JP2005010240A - Active vibration noise control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active vibration noise control unit that can prevent a unpleasant noise from being generated when a cancel signal is cut off and obtain a sufficient cancel signal, and can be constituted with an inexpensive microcomputer and has rapid response. <P>SOLUTION: An adaptive filter 2 generates the cancel signal according to a reference signal of frequency based upon a vibration noise frequency and a speaker 3 is driven with the cancel signal to generate a cancel sound; and an error signal based upon the difference between vibration noise in a cabin and the cancel sound is detected to generate a reference signal based upon the error signal and a 1st filter coefficient arithmetic circuit 6 finds a 1st filter coefficient according to the reference signal and error signal so that the error signal becomes minimum. According to a switching indication from a switching circuit 11, the 1st filter coefficient right before the switching indication is multiplied by a specified value which is smaller than 1 to obtain a 2nd filter coefficient, and the 1st filter coefficient or 2nd filter coefficient is selected as a filter coefficient of the adaptive filter 2 based upon the switching indication. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an active vibration noise control apparatus that actively cancels and controls vehicle interior vibration noise generated by vibration noise of an internal combustion engine.
[0002]
[Prior art]
Conventionally, as this type of active vibration noise control device, in order to prevent the generation of unpleasant noise when the silencing control is turned on and off, the canceling sound for canceling the vehicle interior vibration noise is sequentially increased and decreased, so-called. There is an active vibration noise control device that performs fade-in and fade-out operations (see, for example, Patent Document 1).
[0003]
More specifically, the generation of an unpleasant sound refers to the time when the mute control is turned on (mute control is in operation) to the off state (mute control is stopped) as in the speaker output waveform shown in FIG. Since the canceling sound suddenly disappears at tf, an unpleasant sound (sound “buzz”) schematically shown in FIG. 3A is generated.
[0004]
In such an active vibration noise control device of the prior art, when the output shaft rotation speed of the internal combustion engine falls within the control rotation speed region for controlling the vibration noise, a very small value (for example, 0) is obtained every time the filter coefficient of the adaptive filter is updated. .0002) is obtained to obtain a ratio coefficient (maximum value = 1), the obtained ratio coefficient is multiplied by the cancellation signal output from the adaptive filter, and the multiplication result signal is a speaker which is a cancellation sound generating means. To cancel the sound sequentially.
[0005]
Conversely, when the output shaft rotational speed of the internal combustion engine moves from the control rotational speed region that controls vibration noise to the outside of the control rotational speed region, an extremely small value (for example, 0.0002) is sequentially updated every time the filter coefficient is updated. Generated by subtracting the ratio coefficient (minimum value = 0), multiplying the calculated ratio coefficient by the cancellation signal output from the adaptive filter, and supplying the multiplication result signal to the speaker as cancellation noise generation means Control is performed to sequentially reduce the canceling sound.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-257481 (page 3, FIG. 2)
[0007]
[Problems to be solved by the invention]
However, in the conventional active vibration and noise control apparatus as described above, for example, in the case of fade-out, the ratio coefficient value that is sequentially reduced every time the filter coefficient is updated is obtained by calculation, and the obtained ratio coefficient value and the LMS algorithm calculation processing are performed. Since the canceling signal output from the updated adaptive filter is multiplied and the multiplication result is supplied to the speaker which is the canceling sound generation means so that the canceling sound is sequentially generated, the normal LMS algorithm calculation is performed. In addition, there is a problem that the calculation amount for performing the ratio coefficient update calculation and the secondary sound output calculation is large and the calculation load is large.
[0008]
Further, the active vibration and noise control device is usually composed of a microcomputer, and when using an inexpensive microcomputer that uses a fixed point to perform the calculation in 8 bits, smooth fading in and fading out are possible. There is a problem that an extremely small value (for example, 0.0002) cannot be used to obtain the above-described ratio coefficient for realizing the above, and an expensive microcomputer is required.
[0009]
Furthermore, since the conventional active vibration and noise control device performs fade-in and fade-out separately, the output shaft speed of the internal combustion engine is muffled from outside the mute control operation region to the mute control operation region. In the case of fluctuating across the end of the operation region, the filter coefficient is sequentially updated from the initial value (= 0) every time when the active vibration noise control apparatus enters the mute control operation region from outside the mute control operation region. Therefore, there is a problem that the response for vibration noise control becomes slow.
[0010]
As described in the prior art, the above problem is generally based on an error signal from a microphone and a reference signal such as a crank angle signal or a reference signal obtained by correcting a reference signal with a signal transfer characteristic. Therefore, when the reference signal is changed, that is, when the rotation speed of the crankshaft is changed, the filter coefficient is changed from the initial value. It is updated sequentially (see paragraph [0018] of Patent Document 1).
[0011]
Therefore, when the LMS algorithm calculation is performed outside the silencing control operation area as in the prior art, the reference signal is different between the silencing control operation area and the silencing control operation area, so that the operation returns to the silencing control operation area. Each time, the filter coefficient is sequentially updated from the initial value.
[0012]
An object of the present invention is to provide an active vibration noise control device that can prevent an unpleasant sound that occurs when an offset signal is cut off, can be configured with an inexpensive microcomputer with a reduced calculation load, and has a quick response. Objective.
[0013]
[Means for Solving the Problems]
An active vibration noise control device according to the present invention includes a reference signal generation means for generating a reference signal having a frequency based on a frequency of vibration noise generated from an internal combustion engine,
An adaptive filter for generating a canceling signal based on the reference signal in order to cancel a vehicle interior vibration noise generated based on the vibration noise from the internal combustion engine;
Canceling sound generating means for generating a canceling sound based on the canceling signal output from the adaptive filter;
Error detecting means for detecting a difference between the vehicle interior vibration noise and the canceling sound and outputting a signal based on the difference as an error signal;
Reference signal generation means for generating a reference signal by correcting the reference signal based on a correction value corresponding to a signal transmission characteristic from the canceling sound generation means to the error detection means;
First filter coefficient calculation means for sequentially updating the filter coefficient of the adaptive filter using adaptive calculation so that the error signal is minimized based on the reference signal and the error signal;
Second filter coefficient calculation means for sequentially updating the adaptive filter by multiplying a filter coefficient of the adaptive filter by a predetermined value less than 1,
And a switching means for selectively switching between the first filter coefficient calculation means and the second filter coefficient calculation means.
[0014]
According to the active vibration noise control device of the present invention, when the silence control stop (off) region of the active vibration noise control device is entered, the canceling sound does not suddenly disappear, but by the second filter coefficient updating means. Since the canceling sound is gradually lowered (fade out), it is possible to prevent the occurrence of an unpleasant sound ("buzz" sound) that occurs when the mute control is turned on and off.
[0015]
Further, since the adaptive calculation and the LMS algorithm calculation process are executed by the first filter coefficient updating means in the mute control operation area, and only the multiplication process is executed in the mute control stop area, the calculation amount is small and the calculation load is reduced. Therefore, it can be constituted by an inexpensive microcomputer, and the cost of the apparatus can be reduced.
[0016]
In addition, when the silencing control is stopped after the silencing control is activated, the filter coefficient before the update, that is, the filter coefficient during the silencing control operation immediately before switching is quoted by the second filter coefficient updating means, and the filter coefficient is predetermined as the filter coefficient. A multiplication result obtained by multiplying the values is set in the adaptive filter as a filter coefficient. Then, during the subsequent silencing control stop period (silence control stop region), at each update time, if the result of the calculation is traced, the filter coefficient during the silencing control operation immediately before switching is sequentially multiplied by a predetermined value. Thus, the filter coefficient is updated. Therefore, since the filter coefficient sequentially updated based on the error signal and the reference signal in the silencing control operation area is inherited in the silencing control stop area, the second filter coefficient is restored when returning to the silencing control operation area. The value sequentially updated by the updating means can be used as the initial value of the LMS algorithm calculation processing, and therefore the response of vibration noise suppression is improved compared to the case where the initial value of the filter coefficient must be started from “0”. To do.
[0017]
In addition, even when the mute control operation area and the mute control stop area are repeated, because of the above reasons, the filter coefficient is inherited from one to the other, so that no significant level change of the canceling sound occurs, and unpleasant sound is generated. do not do.
[0018]
In the active vibration noise control apparatus according to the present invention, the switching means may send a switching instruction according to the frequency of the reference signal.
[0019]
In the active vibration noise control apparatus according to the present invention, the switching means may send a switching instruction according to the output shaft rotational speed of the internal combustion engine.
[0020]
Thus, since the signal for switching operation is the frequency of the reference signal or the output shaft rotation speed of the internal combustion engine, it can be switched with the input provided from the beginning, and the cost can be reduced compared to adding another input. Become.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an active vibration noise control apparatus according to the present invention will be described with reference to an embodiment.
[0022]
FIG. 1 is a block diagram showing the configuration of an active vibration noise control apparatus according to an embodiment of the present invention.
[0023]
An active vibration noise control device 15 according to an embodiment of the present invention includes a reference signal generation circuit 1, an adaptive filter 2, a speaker 3 as canceling sound generation means provided in a vehicle interior, a reference signal generation circuit 4, and a filter coefficient. Switching between the arithmetic circuit 5, the first filter coefficient output from the microphone 10 as the error detection means, and the filter coefficient arithmetic circuit 5 and the second filter coefficient are selected as the filter coefficients of the adaptive filter 2. And a switching circuit 11 as means.
[0024]
Here, for example, in the case of canceling out the vibration noise generated from the internal combustion engine which is a vibration noise source, for example, the vehicle interior vibration noise based on the rotation of the output shaft of the 4-cycle 4-cylinder internal combustion engine, 1/1 of the output shaft of the internal combustion engine. Excitation vibration with the internal combustion engine as a base point is generated by torque fluctuation due to gas combustion that occurs every two revolutions, and this causes vibration noise in the passenger compartment. Therefore, in the case of a four-cycle four-cylinder internal combustion engine, a lot of vibration noise called a secondary rotational component having a frequency twice the output shaft rotational speed of the internal combustion engine is generated.
[0025]
Therefore, the output shaft rotation of the internal combustion engine is detected by a sensor, and the output signal from the sensor is supplied to the reference signal generation circuit 1, and the reference signal generation circuit 1 performs the output shaft rotation of the internal combustion engine that is a vibration noise source. A reference signal with a harmonic frequency of the output shaft rotational speed Ne is generated in synchronization with the synchronized output shaft rotational speed Ne.
[0026]
The generated reference signal is supplied to the adaptive filter 2, and the adaptive filter 2 generates a cancellation signal for canceling the vehicle interior vibration noise based on the reference signal. The canceling signal generated in the adaptive filter 2 is supplied to a speaker 3 provided in the vehicle interior, and the canceling sound based on the canceling signal is reproduced to cancel the vehicle interior vibration noise.
[0027]
In the reference signal generation circuit 4, the reference signal is supplied, and the reference signal is corrected according to the signal transmission characteristics in the vehicle interior between the speaker 3 and the microphone 10 with respect to the reference signal. A reference signal is generated.
[0028]
On the other hand, the filter coefficient calculation circuit 5 includes a first filter coefficient calculation circuit 6 that is a first filter coefficient calculation means, a second filter coefficient calculation circuit 7 that is a second filter coefficient calculation means, and a switching circuit 11. I have.
[0029]
The first filter coefficient calculation circuit 6 is supplied with the reference signal and the error signal detected by the microphone 10, and the first filter coefficient calculation circuit 6 performs an LMS algorithm calculation on the error signal based on the reference signal and the error signal. The first filter coefficient of the adaptive filter 2 is calculated so as to be minimized, and the calculated first filter coefficient is alternatively output via the switching circuit 11 to be the filter coefficient of the adaptive filter 2 .
[0030]
The second filter coefficient calculation circuit 7 includes a setting circuit 8 in which a predetermined value λ less than 1, for example, a predetermined value λ (λ = 127/128) is set as a correction coefficient, and a mute control output from the switching circuit 11. A multiplication circuit that sequentially multiplies the first filter coefficient and the correction coefficient immediately before the switching instruction signal is generated based on the switching instruction signal from the operation area to the outside of the mute control operation area; The multiplication output from 9 is alternatively output as the second filter coefficient via the switching circuit 11 and used as the filter coefficient of the adaptive filter 2.
[0031]
The switching circuit 11 selects the first filter coefficient as the filter coefficient of the adaptive filter 2 when the reference signal is input and the frequency of the reference signal is within the silencing control operating area, and the frequency of the reference signal is the silencing control operating area. When it goes out of the silencing control operation area from inside, the second filter coefficient is selected instead of the first filter coefficient as the filter coefficient of the adaptive filter 2, and the frequency of the reference signal is muted from outside the silencing control operation area. When entering the operation region, the selected filter coefficient is switched from the second filter coefficient to the first filter coefficient.
[0032]
The operation of the active vibration noise control device 15 configured as described above will be described with reference to the flowchart of FIG.
[0033]
When the active vibration noise control device 15 starts operating, the frequency of the reference signal is detected (step S1), and it is checked whether or not the detected frequency of the reference signal is a frequency within the mute control operation region ( Step S2). When it is determined in step S2 that it is within the mute control operation region, the first filter coefficient is selected in the switching circuit 11 (step S3). Here, the first filter coefficient W (n + 1) is W (n + 1) = W (n) −μecx. μ represents a step size, e represents an error signal, c represents a correction value for obtaining a reference signal, x represents a reference signal, and n represents a sampling number.
[0034]
The first filter coefficient selected in step S3 is set as the filter coefficient of the adaptive filter 2, the cancellation signal output from the adaptive filter 2 is supplied to the speaker 3, and the speaker 3 is driven by the cancellation signal (step S4). ), The vehicle interior vibration noise is canceled out by the reproduced sound generated in the speaker 3, and the process is repeated from step S1.
[0035]
When it is determined in step S2 that it is outside the mute control operation region, the second filter coefficient is selected in the switching circuit 11 (step S5). The second filter coefficient W (n + 1) is W (n + 1) = W (n) × λ: λ <1.
[0036]
Subsequent to step S5, the second filter coefficient selected in step S5 is set as the filter coefficient of the adaptive filter 2, the cancellation signal output from the adaptive filter 2 is supplied to the speaker 3, and the speaker 3 receives the cancellation signal. When driven, the vehicle interior vibration noise is canceled out by the reproduced sound generated in the speaker 3 (step S4), and then repeatedly executed from step S1.
[0037]
When step S2, step S5, and step S4 are repeatedly executed, it is a case of fading out, and the filter coefficient set in the adaptive filter 2 becomes the second filter coefficient, and the reproduced sound generated by the speaker 3 sequentially decreases. To do.
[0038]
If this state is schematically shown as shown in FIG. 3 (B), when step S1 to step S4 are repeatedly executed, step S5 is first executed at time tf, and thereafter step S2 is executed. If step S5 and step S4 are repeatedly executed, when step S1 to step S4 are repeatedly executed, the state shown before time tf is the state shown in FIG. The room vibration noise is canceled out by the reproduction sound of the speaker 3.
[0039]
When the execution of step 5 is first started from the state in which steps S1 to S4 are repeatedly executed, that is, the first filter coefficient in the silencing control operation region immediately before switching from time tf is the second before the update. The filter coefficient (W (n)), that is, the initial value of the second filter coefficient, is then updated by multiplying the second filter coefficient (W (n + 1)) by a predetermined value λ less than 1. Subsequently, when step S5 to step S4 are repeatedly executed, the second filter coefficient is sequentially decreased by a predetermined value λ times less than 1, and fade-out is executed as shown after time tf in FIG. 3B. As a result, the reproduced sound in the speaker 3 gradually decreases.
[0040]
FIG. 3A shows a case where the fade-out is not performed at time tf and the second filter coefficient is set to 0, and an unpleasant sound “puzzle” is generated as indicated by symbol a at time tf. Since the noise control device 15 fades out, such an unpleasant sound does not occur.
[0041]
As described above, in the active vibration noise control device 15, when it is determined in the check in step S2 that the frequency of the reference signal has gone out of the silencing control operation region from the silencing control operation region, the switching circuit 11 substantially switches. As a result, the second filter coefficient is selected instead of the first filter coefficient by this switching, and is used as the filter coefficient of the adaptive filter 2, and the canceling sound is faded out, so that the canceling signal is cut off. There are no unpleasant sounds that sometimes occur.
[0042]
Further, in the active vibration noise control device 15, when the frequency of the reference signal goes out of the silencing control operation area from the silencing control operation area, the filter coefficient is switched to the first filter coefficient before switching in step S2. Since the second filter coefficient multiplied by the predetermined value λ less than 1 is switched, the cancellation signal obtained by the adaptive filter 2 is multiplied by a ratio coefficient value that is sequentially decreased every time the filter coefficient is updated, thereby generating a cancellation sound. However, the ratio coefficient update calculation, the secondary sound output calculation, and the like are not required, the calculation load is small, and the fade-out is performed smoothly.
[0043]
Further, in the active vibration noise control device 15, when the fade-out is started, the active filter is switched to the second filter coefficient obtained by multiplying the immediately preceding first filter coefficient by a predetermined value λ (= 127/128) less than 1. It is possible to use an inexpensive microcomputer that uses a fixed point and performs the operation in 8 bits.
[0044]
Furthermore, in the active vibration noise control device 15, even when the frequency of the reference signal repeats outside the silencing control operation region and inside the silencing control operation region, the filter coefficient is inherited from one to the other, so that the canceling sound becomes prominent. No unpleasant noise is generated because no significant level changes occur.
[0045]
In the embodiment of the present invention, the active vibration noise control device 15 exemplifies the case where the movement to the outside of the silencing control operation region and the outside of the silencing control operation region is discriminated based on the frequency of the reference signal. As shown, instead of the frequency of the reference signal, the determination may be made based on the output shaft speed of the internal combustion engine. This is because the frequency of the reference signal is synchronized with the output shaft speed of the internal combustion engine and becomes a harmonic frequency of the output shaft speed.
[0046]
You may make it discriminate | determine the movement inside a silencing control operation area | region and the outside of a silencing control operation area | region by a vehicle speed signal, a vehicle door open / close signal, or a cylinder deactivation signal.
[0047]
【The invention's effect】
As described above, according to the active vibration noise control device of the present invention, it is possible to prevent unpleasant noise that occurs when the cancellation signal is cut off, to obtain a sufficient cancellation signal, and to reduce the cost of the micro In addition to being configured by a computer, it is possible to obtain an effect of quick response when returning to the mute control operation region.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an active vibration noise control apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart for explaining the operation of the active vibration noise control apparatus according to the embodiment of the present invention.
3 is a diagram for explaining the operation of the active vibration noise control apparatus according to the embodiment of the present invention, and FIG. 3 (A) shows a case where no fade-out is performed, and FIG. 3 (B). FIG. 10 is a diagram illustrating a case where fade-out is performed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Standard signal generation circuit 2 ... Adaptive filter 3 ... Speaker 4 ... Reference signal generation circuit 5 ... Filter coefficient calculation circuit 6 ... 1st filter coefficient calculation circuit 7 ... 2nd filter coefficient calculation circuit 8 ... Setting circuit 9 ... Multiplication Circuit 10 ... Microphone 11 ... Switching circuit 15 ... Active vibration noise control device

Claims (3)

A reference signal generating means for generating a reference signal having a frequency based on a frequency of vibration noise generated from the internal combustion engine;
An adaptive filter for generating a canceling signal based on the reference signal in order to cancel a vehicle interior vibration noise generated based on the vibration noise from the internal combustion engine;
Canceling sound generating means for generating a canceling sound based on the canceling signal output from the adaptive filter;
Error detection means for detecting a difference between the vehicle interior vibration noise and the canceling sound and outputting a signal based on the difference as an error signal;
Reference signal generation means for generating a reference signal by correcting the reference signal based on a correction value corresponding to a signal transmission characteristic from the canceling sound generation means to the error detection means;
First filter coefficient calculation means for sequentially updating the filter coefficient of the adaptive filter using adaptive calculation so that the error signal is minimized based on the reference signal and the error signal;
Second filter coefficient calculation means for sequentially updating the adaptive filter by multiplying the filter coefficient of the adaptive filter by a predetermined value less than 1,
An active vibration noise control apparatus comprising switching means for selectively switching between the first filter coefficient calculation means and the second filter coefficient calculation means. 2. The active vibration noise control apparatus according to claim 1, wherein the switching means sends a switching instruction according to the frequency of the reference signal. 2. The active vibration noise control apparatus according to claim 1, wherein the switching means sends a switching instruction in accordance with the output shaft rotational speed of the internal combustion engine.

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