JP3241264B2 - Active noise suppression control method - 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 suppression control method which can be used for suppressing vehicle interior noise due to road noise and the like, and more particularly to an active noise suppression control method using an internal model controller.

[0002]

2. Description of the Related Art In a conventional active noise suppression control method, feedback control is performed as shown in FIGS. More specifically, as shown in FIG. 7A, a microphone 21 which is a sensor for detecting an error is provided in the noise suppression area, and noise is canceled by an output sound at a predetermined distance from the microphone 21. A speaker 22 which is a sound source for noise cancellation is provided, a difference between noise and an output sound from the speaker 22 is detected by a microphone 21, and an output signal of the microphone 21 is supplied to a feedback controller 23 having an adaptive filter. The output of the feedback controller 23 drives the speaker 22 to cancel noise.

In FIG. 7A, a transfer function from the speaker 22 to the microphone 21 is represented by P (s), and a transfer function of the feedback controller 23 is represented by K (s).
The active noise suppression control device shown in FIG.
This is shown in the block diagram of FIG. Here, speaker 2
2 to the microphone 21 are regarded as a plant 24.
S is a complex parameter.

[0004] The correspondence between the display of symbols in the text of the present specification and the display in mathematical formulas and drawings is shown in Table 1 below.

[0005]

[Table 1]

The active noise suppression control shown in FIG. 7 is specifically performed by adaptive control. An example is shown in FIG.
This is as shown in FIG. 9 and FIG. In a conventional example of a block diagram schematically shown in FIG. 8, a signal obtained by adding a signal passed through a howling cancel filter 25 to an output signal from a microphone 21 and compensating howling characteristics is used as a reference signal. The signal is supplied to the adaptive filter 26 based on the feedback-type filtered X-LMS signal processing as an input, and the speaker 22 is driven by the output of the adaptive filter 26 to suppress noise. In FIG. 8, ΔE denotes a speaker 22 to a microphone 21.
Represents a transfer function of an FIR filter simulating a transfer function up to, and W represents a transfer function of an adaptive filter whose filter coefficient is controlled based on a filtered-X-LMS signal processing output.

The conventional example of the block diagram schematically shown in FIG. 9 is an example of two-degree-of-freedom active noise suppression control to which feedforward control is added. A noise suppression control controller 27 is a feedback controller 28 which is an adaptive filter. And a feed-forward controller 9, and the feedback controller 28 and the feed-forward controller 29 are provided with a filtered-X-LM.
Noise suppression control is performed using an adaptive filter based on the signal processing of S. In FIG. 9, (Z ^-1 ) indicates a shift operator in the delay direction, Gr (Z ^-1 ) indicates a transfer function between the noise source and the observer, and G (Z ^-1 ) indicates a control function and the observer. E (Z ^-1 ) is G (Z ^-1 )
2 shows the transfer function of the FIR filter excluding. The control source corresponds to the speaker 22, and the observer corresponds to the microphone 21.

In the conventional example shown in the block diagram of FIG.
The feedback controller 30 includes, for example, an adaptive filter 31 controlled by LMS signal processing, an internal model 32 that is a model of the plant 24, and an adder 33, and outputs the output of the adaptive filter 31 to a transfer function P
(S) to the plant 34 and the transfer function to the internal model 32 of P (s). Such a configuration, that is, a configuration in which the plant 34 and a model (internal model) of the plant 34 are arranged in parallel is called an internal model controller (IMC). 10, the difference between the output of the plant 24 and the noise is detected by an adder 35, and the output signal from the adder 35 and the internal model 3
The difference from the output signal from 2 is detected by the adder 33,
The noise suppression control that controls the output signal of the adder 35 to “0” by controlling the adaptive filter 31 based on the output detected by the adder 33 is performed.

The adaptive filter 31 comprises an internal model 31a, a signal processing device 31b for calculating an adaptive algorithm by the LMS method, and a feedback controller 31c whose filter coefficient is updated by the output of the signal processing device 31b.

[0010]

However, as described above, in the conventional active noise suppression control, the adaptive filter is used not only for the feedforward controller but also for the feedback controller. The amount of operation of the adaptive algorithm of Japanese Patent Application No. Hei.
As shown in 162458. For this reason, in the conventional active noise suppression control, the amount of digital arithmetic processing for adaptive algorithm arithmetic is very large, and it takes time to perform arithmetic processing. There is a problem that the suppression control cannot be performed at a high speed and the response for noise suppression is poor.

In order to shorten the operation processing time, a signal processing device having a high operation speed is required, and the active noise suppression control device becomes expensive when mounted as an active noise suppression device. There was a point.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an active noise suppression control method that requires less arithmetic processing, can reduce the load on a signal processing device, and can perform sufficient noise suppression control.

[0013]

According to the present invention, there is provided an active noise suppression control method comprising the steps of:
An error detection sensor for transmitting an error signal based on the sound of the difference between the output sound and the noise in the sound field, and has a transfer function of a sound field from the sound source to the detection error sensor and an approximate transfer function. And an active noise suppression control method for canceling noise including an internal model to which the same signal as the sound source is input, wherein the addition is performed by using the output signal of the internal model and the error signal as inputs and performing algebraic addition. And a feedback controller to which an output signal of the adder is input. The feedback controller includes an IMC filter, and adds a fluctuation amount of a transfer function obtained from a wave equation of the sound field due to disturbance factors and disturbance factors. As a perturbation, a predetermined frequency range is approximated in advance, and the error detection is performed from the approximated value and the sound source. IMC as the absolute value of the product of the distance and the transfer function of the IMC filter to the sensor is less than 1
Adjust the variable parameters of the filter to adjust the IMC filter
Selects a transfer function of the motor, and the output of the adder distance
A signal based on the product of the transfer function of the IMC filter and
It is characterized by being used as an input signal of the sound source .

[0014] According to the active noise suppression control method of the present invention, the variation of the transfer function of the sound field due to the disturbance factor and the disturbance factor is defined as an additive perturbation, and the predetermined frequency range is determined.
Is set in advance so that the absolute value of the product of the approximated value, the distance from the sound source to the error detection sensor, and the transfer function of the IMC filter is less than 1.
Since the variable parameter of the MC filter is selected, noise is suppressed.

Further, according to the active noise suppression control method of the present invention, since the variation of the transfer function is set in advance to the frequency in advance, the amount of the variation of the transfer function and the approximation of the variation from the sound source to the error detection sensor are set. Distance and IMC
IMC so that the product of the filter and the transfer function is less than 1.
It suffices if the variable parameters of the filter are set as constants, so that a large amount of calculation is not required as in the case of adaptive control for following the change of the transfer function, and the amount of calculation is small.

Further, according to the active noise suppression control method of the present invention, the system for noise suppression control can be constituted by a simple feedback controller, and the processing time for noise suppression can be reduced to improve the responsiveness. Also improve. Further, it can be configured at low cost when mounting. If the same processing time as that of the conventional adaptive control is allowed, according to the active noise suppression control method according to the present invention, the signal processing device requires only a low arithmetic processing speed.

The active noise suppression control method according to the present invention is characterized in that the amount of variation of the transfer function set in advance in the active noise suppression control method is a frequency weighting function.

In the active noise suppression control method according to the present invention, when the variation of the transfer function approximately set is used as the frequency weighting function, the variation of the transfer function, the distance from the sound source to the error detection sensor, and the IMC filter Since the product of the transfer function and the transfer function is obtained as a function of the frequency, selection of the variable parameter of the IMC filter is facilitated. The active noise suppression control method according to the present invention is characterized in that the variation amount of the transfer function that is set in advance in the active noise suppression control method is set in advance with respect to the frequency.

In the active noise suppression control method according to the present invention, the amount of change in the transfer function is set in advance with respect to the frequency.
The degree of freedom at the time of approximation of the amount of variation is increased, and the variable parameter of the IMC filter can be accurately selected.

In the active noise suppression control method according to the present invention, in the active noise suppression control method, the variation of the transfer function due to the disturbance factor and the disturbance factor is equal to or more than the actually measured variation amount or the estimated variation amount of the transfer function due to the disturbance factor and the disturbance factor. And a variation amount asymptotically approximating the measured variation amount or the estimated variation amount.

When the variation of the transfer function is set to a variation larger than the actually measured variation or the estimated variation due to the disturbance and disturbance factors of the transfer function, the noise suppression effect is reduced, the remaining noise increases, and When the variation is set to be smaller than the actually measured variation or the estimated variation due to the disturbance factor and the disturbance factor of the transfer function, noise suppression becomes unstable and howling occurs. However, in the active noise suppression control method according to the present invention, the variation amount of the transfer function is equal to or more than the actually measured variation amount or the estimated variation amount due to the internal disturbance factor and the disturbance factor of the transfer function, and asymptotically approaches the actually measured variation amount or the estimated variation amount. When the variation amount is close to the above, the noise suppression effect is maximum, and the noise suppression effect is stably obtained.

The active noise suppression control method according to the present invention is characterized in that in the active noise suppression control method, the variable parameters of the IMC filter are selected such that the absolute value of the product is 0.9 or more and less than 1. I do.

In the active noise suppression control method according to the present invention, since the variable parameter of the IMC filter is selected so that the absolute value of the product is 0.9 or more and less than 1, the noise canceling effect is increased. become.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An active noise suppression control method according to the present invention will be described below with reference to embodiments.

FIGS. 1 and 2 are a block diagram and a block diagram, respectively, of an active noise suppression control device to which an active noise suppression control method according to an embodiment of the present invention is applied.

In FIG. 1, reference numeral 12 denotes a speaker as a sound source for noise cancellation, and reference numeral 11 denotes an error signal which is provided at a sound deadening point and transmits an error signal based on the sum of the noise and the reproduced sound from the speaker 12. A microphone as a sensor is shown, and a distance between the speaker 12 and the microphone 11 is 1 (ell). As described above, the area from the speaker 12 to the microphone 11 is regarded as the plant 16.

The microphone 11 comprises an amplifier for amplifying the output and an A / D converter for A / D converting the output of the amplifier.
The speaker 12 includes a D / A converter for D / A converting a drive signal and an amplifier for amplifying an output from the D / A converter to drive the speaker.

The internal model 14 corresponds to the plant 16
Model, which consists of filters, for example,
The transfer function is almost the same as the transfer function of the plant 16.
~ P (s), and the speaker 1
2 input signals are provided. The output signal from the i centers null model 14, is subtracted by the adder 13 from the output signal of the microphone 11, the output signal from the adder 13 is I
The feedback signal is supplied to the feedback controller 15 including the MC filter 15a, the output signal of the feedback controller 15 is inverted and supplied to the speaker 12 and the internal model 14 to cancel the noise.

In FIG. 2 , P (s) indicates the transfer function of the plant, .about.P (s) indicates the transfer function of the internal model 14, and Qd (s) indicates the transfer function of the feedback controller 15. .

Here, the speaker 12 and the microphone 11
Is defined as a free sound field, and the wave equation of the spherical wave is subjected to Laplace transform to obtain the transfer function P of the plant.
(S) is obtained.

The transfer function P (s) is represented by the following equation (1).

[0032]

(Equation 1)

In the equation (1), A is a constant, and l
(L) is the distance from the speaker 12 to the microphone 11 as described above. When c is a sound speed, τ
(= L (ell) / c) is a dead time. As described above, the plant to be subjected to the feedback active noise suppression control is a dead time system, and the dead time system is an infinite dimensional system.

In the active noise suppression control according to the embodiment of the present invention, -P (s) shown in the following equation (2) obtained by first-order Padé approximation of the dead time is used as the transfer function of the internal model 14.

[0035]

(Equation 2)

The configuration of the control system in which the transfer function of the plant and the transfer function of the internal model, which is the model, are arranged in parallel, the same signal is input, and the difference in the output is fed back as an error, is based on the internal model. It is called a controller (IMC) and is known to have excellent robustness.

In the active noise suppression control according to the embodiment of the present invention, an IMC configuration is used for a feedback system. In the case of the IMC configuration, the transfer function P (s) = 〜P
It is known that the feedback system is stable if the feedback controller 15 is designed stably in the case of (s).

In FIG. 1, the microphone 11
The transfer function S (s) to the error signal generation end is called a sensitivity function and is as shown in the following equations (3) and (4).

[0039]

(Equation 3)

[0040]

(Equation 4)

In the feedback-active noise suppression control, if the sensitivity function S (s) can be made smaller than 1 in the frequency band to be controlled, the sound is muted. That is, the purpose of the control to mute the sound is nothing but to make the control function S (s) smaller than 1.

Here, a case will be described in which a nominal case in which the transfer function P (s) of the internal model 14 is equal to the transfer function P (s) of the plant.

In the case of the nominal case, the transfer function Qd
(S) is described as -Qd (s).

At this time, the above equations (3) and (4) become as shown in the following equations (5) and (6).

[0045]

(Equation 5)

[0046]

(Equation 6)

Therefore, if the plant is a minimum phase system, the influence of disturbance can be reduced to zero by selecting the following equation (7). However, in the case of the active noise suppression control according to the embodiment of the present invention, since the transfer function is a non-minimum phase system, the transfer function ＰP (s) is calculated by the following (8).
Disassemble the inner and outer parts as shown in the formula.

[0048]

(Equation 7)

[0049]

(Equation 8)

In the equation (8), PM (s) is a minimum phase function, and PA (s) is an all-pass function, which are given as in the following equation (9). Here, A = 1 is set.

[0051]

(Equation 9)

From the viewpoint of facilitating this analysis and including a wide frequency component, a step-like disturbance d
Assuming that (s) = 1 / s, the minimum error norm for a step-like disturbance is obtained by the following equation (10).

[0053]

(Equation 10)

The minimum error norm shown in the equation (10) takes a minimum value when the following equation (11) is satisfied.

[0055]

[Equation 11]

The minimum error norm shown in the equation (10) indicates that the achievable H2 norm increases when an unstable zero near the origin exists. Therefore, in the active noise suppression control according to the embodiment of the present invention, the longer the distance 1 (ell) from the speaker 12 to the microphone 11 is, the closer the unstable zero point is to the origin, indicating that the noise suppression control is difficult.

Next, robust stability of the active noise suppression control according to the embodiment of the present invention will be described.

It is assumed that the existence range of a plant (a set of uncertainties) can be described by an additive perturbation shown in the following equation (12).

[0059]

(Equation 12)

Wa (jω) is a frequency weighting function for covering the systematic error of the plant. It is known that the robust stability condition at this time is as shown in Expression (13).

[0061]

(Equation 13)

Here, ~ Ta (s) is a quasi-complementary sensitivity function defined as equation (14).

[0063]

[Equation 14]

In the IMC configuration, the feedback controller 15 includes an IM configured with a low-pass filter.
The C filter 15a is used, and the IMC filter 15a
Is represented by F (s), the transfer function Qd (s) of the feedback controller 15 is represented by the following equation (15).

[0065]

(Equation 15)

Therefore, using the equations (14) and (15), the robust stability condition is such that all the angular velocities ω (=
In the range of 2πf), it can be expressed by the following equation (16).

[0067]

(Equation 16)

Here, since a step-like disturbance is assumed as described above, the transfer function F of the IMC filter 15a is
(S) uses λ as a variable parameter of the IMC filter 15a and selects the transfer function of the following equation (17);
Noting that Qd (s) becomes the following equation (18), the equation (16) indicating the robust stability condition becomes the following equation (19).

[0069]

[Equation 17]

[0070]

(Equation 18)

[0071]

[Equation 19]

Here, the variable parameter λ of the IMC filter 15a is adjusted so as to satisfy the robust stability condition.

The IMC filter 15a shown in the equation (17)
By using the transfer function F (s), the transfer function Qd (s) of the feedback controller 15 can be obtained as the following equation (20).

[0074]

(Equation 20)

Using the transfer function Qd (s) of the feedback controller 15 obtained as described above and the input signal of the feedback controller 15 as e, the output u of the feedback controller 15 is u = Qd (s) e. (21) is obtained.

The structure of the feedback controller 15 obtained by the equations (20) and (21) is simple, and the noise suppression effect obtained by using the feedback controller 15 having such a simple structure is as shown by a broken line b in FIG. This is comparable to the noise suppression effect of the LMS method indicated by the dashed line c. In FIG. 3, a solid line a indicates noise when the noise suppression control is not performed.

A description will be given of a calculation amount in the case of the adaptive control using the conventional LMS method and a calculation amount in the case of the active noise suppression control according to the embodiment of the present invention.

In the adaptive filter 31 shown in FIG. 10, the input signal of the internal model 31a is x, the input of the signal processing device 31b is w, the input signal of the feedback controller 31c is v, the feedback controller 3
When the output signal of 1c is z, the following (22) to (2)
4) The operation of the equation is required.

Z = Q _A v (22)

[0080]

(Equation 21)

Q _A (new) = Q _A (old) + μwx (24) where Q _A is the transfer function of the feedback controller 31c, 〜P ₁ (s) is the transfer function of the internal model 31a, and μ is Step parameters, which are calculated based on the LMS method. On the other hand, in the case of the active noise suppression control according to the embodiment of the present invention, (2
Only the expression (1) is required, and the operations of the expressions (23) and (24) are unnecessary, and the amount of operation is greatly reduced.

In the active noise suppression control method according to the embodiment of the present invention, when applied to, for example, noise suppression control in a vehicle cabin, disturbance factors such as increase / decrease of the number of occupants, opening and closing of windows, microphone 11 and speaker 12 Aging,
Plant transfer function P (s) and internal model 14
The transfer function P (s) of the plant changes on the basis of a disturbance factor due to an error with respect to the transfer function ~ P (s). The variation of the transfer function P (s) is estimated as an additive perturbation in advance with respect to a predetermined frequency range , and is approximated. Here, the additive perturbation shown in the equation (12) corresponds to the estimation of the fluctuation amount of the transfer function of the plant. This estimation is performed before mounting.

The variable parameter λ of the IMC filter 15a is adjusted so as to satisfy the robust stability condition shown in the equation (16).

More specifically, the distance l (ell) from the speaker 12 to the microphone 11 is physically fixed, and the frequency weighting function covering the variation is the variation of the approximated transfer function P (s). Which is set in advance in an approximate manner. Therefore, | l · F (s) · Wa (s) | <1
, That is, by pre-adjusting the variable parameter λ such that the robust stability condition is satisfied.
The transfer function F (s) of the C filter 15a is selected, and the transfer function Qd (s) of the feedback controller 15 is obtained by the equation (20) using the selected transfer function F (s). The configuration is simple.

For this reason, it is not necessary to always perform the calculation so as to follow the change of the transfer function of the plant in real time as in the case of the conventional adaptive control, and the amount of calculation is extremely small as described above. Become. The configuration of the feedback controller 15 is also simplified.

Here, the variable parameter λ is selected so that | l · F (s) · Wa (s) | approaches “1” as much as possible. This is because | l · F (s) · Wa (s) | approaches “1” as much as possible, thereby obtaining a large noise suppression effect.

Specifically, when the distance l (ell) from the speaker 12 to the microphone 11 is 0.2 m, F (s)
= 1 / (0.0002s + 1). The robust stability condition at this time is | l · F (jω) · Wa (jω) |
Was as shown in FIG. 4, and a maximum value of 0.97 was obtained. Note that the robust stability condition is | lF (jω) Wa
It is convenient to select the variable parameter λ such that (jω) | is less than 1 and equal to or more than 0.9.

Next, the estimation of the variation of the transfer function P (s) of the plant 16 will be described.

That is, the frequency weighting function Wa (s) is
The transfer function P (s) of the plant expressed by the equation (1) and (2)
Transfer function of internal model 14 approximated by the following equation: P
(S) is set to cover the difference.

The frequency weighting function Wa (jω) when the distance 1 (ell) from the speaker 12 to the microphone 11 is set to 0.2 m is set as shown by the solid line in FIG. In FIG. 5A, a broken line indicates an additive perturbation (P (j
ω) -〜P (jω)), and the frequency weighting function Wa (j
Although the value of ω) is set by trial and error, it is set so as to be more than the additive perturbation and to asymptotically approximate the additive perturbation. In the example shown in FIG. 5A, the frequency weight function Wa
(S) was set as shown in the following equation (25).

[0091]

(Equation 22)

The frequency weighting function Wa (s) is shown in FIG.
As shown in (b), when the frequency weighting function Wa (jω) ″ is indicated by a dashed line that is equal to or larger than the envelope of the additive perturbation, noise suppression is insufficient, and the additive perturbation is asymptotic. When the frequency weighting function Wa (jω) ′ indicated by a two-dot chain line smaller than the weighting function Wa (s) approximating to (2), instability such as howling occurs.

Therefore, the frequency weighting function Wa (jω)
It is best to set to be greater than or equal to the additive perturbation and to asymptotically approximate the additive perturbation.

Another method of estimating the variation of the transfer function P (s) of the plant 16 will be described with reference to FIG.

In FIG. 6, the dashed line indicates the additive perturbation (P (jω) -ωP (jω)) with respect to the frequency. Another estimation of the amount of change is to estimate the amount of change in the transfer function P (s) using a stepwise amount of change close to the additive perturbation shown by the broken line in FIG.

In the case of such estimation, the transfer function P
Since the variation of (s) is preset for the frequency, the degree of freedom at the time of approximation of the variation increases in accordance with the variation of the variation, and the variable parameter of the IMC filter can be accurately selected. it can.

[0097]

As described above, according to the active noise suppression control method of the present invention, the variation of the transfer function is set in advance to the frequency in advance, so that the variation of the transfer function and the sound source, which have been set approximately, can be used. It is sufficient to set the variable parameter of the IMC filter as a constant so that the product of the distance to the error detection sensor and the transfer function of the IMC filter is less than 1, and it is sufficient for the conventional adaptive control to follow the change of the transfer function. The effect that a large amount of calculation is not required as in the case and the amount of calculation is small is obtained.

Further, according to the active noise suppression control method of the present invention, the system for noise suppression control can be constituted by a simple feedback controller, and the processing time for noise suppression is reduced and the responsiveness is improved. The effect of improving is also obtained. Furthermore, in addition to being inexpensive for mounting, if the same processing time as that of the conventional adaptive control is allowed, according to the active noise suppression control method of the present invention, the signal processing device has a low arithmetic processing speed. The effect is obtained.

In the active noise suppression control method according to the present invention, when the variation of the transfer function approximately set is used as the frequency weighting function, the variation of the transfer function, the distance from the sound source to the error detection sensor, and the IMC filter Since the product of the transfer function and the transfer function is obtained as a function of the frequency, the effect that selection of the variable parameter of the IMC filter is facilitated is obtained.

In the active noise suppression control method according to the present invention, since the variation of the transfer function is set in advance with respect to the frequency,
The degree of freedom at the time of approximation of the fluctuation amount is increased, and an effect is obtained that the variable parameter of the IMC filter can be accurately selected.

When the variation of the transfer function is set to a variation larger than the actually measured variation or the estimated variation due to the disturbance factor and the disturbance factor of the transfer function, the noise suppression effect is reduced, the remaining noise increases, and When the variation is set to a variation smaller than the actually measured variation or the estimated variation due to the disturbance factor and the disturbance factor of the transfer function, noise suppression becomes unstable and howling occurs, but in the active noise suppression control method according to the present invention, By setting the amount of function variation to a value that is greater than or equal to the measured or estimated variation due to the disturbance and disturbance factors in the transfer function, and that asymptotically approximates the measured or estimated variation, the noise suppression effect is reduced. This is the maximum and the noise suppression effect can be obtained stably.

[Brief description of the drawings]

FIG. 1 is a block diagram of an active noise suppression control device to which an active noise suppression control method according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram of an active noise suppression control device to which the active noise suppression control method according to one embodiment of the present invention is applied;

FIG. 3 is a schematic characteristic diagram for describing a noise suppression effect in an active noise suppression control method according to an embodiment of the present invention.

FIG. 4 is a schematic characteristic diagram for describing selection of a variable parameter of an IMC filter in the active noise suppression control method according to one embodiment of the present invention.

FIG. 5 is a schematic characteristic diagram for explaining setting of a frequency weighting function in the active noise suppression control method according to the embodiment of the present invention;

FIG. 6 is a schematic diagram for explaining approximate selection of a variation amount of a transfer function of a plant in the active noise suppression control method according to the embodiment of the present invention.

7A and 7B are block diagrams of a conventional active noise suppression control device, where FIG. 7A is a block diagram and FIG. 7B is a block diagram.

FIG. 8 is another schematic block diagram of a conventional active noise suppression control device.

FIG. 9 is another schematic block diagram of a conventional active noise suppression control device.

FIG. 10 is another schematic block diagram of a conventional active noise suppression control device.

[Explanation of symbols]

 11 Microphone 12 Speaker 13 Adder 14 Internal Model 15 Feedback Controller 15a IMC Filter

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-247497 (JP, A) JP-A-7-248781 (JP, A) JP-A-7-311578 (JP, A) International publication 95/9415 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G10K 11/178 F01N 1/00 F16F 15/02 G05B 13/02 H03H 17/00 601

Claims (5)

(57) [Claims] [Claim 1] and the sound source for noise cancellation, out of the sound source
An error detection sensor for transmitting an error signal based on the sound of the difference between the power sound and the noise is provided in the sound field, and has a transfer function of a sound field from the sound source to the detection error sensor and an approximate transfer function. And an active noise suppression control method for canceling noise including an internal model to which the same signal as the sound source is input, wherein an adder that performs algebraic addition using the output signal of the internal model and the error signal as inputs And a feedback controller to which an output signal of the adder is input. The feedback controller includes an IMC filter, and adds a variation amount of a transfer function obtained from a wave equation of the sound field due to a disturbance factor and a disturbance factor. As a perturbation,
A predetermined frequency range is approximated in advance, and the absolute value of the product of the approximated value, the distance from the sound source to the error detection sensor, and the transfer function of the IMC filter is 1
Adjusting a variable parameter of the IMC filter to less than
The transfer function of the IMC filter is selected by adjusting the output of the adder, the distance, and the transfer function of the IMC filter.
An active noise suppression control method, characterized in that a signal based on a product of the attainment function is used as an input signal of the sound source . 2. The active noise suppression control method according to claim 1, wherein the variation amount of the transfer function, which is set in advance approximately, is:
An active noise suppression control method characterized by using a frequency weight function. 3. The active noise suppression control method according to claim 1, wherein the amount of variation of the transfer function, which is set approximately in advance, is:
An active noise suppression control device, which is preset for a frequency. 4. The active noise suppression control method according to claim 1, wherein the variation of the transfer function due to the disturbance factor and the disturbance factor is measured or estimated by the measurement of the transfer function due to the disturbance factor and the disturbance factor. More than the variation,
And an amount of variation that asymptotically approximates the actually measured variation or the estimated variation. 5. The active noise suppression control method according to claim 1, wherein the variable parameter of the IMC filter is adjusted so that the absolute value of the product is 0.9 or more and less than 1. Active noise suppression control method characterized by the following.