JPH0561486A - Active type noise controller - Google Patents

Abstract

PURPOSE:To execute the noise suppression by executing the identification of a filter coefficient of a digital filter in the case of a closed space state which is not influenced by a variation of a real space transfer function and a sudden variation of acoustic pressure after a door and a window of a vehicle are closed, and also, at the time of closing. CONSTITUTION:The controller is provided with a space state detecting means for detecting whether a nose control space is a closed space or an open space, and an identification stopping means for stopping an identification of a filter coefficient of a filter means at the time when at least an open space state is detected by a space state detecting means. In such a state, within a prescribed time at the time of opening a door or a window, and after closing the door and the window, a convergence coefficient (d) of an updating expression [Wmi(n+1)=Wmi(n)-alpha.SIGMAgammak.ek(n).gammakm(n-1)] of the filter coefficient is set to '0', the filter coefficient holds a value of immediately before opening, and after a prescribed time elapses after closing the door and the window, a set value is applied to a convergence coefficient alpha of the updating expression, and the filter coefficient of an adaptive filter is updated. Also, the identification of the filter coefficient of a digital filter is executed after closing the door, etc.

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 suppressing noise by interfering noise from a noise source with a noise suppression signal generated by a control sound source, and in particular, generation of abnormal sound due to divergence. The present invention relates to an active noise control device capable of preventing the above.

[0002]

2. Description of the Related Art Conventionally, as this type of active noise control device, for example, there is one disclosed in Japanese Patent Application Publication No. 1-501344. This conventional example is an active noise control device that reduces a noise transmitted from a noise source into a vehicle compartment by emitting a control sound from a loudspeaker. The residual noise in the vehicle compartment is detected by a plurality of microphones. And adaptively filtering the reference signal by generating at least one reference signal containing arbitrarily selectable harmonics of the noise source and supplying the residual noise detection signal and the reference signal to a processor / storage unit. Then, the drive signal of the loudspeaker is formed. Here, in the adaptive filter processing, the i-th filter coefficient W _mi (n + 1) is set to minimize the evaluation function J set as the sum of mean squares of the detection signals V _ek of the plurality of microphones according to the LMS algorithm. In addition, the update is performed sequentially according to the following equation (1).

[0003] Here, W _mi (n) is the filter coefficient at the previous time, that is, the n-th sample, μ is the convergence coefficient, V _ek is the k-th microphone output, x is the reference signal correlated to the noise source, and C _km is m.
Is the real space transfer function between the th speaker and the kth microphone.

[0004]

However, in the above-mentioned conventional active noise control device, the noise suppression control is always performed regardless of the open / closed state of the door or window.
Under conditions where the space transfer function in the vehicle compartment changes significantly, such as when opening or closing doors or windows, or under conditions where external noise is significantly mixed in, such as when opening doors or windows,
The filter coefficient of the adaptive filter is not updated properly,
Further, since the filter coefficient of the digital filter representing the model space transfer function is not properly identified, the noise suppression effect deteriorates, and in the worst case, there is a possibility that abnormal noise may be generated due to divergence, which is an unsolved problem. there were.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and takes in a signal indicating the open / closed state of the door and the window into the active noise control device,
The filter coefficient of the adaptive filter and the filter coefficient of the digital filter are not identified when the door or window is opened and within the predetermined time after the door and window are closed. By updating the filter coefficient of the adaptive filter and identifying the filter coefficient of the digital filter later, it is possible to perform stable noise suppression control by eliminating the sudden change of the spatial transfer function and the influence of external noise. Type noise control device.

[0006]

In order to achieve the above object, an active noise control device according to a first aspect of the present invention, as shown in FIG. 1, generates a reference signal according to the noise generation state of a noise source. Reference signal generating means, a control sound source to which the reference signal of the reference signal generating means is supplied via an adaptive filter, residual noise detecting means for detecting residual noise at an observation position, and the reference signal controlling sound source and residual noise. Filter means for filtering with a filter coefficient representing a model space transfer function corresponding to the space transfer function between the detecting means, a filtered reference signal of the filter means, and a residual noise detection signal of the residual noise detecting means In the active noise control device including a filter coefficient updating unit that updates the filter coefficient of the adaptive filter based on the above, the noise control space is a closed space or an open space. A spatial condition detecting means for detecting whether,
And a filter coefficient update stopping means for stopping the update of the filter coefficient by the filter coefficient updating means when at least the open space state is detected by the space state detecting means.

The active noise control device according to a second aspect of the present invention, as shown in FIG. 2, includes reference signal generating means for generating a reference signal according to the noise generation state of the noise source, and the reference signal generating means. The reference signal corresponds to the spatial transfer function between the control sound source to which the reference signal is supplied through the adaptive filter, the residual noise detecting means for detecting the residual noise at the observation position, and the reference signal between the control sound source and the residual noise detecting means. Filter means for filtering with a filter coefficient representing a model space transfer function,
A filter coefficient updating means for updating the filter coefficient of the adaptive filter based on the filtered reference signal of the filter means and the residual noise detection signal of the residual noise detecting means; and a model space transfer function identifying means. In the active noise control device, a space state detecting means for detecting whether the noise control space is a closed space or an open space, and a filter coefficient of the filter means when at least the open space state is detected by the space state detecting means. And an identification stopping means for stopping the identification.

[0008]

In the active noise control device according to the first aspect, when the door or window of the vehicle is open, the filter coefficient of the adaptive filter is not updated and the value of the filter coefficient before opening is set. Use, and only when the vehicle door and window are closed and the space transfer function and air pressure are stable in a closed space state, the filter coefficient of the adaptive filter is updated and the updated filter coefficient value is used. It is not affected by the space transfer function when the door or the window is opened, the space transfer function that changes with the opening and closing of the door and the window, and the external noise.

Further, in the active noise control system according to the second aspect, when the door or window of the vehicle is in an open space state, it corresponds to the spatial transfer function between the control sound source and the residual noise detecting means. The filter coefficient value of the digital filter that represents the model space transfer function is not identified, and the value of the filter coefficient before opening is used, and the door space and window of the vehicle are closed and the space transfer function and air pressure are stable. Since the filter coefficient of the digital filter is identified only occasionally, it is not identified as the spatial transfer function when the door or the window is opened or the spatial transfer function that changes with the opening and closing of the door and the window.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic configuration diagram showing an embodiment when the present invention is applied to a vehicle. In FIG. 3, reference numeral 1 denotes a vehicle body, and a four-cylinder engine 3 as a noise source is arranged in front of a passenger compartment 2. A front seat 4F and a rear seat 4R are provided in the passenger compartment 2, and, for example, a loudspeaker that also serves as a control sound source that outputs an audio signal as a control sound source to the lower part of the dashboard and the rear side of the rear seat 4R. Speakers 5a and 5b are provided, and microphones 6a, 6b and 6c as residual noise detecting means are provided at the front, center and rear of the ceiling, respectively.

Further, the engine 3 includes a crank angle sensor.
7 is attached, and the crank angle sensor 7
Noise is generated by one pulse each time the shaft rotates 180 degrees
The state detection signal x is output. And a microphone
Residual noise detection signal e output from 6a to 6c₁~ E ₃
Is input to the processor unit 15 and
The detection signal x of the angle sensor 7 and the door 10 are provided.
Doors and windows from the door switch 11 and the window opening / closing sensor 12
The open / close status signal indicating the open / close status of the processor unit 1
Input to 5.

The processor unit 15 is shown in FIG.
As described above, the input reference signal x is A / D converted and output.
A / D conversion circuit 22 and output of this A / D conversion circuit 22
Digital filter 2 for inputting signal as reference signal x
4 and adaptive digital filter 26, and microphone
Residual noise correction signal e from 6a to 6c₁~ E₃A / D
A / D converters 30a to 30c for conversion and these A / D converters
Converted signals by the converters 30a to 30c and the digitizer
Output signal r of the filter 24_kmTo enter the micro professional
Processing signal of the sessor 34 and the adaptive digital filter 26
And D / A converters 36a and 36b for D / A converting
ing. Furthermore, the identification timing of the model space transfer function
For example, the vehicle speed detection value of the vehicle speed sensor 41
The signal is input to the processor unit 15. Also,
A microprocessor is used to identify the Dell space transfer function.
It is started by the test signal generation signal output from the server 34.
Test signal generation circuit 25 and the reference signal
No. x and drive signal y₁, Y ₂To test signal
It is provided with analog switches 8a to 8c.

Here, the digital filter 24 receives the reference signal x, and is filtered by the filter coefficient corresponding to the modeled model spatial transfer function according to the number of combinations of the spatial transfer functions between the microphone and the speaker. is intended to generate a reference signal r _miles, the adaptive digital filter 26 is functionally has a filter corresponding to the number of output channels to the speakers 5a and 5b individually inputs the reference signal x, set at the time Speaker driving signals y _1, y
₂ is output to the loudspeakers 5a and 5b via the analog switches 8a and 8b.

The microprocessor 34 includes a residual noise detection signal e ₁ -e ₃ as well as a filtered reference signal r _Km.
And the open / close state signals of doors and windows are input, and the adaptive filter 2
The noise suppression process of changing the filter coefficient of No. 6 using the LMS (Least Mean Square) algorithm is executed, and the filter coefficient of the digital filter 24 is also identified using the LMS algorithm at a predetermined timing.

Here, the control principle of the processor unit 15 will be described using a general formula. Now, the residual noise detection signal detected by the kth microphones 6a to 6c is e _k (n)
, The residual noise detection signals detected by the k-th microphones 6a to 6c when there is no control sound (secondary sound) from the loudspeakers 5a and 5b, e _pt (n), and the m-th loudspeakers 5a and 5b and k. Th microphone 6a-
When the transfer function H _km with 6c is represented by the FIR (finite impulse response) function, the j-th (j = 0, 1, 2, ──)
I _c -1), the filter coefficient corresponding to the term of I _c -1) is C _kmj ′, the reference signal is x (n), the reference signal x (n) is input, and the i-th adaptive filter for driving the m-th loudspeakers 5a and 5b _{(i = 0,1,2, ─I F -1} ) When the coefficients of the W _mi, the following equation (2) is satisfied.

[0016] Here, the terms with (n) are all sample values at the sampling time n, and K is the microphone 6a.
6c (three in this embodiment), M is the number of loudspeakers 5a and 5b (two in this embodiment), and I _C is FIR
The number of taps (filter order) of the filter coefficient C _km ′ represented by a digital filter, I _F is the number of taps (filter order) of the adaptive filter W _m .

The second term on the right side of the above equation (2) represents the sum of the secondary sounds reaching the kth microphones 6a to 6c. Then, the update formula of the filter coefficient of the adaptive filter using the LMS algorithm which is the steepest descent method is as follows (3)
It is represented by a formula. Here, α is a convergence coefficient and is involved in the speed at which the filter converges optimally and the stability at that time.

In this way, the adaptive digital filter 26
Of the filter coefficients W _mi (n + 1) of the microphones 6a to 6
L based on the residual noise detection signals e ₁ (n) to e ₃ (n) output from c and the reference signal x (n) from the crank angle sensor 7.
By sequentially updating according to the MS algorithm, drive signals y ₁ (n) and y ₂ (n) that minimize the input residual noise detection signals e ₁ (n) to e ₃ (n) are formed. Noise in the vehicle interior 2 is canceled by the control sounds supplied to the loudspeakers 5a and 5b and output from them.

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG. 5 showing the processing procedure of the microprocessor 34. In the entire system, when the key switch is turned on, the power is turned on and the microprocessor 34 executes the timer interrupt process shown in FIG. 5 every predetermined time (for example, 1 msec). That is, step S1
Then, the residual noise detection signals e _{1 to} e ₃ , the reference signal x, the filtered reference signal r _km output from the digital filter 24, and the open / close state signal of the door or window are read. It is determined from the open / closed state signal whether the door or window is in the open state or the closed state. If the door or the window is in the open state, the process proceeds to step S10, and if the door or the window is in the closed state, the process proceeds to step S3.

In step S3, it is determined whether or not the flag 1 which is set when the delay timer T1 for inhibiting the coefficient update for a fixed time (for example, 1 second) from the time when the door and the window are closed is set. If it is set, the process proceeds to step S6. If it is not set, the process proceeds to step S4. In step S4, the delay timer T1 starts counting, flag 1 is set in step S5, and the process proceeds to step S6. In step S6, it is determined whether or not the delay timer T1 has timed out. If the time has expired, the process proceeds to step S7, and if the time has not expired, the process proceeds to step S12.
If the door or window is open, the flag 1 is reset in step S10, the delay timer T1 is reset in step S11, and the process proceeds to step S12.

In step S7, a preset value is applied to the convergence coefficient α in the equation (3), and in step S12
The convergence coefficient α in the equation (3) is set to 0, and the process proceeds to step S8. In step S8, the filter coefficient W _mi (n + 1) is calculated according to the equation (3), and then the calculated filter coefficient W _mi (n + 1) is output to the adaptive digital filter 26 before the step The identification process 13 is executed and the process returns to the main program.

Here, step S2 corresponds to the opening / closing detecting means, and steps S3 to S6 and steps S10 to S12.
Corresponds to the filter coefficient update stopping means. Next, the operation of the identification processing will be described based on FIG. This identification processing program is called from step S13. That is, in step S20, it is determined whether it is a predetermined identification timing. This determination is made by, for example, the vehicle speed sensor 4
By determining whether or not the vehicle speed detection value of 1 exceeds the preset vehicle speed set value, the sound level in the vehicle interior 2 becomes high, and the preset time or more has elapsed since the previous identification. If the identification timing is not reached, step S
27, and if it is the identification timing, step S21
Move to.

Next, at step S21, it is judged from the opening / closing state signal of the door and window whether the door and window are in the open state or the closed state. If the door and the window are in the open state, the process proceeds to step S27. The process moves to S22.
In step S22, it is determined whether or not the flag 2 which is set when the delay timer T2 for prohibiting the identification for a fixed time (for example, 1 second) from the time when the door and the window are closed is set, and is set. If so, the process proceeds to step S25, and if not set, the process proceeds to step S23. In step S23, the delay timer T
The clock 2 is started, the flag 2 is set in step S24, and the process proceeds to step S25. In step S25, it is determined whether or not the delay timer T2 has timed up, and if timed up, the process proceeds to step S26.
If the time is not up, return as it is.

Then, in step S26, identification processing is performed. First, for identification, the test signal generation signal for starting the test signal generation circuit 25 is turned on, and the switching signal is turned on for supplying the test signal to the digital filter 24 and the loudspeakers 5a and 5b. To switch the analog switches 8a to 8c. Next, a test signal e _k emitted from the loudspeakers 5a and 5b and detected by the microphones 6a to 6c,
Test signal x _w supplied from the digital filter 24
And the deviation ε _k from Then, the filter coefficient C _km ′ (n + 1) of the digital filter is calculated for all filter orders by the following equation (4) according to the LMS algorithm so that ε _k is minimized, and the calculated filter coefficient C _km ′ (n + 1) is calculated. The filter coefficient of the digital filter is updated. Then, after turning off the test signal generation signal and the switching signal, the process returns.

C _kmi ′ (n + 1) = C _kmi ′ (n) −μ · ε _k (n) · x _w (n−i) (4) Further, it is not the identification timing in step S20, or If the door or the window is open in S21, the flag 2 is reset in step S27, the delay timer T2 is reset in step S28, and the process directly returns. Here, step S21 corresponds to the open / closed state detecting means, and steps S22 to S25, S27 and S28.
Corresponds to the identification stopping means.

Therefore, assuming that the door and the window are now closed, it is determined in step S3 whether or not the flag 1 is set because the open / closed state signal indicates "closed" in step S2 of FIG. If not set, the delay timer T1 is started in step S4,
The flag 1 is set in step S5 and the process proceeds to step S6. If the flag 1 is set in step S3, the process proceeds to step S6. In this step S6, it is judged whether or not the delay timer T1 which starts timing at the same time as closing the door and the window has timed up, and if it has not timed out, in step S12 the convergence coefficient α of the equation (3) is Is set to 0. If the time is up, the set value is applied as the convergence coefficient α in step S7.

Then, in step S8, the filter coefficient W _mi (n + 1) is calculated by the equation (3). Therefore, if the delay timer T1 has not timed up, the second side of the right side of equation (3)
The term becomes 0, so W _mi (n + 1) = W _mi (n). This is a delay timer T after the doors and windows are closed.
Since the real space transfer function changes within the time set by 1, the stop of the update of the filter coefficient is continued, and the delay timer T1
It means that the update of the filter coefficient is restarted after the lapse of the time set in.

If it is the identification timing in step S20 of FIG. 6, since the door and the window are "closed" in step S21, it is determined in step S22 whether or not flag 2 is set, and it must be set. For example, the delay timer T2 is started in step S23, the flag 2 is set in step S24, and the process proceeds to step S25. If the flag 2 is set in step S22, the process proceeds to step S25. In step S25, it is determined whether or not the delay timer T2, which starts timing at the same time as the door and the window are closed, has timed up, and if not, the process returns as it is. If the time is up, the identification process is performed according to the equation (4) in step S26, and the process returns. This is because after the doors and windows are closed, the real space transfer function changes within the time set by the delay timer T2, so that the identification continues to be stopped, and the identification is performed after the time set by the delay timer T2 has elapsed. Is to restart.

Next, if the door or window is opened, the open / close state signal indicates "open" in step S2 of FIG. 5, so flag 1 is reset in step S10, and delay timer T1 is set in step S11. After resetting, the convergence coefficient α of the equation (3) is set to 0 in step S12, and then the filter coefficient W _mi (n + 1) is calculated by the equation (3) in step S8. Therefore, the second term on the right side of equation (3) is 0, and therefore W _mi (n + 1) = W
_mi (n). This means that the updating of the filter coefficient of the adaptive digital filter 26 is stopped immediately after the door or the window is opened, and the filter coefficient value immediately before the opening is held.

At the identification timing in step S20 of FIG. 6, since the door or window is "open" in step S21, the flag 2 is reset in step S27, and the delay timer T2 is reset in step S28. , Returns without performing the identification process. This means that the identification will stop as soon as the door or window is opened.

In the above embodiment, the case where the loudspeaker is applied as the control sound source has been described, but the present invention is not limited to this, and a vibrator can be applied, and the residual noise detecting means can be used. An acceleration vibration sensor can also be applied to the microphone. Further, the number of loudspeakers and microphones to be installed is not limited to the number in the above embodiment, and may be any number of 1 or more.

Further, although the case where the engine noise is suppressed has been described in the above embodiment, the present invention is not limited to this, and the road noise can be suppressed by detecting the vibration input from the road surface to the wheel or the window glass. Vibrations can be detected to suppress wind noise, and composite sounds of these can also be suppressed. Furthermore, in the above-described embodiment, the filtered reference signal r _km is output to the digital filter 24.
However, the present invention is not limited to this, and the reference signal x is directly input to the microprocessor 34,
The microprocessor 34 may perform digital filter processing, and the digital filter 24, the adaptive filter 26, and the microprocessor 28 may be configured by one microprocessor.

Furthermore, in the above-mentioned embodiment, the case where the present invention is applied to a vehicle has been described, but the present invention is not limited to this, and can be applied to the case of reducing noise in the cabin of an aircraft.

[0034]

As described above, according to the active noise control device of the first aspect, the filter coefficient of the adaptive filter is updated when the vehicle door or window is in the open space state. Without using the value of the filter coefficient before opening, after closing the vehicle door or window, and in the case of a closed space state that is not affected by changes in the real space transfer function or sudden changes in sound pressure at the time of closing, Since the filter coefficient of the adaptive filter is updated and the updated filter coefficient value is used, it is caused by a change in the real space transfer function when the door or window is opened and a sudden change in the vehicle interior air pressure when the door or window is opened or closed. It is possible to prevent the control sound from diverging and to perform stable noise suppression control.

According to the active noise control device of the second aspect, when the door or window of the vehicle is open, the filter coefficient of the digital filter is not identified and the filter coefficient before opening is not identified. The value of is used for the closed space condition after the vehicle door or window is closed and not affected by the change of the real space transfer function or the sudden change of the sound pressure at the time of closing,
Since the filter coefficient of the digital filter is identified,
It is possible to prevent the control sound from diverging due to a change in the real space transfer function when the door or window is opened and a sudden change in the vehicle interior air pressure when opening or closing the door or window, and to perform stable noise suppression control.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a basic configuration of the present invention.

FIG. 2 is a functional block diagram showing a basic configuration of the present invention.

FIG. 3 is a schematic configuration diagram of an example.

FIG. 4 is a block diagram of a processor unit according to an embodiment.

FIG. 5 is a flowchart of an example.

FIG. 6 is a flowchart of an example.

[Explanation of symbols]

 5 loudspeaker 6 microphone 8 switch 24 digital filter 26 adaptive filter 34 microprocessor

Claims (2)

[Claims] 1. A reference signal generating means for generating a reference signal according to a noise generation state of a noise source, a control sound source to which the reference signal of the reference signal generating means is supplied through an adaptive filter, and residual observation positions. Residual noise detecting means for detecting noise, filter means for filtering the reference signal with a filter coefficient representing a model space transfer function corresponding to the spatial transfer function between the control sound source and the residual noise detecting means, and the filter means In the active noise control device, the noise control space is provided with a filter coefficient updating means for updating the filter coefficient of the adaptive filter based on the filtered reference signal and the residual noise detection signal of the residual noise detecting means. Space state detecting means for detecting whether the space is an open space or an open space, and the space state detecting means detects the open space state at least when the space state detecting means detects An active noise control device comprising: a filter coefficient update stopping means for stopping the update of the filter coefficient by the filter coefficient updating means. 2. A reference signal generating means for generating a reference signal according to a noise generation state of a noise source, a control sound source to which the reference signal of the reference signal generating means is supplied via an adaptive filter, and residual observation positions. Residual noise detecting means for detecting noise, filter means for filtering the reference signal with a filter coefficient representing a model space transfer function corresponding to the spatial transfer function between the control sound source and the residual noise detecting means, and the filter means Active noise comprising a filter coefficient updating means for updating the filter coefficient of the adaptive filter based on the filtered reference signal and the residual noise detecting signal of the residual noise detecting means and a model space transfer function identifying means. In the control device, a space state detection unit that detects whether the noise control space is a closed space or an open space, and at least the space state detection unit opens the noise control space. An active noise control device comprising: an identification stopping means for stopping the identification of the filter coefficient of the filter means when a spatial state is detected.