repeatedly executed as long as a "NO", so that the stabilization control coefficient gamma _mi corresponding to the filter coefficient W _mi in divergent gradually becomes smaller.

In step 112, the control stabilization coefficient γ
When it is determined that _mi is smaller than 0, it is determined that the divergence cannot be suppressed, and the processing of the controller 10 is stopped. Then, the controller 10 incorporates the control stabilization coefficient γ _mi newly set in step 103, 105, or 111 into the update equation of the above equation (6), updates the filter coefficient W _mi, and outputs the drive signal y _m.
Is calculated and is output to each of the loudspeakers 7a to 7d.

Thus, even with the configuration of this embodiment,
As a result of executing the processing shown in FIG. 6 and appropriately setting the control stabilization coefficient γ _mi , it is possible to prevent the filter coefficient W _mi , which tends to diverge, from becoming extremely prominent and large, as in the first embodiment. In addition, since the control stabilization coefficient γ _mi is set for each filter coefficient W _mi , it is possible to obtain the same effect as that of the first embodiment.

Here, in the present embodiment, the crank angle sensor 5 and the impulse generator 20 constitute a reference signal generating means. Next, a third embodiment of the present invention will be described. That is, the third embodiment is intended to reduce the muffled sound in the passenger compartment by the same configuration and processing contents as those of the first embodiment, but the evaluation function J expressed by the above equation (2) is used.
Let e be the following expression (12).

[0055] Then, the updating formula of the filter coefficient W _mi for minimizing the evaluation function Je is as the following formula (13) based on the LMS algorithm.

[0056] Here, γ _m is a control stabilizing coefficient, and in this embodiment as well, it is set for each filter coefficient W _mi by the same processing as in the first or second embodiment. Therefore, the above equation (13) becomes the following equation (14).

[0057] That is, in the present embodiment, the control stabilization coefficient γ _mi is
The value is multiplied by the value of the product of the signal y _m for driving the loudspeakers 7a to 7d and the reference signal x, and is incorporated in the update formula of the filter coefficient W _mi .

However, in this embodiment, as can be seen from the above equation (14), the sign of the term including the control stabilizing coefficient γ _mi is negative, so this control stabilizing coefficient γ _mi is Contrary to the embodiment or the second embodiment, it is 1 when there is a tendency to diverge.
Is set to a value close to, and 0 when stable control is being performed.
It should be close to. As a result, even in the present embodiment, it is possible to prevent the filter coefficient W _mi , which tends to diverge, from extremely protruding and become large, and for normal filter coefficients that do not tend to diverge, The control stabilization coefficient γ _mi has a value close to 0 and does not hinder the convergence of the filter coefficient, so that the same operational effect as that of the first embodiment is exhibited.

Also in this embodiment, if the reference signal x is an impulse train having the same period as noise as in the second embodiment, the convolution operation is simplified and the processing speed is increased. Become. In each of the above embodiments, the case where the active noise control device according to the present invention is applied to a vehicle active noise control device for reducing muffled noise transmitted to the interior of a vehicle has been described. The object of application of the invention is not limited to this. For example, a pickup signal of suspension vibration correlated with road noise,
Pickup signal of wind noise near door mirrors,
Pickup signals for the case vibration of differential gears and transmission gears (signals that correlate with noise caused by case vibrations of the drive force transmission system), pulse signals according to rotation of the output shaft of the vehicle speed measurement transmission (differential gears and transmissions It is also possible to provide a device for reducing each of these noises by adopting a configuration in which a signal having a correlation with noise due to the meshing of the above) is detected. Further, the application target of the present invention is not limited to the vehicle.

In the above embodiment, four loudspeakers 7a to 7d as control sound sources and eight microphones 8a to 8h as residual noise detecting means are provided, but the number of them is arbitrary.

[0061]

As described above, according to the present invention,
Since the control coefficient that is variable according to the value of the filter coefficient to be updated is incorporated in the filter coefficient update formula of the adaptive digital filter, it is possible to prevent the filter coefficient, which tends to diverge, from becoming extremely prominent and large. , Therefore,
For example, even if the accuracy of the adaptive processing means is relatively reduced due to a change in the acoustic transfer characteristic between the control sound source and the residual noise detecting means, stable control can be performed, and a normal filter that does not tend to diverge. Since the control stabilization coefficient does not particularly affect the coefficient, it is possible to obtain an effect that good noise reduction control can be performed without hindering the convergence of the filter coefficient to be updated.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a first embodiment.

FIG. 2 is a block diagram showing a functional configuration of a controller.

FIG. 3 is a flowchart showing an outline of processing executed in a controller.

FIG. 4 is a diagram illustrating an example of a state of filter coefficients when there is a diverging tendency.

FIG. 5 is a block diagram showing a main part of the configuration of the second embodiment.

FIG. 6 is a flowchart showing a procedure for setting a control stabilization coefficient according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Active noise control device 4 Engine (noise source) 5 Crank angle sensor (reference signal generation means) 6 Vehicle compartment (space) 7a to 7d Loudspeaker (control sound source) 8a to 8h Microphone (residual noise detection means) 10 Controller 12 Digital filter 13 Adaptive digital filter 16 Microprocessor 20 Impulse generator W _m Adaptive digital filter W _mi Filter coefficient of adaptive digital filter γ _mi Control stabilization coefficient x Reference signal y _m Drive signal e _l Residual noise signal

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiharu Nakaji 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Tsutomu Hamabe 2 Takaracho, Kanagawa-ku, Yokohama, Nissan Nissan Motor Co., Ltd. (56) References JP-A 61-116434 (JP, A) JP-A 4-203406 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G10K 11/178 B60R 11 / 02 H03H 17/00-21/00

Claims (4)

(57) [Claims] 1. A control sound source capable of generating a control sound in a space where noise is transmitted from a noise source, reference signal generating means for generating a reference signal indicating a noise generation state of the noise source, and a predetermined inside the space. A residual noise detecting means for detecting residual noise at a position; an adaptive digital filter with a variable filter coefficient; an adaptive processing means for updating the filter coefficient of the adaptive digital filter in a direction in which the residual noise is reduced; Drive signal generating means for generating a signal for driving the control sound source by convolving a value and the reference signal, and the adaptive processing means has another value of a filter coefficient to be updated .
If it is outstanding compared to the value of the filter coefficient,
The value of the filter coefficient to be updated is close to the values of other filter coefficients.
The stabilization control coefficient that varies brute direction, before updating fill
An active noise control device, characterized in that the filter coefficient is updated based on an update equation taken in a form of being multiplied by a filter coefficient. 2. Control to a space where noise is transmitted from a noise source
Control sound source that can generate sound and noise generation state of the noise source
A reference signal generating means for generating a reference signal representing
Residual noise detection to detect residual noise at a predetermined position in the room
Output means and adaptive digital filter with variable filter coefficient
And the adaptive digital signal in the direction of reducing the residual noise.
An adaptive processing means for updating the filter coefficient of the filter;
The value of the adaptive digital filter is convolved with the reference signal.
Drive signal for generating a signal for driving the control sound source
And generating means, In the adaptive processing means, the value of the filter coefficient to be updated is
If it is outstanding compared to the value of the filter coefficient,
The value of the filter coefficient to be updated is close to the values of other filter coefficients.
Drives the control sound source with a control stabilization coefficient that changes in the following direction
Captured in the form of being multiplied by the product value of the reference signal and the reference signal
Update the filter coefficient based on the updated expression
Active noise control device characterized by. 3. The reference signal generating means generates a reference signal composed of an impulse train having the same cycle as noise, or the contract.
Active noise control apparatus Motomeko 2 wherein. 4. The control stabilizing coefficient changes according to the ratio of the value of the filter coefficient to be updated and the sum of the absolute values of the filter coefficients included in the adaptive digital filter.
The active noise control device according to claim 3 .