Active noise control device, active noise control method and active noise control program

Abstract

To provide an active noise control device, an active noise control method and an active noise control program that perform active noise cancellation (ANC) stably under any conditions.SOLUTION: In a vehicle, an active noise control device 1 using an adaptive filter comprises: a reference signal generation unit that generates a reference signal based on noise in the vehicle; an adaptive filter update unit that updates the adaptive filter based on a result of integrating acoustic characteristics with the reference signal and an error signal; and an output signal generation unit that convolves the updated adaptive filter with the reference signal to generate an output signal. The adaptive filter update unit updates the adaptive filter using a coefficient update algorithm. It compares amplitude of the updated adaptive filter with upper limit amplitude information, which indicates the relationship between the upper limit amplitude value (the upper limit value of the amplitude of the adaptive filter) and a frequency, for each frequency. If the amplitude of the updated adaptive filter is greater than the upper limit amplitude information, the amplitude of the adaptive filter is replaced with the upper limit amplitude value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an active noise control device, an active noise control method, and an active noise control program. [Background technology]

[0002] Active noise controllers (ANC) are known that detect noise with a microphone and cancel it out by outputting a control sound of the same amplitude but opposite phase from a speaker. For example, there are in-vehicle ANCs that reduce engine rumble and road noise.

[0003] Patent Document 1 discloses an active noise cancellation (ANC) system including: at least one controllable filter configured to generate an anti-noise signal based on an adaptive transfer characteristic and a noise signal received from a sensor, the adaptive transfer characteristic of the at least one controllable filter being characterized by a set of filter coefficients; an adaptive filter controller including a processor and a memory and programmed to adapt the set of filter coefficients based on the noise signal and an error signal received from a microphone located within the vehicle cabin; and a divergence controller communicating with at least the adaptive filter controller, the divergence controller including a processor and a memory programmed to receive a set of filter coefficients corresponding to a current adaptation of the adaptive transfer characteristic of the at least one controllable filter, calculate parameters based on an analysis of at least a portion of the set of filter coefficients, and detect divergence of the at least one controllable filter based on a comparison of the parameters to a threshold value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-184070 Summary of the Invention [Problem to be solved by the invention]

[0005] In-vehicle ANC can become unstable due to a variety of factors. Possible causes of ANC instability include (1) the step size μ being too large, (2) a dip in the acoustic characteristics from the speaker 22 to the microphone 21, (3) the acoustic characteristics deviating from the measured values ​​due to factors such as opening a window or placing an obstacle near the microphone, and (4) an extremely large signal being input due to wind pressure from opening a window or hitting the area near the microphone. When ANC becomes unstable, a loud "boing" sound may be heard, or in the worst case scenario, the output may diverge and a loud sound may continue.

[0006] In the invention described in Patent Document 1, when the amplitude of the adaptive filter exceeds a predetermined threshold, divergence is detected and the ANC is stopped or the ANC control is weakened, so an extremely loud sound is generated before the divergence is detected. In other words, the invention described in Patent Document 1 cannot perform ANC stably.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide an active noise control device, an active noise control method, and an active noise control program that can perform ANC stably in any situation. [Means for solving the problem]

[0008] In order to solve the above problems, an active noise control device according to the present invention is, for example, an active noise control device that sequentially updates an adaptive filter that generates an output signal by signal processing a reference signal generated based on noise in a vehicle, based on an error signal input from a microphone when the output signal is output from a speaker, and includes: a reference signal generation unit that generates the reference signal; an adaptive filter update unit that updates the adaptive filter based on the error signal and a result of integrating the reference signal with acoustic characteristics; and an output signal generation unit that convolutes the reference signal with the adaptive filter updated by the adaptive filter update unit to generate the output signal, wherein the adaptive filter update unit updates the adaptive filter using a coefficient update algorithm, compares the amplitude of the adaptive filter after the update with upper limit value information that indicates the relationship between an amplitude upper limit value that is an upper limit value of the amplitude of the adaptive filter and frequency, and if the amplitude of the adaptive filter after the update is greater than the upper limit value information, replaces the amplitude of the adaptive filter after the update with the amplitude upper limit value.

[0009] In order to solve the above-mentioned problems, an active noise control method according to the present invention is, for example, an active noise control method that sequentially updates an adaptive filter that generates an output signal by signal processing a reference signal that is generated based on noise in a vehicle, based on an error signal that is input from a microphone when the output signal is output from a speaker, and includes: a reference signal generating step that generates the reference signal; an adaptive filter updating step that updates the adaptive filter based on the error signal and a result of integrating the reference signal with acoustic characteristics; and an output signal generating step that convolutes the reference signal with the adaptive filter updated in the adaptive filter updating step, to generate the output signal; wherein the adaptive filter updating step updates the adaptive filter using a coefficient update algorithm, compares the amplitude of the adaptive filter after the update with upper limit value information that indicates the relationship between an amplitude upper limit value that is an upper limit value of the amplitude of the adaptive filter and frequency, and if the amplitude of the adaptive filter after the update is greater than the upper limit value information, replaces the amplitude of the adaptive filter after the update with the amplitude upper limit value.

[0010] In order to solve the above-mentioned problems, an active noise control program according to the present invention is, for example, an active noise control program that sequentially updates an adaptive filter that generates an output signal by signal processing a reference signal generated based on noise in a vehicle, based on an error signal input from a microphone when the output signal is output from a speaker, and causes a computer to function as a reference signal generation unit that generates the reference signal, an adaptive filter update unit that updates the adaptive filter based on the error signal and a result of integrating the reference signal with acoustic characteristics, and an output signal generation unit that convolutes the reference signal with the adaptive filter updated by the adaptive filter update unit to generate the output signal, and is characterized in that the adaptive filter update unit updates the adaptive filter using a coefficient update algorithm, compares the amplitude of the adaptive filter after the update with upper limit value information that indicates the relationship between an upper limit value of the amplitude of the adaptive filter and frequency, and, if the amplitude of the adaptive filter after the update is greater than the upper limit value information, replaces the amplitude of the adaptive filter after the update with the upper amplitude value. The computer program can be provided by downloading it via a network such as the Internet, or by recording it on various computer-readable recording media such as a CD-ROM.

[0011] In any of the above aspects of the present invention, the adaptive filter is updated using a coefficient update algorithm, and the amplitude of the updated adaptive filter is compared with upper limit information for each frequency. If the amplitude of the updated adaptive filter is greater than the upper limit information, the amplitude of the updated adaptive filter is replaced with the value of the upper limit information. Therefore, even if the ANC becomes unstable, sounds above a predetermined volume are not output from the speaker. This allows stable ANC to be performed in any situation.

[0012] The maximum amplitude value obtained by operating the reference signal generator and the adaptive filter updater for a given period of time may be set as the upper amplitude limit value, thereby making it possible to set an appropriate upper amplitude limit value when reducing road noise using ANC.

[0013] The upper amplitude limit value is a value obtained by multiplying the maximum value by a correction coefficient, and the correction coefficient may be any value between 1 and 2. This makes it possible to avoid a situation where the upper amplitude limit value is too small to produce a sufficient volume.

[0014] The adaptive filter updating unit may vary the upper limit information based on the vehicle speed acquired by the vehicle speed acquiring unit, thereby enabling appropriate ANC according to the vehicle speed.

[0015] The adaptive filter update unit may hold at least first upper limit information, which is the upper limit information at a first vehicle speed, and second upper limit information, which is the upper limit information at a second vehicle speed different from the first vehicle speed, and may limit the upper limit value of the amplitude of the adaptive filter using the first upper limit information or the second upper limit information based on the vehicle speed acquired by the vehicle speed acquisition unit. This makes it possible to limit the upper limit value of the amplitude of the adaptive filter by switching the upper limit information.

[0016] The adaptive filter updater may vary the upper limit information based on the roughness of the road surface acquired by the road surface condition acquisition unit, thereby enabling appropriate ANC to be performed according to the roughness of the road surface.

[0017] The adaptive filter updater may vary the upper limit information based on the gear position acquired by the gear position acquisition unit, thereby performing appropriate ANC according to the gear position to eliminate engine booming noise.

[0018] The reference signal generating unit generates the reference signal based on the rotation speed of the engine of the vehicle, and the upper amplitude limit value is a value obtained by multiplying the maximum amplitude obtained by operating the reference signal generating unit and the adaptive filter updating unit for an arbitrary period of time by a correction coefficient, and the correction coefficient may be any value not less than 1 and not more than 2. This makes it easy to perform appropriate ANC according to the gear position. [Effects of the Invention]

[0019] According to the present invention, ANC can be performed stably in any situation. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram schematically illustrating a vehicle 100 provided with an active noise control device 1. FIG. [Figure 2] 1 is a block diagram showing an outline of the functional configuration of an active noise control device 1. FIG. [Figure 3] 10 is a flowchart showing a process for obtaining an upper limit value table in advance. [Figure 4] FIG. 10 is a diagram showing an example of a maximum value Wabsmax(f). [Figure 5] 3 is a flowchart showing the flow of processing performed by the active noise control device 1. [Figure 6] 10A and 10B are diagrams illustrating a state in which an upper limit value table is used to limit the upper limit value of the amplitude of an adaptive filter in amplitude limiting processing. [Figure 7] (A) is a graph showing an example of the results when using a conventional active noise control device that does not perform amplitude limiting processing, and (B) is a graph showing an example of the results when using the active noise control device 1 that performs amplitude limiting processing. [Figure 8] 2 is a block diagram showing an outline of the functional configuration of the active noise control device 2. FIG. [Figure 9] 4 is a flowchart showing the flow of processing performed by the active noise control device 2. [Figure 10]2 is a block diagram showing an outline of the functional configuration of the active noise control device 3. FIG. [Figure 11] 4 is a flowchart showing the flow of processing performed by the active noise control device 3. [Figure 12] 2 is a block diagram showing an outline of the functional configuration of the active noise control device 4. FIG. [Figure 13] 10 is a flowchart showing a process for obtaining an upper limit value table in advance. [Figure 14] 4 is a flowchart showing the flow of processing performed by the active noise control device 4. [Figure 15] (A) is a graph showing an example of the results when ANC is not performed, (B) is a graph showing an example of the results when a conventional active noise control device that does not perform amplitude limiting processing is used, and (C) is a graph showing an example of the results when an active noise control device 4 that performs amplitude limiting processing is used. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of an active noise control device according to the present invention will be described in detail with reference to the drawings. The active noise control device is a device that sequentially updates an adaptive filter that generates an output signal by processing a reference signal generated based on noise in a vehicle, based on an error signal input from a microphone when the output signal is output from a speaker. Hereinafter, the present invention will be described using examples of suppressing noise such as road noise generated when tires ride over unevenness in the road surface while a vehicle is traveling, and booming noise generated when vibrations from the vehicle engine resonate in the passenger compartment, but the active noise control device of the present invention is not limited to these forms.

[0022] First Embodiment The first embodiment of the present invention is an active noise control device 1 that reduces road noise. Fig. 1 is a diagram that schematically shows a vehicle 100 equipped with the active noise control device 1. The active noise control device 1 is connected to a microphone 21, a speaker 22, a CAN (Control Area Network) 30, a vibration sensor 31, and the like that are provided in the vehicle 100. Note that the connection between the active noise control device 1 and the CAN 30 is not essential.

[0023] The microphone 21 and the speaker 22 are provided in the passenger compartment 101 of the vehicle 100. In particular, it is desirable to provide the microphone 21 in a position close to the ears, such as on the ceiling or headrest of the passenger compartment 101. The vibration sensor 31 is provided, for example, near the suspension or knuckle arm of the vehicle 100. In Fig. 1, P is the transfer function (primary path) from the noise source to the microphone 21, and S is the transfer function (secondary path) from the speaker 22 to the microphone 21.

[0024] The active noise control device 1 acquires information such as vehicle speed and engine rotation speed from the CAN 30, etc. The active noise control device 1 also generates a control signal by multiplying noise (reference signal) by an adaptive filter coefficient and outputs it from the speaker 22. The sound output from the speaker 22 is in antiphase with the noise, and this sound cancels out the noise. The noise and the sound output from the speaker 22 are input to the microphone 21. The active noise control device 1 then adjusts the phase and amplitude of the reference signal using an adaptive filter so that the sound detected by the microphone 21 is reduced.

[0025] The active noise control device 1 may be configured, for example, primarily by a computer system including an arithmetic device 111 such as a CPU (Central Processing Unit) for executing information processing, and a storage device 112 such as a RAM (Random Access Memory) or a ROM (Read Only Memory), and software (an active noise control program). The active noise control device 1 may also be configured, for example, as a dedicated board mounted on a communication terminal or the like (e.g., an in-vehicle device) in the vehicle 100. The active noise control program may be stored in advance in an SSD as a storage medium built into a device such as a computer, or in a ROM in a microcomputer having a CPU, and then installed into the computer from there. The active noise control program may also be temporarily or permanently stored (memorized) in a removable storage medium such as a semiconductor memory, a memory card, an optical disk, a magneto-optical disk, or a magnetic disk.

[0026] 2 is a block diagram showing an outline of the functional configuration of the active noise control device 1. Functionally, the active noise control device 1 mainly includes a reference signal generating unit 11, an output signal generating unit 12, a storage unit 13, and an adaptive filter updating unit 14. Note that the functional components of the active noise control device 1 may be further divided into more components depending on the processing content, or one component may perform the processing of multiple components.

[0027] The reference signal generating unit 11 is a functional unit that generates a reference signal based on noise in the vehicle. The reference signal generation unit 11 acquires a reference signal x(t) from the vibration sensor 31. The reference signal x(t) is output to the output signal generation unit 12 and the Filtered-x generation unit 141. Note that (t) means that the signal is time-dependent.

[0028] The output signal generation unit 12 is a functional unit that convolves (performs a product-sum operation) the reference signal x(t) with an adaptive filter w(t) to generate an output signal to be output to the speaker 22. The output signal generation unit 12 generates the output signal y(t) using the following equation (1), where N is the number of taps.

number

[0029] Furthermore, the output signal generating unit 12 outputs the generated control signal to a speaker amplifier (not shown). The speaker amplifier amplifies the control signal and outputs it to the speaker 22. Note that the speaker amplifier is not essential.

[0030] The storage unit 13 is a functional unit that stores information used by the adaptive filter update unit 14. The storage unit 13 mainly has an acoustic characteristic table storage unit 131 that stores the acoustic characteristic S(f) of the secondary path, and an upper limit table storage unit 132 that stores an upper limit table (upper limit information of the present invention). The acoustic characteristic S(f) and the upper limit table are measured and calculated in advance before the active noise control device 1 performs processing, and the results are stored in the storage unit 13. Note that (f) means that the signal is frequency-dependent.

[0031] The acoustic characteristic S(f) is generated, for example, by transmitting a sweep signal whose frequency changes over time from the speaker 22 and obtaining a signal from the microphone 21. The frequency band of the sweep signal is, for example, 20 Hz to 500 Hz. The acoustic characteristic S(f) is, for example, a table in which values ​​are associated with each frequency. Note that the method of measuring the acoustic characteristic S(f) is not limited to using a sweep signal, and pseudo-random noise such as white noise or an M sequence may also be used.

[0032] The upper limit value table is obtained by operating the active noise control device 1 for a certain period of time in a stable state (such as with the windows closed) and adopting as the upper limit the maximum value of the amplitude of the adaptive filter obtained. The upper limit value table is, for example, a table in which values ​​are associated with each frequency. The upper limit value table will be described in detail later.

[0033] The adaptive filter update unit 14 is a functional unit that updates the adaptive filter using an adaptive algorithm. The adaptive filter update unit 14 mainly includes a Filtered-x generation unit 141 and an update unit 142.

[0034] The Filtered-x generation unit 141 is a functional unit that generates a Filtered-x signal by multiplying a reference signal x(t) by an acoustic characteristic. First, as shown in Equation (2), the Filtered-x generation unit 141 performs a discrete Fourier transform on the reference signal x(t) to convert the reference signal x into a frequency domain signal X. Note that the method of converting a time domain signal into a frequency domain signal is not limited to the discrete Fourier transform.

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[0035] Next, the Filtered-x generation unit 141 generates the Filtered-x signal X'(f) by multiplying the reference signal X(f) converted into the frequency domain by the acoustic characteristic S(f), as shown in Equation 3. The Filtered-x signal X'(f) is output to the update unit 142.

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[0036] The update unit 142 is a functional unit that updates the adaptive filter based on the error signal and the Filtered-x signal, which is a reference signal multiplied by acoustic characteristics, and replaces the amplitude of the updated adaptive filter with a value in an upper limit value table (described in detail later). The update unit 142 converts the adaptive filter w and the error signal e(t) into signals in the frequency domain.

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[0037] Then, the update unit 142 updates the adaptive filter using an arbitrary adaptive algorithm. In this embodiment, the update unit 142 updates the adaptive filter using the NLMS (Normalized Least Mean Squares) algorithm as shown in Equation (6). Here, μ is a step size, and is set in the range of 0<μ<1. Note that adaptive filters are already well known, so a description thereof will be omitted.

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[0038] In this embodiment, the NLMS algorithm is used as the adaptive algorithm, but the adaptive algorithm is not limited to this, and for example, the LMS algorithm or the RLS algorithm may also be used.

[0039] Next, the update unit 142 performs amplitude limiting processing to limit the upper limit of the amplitude of the adaptive filter based on the upper limit table. The amplitude limiting processing will be described in detail later. The update unit 142 then converts the adaptive filter whose upper limit has been limited into a time domain signal by inverse Fourier transform or the like (see Equation (7)), and outputs this to the output signal generation unit 12.

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[0040] 3 is a flowchart showing the flow of processing for obtaining an upper limit value table in advance. This processing is performed in a stable state, such as with the windows closed. First, the reference signal generation unit 11 generates a reference signal and outputs the generated reference signal to the Filtered-x generation unit 141 (step SP11). Next, the Filtered-x generation unit 141 acquires acoustic characteristics stored in the storage unit 13 (step SP12), generates a Filtered-x signal based on the acoustic characteristics, and outputs the generated Filtered-x signal to the update unit 142 (step SP13).

[0041] The update unit 142 updates the amplitude of the adaptive filter using the Filtered-x signal and the error signal e(t) and holds the maximum value (step SP14). In step SP14, to perform processing in a stable state, the step size μ is set to a sufficiently small value (for example, the step size μ is 0.01).

[0042] The update unit 142 determines whether the process of step SP14 has been performed for a certain period of time (step SP15), and if the process has not been performed for a certain period of time (NO in step SP15), the process returns to step SP11. If the process has been performed for a certain period of time (YES in step SP15), the update unit 142 updates the maximum value W obtained in step SP14 for each frequency. absmax As the amplitude upper limit, the upper limit table W limit (f) is generated (step SP16).

[0043] Upper limit table W limit (f) is a signal that depends on frequency, and is stored, for example, as a table in which values ​​are associated with each frequency. limit (f) is the maximum value W of the amplitude of the adaptive filter during a certain time. absmax (f) (see equation (8)), and the maximum value W absmax (f) is calculated by executing equation (9) at each time instant, where |W(f)| is the amplitude at the current frequency f.

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[0044] Figure 4 shows the maximum value W absmax 4(f), the horizontal axis represents frequency, and the vertical axis represents maximum amplitude W absmax In addition, in FIG. 4, the dotted line indicates the maximum value W absmaxThe solid line indicates the maximum value W when 240 seconds have passed since the start of the process shown in Fig. 3. absmax The graph in Figure 4 shows the results obtained when the step size μ was set to 0.01.

[0045] In the example shown in Figure 4, the value has not converged after 30 seconds, and the maximum value W absmax rises, but after a certain time (for example, 240 seconds) the maximum value W absmax Therefore, the fixed time in step SP15 is the maximum value W absmax The convergence time (for example, 240 seconds or more) can be set to any value. Then, the converged maximum value W for each frequency absmax Here, the upper limit table is represented by the solid line in Fig. 4. In this way, an appropriate upper limit table is set.

[0046] 5 is a flowchart showing the flow of processing performed by the active noise control device 1. First, the reference signal generation unit 11 generates a reference signal and outputs the generated reference signal to the Filtered-x generation unit 141 (step SP21). Next, the Filtered-x generation unit 141 acquires acoustic characteristics stored in the storage unit 13 (step SP22), generates a Filtered-x signal based on the acoustic characteristics, and outputs the generated Filtered-x signal to the update unit 142 (step SP23).

[0047] The update unit 142 updates the amplitude of the adaptive filter using the Filtered-x signal and the error signal e(t) (step SP24). Thereafter, the update unit 142 acquires the upper limit value table stored in the storage unit 13 (step SP25), and performs amplitude limiting processing to limit the upper limit value of the amplitude of the adaptive filter using the upper limit value table as necessary (step SP26).

[0048] The amplitude limiting process of step SP26 will now be described in detail. Fig. 6 is a diagram showing a schematic diagram of how the upper limit value of the amplitude of the adaptive filter is limited using an upper limit value table in the amplitude limiting process. In the graph shown in Fig. 6, the horizontal axis represents frequency and the vertical axis represents the amplitude of the adaptive filter.

[0049] 6, A is the current amplitude of the adaptive filter, i.e., before amplitude limiting processing, and B is the upper limit value table acquired in step SP25. In the example shown in FIG. 6, the amplitude of the adaptive filter before updating in region C is larger than that in the upper limit value table. Therefore, the update unit 142 updates the amplitude of the adaptive filter in region C to the value W in the upper limit value table. limit This process is expressed in mathematical formulas as follows:

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[0050] Returning to the explanation of Fig. 5, the update unit 142 converts the adaptive filter updated in steps SP24 to SP26 back into a time domain signal and outputs it to the output signal generation unit 12 (step SP27). Then, the output signal generation unit 12 convolutes the adaptive filter acquired from the update unit 142 with the reference signal to generate an output signal (step SP28). The output signal generated in step SP28 is output from the speaker 22.

[0051] This completes one processing cycle of the active noise control device 1. The active noise control device 1 repeatedly performs the processing shown in FIG.

[0052] Next, the effect of the active noise control device 1 will be described with reference to Fig. 7. Fig. 7(A) is a graph showing an example of the results when a conventional active noise control device that does not perform amplitude limiting processing is used, and Fig. 7(B) is a graph showing an example of the results when an active noise control device 1 that performs amplitude limiting processing is used. The graph shown in Fig. 7 shows the results when the step size μ is 0.03 and the upper limit value table W obtained by Fig. 4 is used. limitThese are the results obtained by performing amplitude limiting processing using (f). Because the step size μ was large, the ANC had the opposite effect when amplitude limiting processing was not performed (see FIG. 7(A)), but when amplitude limiting processing was performed by the active noise control device 1 (see FIG. 7(B)), the ANC effect was obtained correctly.

[0053] According to this embodiment, the amplitude of the adaptive filter after updating is compared with the upper limit value table for each frequency, and if the amplitude of the adaptive filter is larger than the upper limit value table information, the amplitude of the adaptive filter is replaced with the value in the upper limit value table. This prevents sound above a predetermined volume from being output from speaker 22 even if the ANC becomes unstable, allowing stable ANC to be performed in any situation.

[0054] For example, in conventional technology that detects divergence and stops ANC, there is a risk that an extremely loud sound will be output from the speaker 22 before divergence is detected. In contrast, in the active noise control device 1 of the present invention, it is possible to set the speaker 22 so that sounds above a predetermined volume will not be output, and divergence does not occur in the first place. Therefore, loud sounds will not be output under any circumstances, and ANC can be performed stably.

[0055] In this embodiment, the maximum value W absmax (f) Upper limit table W limit (f), but the maximum value W absmax The upper limit value table may be obtained by multiplying (f) by the correction coefficient c. In this case, the upper limit value table W limit (f) is expressed by the following formula (13).

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[0056] The value of the correction coefficient is between 1 and 2 (greater than or equal to 1 and less than or equal to 2), and it is desirable to set it to a value slightly greater than 1. For example, since the difference in road noise between a normal road surface and a rough road surface is about 6 dB, it is appropriate to set the correction coefficient to between 1 and 2.

[0057] Thus, the maximum value W absmax (f) multiplied by the correction coefficient c is stored in the upper limit table W limit (f) gives the maximum value W absmax This avoids the situation where (f) is too small to produce sufficient volume.

[0058] <Second embodiment> The second embodiment of the present invention is an active noise control device 2 that reduces road noise, similar to the first embodiment. In an ANC that reduces road noise, road noise increases as the vehicle speed increases, so it is desirable to increase the volume of the sound output from the speaker 22 in accordance with the vehicle speed. In the active noise control device 2, the upper limit value table is changed depending on the vehicle speed.

[0059] The following describes an active noise control device 2 according to a second embodiment. Note that the same parts as those in the active noise control device 1 are given the same reference numerals and descriptions thereof will be omitted.

[0060] Similar to the active noise control device 1, the active noise control device 2 is connected to a microphone 21, a speaker 22, a CAN 30, a vibration sensor 31, and the like, which are provided in the vehicle 100.

[0061] 8 is a block diagram showing an outline of the functional configuration of the active noise control device 2. Functionally, the active noise control device 2 mainly includes a reference signal generation unit 11, an output signal generation unit 12, a storage unit 13A, and an adaptive filter update unit 14A. Note that the functional components of the active noise control device 2 may be further divided into more components depending on the processing content, or one component may perform the processing of multiple components.

[0062] The storage unit 13A is a functional unit that stores information used by the adaptive filter update unit 14. The storage unit 13A mainly includes an acoustic characteristics table storage unit 131 and an upper limit table storage unit 132A.

[0063] The upper limit value table storage unit 132A stores multiple upper limit value tables set for each vehicle speed. The multiple upper limit value tables include at least two upper limit value tables. For example, the upper limit value table storage unit 132A stores an upper limit value table i (corresponding to first upper limit value information of the present invention) when the vehicle speed is greater than 0 km / h and equal to or less than 50 km / h (corresponding to the first vehicle speed of the present invention), an upper limit value table ii (corresponding to second upper limit value information of the present invention) when the vehicle speed is greater than 50 km / h and equal to or less than 70 km / h (corresponding to the second vehicle speed of the present invention), and an upper limit value table iii when the vehicle speed is greater than 70 km / h.

[0064] Here, the upper limit value tables i to iii will be explained. The maximum amplitude W of the adaptive filter obtained by operating the active noise control device 2 for a certain period of time in a stable state while the vehicle 100 is traveling at a speed of 50 km / h is absmax_50kmh (f) is the upper limit table iW limit_0~50kmh The maximum amplitude W of the adaptive filter obtained by operating the active noise control device 1 for a certain period of time in a stable state while the vehicle 100 is traveling at a speed of 70 km / h is shown in (f). absmax_70kmh (f) is the upper limit table iiW limit_50~70kmh Furthermore, the maximum amplitude W of the adaptive filter obtained by operating the active noise control device 1 for a certain period of time in a stable state while the vehicle 100 is traveling at a speed of 90 km / h is absmax_90kmh (f) is the upper limit table iiiW limit_70kmh~ (f). This can be expressed as formulas (14) to (16). Note that the maximum value W absmax_50kmh (f), maximum value W absmax_70kmh (f) and maximum value W absmax_90kmh The method for finding (f) is the maximum value W absmax The method for finding (f) is the same as above, so the explanation will be omitted.

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[0065] The adaptive filter update unit 14A is a functional unit that updates the adaptive filter using an adaptive algorithm and limits the amplitude of the adaptive filter as necessary. Furthermore, when limiting the amplitude of the adaptive filter, the adaptive filter update unit 14A changes the upper limit value table based on the vehicle speed acquired by the vehicle speed acquisition unit. The adaptive filter update unit 14 mainly includes a Filtered-x generation unit 141 and an update unit 142A. For example, the update unit 142A acquires the vehicle speed from the CAN 30 and switches the upper limit value table to be used from among multiple upper limit value tables based on the acquired vehicle speed.

[0066] 9 is a flowchart showing the flow of processing performed by the active noise control device 2. First, the reference signal generation unit 11 generates a reference signal and outputs the generated reference signal to the Filtered-x generation unit 141 (step SP31). Next, the Filtered-x generation unit 141 acquires acoustic characteristics stored in the storage unit 13A (step SP32), generates a Filtered-x signal based on the acoustic characteristics, and outputs the generated Filtered-x signal to the update unit 142A (step SP33). Next, the update unit 142A updates the amplitude of the adaptive filter using the Filtered-x signal and the error signal e(t) (step SP34). Note that the processing of steps SP31 to SP34 is the same as the processing of steps SP21 to SP24, and therefore description thereof will be omitted.

[0067] Thereafter, the update unit 142A acquires a plurality of upper limit value tables stored in the storage unit 13A (step SP35), and updates the upper limit value of the amplitude of the adaptive filter as needed using the upper limit value tables to the value W limit (step SP36).

[0068] The process of step SP36 will be described in detail. First, the update unit 142A acquires the vehicle speed of the vehicle 100 from the CAN 30 and updates the upper limit value table iW limit_0~50kmh (f), Upper limit table iiW limit_50~70kmh (f), Upper limit table iiiW limit_70~90kmhFor example, if the vehicle speed is 60 km / h, the update unit 142A selects an appropriate upper limit value table from the upper limit value table iiW. limit_50~70kmh Next, the update unit 142A selects (f) in the selected upper limit table iiW limit_50~70kmh The amplitude limiting process is performed using (f). Note that the amplitude limiting process is the same as that in step SP26, so a description thereof will be omitted.

[0069] The update unit 142A restores the adaptive filter updated in steps SP34 to SP36 to a time domain signal and outputs it to the output signal generation unit 12 (step SP37). Then, the output signal generation unit 12 convolves the adaptive filter acquired from the update unit 142A with the reference signal to generate an output signal (step SP38). Steps SP37 and SP38 are the same as steps SP27 and SP28. The active noise control device 2 repeatedly performs the processing shown in FIG. 9.

[0070] According to this embodiment, by switching the upper limit value table in accordance with the vehicle speed, it is possible to perform ANC appropriate for the vehicle speed.

[0071] In this embodiment, a plurality of upper limit value tables i, ii, iii set for each speed are stored in the storage unit 13A, and the update unit 142A updates the upper limit value table iW based on the vehicle speed of the vehicle 100. limit_0~50kmh (f), Upper limit table iiW limit_50~70kmh (f), Upper limit table iiiW limit_70~90kmh Although an appropriate upper limit value table is selected from (f), the manner in which appropriate ANC is performed according to the vehicle speed is not limited to this. For example, the correction coefficient c to be added to the upper limit value table may be changed based on the speed of the vehicle 100.

[0072] When changing the correction coefficient c to be added to the upper limit value table based on the vehicle speed of the vehicle 100, for example, the upper limit value table iW limit_0~50kmh (f) is stored in the storage unit, and when the vehicle speed is 60 km / h, the correction coefficient c1 (for example, 1.2) is stored in the upper limit value table iW limit_0~50kmh(f), and when the vehicle speed is 100 km / h, the correction coefficient c2 (for example, 1.5) is added to the upper limit value table iW limit_0~50kmh (f). It is appropriate that the correction coefficients c1 and c2 are set to 1 to 2. The form of the correction coefficients is not limited to discrete values ​​such as the correction coefficients c1 and c2, and for example, a correction coefficient according to the speed may be calculated based on an equation showing the relationship between the speed and the correction coefficient.

[0073] <Third embodiment> The third embodiment of the present invention is an active noise control device 3 that reduces road noise, similar to the first and second embodiments. In ANC that reduces road noise, the road noise changes depending on the roughness of the road surface, so it is desirable to increase the volume of the sound output from the speaker 22 depending on the roughness of the road surface. In the active noise control device 3, the upper limit value table is changed depending on the vehicle speed and the roughness of the road surface.

[0074] The following describes an active noise control device 3 according to the third embodiment. Note that the same parts as those in the active noise control devices 1 and 2 are given the same reference numerals and descriptions thereof will be omitted.

[0075] Similar to the active noise control device 1, the active noise control device 3 is connected to a microphone 21, a speaker 22, a CAN 30, a vibration sensor 31, and the like, which are provided in the vehicle 100.

[0076] 10 is a block diagram showing an outline of the functional configuration of the active noise control device 3. Functionally, the active noise control device 3 mainly includes a reference signal generation unit 11, an output signal generation unit 12, a storage unit 13B, and an adaptive filter update unit 14B. Note that the functional components of the active noise control device 3 may be further divided into more components depending on the processing content, or one component may perform the processing of multiple components.

[0077] The storage unit 13B is a functional unit that stores information used by the adaptive filter update unit 14B. The storage unit 13B mainly includes an acoustic characteristics table storage unit 131 and an upper limit table storage unit 132B.

[0078] The upper limit value table storage unit 132B stores a plurality of sets of upper limit value tables set for each vehicle speed. In this embodiment, the upper limit value table storage unit 132B stores upper limit value groups for normal road surfaces and rough road surfaces (hereinafter referred to as rough road surfaces). The upper limit value table storage unit 132B also stores upper limit value tables i, ii, and iii, which differ in vehicle speed for normal road surfaces and rough road surfaces, respectively. Here, a rough road surface is a road surface with greater unevenness than a normal road surface, and it is assumed that the road noise on a rough road surface is greater than that on a normal road surface.

[0079] The vehicle 100 is driven on a normal road surface at speeds of 50 km / h, 70 km / h, and 90 km / h, and the active noise control device 1 is operated for a certain period of time in a stable state. The maximum amplitude W of the adaptive filter is obtained. absmax_normal_50kmh (f), maximum value W absmax_normal_70kmh (f) and maximum value W absmax_normal_90kmh (f) is the upper limit table iW limit_normal_0~50kmh (f), Upper limit table iiW limit_normal_50~70kmh (f), Upper limit table iiiW limit_normal_70kmh~ The maximum amplitude W of the adaptive filter obtained by operating the active noise control device 1 for a certain period of time in a stable state while the vehicle 100 is running on a rough road surface at speeds of 50 km / h, 70 km / h, and 90 km / h is expressed as (f). absmax_rough_50kmh (f), maximum value W absmax_rough_70kmh (f) and maximum value W absmax_rough_90kmh (f) is the upper limit table iW limit_rough_0~50kmh (f), Upper limit table iiW limit_rough_50~70kmh (f), Upper limit table iiiW limit_rough_70kmh~ (f). The maximum value W absmax_normal_50kmh (f), maximum value W absmax_normal_70kmh (f), maximum value W absmax_normal_90kmh (f) Maximum value W absmax_rough_50kmh(f), maximum value W absmax_rough_70kmh (f) and maximum value W absmax_rough_90kmh The method for finding (f) is the maximum value W absmax The method for finding (f) is the same as above, so the explanation will be omitted.

[0080] The adaptive filter update unit 14B is a functional unit that updates the adaptive filter using an adaptive algorithm. The adaptive filter update unit 14B mainly includes a Filtered-x generation unit 141 and an update unit 142B. The update unit 142B acquires the vehicle speed from the CAN 30 and the vibration magnitude from the vibration sensor 31, and switches the upper limit value table to be used from among a plurality of upper limit value tables based on the acquired vehicle speed and vibration magnitude.

[0081] Generally, the vibration sensor 31 is provided on a suspension (not shown) or the vehicle body, and the roughness of the road surface can be determined from the magnitude of the vibration acquired by the vibration sensor 31. In this embodiment, the update unit 142B determines that the vehicle 100 is traveling on a rough road surface when the average value of the values ​​acquired by the vibration sensor 31 over a certain period is equal to or greater than a threshold value. For example, if the magnitude of the vibration when the vehicle 100 is traveling at a speed of 50 km / h is an average of 0.2 G on a normal road surface and an average of 0.6 G on a rough road surface, setting the intermediate value of 0.4 G as the threshold value makes it possible to easily determine whether the road surface is rough.

[0082] 11 is a flowchart showing the flow of processing performed by the active noise control device 3. First, the reference signal generation unit 11 generates a reference signal and outputs the generated reference signal to the Filtered-x generation unit 141 (step SP41). Next, the Filtered-x generation unit 141 acquires acoustic characteristics stored in the storage unit 13B (step SP42), generates a Filtered-x signal based on the acoustic characteristics, and outputs the generated Filtered-x signal to the update unit 142B (step SP43). Next, the update unit 142B updates the amplitude of the adaptive filter using the Filtered-x signal and the error signal e(t) (step SP44). Note that the processing of steps SP41 to SP44 is similar to the processing of steps SP21 to SP24, and therefore description thereof will be omitted.

[0083] Thereafter, the update unit 142B acquires a plurality of upper limit value tables stored in the memory unit 13B (step SP45), and performs amplitude limiting processing to limit the upper limit value of the amplitude of the adaptive filter as necessary using the upper limit value table (step SP46).

[0084] The processing of step SP46 will be described in detail. First, the update unit 142B determines whether the vehicle 100 is traveling on a normal road surface or a rough road surface based on the measurement value of the vibration sensor 31, and selects either an upper limit value table for normal road surfaces or a rough road surface based on the determination result. Next, the update unit 142B selects an appropriate upper limit value table based on the vehicle speed of the vehicle 100 acquired from the CAN 30. For example, if the vehicle 100 is traveling on a normal road surface and the vehicle speed is 60 km / h, the update unit 142B selects an appropriate upper limit value table from the upper limit value table iiW. limit_normal_50~70kmh Select (f).

[0085] Next, the update unit 142B updates the selected upper limit table (here, upper limit table iiW limit_normal_50~70kmh The amplitude limiting process is performed using (f). Note that the amplitude limiting process is the same as that in step SP26, and therefore its explanation will be omitted.

[0086] The update unit 142B converts the adaptive filter updated in steps SP44 to SP46 back into a time domain signal and outputs it to the output signal generation unit 12 (step SP47). Then, the output signal generation unit 12 convolves the adaptive filter acquired from the update unit 142B with the reference signal to generate an output signal (step SP48). Steps SP47 and SP48 are the same as steps SP27 and SP28. The active noise control device 3 repeatedly performs the processing shown in FIG. 11.

[0087] According to this embodiment, by switching the upper limit value table depending on the roughness of the road surface, it is possible to perform ANC appropriate for the roughness of the road surface.

[0088] In this embodiment, upper limit value tables i, ii, and iii with different vehicle speeds for normal road surfaces and rough road surfaces are stored in upper limit value table storage unit 132B, but the method of changing the upper limit value table depending on the road surface conditions is not limited to this. For example, three upper limit value tables i, ii, and iii with different vehicle speeds are stored in upper limit value table storage unit 132B. limit_0~50kmh (f), Upper limit table iiW limit_50~70kmh (f), Upper limit table iiiW limit_70~90kmh (f) is stored in the upper limit table iW limit_0~50kmh (f), Upper limit table iiW limit_50~70kmh (f), Upper limit table iiiW limit_70~90kmh The correction coefficient c to be multiplied in (f) may be changed. This correction coefficient c can be set to 1 for normal road surfaces and to a value greater than 1 (for example, 1.2) for rough road surfaces.

[0089] In this embodiment, the road surface conditions are classified into two types, normal road surface and rough road surface, but the road surface conditions may be classified into three or more types. For example, the upper limit value table iW limit_0~50kmh (f), Upper limit table iiW limit_50~70kmh (f), Upper limit table iiiW limit_70~90kmh The correction coefficient c to be multiplied in (f) may be changed.

[0090] <Fourth embodiment> The fourth embodiment of the present invention is an active noise control device 4 that reduces booming noise caused by an engine, which is a vibration source. The booming noise of an engine is generated, for example, when sound emitted from the engine resonates and is amplified in the engine room and enters the vehicle interior 101, and has a frequency band of approximately 20 Hz to 300 Hz.

[0091] The active noise control device 4 acquires information about the engine speed and generates a sine wave (reference signal) with the same frequency as the muffled sound, and generates a control signal by multiplying the reference signal by an adaptive filter coefficient and outputs it from the speaker 22. As a result, the muffled sound caused by the vibration source (engine) and the sound output from the speaker 22 are input to the microphone 21. The active noise control device 4 then adjusts the phase and amplitude of the reference signal using the adaptive filter W so that the sound detected by the microphone 21 is reduced, thereby canceling out the muffled sound and reducing noise.

[0092] The following describes an active noise control device 4 according to the fourth embodiment. Note that the same parts as those in the active noise control devices 1 to 3 are given the same reference numerals and descriptions thereof will be omitted.

[0093] Similar to the active noise control device 1, the active noise control device 4 is connected to the microphone 21, the speaker 22, the CAN 30, and the like provided in the vehicle 100.

[0094] 12 is a block diagram showing an outline of the functional configuration of the active noise control device 4. Functionally, the active noise control device 2 mainly includes a reference signal generation unit 11A, an output signal generation unit 12A, a storage unit 13C, an adaptive filter update unit 14C, and a frequency calculation unit 15. Note that the functional components of the active noise control device 4 may be further divided into more components depending on the processing content, or one component may perform the processing of multiple components.

[0095] The frequency calculation unit 15 is a functional unit that acquires information about the engine rotation speed from the CAN 30 and calculates the frequency f of the noise to be reduced. The frequency f is calculated by the following equation (17).

number

[0096] For example, when it is desired to reduce secondary rotational booming noise, f=RPM / 30. The frequency calculation unit 15 outputs the calculated frequency f to the reference signal generation unit 11A.

[0097] The reference signal generating unit 11A is a functional unit that generates a reference signal based on the frequency f acquired from the frequency calculating unit 15, i.e., information on the engine rotation speed. The method by which the reference signal generating unit 11A generates the reference signal will be described below. The reference signal generating unit 11A calculates the phase using the following equation (18). The reference signal generating unit 11A also generates a sine wave (reference sine wave) of the same frequency as the muffled sound as a reference signal using the following equations (19) and (20). Here, fs is the sampling frequency.

number

number

[0098] The output signal generation unit 12A is a functional unit that convolves the reference signal x(t) with an adaptive filter w(t) to generate an output signal to be output to the speaker 22. The output signal generation unit 12A generates the output signal y(t) using the following equation (21). The output signal generation unit 12A also outputs the generated control signal to the speaker 22 via a speaker amplifier (not shown).

number

[0099] The memory unit 13C is a functional unit that stores information used by the adaptive filter update unit 14C. The memory unit 13C mainly stores the acoustic characteristics s o The acoustic characteristic table storage unit 131A stores acoustic characteristic s(f) and s1(f), and an upper limit table storage unit 132C stores an upper limit table (upper limit information of the present invention). o (f), s1(f) and the upper limit value table are measured and calculated in advance before the active noise control device 4 performs processing, and the results are stored in the storage unit 13C.

[0100] Acoustic characteristics o For example, s(f) and s1(f) are generated based on the error signal e(t) by transmitting a sweep signal (cosΩ(t)) whose frequency changes over time from the speaker 22. The frequency band of the sweep signal is, for example, 30 Hz to 200 Hz. o (f) and s1(f) are calculated using equations (22) and (23). o (f) and s1(f) are, for example, tables in which values ​​are associated with each frequency.

number

[0101] The upper limit value table is obtained by operating the active noise control device 4 for a certain period of time in a stable state (such as with the windows closed) and using the maximum amplitude value of the adaptive filter obtained as the upper limit value. In the upper limit value table, values ​​are associated with each frequency. The upper limit value table will be described in detail later.

[0102] The adaptive filter update unit 14C is a functional unit that updates the adaptive filter using an adaptive algorithm. The adaptive filter update unit 14 mainly includes a Filtered-x generation unit 141A and an update unit 142C.

[0103] The Filtered-x generation unit 141A is a functional unit that generates a Filtered-x signal by multiplying the reference signal x(t) by an acoustic characteristic. The Filtered-x generation unit 141A multiplies the reference signal x(t) by the acoustic characteristic s o (f) and s1(f) are integrated to generate the Filtered-x signal.

number

[0104] The update unit 142C updates the adaptive filter using an arbitrary adaptive algorithm. In this embodiment, the update unit 142 updates the adaptive filter using the NLMS (Normalized Least Mean Squares) algorithm as shown in Equations (26) to (28). Note that adaptive filters are already well known, and therefore their description will be omitted. Furthermore, the adaptive algorithm is not limited to the NLMS algorithm, and may be, for example, an LMS algorithm or an RLS algorithm.

number

[0105] Next, the update unit 142C performs amplitude limiting processing to limit the upper limit of the amplitude of the adaptive filter based on the upper limit table. The amplitude limiting processing will be described in detail later. The update unit 142C then outputs the adaptive filter with the limited upper limit to the output signal generation unit 12A.

[0106] 13 is a flowchart showing the flow of processing for obtaining the upper limit value table in advance. First, the frequency calculation unit 15 acquires engine speed information from the CAN 30 (step SP51), and calculates the noise frequency f (step SP52). Next, the reference signal generation unit 11A generates a reference signal based on the frequency f acquired from the frequency calculation unit 15, and outputs the reference signal to the Filtered-x generation unit 141A (step SP53).

[0107] The Filtered-x generation unit 141A acquires the acoustic characteristics stored in the storage unit 13C (step SP54), generates a Filtered-x signal based on the acoustic characteristics and the reference signal, and outputs the generated Filtered-x signal to the update unit 142C (step SP55).

[0108] The update unit 142C updates the amplitude of the adaptive filter using the Filtered-x signal and the error signal e(t) and holds the maximum value (step SP56).The update unit 142C then uses the maximum value obtained in step SP56 as the upper limit value table, thereby creating the upper limit value table W limit (f) is generated (step SP57).

[0109] 14 is a flowchart showing the flow of processing performed by the active noise control device 4. First, the frequency calculation unit 15 acquires engine speed information from the CAN 30 (step SP61), and calculates the noise frequency f (step SP62). Next, the reference signal generation unit 11A generates a reference signal based on the frequency f acquired from the frequency calculation unit 15, and outputs the reference signal to the Filtered-x generation unit 141A (step SP63).

[0110] The Filtered-x generation unit 141A acquires the acoustic characteristics stored in the memory unit 13C (step SP64), generates a Filtered-x signal based on the acoustic characteristics and the reference signal, and outputs the generated Filtered-x signal to the update unit 142C (step SP65).

[0111] The update unit 142C updates the amplitude of the adaptive filter using the Filtered-x signal and the error signal e(t) (step SP66). Thereafter, the update unit 142C acquires the upper limit value table stored in the storage unit 13C (step SP67), and performs amplitude limiting processing to limit the upper limit value of the amplitude of the adaptive filter using the upper limit value table as necessary (step SP68).

[0112] In step SP68, the update unit 142C compares the amplitude of the adaptive filter after updating with the upper limit value table for each frequency, and for the part where the amplitude |w| of the adaptive filter before updating is larger than the value W in the upper limit value table, updates the amplitude |w| of the adaptive filter to the value W in the upper limit value table. limit This process is expressed by the following formulas (29) to (33).

number

[0113] The update unit 142C outputs the adaptive filter updated in steps SP66 to SP68 to the output signal generation unit 12A (step SP69). Then, the output signal generation unit 12A convolutes the adaptive filter acquired from the update unit 142C with the reference signal to generate an output signal (step S70). The output signal generated in step SP70 is output from the speaker 22.

[0114] This completes one processing cycle of the active noise control device 4. The active noise control device 4 repeatedly performs the processing shown in FIG.

[0115] Next, the effects of the active noise control device 4 will be described using Fig. 15. Fig. 15(A) is a graph showing an example of the results when ANC is not performed, Fig. 15(B) is a graph showing an example of the results when a conventional active noise control device that does not perform amplitude limitation processing is used, and Fig. 15(C) is a graph showing an example of the results when the active noise control device 4 that performs amplitude limitation processing is used. When amplitude limitation processing was not performed (see Fig. 15(B)), divergence occurred, but when amplitude limitation processing was performed by the active noise control device 4 (see Fig. 15(C)), the effect of ANC was properly obtained and noise was reduced.

[0116] According to this embodiment, the amplitude of the adaptive filter after updating is compared with the upper limit table for each frequency, and if the amplitude of the adaptive filter is greater than the upper limit table information, the amplitude of the adaptive filter is replaced with the value in the upper limit table, so that even if the ANC becomes unstable, sound above a predetermined volume is not output from speaker 22. Therefore, ANC can be performed stably in any situation.

[0117] In this embodiment, the maximum value W absmax (f) Upper limit table W limit (f), but the maximum value W absmax The upper limit value table may be obtained by multiplying (f) by the correction coefficient c.

[0118] Since this embodiment is an active noise control device 4 that reduces engine booming noise, the correction coefficient c may be changed depending on the gear position. Generally, even if the engine speed is the same, the load on the engine increases as the gear position increases, resulting in increased booming noise. Therefore, the update unit 142C may acquire information about the gear position from the CAN 30 (corresponding to the gear position acquisition unit of the present invention) and increase the correction coefficient c as the gear position increases, thereby using a different upper limit value table depending on the gear position. It is appropriate that the correction coefficient be set to 1 to 2.

[0119] Note that the mode of varying the upper limit value table based on the gear position is not limited to the mode of changing the correction coefficient c according to the gear position. For example, an upper limit value table set for each gear position may be stored in the storage unit. If the vehicle 100 has a five-speed transmission, the upper limit value table storage unit 132C stores upper limit value tables for each of the gear positions of low gear, second gear, third gear, fourth gear, and fifth gear, i.e., five upper limit value tables, and the update unit 142C may use the upper limit value table corresponding to the gear position obtained from the CAN 30.

[0120] The above describes an embodiment of the present invention in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0121] 1, 2, 3, 4: Active noise control device 11, 11A: Reference signal generation section 12, 12A: Output signal generation section 13, 13A, 13B, 13C: Storage section 14, 14A, 14B, 14C: Adaptive filter update section 15: Frequency calculation section 21: Microphone 22: Speaker 30: CAN (Control Area Network) 31: Vibration sensor 100: Vehicle 101: Vehicle interior 111: Arithmetic device 112: Storage device 131, 131A: Acoustic characteristic table storage section 132, 132A, 132B, 132C: Upper limit table storage section 141, 141A: Filtered-x generation section 142, 142A, 142B, 142C: Update section

Claims

1. An active noise control device that sequentially updates an adaptive filter that generates an output signal by signal processing a reference signal generated based on noise in a vehicle, based on an error signal input from a microphone when the output signal is output from a speaker, a reference signal generator that generates the reference signal; an adaptive filter update unit that updates the adaptive filter based on a result of integrating the reference signal with an acoustic characteristic and the error signal; an output signal generation unit that generates the output signal by convolving the reference signal with the adaptive filter updated by the adaptive filter update unit; Equipped with The adaptive filter update unit updating the adaptive filter using a coefficient update algorithm; The amplitude of the adaptive filter after the update is compared with upper limit value information indicating the relationship between the frequency and an upper limit value of the amplitude of the adaptive filter, which is the upper limit value of the amplitude of the adaptive filter, and if the amplitude of the adaptive filter after the update is greater than the upper limit value information, the amplitude of the adaptive filter after the update is replaced with the upper limit value of the amplitude.

1. An active noise control device comprising:

2. The maximum value of the amplitude obtained by operating the reference signal generating unit and the adaptive filter updating unit for an arbitrary period of time is set as the amplitude upper limit value.

2. The active noise control device according to claim 1.

3. the amplitude upper limit value is a value obtained by multiplying the maximum value by a correction coefficient, The correction coefficient is an arbitrary value between 1 and 2.

3. The active noise control device according to claim 2.

4. a vehicle speed acquisition unit that acquires a vehicle speed of the vehicle; The adaptive filter update unit varies the upper limit value information based on the vehicle speed acquired by the vehicle speed acquisition unit.

4. An active noise control device according to claim 1.

5. The adaptive filter update unit At least first upper limit value information, which is the upper limit value information at a first vehicle speed, and second upper limit value information, which is the upper limit value information at a second vehicle speed that is different from the first vehicle speed, are stored, limiting an upper limit value of amplitude of the adaptive filter using the first upper limit value information or the second upper limit value information based on the vehicle speed acquired by the vehicle speed acquisition unit; 5. The active noise control device according to claim 4.

6. a road surface condition acquisition unit that acquires the roughness of the road surface on which the vehicle is traveling; The adaptive filter update unit varies the upper limit value information based on the roughness of the road surface acquired by the road surface condition acquisition unit.

6. An active noise control device according to claim 4 or 5.

7. a gear speed acquisition unit that acquires a gear speed of the vehicle; The adaptive filter update unit varies the upper limit information based on the gear position acquired by the gear position acquisition unit.

2. The active noise control device according to claim 1.

8. the reference signal generator generates the reference signal based on a rotation speed of an engine of the vehicle; the upper amplitude limit value is a value obtained by multiplying a maximum amplitude value obtained by operating the reference signal generating unit and the adaptive filter updating unit for an arbitrary time by a correction coefficient; The correction coefficient is an arbitrary value between 1 and 2.

8. The active noise control device according to claim 7.

9. 1. An active noise control method for sequentially updating an adaptive filter that generates an output signal by signal processing a reference signal generated based on noise in a vehicle, based on an error signal input from a microphone when the output signal is output from a speaker, comprising: a reference signal generating step of generating the reference signal; an adaptive filter updating step of updating the adaptive filter based on a result of multiplying the reference signal by an acoustic characteristic and the error signal; an output signal generating step of generating the output signal by convolving the reference signal with the adaptive filter updated in the adaptive filter updating step; Including, The adaptive filter updating step updating the adaptive filter using a coefficient update algorithm; The amplitude of the adaptive filter after the update is compared with upper limit value information indicating the relationship between the frequency and an upper limit value of the amplitude of the adaptive filter, which is the upper limit value of the amplitude of the adaptive filter, and if the amplitude of the adaptive filter after the update is greater than the upper limit value information, the amplitude of the adaptive filter after the update is replaced with the upper limit value of the amplitude.

1. An active noise control method comprising:

10. An active noise control program that sequentially updates an adaptive filter that generates an output signal by processing a reference signal generated based on noise in a vehicle, based on an error signal input from a microphone when the output signal is output from a speaker, Computer, a reference signal generator that generates the reference signal; an adaptive filter update unit that updates the adaptive filter based on the result of integrating the reference signal with an acoustic characteristic and the error signal; an output signal generation unit that generates the output signal by convolving the reference signal with the adaptive filter updated by the adaptive filter update unit; It functions as The adaptive filter update unit updating the adaptive filter using a coefficient update algorithm; The amplitude of the adaptive filter after the update is compared with upper limit value information indicating the relationship between the frequency and an upper limit value of the amplitude of the adaptive filter, which is the upper limit value of the amplitude of the adaptive filter, and if the amplitude of the adaptive filter after the update is greater than the upper limit value information, the amplitude of the adaptive filter after the update is replaced with the upper limit value of the amplitude. An active noise control program.

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