JP2021162849A - Active noise controller - Google Patents

Abstract

To provide an active noise controller which can reduce noise even when a transmission characteristic is changed.SOLUTION: An active noise controller comprises an updated value table operation unit 64 for, upon starting an active noise control, writing an initial value of an initial value table 56 as an update value in an updated value table 58 and for writing, in the updated value table 58, as an updated value, a coefficient of a secondary path filter C^ updated in a secondary path filter coefficient updating unit 40 during an active noise control. The secondary path filter coefficient updating nit 40 reads an updated value corresponding to a frequency of the updated value table 58 before updating the coefficient of the secondary path filter C^, and updates the coefficient of the secondary path filter C^ by using the read updated value as a previous value.SELECTED DRAWING: Figure 3

Description

The present invention performs active noise control that controls a speaker based on an error signal that changes according to the combined sound of the noise transmitted from the vibration source and the canceling sound output from the speaker to cancel the noise. Regarding noise control devices.

In Patent Document 1 below, a reference signal based on the rotation frequency of the propeller shaft is generated, the reference signal is processed by an adaptive filter, and a canceling sound for canceling the noise transmitted from the propeller shaft into the vehicle is generated from the speaker. Those that generate a control signal to be output are disclosed. The adaptive filter is updated based on the error signal output by the microphone provided in the vehicle and the reference signal generated by correcting the reference signal with the correction value.

Japanese Unexamined Patent Publication No. 2008-239098

In Patent Document 1, since the transmission characteristic of the canceling sound between the speaker and the microphone is measured in advance and the measured transmission characteristic is used as a correction value, noise may not be reduced if the transmission characteristic changes.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an active noise control device capable of reducing noise even if the transmission characteristics change.

An aspect of the present invention is an active noise that controls the speaker based on an error signal that changes according to a combined sound of the noise transmitted from the vibration source and the canceling sound output from the speaker to cancel the noise. An active noise control device that controls the speaker by processing the reference signal with a reference signal generator that generates a reference signal according to the frequency to be controlled and a control filter that is an adaptive notch filter. A control signal generation unit that generates a control signal, an estimated noise signal generation unit that generates an estimated noise signal by processing the reference signal with a primary path filter that is an adaptive notch filter, and an adaptive notch filter for the control signal. A first estimated offset signal generator that processes a signal by a secondary path filter to generate a first estimated offset signal, and a reference signal that processes the reference signal by the secondary path filter to generate a reference signal. From the generation unit, the second estimated offset signal generation unit that generates the second estimated offset signal by signal processing the reference signal with the control filter, the error signal, the first estimated offset signal, and the estimated noise signal. A first virtual error signal generation unit that generates a first virtual error signal, a second virtual error signal generation unit that generates a second virtual error signal from the second estimated offset signal and the estimated noise signal, the control signal, and the control signal. Based on the first virtual error signal, the secondary path filter coefficient update unit that continuously adaptively updates the coefficient of the secondary path filter so that the magnitude of the first virtual error signal is minimized, and the reference signal. And the control filter coefficient update unit that sequentially adapts and updates the coefficient of the control filter so that the magnitude of the second virtual error signal is minimized based on the second virtual error signal, and the secondary path filter. An initial value table that stores the initial value of the coefficient in a table format in association with the frequency, an update value table that stores the update value of the coefficient of the secondary route filter in a table format in association with the frequency, and the above. At the start of active noise control, the initial value of the initial value table is written as the update value in the update value table, and the secondary path filter updated by the secondary path filter coefficient update unit during the active noise control. It has an update value table operation unit that writes the coefficient of The update value corresponding to the frequency in the table is read, and the read update value is read. The coefficient of the secondary path filter is updated by using it as the previous value.

The active noise control device of the present invention can reduce noise even if the transmission characteristics change.

It is a figure explaining the outline of active noise control. It is a block diagram of an active noise control device. It is a block diagram of an active noise control device. It is a figure explaining the update of a filter coefficient. It is a flowchart which shows the flow of the update process of a filter coefficient. FIG. 6A is a diagram showing a gain characteristic of the secondary path transmission characteristic. FIG. 6B is a diagram showing the phase characteristics of the secondary path transmission characteristics. It is a graph which shows the sound pressure level of the noise in a vehicle interior. It is a graph which shows the sound pressure level of the noise in a vehicle interior. It is a graph which shows the sound pressure level of the noise in a vehicle interior. It is a graph which shows the phase characteristic of an updated value. It is a graph which shows the sound pressure level of the noise in a vehicle interior. It is a graph which shows the phase characteristic of an updated value. It is a graph which shows the phase characteristic of an updated value. It is a graph which shows the sound pressure level of the noise in a vehicle interior. It is a graph which shows the sound pressure level of the noise in a vehicle interior. It is a block diagram of a signal processing part. It is a block diagram of a signal processing part. It is a block diagram of a signal processing part. It is a block diagram of a signal processing part. It is a block diagram of a signal processing part. It is a graph which shows the amplitude of a control filter. It is a graph which shows the sound pressure level of the noise in a vehicle interior.

[First Embodiment]
FIG. 1 is a diagram illustrating an outline of active noise control executed by the active noise control device 10.

The active noise control device 10 outputs a canceling sound from a speaker 16 provided in the passenger compartment 14 of the vehicle 12, and causes an engine noise (hereinafter, referred to as an engine noise control sound) transmitted to the occupants in the passenger compartment 14 due to the vibration of the engine 18. (Described as noise) is reduced. The active noise control device 10 is a speaker based on an error signal e output from the microphone 22 provided on the headrest 20a of the seat 20 in the vehicle interior 14 and an engine rotation speed Ne detected by the engine rotation speed sensor 24. A control signal u0 for outputting the canceling sound to 16 is generated. The error signal e is a signal output from the microphone 22 that detects the offset error noise, which is a combination of the offset sound and the noise, according to the offset error noise.

[Conventional active noise control device]
Conventionally, an active noise control device using an adaptive notch filter (for example, a SAN (Single-frequency Adaptive Notch) filter) with a small amount of arithmetic processing has been proposed.

In the conventional active noise control device, first, a reference signal x having a frequency of noise to be muted (control target frequency) is generated. A control signal u0 is generated by processing the generated reference signal x with the control filter W which is an adaptive notch filter, and the speaker 16 is controlled by the control signal u0 to cancel the noise from the speaker 16. Output sound.

The control filter W is updated by an adaptive algorithm (for example, LMS (Least Mean Square) algorithm) so that the error signal e output from the microphone 22 is minimized.

However, since the transmission characteristic C exists in the transmission path between the speaker 16 and the microphone 22, it is necessary to consider this transmission characteristic C when updating the control filter W. The transmission characteristic C also includes electronic circuit characteristics and the like. Therefore, the transmission characteristic C is identified in advance as the filter C ^, and the reference signal x corrected by the filter C ^ is used for updating the control filter W. Such a control system is called a Filtered-X type.

Since the filter C ^ is a fixed filter identified in advance, a difference may occur between the filter C ^ and the transmission characteristic C when the transmission characteristic C is changed. In that case, the control filter W may diverge due to the update, and noise amplification or abnormal noise may occur.

Therefore, the present inventors have proposed a method in which the filter C ^ can follow the change in the transmission characteristic C during active noise control without the need to identify the transmission characteristic C in advance. The present invention is a further improvement of the method proposed by the present inventors. The outline of the active noise control device 100 using the method proposed by the present inventors will be described below.

FIG. 2 is a block diagram of an active noise control device 100 using the method proposed by the present inventors. The transmission path from the engine 18 to the microphone 22 may be referred to as a primary path below. Further, the transmission path from the speaker 16 to the microphone 22 may be referred to as a secondary path below.

The active noise control device 100 includes a reference signal generation unit 26, a control signal generation unit 28, a first estimation offset signal generation unit 30, an estimation noise signal generation unit 32, a reference signal generation unit 34, and a second estimation cancellation signal generation unit 36. It has a primary route filter coefficient updating unit 38, a secondary route filter coefficient updating unit 40, and a control filter coefficient updating unit 42.

The reference signal generation unit 26 generates reference signals xc and xs based on the engine speed Ne. The reference signal generator 26 includes a frequency detection circuit 26a, a cosine signal generator 26b, and a sine signal generator 26c.

The frequency detection circuit 26a detects the control target frequency f. The control target frequency f is the vibration frequency of the engine 18 detected based on the engine speed Ne. The cosine signal generator 26b generates a reference signal xc (= cos (2πft)) which is a cosine signal of the control target frequency f. The sine signal generator 26c generates a reference signal xs (= sin (2πft)) which is a sine signal of the controlled frequency f. Here, t indicates the time.

The control signal generation unit 28 generates control signals u0 and u1 based on the reference signals xc and xs. The control signal generation unit 28 includes a first control filter 28a, a second control filter 28b, a third control filter 28c, a fourth control filter 28d, an adder 28e, and an adder 28f.

In the control signal generation unit 28, a SAN filter is used as the control filter W. The control filter W has a filter W0 for the reference signal xc and a filter W1 for the reference signal xs. The control filter W is optimized by updating the coefficient W0 of the filter W0 and the coefficient W1 of the filter W1 in the control filter coefficient updating unit 42 described later.

The first control filter 28a has a filter coefficient W0. The second control filter 28b has a filter coefficient W1. The third control filter 28c has a filter coefficient −W0. The fourth control filter 28d has a filter coefficient W1.

The reference signal xc corrected by the first control filter 28a and the reference signal xs corrected by the second control filter 28b are added by the adder 28e to generate the control signal u0. The reference signal xs corrected by the third control filter 28c and the reference signal xc corrected by the fourth control filter 28d are added by the adder 28f to generate the control signal u1.

The control signal u0 is converted into an analog signal by the digital-to-analog converter 17 and output to the speaker 16. The speaker 16 is controlled based on the control signal u0, and the canceling sound is output from the speaker 16.

The first estimated offset signal generation unit 30 generates the first estimated offset signal y1 ^ based on the control signals u0 and u1. The first estimation offset signal generation unit 30 includes a first secondary path filter 30a, a second secondary path filter 30b, and an adder 30c.

In the first estimation offset signal generation unit 30, a SAN filter is used as the secondary path filter C ^. The secondary path transmission characteristic C is identified as the secondary path filter C ^ by updating the coefficient (C0 ^ + iC1 ^) of the secondary path filter C ^ in the secondary path filter coefficient updating unit 40 described later.

The first secondary path filter 30a has a filter coefficient C0 ^ which is a real part of the coefficient of the secondary path filter C ^. The second secondary path filter 30b has a filter coefficient C1 ^ which is an imaginary part of the coefficient of the secondary path filter C ^. The control signal u0 corrected by the first secondary path filter 30a and the control signal u1 corrected by the second secondary path filter 30b are added by the adder 30c to generate the first estimated offset signal y1 ^. NS. The first estimated canceling signal y1 ^ is an estimated signal of a signal corresponding to the canceling sound y input to the microphone 22.

The estimated noise signal generation unit 32 generates an estimated noise signal d ^ based on the reference signals xc and xs. The estimated noise signal generation unit 32 includes a first primary path filter 32a, a second primary path filter 32b, and an adder 32c.

In the estimated noise signal generation unit 32, a SAN filter is used as the primary path filter H ^. In the primary path filter coefficient updating unit 38, which will be described later, the coefficient (H0 ^ + iH1 ^) of the primary path filter H ^ is updated, so that the transmission characteristic H of the primary path (hereinafter referred to as the primary path transmission characteristic H) becomes the primary path. Identified as filter H ^.

The first primary path filter 32a has a filter coefficient H0 ^ which is a real part of the coefficient of the primary path filter H ^. The second primary path filter 32b has a filter coefficient −H1 ^ in which the polarity of the imaginary portion of the coefficient of the primary path filter H ^ is inverted. The reference signal xc corrected by the first primary path filter 32a and the reference signal xs corrected by the second primary path filter 32b are added by the adder 32c to generate an estimated noise signal d ^. The estimated noise signal d ^ is an estimated signal of a signal corresponding to the noise d input to the microphone 22.

The reference signal generation unit 34 generates reference signals r0 and r1 based on the reference signals xc and xs. The reference signal generation unit 34 has a third secondary route filter 34a, a fourth secondary route filter 34b, a fifth secondary route filter 34c, a sixth secondary route filter 34d, an adder 34e, and an adder 34f. There is.

In the reference signal generation unit 34, a SAN filter is used as the secondary path filter C ^. In the secondary route filter coefficient updating unit 40 described later, the coefficient (C0 ^ + iC1 ^) of the secondary route filter C ^ is updated to update the transmission characteristic C of the secondary route (hereinafter referred to as the secondary route transmission characteristic C). ) Is identified as the secondary pathway filter C ^.

The third secondary path filter 34a has a filter coefficient C0 ^ which is a real part of the coefficient of the secondary path filter C ^. The fourth secondary path filter 34b has a filter coefficient −C1 ^ in which the polarity of the imaginary portion of the coefficient of the secondary path filter C ^ is inverted. The fifth secondary path filter 34c has a filter coefficient C0 ^ which is a real part of the coefficient of the secondary path filter C ^. The sixth secondary path filter 34d has a filter coefficient C1 ^ which is an imaginary part of the coefficient of the secondary path filter C ^.

The reference signal xc corrected by the third secondary path filter 34a and the reference signal xs corrected by the fourth secondary path filter 34b are added by the adder 34e to generate the reference signal r0. The reference signal xs corrected by the fifth secondary path filter 34c and the reference signal xc corrected by the sixth secondary path filter 34d are added by the adder 34f to generate the reference signal r1.

The second estimated offset signal generation unit 36 generates the second estimated offset signal y2 ^ based on the reference signals r0 and r1. The second estimation offset signal generation unit 36 includes a fifth control filter 36a, a sixth control filter 36b, and an adder 36c.

In the second estimation offset signal generation unit 36, a SAN filter is used as the control filter W. The fifth control filter 36a has a filter coefficient W0. The sixth control filter 36b has a filter coefficient W1.

The reference signal r0 corrected by the fifth control filter 36a and the reference signal r1 corrected by the sixth control filter 36b are added by the adder 36c to generate the second estimated offset signal y2 ^. The second estimated canceling signal y2 ^ is an estimated signal of a signal corresponding to the canceling sound y input to the microphone 22.

The analog-digital converter 44 converts the error signal e output from the microphone 22 from an analog signal to a digital signal.

The error signal e is input to the adder 46. The polarity of the estimated noise signal d ^ generated by the estimated noise signal generation unit 32 is inverted by the reversing device 48, and is input to the adder 46. The polarity of the first estimated offset signal y1 ^ generated by the first estimated offset signal generation unit 30 is inverted by the inverter 50 and input to the adder 46. In the adder 46, the first virtual error signal e1 is generated. The adder 46 corresponds to the first virtual error signal generation unit of the present invention.

The estimated noise signal d ^ generated by the estimated noise signal generation unit 32 is input to the adder 52. The second estimated offset signal y2 ^ generated by the second estimated offset signal generation unit 36 is input to the adder 52. In the adder 52, the second virtual error signal e2 is generated. The adder 52 corresponds to the second virtual error signal generation unit of the present invention.

The primary path filter coefficient update unit 38 updates the filter coefficients H0 ^ and H1 ^ based on the reference signals xc and xs and the first virtual error signal e1. The primary path filter coefficient update unit 38 updates the coefficients of the filter coefficients H0 ^ and H1 ^ based on the LMS algorithm. The primary route filter coefficient updating unit 38 has a primary route filter coefficient updating unit 38a and a second primary route filter coefficient updating unit 38b.

The first primary route filter coefficient updating unit 38a and the second primary route filter coefficient updating unit 38b update the filter coefficients H0 ^ and H1 ^ based on the following equations. In the equation, n indicates a time step (n = 0, 1, 2, ...), And μ0 and μ1 indicate a step size parameter.

The primary path transmission characteristic H is identified as the primary path filter H ^ by repeatedly updating the filter coefficients H0 ^ and H1 ^ in the primary path filter coefficient updating unit 38. In the active noise control device 100 using the SAN filter, the coefficient update formula of the primary path filter H ^ is composed of four arithmetic operations and does not include the convolution operation. Therefore, the filter coefficients H0 ^ and H1 ^ are updated. The calculation load can be suppressed.

The secondary path filter coefficient update unit 40 updates the filter coefficients C0 ^ and C1 ^ based on the control signals u0 and u1 and the first virtual error signal e1. The secondary path filter coefficient update unit 40 updates the filter coefficients C0 ^ and C1 ^ based on the LMS algorithm. The secondary route filter coefficient updating unit 40 includes a primary route filter coefficient updating unit 40a and a secondary route filter coefficient updating unit 40b.

The first secondary route filter coefficient updating unit 40a and the second secondary route filter coefficient updating unit 40b update the filter coefficients C0 ^ and C1 ^ based on the following equations. Μ2 and μ3 in the formula indicate step size parameters.

The secondary path transmission characteristic C is identified as the secondary path filter C ^ by repeatedly updating the filter coefficients C0 ^ and C1 ^ in the secondary path filter coefficient updating unit 40. In the active noise control device 100 using the SAN filter, the update formulas of the filter coefficients C0 ^ and C1 ^ are composed of four rules operations and do not include the convolution operation. Therefore, the update processing of the filter coefficients C0 ^ and C1 ^ is performed. The calculation load can be suppressed.

The control filter coefficient updating unit 42 updates the filter coefficients W0 and W1 based on the reference signals r0 and r1 and the second virtual error signal e2. The control filter coefficient updating unit 42 updates the filter coefficients W0 and W1 based on the LMS algorithm. The control filter coefficient updating unit 42 has a first control filter coefficient updating unit 42a and a second control filter coefficient updating unit 42b.

The first control filter coefficient updating unit 42a and the second control filter coefficient updating unit 42b update the filter coefficients W0 and W1 based on the following equations. Μ4 and μ5 in the equation indicate step size parameters.

The control filter W is optimized by repeatedly updating the filter coefficients W0 and W1 in the control filter coefficient updating unit 42. In the active noise control device 100 using the SAN filter, the update formulas of the filter coefficients W0 and W1 are composed of four rules and do not include the convolution calculation, so that the calculation load due to the update processing of the filter coefficients W0 and W1 is suppressed. can.

[About improvements]
The improvement points of the present invention with respect to the active noise control device 100 in which the method proposed by the present inventors described above is used will be described.

FIG. 3 is a block diagram of the active noise control device 10 of the present embodiment. The active noise control device 10 of the present embodiment has an active noise control device 100 as a signal processing unit 54, in which the method proposed by the present inventors has been used. The active noise control device 10 further includes an initial value table 56, an update value table 58, a result value table 60, an initial value table operation unit 62, an update value table operation unit 64, a result value table operation unit 66, and an abnormality determination unit 68. Have.

The active noise control device 10 has an arithmetic processing unit and storage (not shown). The arithmetic processing unit has, for example, a memory including a processor such as a central processing unit (CPU) and a microprocessing unit (MPU), and a non-temporary or temporary tangible computer-readable recording medium such as ROM or RAM. ing. The storage is, for example, a non-temporary tangible computer-readable recording medium such as a hard disk or flash memory.

The initial value table 56 is a table-type memory area provided in the ROM, and the initial values of the filter coefficients C0 ^ and C1 ^ of the secondary path filter C ^ described later are stored. The update value table 58 is a table-type memory area provided in the RAM, and the update values of the filter coefficients C0 ^ and C1 ^ are stored. The result value table 60 is a table-type memory area provided in the ROM, and the result values of the filter coefficients C0 ^ and C1 ^ are stored.

The initial value table operation unit 62 writes the initial value to the initial value table 56 and the like. The update value table operation unit 64 writes the update value to the update value table 58 and the like. The result value table operation unit 66 writes the result value to the result value table 60 and the like. When the active noise control is completed, the abnormality determination unit 68 determines the abnormality or divergence of the active noise control. The abnormality determination unit 68 corresponds to the determination unit of the present invention.

The signal processing unit 54, the initial value table operation unit 62, the update value table operation unit 64, the result value table operation unit 66, and the abnormality determination unit 68 perform arithmetic processing in the arithmetic processing unit according to the program stored in the storage. It is realized by being told.

The update processing of the filter coefficients C0 ^ and C1 ^ in the secondary path filter coefficient updating unit 40 of the present embodiment is performed by the above-mentioned filter coefficients C0 ^ and C1 ^ in the secondary path filter coefficient updating unit 40 of the active noise control device 100. Partially different from the update process.

In the secondary path filter coefficient updating section 40 of the active noise control device 100 in which the proposed method is used, the following equation is used in the primary path filter coefficient updating section 40a and the secondary path filter coefficient updating section 40b. The filter coefficients C0 ^ and C1 ^ are updated based on.

On the other hand, in the secondary path filter coefficient updating unit 40 of the active noise control device 10 (signal processing unit 54) of the present embodiment, the primary path filter coefficient updating unit 40a and the secondary path filter coefficient updating unit 40b , Update the filter coefficients C0 ^ and C1 ^ based on the following equation.

In the coefficients C0 ^ (f) _u and C1 ^ (f) _u in the above equation, update values corresponding to the controlled frequency f stored in the update value table 58 are input. Hereinafter, the first term on the right side of the update formula of the filter coefficients C0 ^ and C1 ^ may be referred to as the previous value.

_{In the proposed method, the filter coefficients C0 ^ n} and C1 ^ _n after the update in the previous time (time step n) are used as the previous values of the update formula. That is, even if the control target frequency f changes between the previous update (time step n) and the current update (time step n + 1), the filter coefficients C0 ^ _n and C1 ^ _n after the previous update are updated. Used as the previous value of the expression.

On the other hand, in the present embodiment, as the previous value of the update formula, the update value corresponding to the control target frequency f at the time of this update (time step n + 1) is used. That is, the latest updated filter coefficients C0 ^ (f) _u and C1 ^ (f) _u updated at the control target frequency f are used as the previous values of the update formula. That is, the previous value is not necessarily the value updated in the previous time (time step n).

Further, the secondary path filter coefficient updating unit 40 uses the updated filter coefficients C0 ^ and C1 ^ as the third secondary path filter 34a, the fourth secondary path filter 34b, and the fifth secondary of the reference signal generation unit 34. Copy to the route filter 34c and the sixth secondary route filter 34d.

[Update the coefficient of the secondary route filter]
FIG. 4 is a diagram for explaining the update of the filter coefficients C0 ^ and C1 ^. As shown in FIG. 4, the initial value table 56 stores the initial values C0 ^ (f) _i and C1 ^ (f) _i in a table format in association with the frequency. The update value table 58 stores the update values C0 ^ (f) _u and C1 ^ (f) _u in a table format in association with the frequency. Further, the result value table 60 stores the result values C0 ^ (f) _r and C1 ^ (f) _r in a table format in association with the frequency.

The initial value corresponding to each frequency stored in the initial value table 56 is set to any of the following (i) to (v).

ここで、Ｔは音がスピーカ１６からマイクロフォン２２に届くまでの時間、ａは振幅定数である。
（ｖ）都合のよい小さな値（システム設定の効率等の便宜上、初期値を特に設定しない場合） (I) Measured value of secondary path transmission characteristic C for each frequency (ii) Phase information of measured value of secondary path transmission characteristic C for each frequency (iii) Measure secondary path transmission characteristic C of typical frequency , Estimated value of secondary path transmission characteristic C complemented from the measured value, or phase information of the estimated value of secondary path transmission characteristic C (iv) Estimated value of secondary path transmission characteristic C estimated by the following equation

Here, T is the time until the sound reaches the microphone 22 from the speaker 16, and a is the amplitude constant.
(V) A convenient small value (when the initial value is not set for convenience such as efficiency of system setting)

FIG. 5 is a flowchart showing the flow of the update processing of the filter coefficients C0 ^ and C1 ^. The update processing of the filter coefficients C0 ^ and C1 ^ is executed every time the active noise control is performed.

In step S1, the update value table operation unit 64 writes the initial value corresponding to each frequency in the initial value table 56 to the update value corresponding to each frequency in the update value table 58 ((A) in FIG. 4). The process proceeds to step S2.

In step S2, the frequency detection circuit 26a of the signal processing unit 54 detects the frequency f to be controlled and proceeds to step S3.

In step S3, the secondary path filter coefficient update unit 40 reads the update value corresponding to the control target frequency f as the previous value ((B) in FIG. 4), and proceeds to step S4.

In step S4, the secondary route filter coefficient updating unit 40 updates the filter coefficients C0 ^ and C1 ^, and proceeds to step S5.

In step S5, the update value table operation unit 64 writes the updated filter coefficients C0 ^ and C1 ^ in the update value corresponding to the control target frequency f ((C) in FIG. 4), and proceeds to step S6. ..

In step S6, the abnormality determination unit 68 determines whether or not the active noise control has been completed. The active noise control ends when the engine 18 is stopped, when an abnormality occurs in the active noise control, or when the active noise control diverges. If the active noise control is not completed, the process returns to step S2, and if the active noise control is completed, the process proceeds to step S7.

In step S7, the abnormality determination unit 68 determines whether or not the active noise control has ended normally. If it is determined that the active noise control has ended normally, the process proceeds to step S8, and if it is determined that the active noise control has not ended due to an abnormality or divergence of the active noise control, the process proceeds to step S10.

In step S8, the initial value table operation unit 62 determines whether or not the rewriting of the initial value of the initial value table 56 is permitted. If the rewriting of the initial value table 56 is permitted, the process proceeds to step S9, and if the rewriting of the initial value table 56 is not permitted, the update processing of the filter coefficients C0 ^ and C1 ^ is terminated.

In step S9, the initial value table operation unit 62 rewrites the initial value corresponding to each frequency in the initial value table 56 to the updated value corresponding to each frequency in the updated value table 58 ((D) in FIG. 4). The update processing of the filter coefficients C0 ^ and C1 ^ is completed.

In step S10, the result value table operation unit 66 writes the update value corresponding to each frequency of the update value table 58 to the result value corresponding to each frequency of the result value table 60 ((E) in FIG. 4). The update processing of the filter coefficients C0 ^ and C1 ^ is completed.

The initial value table 56 and the result value table 60 can be copied to a personal computer or the like connected to the vehicle 12. Therefore, when an abnormality or divergence occurs in the active noise control, the active noise control is performed by comparing the updated value stored in the initial value table 56 with the result value stored in the result value table 60. It is possible to verify the cause of the occurrence of anomalies or divergence.

[Experimental result]
The present inventors conducted an experiment on muffling performance by active noise control. The experimental results are shown below. Each of the following experiments was performed under the secondary path transfer characteristic C having the gain characteristic shown by the thin line in FIG. 6A and the phase characteristic shown by the thin line in FIG. 6B.

<Experiment (1)>
In the experiment (1), the sound pressure level of the noise in the vehicle interior 14 when the vehicle 12 is accelerated from the stopped state is measured while the active noise control is off.

<Experiment (2)>
In the experiment (2), the passenger compartment 14 when the vehicle 12 is accelerated from the stopped state while the active noise control device 100 using the method proposed by the present inventors is performing the active noise control. The sound pressure level of the noise inside is measured.

<Experiment (3)>
In the experiment (3), the sound pressure level of the noise in the vehicle interior 14 when the vehicle 12 is accelerated from the stopped state while the active noise control device 10 of the present embodiment is performing the active noise control is measured. Is done. In the experiment (3), the initial value of each frequency in the initial value table 56 is set to the measured value of the secondary path transmission characteristic C of each frequency.

<Experiment (4)>
In the experiment (4), the sound pressure level of the noise in the vehicle interior 14 when the vehicle 12 is accelerated from the stopped state while the active noise control device 10 of the present embodiment is performing the active noise control is measured. Is done. In the experiment (4), the initial value of each frequency in the initial value table 56 is set to the estimated value of the secondary path transmission characteristic C estimated by the following equation.

Here, T is set to 0.01 s. The gain characteristics and phase characteristics of the estimated values of the secondary path transmission characteristic C are shown by thick lines in FIGS. 6A and 6B.

<< Comparison of the results of experiments (1) to (3) >>
FIG. 7 is a graph showing the sound pressure level of the noise in the passenger compartment 14 measured in the experiments (1) to (3).

As shown in FIG. 7, at the start of running of the vehicle 12 (engine speed is 1600 RPM to 2000 RPM), the muffling performance in the experiment (3) is higher than that in the experiment (2) by 10 dB or more. In particular, immediately after the start of running of the vehicle 12 (engine speed is around 1600 RPM), the sound was not muted in the experiment (2), whereas the sound was muted by about 10 dB in the experiment (3).

<< Comparison of the results of experiments (1), (2), and (4) >>
FIG. 8 is a graph showing the sound pressure level of the noise in the passenger compartment 14 measured in the experiments (1), (2), and (4).

As shown in FIG. 8, even when an accurate estimate of the secondary path transmission characteristic C cannot be obtained as in the experiment (4), in the range of the engine speed of 4500 RPM or less, the experiment (2) The muffling performance in the experiment (4) is about the same or higher than that of the above. In the range where the engine speed exceeds 4500 RPM, the muffling performance in the experiment (4) is lower than that in the experiment (2). This is because, as shown in FIGS. 6A and 6B, the estimated value of the secondary path transmission characteristic C deviates from the actual secondary path transmission characteristic C in the range where the engine speed exceeds the frequency 150 Hz corresponding to 4500 RPM. Because it is doing. However, by repeating the number of updates of the filter coefficients C0 ^ and C1 ^, the secondary path filter C ^ approaches the secondary path transmission characteristic C, so that the muffling performance is improved.

<Experiment (5)>
In the experiment (5), the noise in the passenger compartment 14 during the first traveling when the vehicle 12 is accelerated from the stopped state while the active noise control device 10 of the present embodiment is performing the active noise control. Sound pressure level is measured. In the experiment (5), the initial value of each frequency in the initial value table 56 is set to a convenient small value.

<Experiment (6)>
In the experiment (6), the noise in the passenger compartment 14 during the third traveling when the vehicle 12 is accelerated from the stopped state while the active noise control device 10 of the present embodiment is performing the active noise control. Sound pressure level is measured. In the experiment (6), the initial value of each frequency in the initial value table 56 is set to a convenient small value.

<< Comparison of the results of experiments (1), (5), and (6) >>
FIG. 9 is a graph showing the sound pressure level of the noise in the passenger compartment 14 measured in the experiments (1), (5), and (6).

As shown in FIG. 9, the sound pressure level during the first run of the experiment (5) is higher than the sound pressure level when the active noise control of the experiment (1) is turned off. However, as in the experiment (6), the muffling performance is improved even during the third run in which the number of updates of the filter coefficients C0 ^ and C1 ^ is relatively small.

FIG. 10 shows the phase characteristic of the secondary path transmission characteristic C, the phase characteristic of the updated value after the end of the first run in the experiment (5), and the phase of the updated value after the end of the third run in the experiment (6). It is a graph which shows the characteristic.

As shown in FIG. 10, there is a tendency that the random error, which was large at the update value after the end of the first run, converges toward the secondary route transmission characteristic C at the update value after the end of the third run. To be done. By rewriting the initial value of the initial value table 56 with the updated filter coefficients C0 ^ and C1 ^ in the secondary path filter coefficient update unit 40, the highly accurate initial value is used at the next start of active noise control. , The filter coefficients C0 ^ and C1 ^ can be updated. Therefore, the muffling performance by active noise control can be improved.

ここで、Ｔは音がスピーカ１６からマイクロフォン２２に届くまでの時間、ａは振幅定数である。
（ｖ）都合のよい小さな値（システム設定の効率等の便宜上、初期値を特に設定しない場合） [Action effect]
In the active noise control device 10 of the present embodiment, the initial value table 56 stores the initial values C0 ^ (f) _i and C1 ^ (f) _i in a table format in association with the frequency. The initial value corresponding to each frequency stored in the initial value table 56 is set to any of the following (i) to (v).
(I) Measured value of secondary path transmission characteristic C for each frequency (ii) Phase information of measured value of secondary path transmission characteristic C for each frequency (iii) Measure secondary path transmission characteristic C of typical frequency , Estimated value of secondary path transmission characteristic C complemented from the measured value, or phase information of the estimated value of secondary path transmission characteristic C (iv) Estimated value of secondary path transmission characteristic C estimated by the following equation

Here, T is the time until the sound reaches the microphone 22 from the speaker 16, and a is the amplitude constant.
(V) A convenient small value (when the initial value is not set for convenience such as efficiency of system setting)

Further, the update value table operation unit 64 writes the initial value corresponding to the control target frequency f of the initial value table 56 to the update value corresponding to the control target frequency f of the update value table 58 at the start of active noise control. The secondary path filter coefficient update unit 40 reads the update value corresponding to the control target frequency f from the update value table 58 before updating the filter coefficients C0 ^ and C1 ^. Then, the secondary route filter coefficient update unit 40 updates the filter coefficients C0 ^ and C1 ^ using the read update value as the previous value. The update value table operation unit 64 writes the updated filter coefficients C0 ^ and C1 ^ in the update value corresponding to the controlled frequency f in the update value table 58. By providing the initial value table 56 and the updated value table 58, the active noise control device 10 sets the initial values of the filter coefficients C0 ^ and C1 ^ for each frequency, and also sets the filter coefficients C0 ^ and C1 for each frequency. It is possible to update ^. As a result, the active noise control device 10 can significantly improve the initial muffling performance, especially after the start of active noise control.

Further, in the active noise control device 10 of the present embodiment, when the abnormality determination unit 68 does not determine that the active noise control is abnormal or divergent at the end of the active noise control, the initial value table operation unit 62 sets the initial value. The initial value of the table 56 is rewritten with the update value of the update value table 58. As a result, at the next start of active noise control, the filter coefficients C0 ^ and C1 ^ can be updated using highly accurate initial values. Therefore, the muffling performance by active noise control can be improved.

Further, in the active noise control device 10 of the present embodiment, when the abnormality determination unit 68 determines that the active noise control is abnormal or divergent at the end of the active noise control, the initial value table operation unit 62 sets the initial value table 56. The initial value of is not rewritten to the update value of the update value table 58. As a result, in the next active noise control, the filter coefficients C0 ^ and C1 ^ when the active noise control is abnormal or diverged are not written as update values in the update value table 58, so that the active noise control is returned to normal. be able to.

Further, in the active noise control device 10 of the present embodiment, when the abnormality determination unit 68 determines that the active noise control is abnormal or divergent at the end of the active noise control, the result value table operation unit 66 causes the result value table 60. The result value of is rewritten to the update value of the update value table 58. As a result, when an abnormality or divergence occurs in the active noise control, the updated value stored in the initial value table 56 and the result value stored in the result value table 60 are compared with each other to perform active noise. The cause of the occurrence of control abnormality or divergence can be verified.

[Second Embodiment]
In the active noise control device 10 of the present embodiment, the filter coefficients C0 ^ and C1 ^ updated based on the update formula in the secondary path filter coefficient update unit 40 and the update values stored in the update value table 58. Performs weighted averaging processing.

The first secondary route filter coefficient updating unit 40a and the second secondary route filter coefficient updating unit 40b perform weighted averaging processing of the filter coefficients C0 ^ and C1 ^ based on the following equations. In the equation, L is the frequency range for weight averaging, and θ is the weighting coefficient.

The weighting coefficient θ is set based on the following equation.

[Random error reduction principle]
By repeating the update of the filter coefficients C0 ^ and C1 ^, the random error of the secondary path filter C ^ is reduced, and the muffling performance by active noise control is improved. In the present embodiment, the weighted averaging process of the filter coefficients C0 ^ and C1 ^ updated based on the update formula and the update values stored in the update value table 58 is performed, so that the number of updates is small. The random error of the next path filter C ^ can be reduced.

ここで、Ｅ［Ｃ０＾（ｆ）］はＣ０＾の期待値、Ｅ［Ｃ１＾（ｆ）］はＣ１＾の期待値、σはシステム誤差、δはランダム誤差を示す。期待値Ｅ［Ｃ０＾（ｆ）］及び期待値Ｅ［Ｃ１＾（ｆ）］は、時間によって変化しない値である。 The filter coefficients C0 ^ and C1 ^ are indicated by the following equations in a format in which the true value includes an error.

Here, E [C0 ^ (f)] is the expected value of C0 ^, E [C1 ^ (f)] is the expected value of C1 ^, σ is the system error, and δ is the random error. The expected value E [C0 ^ (f)] and the expected value E [C1 ^ (f)] are values that do not change with time.

Here, if the system error σ is omitted, the filter coefficient C0 ^ is rewritten by the following equation.

When the frequency range L for weight averaging is sufficiently large, the random error δ satisfies the following equation.

ここで、σＭ０は平均化処理によって発生するシステム誤差であり、βの値が１に近いほど、σＭ０の大きさは小さくなる。ランダム誤差δは時間ステップｎ＝１のときのランダム誤差δを用いて次の式により表される。

Therefore, the filter coefficient C0 ^ is further rewritten by the following equation.

Here, σM0 is a system error generated by the averaging process, and the closer the value of β is to 1, the smaller the magnitude of σM0. The random error δ is expressed by the following equation using the random error δ when the time step n = 1.

From this equation, it can be seen that by setting β to be 1 / (2L) <β <1, the random error δ becomes smaller as the number of updates (time step n) increases. As the number of updates (time step n) increases, the random error δ converges to 0. As a result, the filter coefficient C0 ^ can be expressed in a form that does not include the random error δ, as shown in the following equation.

Similarly, the filter coefficient C1 ^ can be expressed in a form that does not include the random error δ, as shown in the following equation that does not include the random error δ.

[Experimental result]
The present inventors conducted an experiment on muffling performance by active noise control. The experimental results are shown below. Each of the following experiments was performed under the secondary path transfer characteristic C having the gain characteristic shown by the thin line in FIG. 6A and the phase characteristic shown by the thin line in FIG. 6B.

<Experiment (7)>
In the experiment (7), the noise in the passenger compartment 14 during the third traveling when the vehicle 12 is accelerated from the stopped state while the active noise control device 10 of the present embodiment is performing the active noise control. Sound pressure level is measured. In the experiment (7), the initial value of each frequency in the initial value table 56 is set to a convenient small value.

<< Comparison of experiments (1), (6), and (7) >>
FIG. 11 is a graph showing the sound pressure level of the noise in the passenger compartment 14 measured in the experiments (1), (6), and (7).

As shown in FIG. 11, at an engine speed of 1800 to 2400 RPM, in the experiment (7), the muffling performance is improved by 10 dB or more as compared with the experiment (6).

FIG. 12 shows the phase characteristic of the secondary path transmission characteristic C, the phase characteristic of the updated value after the end of the third run in the experiment (6), and the phase of the updated value after the end of the third run in the experiment (7). It is a graph which shows the characteristic. In the experiment (7), the random error is greatly reduced as compared with the experiment (6) at the frequency 60 to 80 Hz corresponding to the engine speed of 1800 to 2400 RPM.

In both the experiment (6) and the experiment (7), the number of runs was three, and from FIGS. 11 and 12, in the experiment (7), the updated value became the secondary route transmission characteristic C as compared with the experiment (6). It can be read that it is converging early.

[Action effect]
In the active noise control device 10 of the present embodiment, the secondary path filter coefficient update unit 40 weighted averages the updated filter coefficients C0 ^ and C1 ^ based on the update formula and the updated values in the updated value table 58. Perform processing. As a result, the random error of the secondary path filter C ^ can be converged at an early stage, and the muffling performance of the active noise control can be improved.

ここで、Ｃｔ０＾_ｎ、Ｃｔ１＾_ｎは、前回（時間ステップｎ）のフィルタ係数Ｃ０＾、Ｃ１＾の更新結果を保持させるための変数である。変数Ｃｔ０＾_ｎ、Ｃｔ１＾_ｎの初期値であるＣｔ０＾₁、Ｃｔ１＾₁は、０等小さい値が設定される。γは０≦γ≦１を満たす係数である。 [Third Embodiment]
In the active noise control device 10 of the present embodiment, the primary path filter coefficient updating section 40a and the secondary path filter coefficient updating section 40b of the secondary path filter coefficient updating section 40 are based on the following equations, respectively. The filter coefficients C0 ^ and C1 ^ are updated.

Here, Ct0 ^ _n and Ct1 ^ _n are variables for holding the update results of the filter coefficients C0 ^ and C1 ^ of the previous time (time step n). The initial values of the variables Ct0 ^ _n and Ct1 ^ _{n , Ct0 ^ 1} and Ct1 ^ ₁ , are set to values as small as 0. γ is a coefficient that satisfies 0 ≦ γ ≦ 1.

FIG. 13 is a diagram showing the phase characteristics of the updated values stored in the updated value table 58 and the phase characteristics of the secondary path transmission characteristic C. The engine speed range that is often used in normal driving is an engine speed of 3600 RPM or less, and the frequency of the noise generated at that time is 120 Hz or less. Therefore, in the frequency range of 120 Hz or less, the filter coefficients C0 ^ and C1 ^ are updated repeatedly, and the phase characteristic of the updated value substantially converges on the secondary path transmission characteristic C.

On the other hand, a range larger than the engine speed of 3600 RPM is used for traveling in limited situations such as when accelerating when merging from a side road of a highway to the main line, or when climbing a steep uphill. Therefore, even when the active noise control is continued for a certain period of time, the filter coefficients C0 ^ and C1 ^ are not updated in the range where the frequency is higher than 120 Hz, and the updated values are equal to the initial values. Alternatively, the filter coefficients C0 ^ and C1 ^ are not sufficiently updated, and the secondary path filter C ^ is in a state of deviating from the secondary path transmission characteristic C. Therefore, when the engine speed exceeds 3600 RPM, the muffling performance by active noise control deteriorates, and the engine noise may suddenly increase.

Since the control target frequency f changes continuously with the passage of time, the control target frequency f of the previous time (time step n) is often a frequency near the control target frequency f of this time (time step n + 1). .. Further, since the secondary path transmission characteristic C changes continuously according to the controlled frequency f, the secondary path transmission characteristic C in the previous time (time step n) and the secondary path transmission characteristic in this time (time step n + 1) C has similar characteristics.

Therefore, the filter coefficients C0 ^ and C1 ^ after the update in the previous time (time step n) and the update value corresponding to the controlled frequency f of this time (time step n + 1) in the update value table 58 are added at a predetermined ratio. The filter coefficients C0 ^ and C1 ^ are updated by using the value as the previous value of the update formula.

ここで、Ｃｏｅｆ_ｄは１より小さい正数とする減衰係数である。この場合γの初期値を１又は１に近い値に設定してもよい。 The coefficient γ may be provided for each frequency, and the number of updates of the filter coefficients C0 ^ and C1 ^ may increase according to the following equation, and the coefficient γ may be attenuated.

Here, Coef _d is an attenuation coefficient that is a positive number smaller than 1. In this case, the initial value of γ may be set to 1 or a value close to 1.

When the number of updates of the filter coefficients C0 ^ and C1 ^ at the control target frequency f at the time of this update is the first, γ becomes a value close to 1. Therefore, since the filter coefficients C0 ^ and C1 ^ are updated this time mainly based on the filter coefficients C0 ^ and C1 ^ after the previous update, the deterioration of the muffling performance due to the active noise control can be suppressed.

When the number of updates of the filter coefficients C0 ^ and C1 ^ at the control target frequency f at the time of this update is large, γ is attenuated to 0. Therefore, since the filter coefficients C0 ^ and C1 ^ are updated this time mainly based on the updated values in the updated value table 58, the muffling performance by active noise control can be improved.

係数γに最低値を設けることで、フィルタ係数Ｃ０＾、Ｃ１＾の更新に、常に前回の更新後のフィルタ係数Ｃ０＾、Ｃ１＾の成分が含まれることになる。そのため、能動騒音制御中に二次経路伝達特性Ｃが急変する場合であっても、早期に能動騒音制御により消音性能を回復させることができる。 Further, the coefficient γ may be set to a minimum value.

By setting the minimum value for the coefficient γ, the update of the filter coefficients C0 ^ and C1 ^ always includes the components of the filter coefficients C0 ^ and C1 ^ after the previous update. Therefore, even if the secondary path transmission characteristic C suddenly changes during active noise control, the muffling performance can be restored by active noise control at an early stage.

[Experimental result]
The present inventors conducted an experiment on muffling performance by active noise control. The experimental results are shown below. Each of the following experiments was performed under the secondary path transfer characteristic C having the gain characteristic shown by the thin line in FIG. 6A and the phase characteristic shown by the thin line in FIG. 6B.

<Experiment (8)>
In the experiment (8), the noise in the passenger compartment 14 during the first traveling when the vehicle 12 is accelerated from the stopped state while the active noise control device 10 of the present embodiment is performing the active noise control. Sound pressure level is measured. In the experiment (8), the initial value of each frequency in the initial value table 56 is set to a convenient small value. In experiment (8), γ = 0.5 is set.

<Experiment (9)>
In the experiment (9), the noise in the passenger compartment 14 during the third traveling when the vehicle 12 is accelerated from the stopped state while the active noise control device 10 of the present embodiment is performing the active noise control. Sound pressure level is measured. In the experiment (9), the initial value of each frequency in the initial value table 56 is set to a convenient small value. In experiment (9), γ = 0.5 is set.

<< Comparison of experiments (1), (5), and (8) >>
FIG. 14 is a graph showing the sound pressure level of the noise in the passenger compartment 14 measured in the experiments (1), (5), and (8).

As shown in FIG. 14, immediately after the start of running of the vehicle 12 having an engine speed of around 1600 RPM, almost no noise could be muted in the experiment (8), but after that, in the experiment (8), the noise was hardly eliminated, as opposed to the experiment (5). The muffling performance is improved.

<< Comparison of experiments (1), (6), and (9) >>
FIG. 15 is a graph showing the sound pressure level of the noise in the passenger compartment 14 measured in the experiments (1), (6), and (9). When the number of runs reaches the third time, in the experiment (9), the noise reduction immediately after the start of the run of the vehicle 12 near the engine speed of 1600 RPM is also improved.

[Action effect]
In the active noise control device 10 of the present embodiment, the secondary route filter coefficient updating unit 40 is based on the coefficient of the secondary route filter C ^ updated last time in the secondary route filter coefficient updating unit 40 and the updated value table 58. The coefficient of the secondary route filter C ^ this time is updated using the value obtained by adding the read update value at a predetermined ratio as the previous value. As a result, even when the accuracy of the updated values in the updated value table 58 is not high, the muffling performance by active noise control can be improved.

[Fourth Embodiment]
In the present embodiment, it is possible to prevent the loudness of the canceling sound output from the speaker 16 from becoming excessive. Five methods 1 to 5 are shown below as signal processing methods for suppressing the loudness of the canceling sound output from the speaker 16 from becoming excessive.

[Method 1]
FIG. 16 is a block diagram of the signal processing unit 54. As shown in FIG. 16, a multiplier 70 for multiplying the magnitude of the apparent second estimated offset signal y2 ^ input to the adder 52 by (1 + α) with respect to the block diagram of FIG. 2 is provided. Has been added. As a result, the apparent second estimated offset signal y2 ^ increases (1 + α) times, so that the size of the control filter W can be suppressed.

[Method 2]
FIG. 17 is a block diagram of the signal processing unit 54. As shown in FIG. 17, a multiplier 72 for multiplying the magnitude of the apparent estimated noise signal d ^ input to the adder 52 by (1-α) with respect to the block diagram of FIG. 2 is provided. Has been added. As a result, the apparent estimated noise signal d ^ is reduced by (1-α) times, so that the size of the control filter W can be suppressed.

[Method 3]
FIG. 18 is a block diagram of the signal processing unit 54. As shown in FIG. 18, a multiplier for multiplying the magnitude of the apparent first estimated offset signal y1 ^ input to the adder 46 by (1-α) with respect to the block diagram of FIG. 74 has been added.

[Method 4]
FIG. 19 is a block diagram of the signal processing unit 54 to which the method 4 is applied. As shown in FIG. 19, a multiplier 76 for multiplying the magnitude of the apparent estimated noise signal d ^ input to the adder 46 by (1 + α) is added to the block diagram of FIG. ing.

[Method 5]
FIG. 20 is a block diagram of the signal processing unit 54. As shown in FIG. 20, a filter 78 for multiplying the magnitude of the apparent second estimated offset signal y2 ^ input to the adder 52 by (1 + α) is added to the block diagram of FIG. ing. The filter coefficient α of the filter 78 is updated by the filter coefficient updating unit 80.

In the method 5, the minimum value α _min is set in the filter coefficient α. The filter coefficient α satisfies the following equation.

As a result, when the secondary route transmission characteristic C changes significantly, such as when the backrest of the seat 20 is tilted down, the difference between the updated value in the update value table 58 and the secondary route transmission characteristic C becomes large. In the active noise control of the present embodiment, the coefficients C0 ^ and C1 ^ of the secondary path filter C ^ change following the change of the secondary path transmission characteristic C. Therefore, the sound pressure level of the canceling sound output from the speaker 16 may suddenly change, giving the occupant a sense of discomfort. The canceling sound output from the speaker 16 during the transitional period in which the filter coefficient updating unit 80 updates the filter coefficient α in a _{range larger than the minimum value α min to follow the change in the secondary path transmission characteristic C.} It is possible to prevent the size of the element from becoming excessive. As a result, the discomfort given to the occupant can be reduced.

[Experimental result]
The present inventors conducted an experiment on muffling performance by active noise control. The experimental results are shown below. Each of the following experiments was performed under the secondary path transfer characteristic C having the gain characteristic shown by the thin line in FIG. 6A and the phase characteristic shown by the thin line in FIG. 6B.

<Experiment (10)>
In the experiment (10), the amplitude of the control filter W when the vehicle 12 is accelerated from the stopped state is measured while the active noise control device 10 of the present embodiment is performing the active noise control. Further, in the experiment (10), the sound pressure level of the noise in the vehicle interior 14 when the vehicle 12 is accelerated from the stopped state is measured while the active noise control is on. In the experiment (10), α = 0 was set in the above method 1. In the experiment (10), the initial value of each frequency in the initial value table 56 is set to the measured value of the secondary path transmission characteristic C of each frequency shown by the thin line in FIGS. 6A and 6B.

<Experiment (11)>
In the experiment (11), the amplitude of the control filter W when the vehicle 12 is accelerated from the stopped state is measured while the active noise control device 10 of the present embodiment is performing the active noise control. Further, in the experiment (11), the sound pressure level of the noise in the vehicle interior 14 when the vehicle 12 is accelerated from the stopped state is measured while the active noise control is on. In the experiment (11), α = 0.25 was set in the above method 1. In the experiment (11), the initial value of each frequency in the initial value table 56 is set to the measured value of the secondary path transmission characteristic C of each frequency shown by the thin line in FIGS. 6A and 6B.

<< Comparison of the results of experiments (10) and (11) >>
FIG. 21 is a graph showing the amplitude of the control filter W measured in the experiments (10) and (11). As shown in FIG. 21, the magnitude of the amplitude of the control filter W is reduced in the experiment (11) in which α = 0.25 as opposed to the experiment (10) in which α = 0.

<< Comparison of experiments (1), (10), and (11) >>
FIG. 22 is a graph showing the sound pressure level of the noise in the passenger compartment 14 measured in the experiments (1), (10), and (11). As shown in FIG. 22, it can be seen that the muffling performance is improved in the experiment (11) in which α = 0.25 as opposed to the experiment (10) in which α = 0.

[Action effect]
In the active noise control device 10 of the present embodiment, the signal processing unit 54 has a multiplier 70 and a second virtual error that greatly correct the magnitude of the second estimated canceling signal y2 ^ used for generating the second virtual error signal e2. A multiplier 72 that reduces the magnitude of the estimated noise signal d ^ used to generate the signal e2, and a multiplier that corrects the magnitude of the first estimated offset signal y1 ^ used to generate the first virtual error signal e1. It has 74 or a multiplier 76 that greatly corrects the magnitude of the estimated noise signal d ^ used to generate the first virtual error signal e1. As a result, it is possible to prevent the loudness of the canceling sound output from the speaker 16 from becoming excessive.

[Technical Thought Obtained from the Embodiment]
The technical ideas that can be grasped from the above embodiments are described below.

Active noise control for controlling the speaker is performed based on an error signal that changes according to the combined sound of the noise transmitted from the vibration source and the canceling sound output from the speaker (16) to cancel the noise. The active noise control device (10) is a reference signal generation unit (26) that generates a reference signal according to a controlled frequency, and the reference signal is signal-processed by a control filter that is an adaptive notch filter to process the speaker. A control signal generation unit (28) that generates a control signal for controlling the above, and an estimated noise signal generation unit (32) that processes the reference signal with a primary path filter that is an adaptive notch filter to generate an estimated noise signal. The control signal is signal-processed by the secondary path filter which is an adaptive notch filter to generate the first estimated offset signal, and the reference signal is generated by the secondary path filter. A reference signal generation unit (34) that performs signal processing to generate a reference signal, and a second estimation cancellation signal generation unit (36) that processes the reference signal by the control filter to generate a second estimation cancellation signal. From the error signal, the first estimated offset signal, the first virtual error signal generation unit (46) that generates the first virtual error signal from the estimated noise signal, the second estimated offset signal, and the estimated noise signal. Based on the second virtual error signal generation unit (52) that generates the second virtual error signal, the control signal, and the first virtual error signal, the size of the first virtual error signal is minimized. Based on the secondary path filter coefficient update unit (40) that continuously adaptively updates the coefficient of the secondary path filter, the reference signal, and the second virtual error signal, the magnitude of the second virtual error signal is set to the minimum. The control filter coefficient update unit (42) that sequentially adapts and updates the coefficient of the control filter, and the initial value table that stores the initial value of the coefficient of the secondary path filter in a table format in association with the frequency ( 56), an update value table (58) that stores the update value of the coefficient of the secondary path filter in a table format in association with the frequency, and the initial value of the initial value table at the start of the active noise control. Is written to the update value table as the update value, and the coefficient of the secondary path filter after being updated by the secondary path filter coefficient update unit during the active noise control is written to the update value table as the update value. It has a value table operation unit (64), and the secondary route filter coefficient update unit is the secondary route filter. Before updating the coefficient of, the updated value corresponding to the frequency in the updated value table is read, and the read updated value is used as the previous value to update the coefficient of the secondary route filter.

In the active noise control device, the coefficients of the primary path filter are sequentially adaptively updated so that the magnitude of the first virtual error signal is minimized based on the reference signal and the first virtual error signal. It may have a primary path filter coefficient update part (38).

The active noise control device includes an initial value table operation unit (62) that rewrites the initial value of the initial value table to the updated value of the updated value table at the end of the active noise control. May be good.

The active noise control device includes a determination unit (68) for determining an abnormality or divergence of the active noise control at the end of the active noise control, and the determination unit determines the abnormality or divergence of the active noise control. When it is determined, the initial value table operation unit may not rewrite the initial value of the initial value table to the updated value of the updated value table.

In the active noise control device, the secondary path filter coefficient update unit performs a weighted averaging process of the coefficient of the secondary path filter after updating by an update formula and the update value of the update value table. May be done.

In the active noise control device, the secondary path filter coefficient updating unit uses the coefficient of the secondary path filter after the previous update in the secondary path filter coefficient updating unit and the read updated value. The coefficient of the secondary route filter may be updated by using the value added at a predetermined ratio as the previous value.

In the active noise control device, at the end of the active noise control, a determination unit for determining an abnormality or divergence of the active noise control and a result value of a coefficient of the secondary path filter are associated with the frequency. When the result value table (60) stored in the table format and the determination unit determines that the active noise control is abnormal or divergent, the result value in the result value table is used as the result value in the update value table. It may have a result value table operation unit (66) to be rewritten to an updated value.

The estimated noise signal used in the generation of the second virtual error signal, which is the active noise control device and greatly corrects the magnitude of the second estimated offset signal used in the generation of the second virtual error signal. The magnitude of the first estimated noise signal used to generate the first virtual error signal is corrected to be smaller, or the estimated noise signal used to generate the first virtual error signal is corrected to be smaller. You may have a multiplier (70, 72, 74, 76) that greatly corrects the magnitude of.

10 ... Active noise control device 16 ... Speaker 26 ... Reference signal generation unit 28 ... Control signal generation unit 30 ... First estimated offset signal generation unit 32 ... Estimated noise signal generation unit 34 ... Reference signal generation unit 36 ... Second estimated offset signal Generation unit 38 ... Primary path filter coefficient update unit 40 ... Secondary route filter coefficient update unit 46 ... Adder (first virtual error signal generation unit) 52 ... Adder (second virtual error signal generation unit)
56 ... Initial value table 58 ... Update value table 60 ... Result value table 64 ... Update value table operation unit 66 ... Result value table operation unit 70, 72, 74, 76 ... Multiplier

Claims (8)

Active noise control that controls the speaker based on an error signal that changes according to the combined sound of the noise transmitted from the vibration source and the canceling sound output from the speaker to cancel the noise. It ’s a device,
A reference signal generator that generates a reference signal according to the frequency to be controlled,
A control signal generation unit that generates a control signal that controls the speaker by processing the reference signal with a control filter that is an adaptive notch filter.
An estimated noise signal generator that generates an estimated noise signal by processing the reference signal with a primary path filter that is an adaptive notch filter.
A first estimated offset signal generator that generates a first estimated offset signal by processing the control signal with a secondary path filter that is an adaptive notch filter.
A reference signal generation unit that generates a reference signal by processing the reference signal with the secondary path filter.
A second estimated offset signal generation unit that generates a second estimated offset signal by processing the reference signal with the control filter.
A first virtual error signal generation unit that generates a first virtual error signal from the error signal, the first estimated offset signal, and the estimated noise signal.
A second virtual error signal generation unit that generates a second virtual error signal from the second estimated offset signal and the estimated noise signal, and a second virtual error signal generation unit.
Based on the control signal and the first virtual error signal, a secondary path filter coefficient updating unit that sequentially adaptively updates the coefficient of the secondary path filter so that the magnitude of the first virtual error signal is minimized. ,
A control filter coefficient update unit that sequentially adaptively updates the coefficient of the control filter so that the magnitude of the second virtual error signal is minimized based on the reference signal and the second virtual error signal.
An initial value table that stores the initial value of the coefficient of the secondary path filter in a table format in association with the frequency,
An update value table that stores the update value of the coefficient of the secondary route filter in a table format in association with the frequency, and
At the start of the active noise control, the initial value of the initial value table is written in the update value table as the update value, and the secondary path after being updated by the secondary path filter coefficient update unit during the active noise control. An update value table operation unit that writes the filter coefficient as the update value to the update value table, and
Have,
The secondary route filter coefficient update unit reads the update value corresponding to the frequency in the update value table before updating the coefficient of the secondary route filter, and uses the read update value as the previous value. An active noise control device that updates the coefficient of the secondary path filter. The active noise control device according to claim 1.
Based on the reference signal and the first virtual error signal, it has a primary path filter coefficient updating unit that sequentially adaptively updates the coefficient of the primary path filter so that the magnitude of the first virtual error signal is minimized. Active noise control device. The active noise control device according to claim 1 or 2.
An active noise control device having an initial value table operation unit that rewrites the initial value of the initial value table to the updated value of the updated value table at the end of the active noise control. The active noise control device according to claim 3.
It has a determination unit for determining an abnormality or divergence of the active noise control at the end of the active noise control.
When the determination unit determines that the active noise control is abnormal or divergent, the initial value table operation unit does not rewrite the initial value in the initial value table to the update value in the update value table. Active noise control device. The active noise control device according to any one of claims 1 to 4.
The secondary path filter coefficient update unit is an active noise control device that performs a weighted averaging process of the coefficient of the secondary path filter after updating by an update formula and the update value of the update value table. The active noise control device according to any one of claims 1 to 5.
The secondary route filter coefficient update unit is the previous value obtained by adding the coefficient of the secondary route filter after the previous update in the secondary route filter coefficient update unit and the read update value at a predetermined ratio. An active noise control device that updates the coefficient of the secondary path filter. The active noise control device according to any one of claims 1 to 6.
At the end of the active noise control, a determination unit for determining an abnormality or divergence of the active noise control,
A result value table that stores the result values of the coefficients of the secondary path filter in a table format in association with the frequencies, and
When the determination unit determines that the active noise control is abnormal or divergent, the result value table operation unit that rewrites the result value in the result value table to the update value in the update value table.
Active noise control device. The active noise control device according to any one of claims 1 to 7.
The second, which largely corrects the magnitude of the second estimated offset signal used to generate the second virtual error signal, reduces the magnitude of the estimated noise signal used to generate the second virtual error signal. 1 A multiplier that corrects the magnitude of the first estimated offset signal used for generating the virtual error signal to be small, or corrects the magnitude of the estimated noise signal used to generate the first virtual error signal to be large. Active noise control device.

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