Active noise control device and vehicle

Abstract

An active noise control device and a vehicle. The active noise control device (10) comprises a control signal generating unit (34), an identification unit (24), a peak frequency storage unit (70), a first determination unit (26), and a control unit (28). The control signal generating unit includes a first adaptive filter (36) that generates a control signal (u) by filtering a reference signal (r) corresponding to noise. The identification unit identifies a peak frequency (f0) in the impedance-frequency characteristic of an actuator (16). The peak frequency storage unit stores an initial peak frequency (f0org) of the actuator (16). The first determination unit determines whether a difference between the currently identified peak frequency (f0) and the initial peak frequency (f0org) is greater than a threshold value (TH). If the first determination unit determines that the difference is greater than the threshold value, the control unit changes the characteristics of the control signal generated by the control signal generating unit. Thus, noise can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to an active noise control device and a vehicle. Background Art

[0002] An active silencer is disclosed in Japanese Patent Application Laid-Open No. 6-59688. The active silencer disclosed in Japanese Patent Application Laid-Open No. 6-59688 comprises a sound generator, a sound detection sensor, and a vibration sensor. The sound generator is disposed in the silenced space. The sound detection sensor is disposed in the silenced space. The vibration sensors are respectively disposed at each of the multiple vibration sources propagating in the silenced space. The active silencer of Japanese Patent Application Laid-Open No. 6-59688 also comprises a vibration signal generating mechanism and a driving mechanism. The vibration signal generating mechanism generates a vibration signal having a phase opposite to that of the sound detected by the sound detection sensor based on the output signals of the multiple vibration sensors. The driving mechanism drives the sound generator based on the vibration signal. Summary of the Invention

[0003] However, in Japanese Patent Application Laid-Open No. 6-59688, when the characteristics of the sound generating device change, it is not necessarily possible to satisfactorily reduce noise.

[0004] An object of the present invention is to provide an active noise control device and a vehicle that can effectively reduce noise.

[0005] An active noise control device according to one embodiment of the present invention causes an actuator to output a canceling sound based on a control signal to reduce noise within a vehicle cabin. The device comprises a control signal generator, an identification unit, a peak frequency storage unit, a first determination unit, and a control unit. The control signal generator includes a first adaptive filter that generates the control signal by filtering a reference signal corresponding to the noise. The identification unit identifies a peak frequency in an impedance-frequency characteristic, wherein the impedance-frequency characteristic is the frequency characteristic of the impedance of the actuator. The peak frequency storage unit stores an initial peak frequency, which is the peak frequency in the initial impedance-frequency characteristic. The first determination unit determines whether a difference between the peak frequency identified by the identification unit and the initial peak frequency stored in the peak frequency storage unit is greater than a threshold value. If the first determination unit determines that the difference is greater than the threshold value, the control unit changes the characteristics of the control signal generated by the control signal generator.

[0006] A vehicle according to another aspect of the present invention includes the above-described active noise control device.

[0007] According to the present invention, an active noise control device and a vehicle capable of effectively reducing noise can be provided.

[0008] The above-mentioned objects, features and advantages will be easily understood from the following description of the embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a diagram showing an overview of active noise control.

[0010] Figure 2 This is a block diagram showing a portion of a vehicle including an active noise control device according to an embodiment.

[0011] Figure 3 This is a block diagram showing an example of a control signal generating unit.

[0012] Figure 4 This is a block diagram showing an example of an identification unit.

[0013] Figure 5 This is a graph showing an example of the impedance-frequency characteristics of an actuator.

[0014] Figure 6 This is a block diagram showing another example of the identification unit.

[0015] Figure 7 This is a block diagram showing an example of an impedance characteristic evaluation unit.

[0016] Figure 8 It is a figure which shows an example of a table.

[0017] Figure 9 This is a flowchart showing an example of the operation of the active noise control device according to one embodiment.

[0018] Figure 10 This is a flowchart showing an example of the operation of the active noise control device according to one embodiment. DETAILED DESCRIPTION

[0019] Hereinafter, the active noise control device and the vehicle according to the present invention will be described in detail with reference to the accompanying drawings while listing preferred embodiments.

[0020] [One embodiment]

[0021] use Figures 1 to 10 An active noise control device and a vehicle according to an embodiment will be described. Figure 1 It is a diagram showing an overview of active noise control.

[0022] The active noise control device 10 causes the actuator 16 to output a canceling sound for reducing noise (vibration noise) in the cabin 14 of the vehicle 12 .

[0023] The noise in the vehicle cabin 14 may include, for example, road noise, etc. Road noise is noise caused by the wheels vibrating due to the force from the road surface, and the wheel vibration is transmitted to the vehicle body through the suspension and then to the passengers in the vehicle cabin 14 .

[0024] The vehicle 12 includes a vibration sensor that detects vibrations of the vehicle 12. Specifically, the vehicle 12 includes an acceleration sensor 18 that detects vibrations of the vehicle 12. A signal r detected by the acceleration sensor 18 is supplied as a reference signal r to the active noise control device 10. Specifically, the signal r indicating vibrations is supplied as a reference signal r to the active noise control device 10. Figure 1 While the example in which the signal detected by the acceleration sensor 18 is used as the reference signal r is shown, the present invention is not limited thereto. A signal related to the vibration of the vehicle 12 can be appropriately used as the reference signal r. In other words, a signal corresponding to noise can be appropriately used as the reference signal r.

[0025] A microphone 20 is also provided in the vehicle cabin 14. The microphone 20 detects residual noise (cancellation error noise) generated by interference between the canceling sound output from the actuator 16 and the noise. The residual noise detected by the microphone 20 is supplied to the active noise control device 10. In other words, the error signal e detected by the microphone 20 is supplied to the active noise control device 10.

[0026] Active noise control device 10 generates a control signal u for causing actuator 16 to output a canceling sound based on error signal e detected by microphone 20 and reference signal r. More specifically, active noise control device 10 generates control signal u to minimize error signal e detected by microphone 20. Actuator 16 outputs the canceling sound based on control signal u that minimizes error signal e detected by microphone 20. Therefore, noise within vehicle cabin 14 is effectively canceled by the canceling sound. Thus, active noise control device 10 can reduce the noise transmitted to occupants within vehicle cabin 14.

[0027] However, if the characteristics of the actuator 16 change due to aging, etc., it may not be possible to satisfactorily cancel the noise in the vehicle cabin 14. As a result of intensive research, the inventors of the present application have conceived the following active noise control device 10.

[0028] Figure 2 This is a block diagram showing a portion of a vehicle including the active noise control device according to the present embodiment.

[0029] like Figure 2As shown, the active noise control device 10 includes a calculation unit 22 , a storage unit 30 , and an output unit 32 .

[0030] The computing unit 22 can be composed of, but is not limited to, a processor such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor). The computing unit 22 can include, for example, a direct digital synthesizer (DDS) or a digitally controlled oscillator (DCO). Furthermore, the computing unit 22 can include, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0031] The storage unit 30 can be composed of volatile memory (not shown) and non-volatile memory (not shown). Examples of volatile memory include RAM. Examples of non-volatile memory include ROM and flash memory. Data, etc., can be stored in the volatile memory. Programs, tables, maps, etc., can be stored in the non-volatile memory. The storage unit 30 can include a peak frequency storage unit 70, an abnormality information storage unit 72, and a table 74.

[0032] The output unit 32 can be composed of an output interface circuit or the like.

[0033] The computing unit 22 includes a control signal generating unit 34, an identification unit 24, a first determination unit 26, a second determination unit 27, and a control unit 28. The control signal generating unit 34, the identification unit 24, the first determination unit 26, the second determination unit 27, and the control unit 28 can be implemented by the computing unit 22 executing a program stored in the storage unit 30.

[0034] The reference signal r can be supplied to the active noise control device 10. The reference signal r can be obtained, for example, by the acceleration sensor 18 (refer to Figure 1 ) is supplied, but is not limited thereto. As described above, a signal related to the vibration of the vehicle 12 can be appropriately used as the reference signal r. That is, a signal corresponding to noise can be appropriately used as the reference signal r.

[0035] As mentioned above, the carriage 14 (refer to Figure 1 ) is provided with a microphone 20, which detects the residual noise generated by the interference between the noise and the canceling sound. That is, the microphone 20 for detecting the error signal e is provided in the vehicle cabin 14.

[0036] In addition, as described above, the carriage 14 (see Figure 1 ) has an actuator 16 that outputs a canceling sound based on a control signal u. An example of the actuator 16 is a speaker.

[0037] Figure 3 This is a block diagram showing an example of a control signal generating unit.

[0038] The control signal generating unit (filter unit) 34 includes an adaptive filter 36 , an acoustic characteristic filter 38 , and a filter coefficient updating unit 40 .

[0039] Adaptive filter (first adaptive filter) 36 generates control signal u by filtering reference signal r. Adaptive filter 36 can employ, for example, a FIR (Finite Impulse Response) filter, but is not limited thereto. As described later, filter coefficients W of adaptive filter 36 are updated by filter coefficient update unit 40. The FIR filter generates control signal u by performing a convolution operation on reference signal r.

[0040] The acoustic characteristic filter 38 modifies the reference signal r by filtering the reference signal r according to the acoustic characteristic (transfer characteristic) from the actuator 16 to the microphone 20. The acoustic characteristic from the actuator 16 to the microphone 20, ie, the transfer characteristic C^, has been acquired in advance.

[0041] The filter coefficient updating unit 40 updates the filter coefficient W in the adaptive filter 36 based on the error signal e obtained by detecting the residual noise using the microphone 20 and the reference signal r corrected by the acoustic characteristic filter 38. More specifically, the filter coefficient updating unit 40 updates the filter coefficient W in the adaptive filter 36 so as to minimize the error signal e obtained by detecting the residual noise using the microphone 20. For example, the Filtered-XLMS algorithm can be used to update the filter coefficient W, but the algorithm is not limited thereto.

[0042] In this way, the control signal u is generated by filtering the reference signal r corresponding to the noise using the adaptive filter 36. Figure 2 As shown, the control signal u generated by the control signal generating unit 34 is supplied to the actuator 16 via the power amplifier 15 .

[0043] The identification unit 24 identifies the peak frequency (resonance frequency) f0 in the impedance-frequency characteristic, which is the frequency characteristic of the impedance of the actuator 16 .

[0044] Figure 4 This is a block diagram showing an example of an identification unit.

[0045] Figure 4 The illustrated identification unit 24 includes a voltage detection unit 46 , a current detection unit 48 , an impedance-frequency characteristic calculation unit 50 , and a peak frequency identification unit 52 .

[0046] The voltage detection unit 46 detects a voltage signal Vspk, which is a time waveform signal of a voltage applied to the actuator 16. Figure 2 As shown, the time waveform signal of the voltage supplied from power amplifier 15 to actuator 16 is also supplied to active noise control device 10. That is, voltage signal Vspk is also supplied to active noise control device 10. Voltage detection unit 46 detects voltage signal Vspk thus supplied.

[0047] The current detection unit 48 detects a current signal Ispk which is a time waveform signal of the current consumed in the actuator 16. Figure 2 As shown, a current detector 17 is connected to the actuator 16. The current detector 17 is configured to detect the current consumed by the actuator 16. The current detector 17 detects the current consumed by the actuator 16 and supplies a current signal Ispk, which is a time waveform signal of the current, to the active noise control device 10. The current detection unit 48 detects the current signal Ispk supplied by the current detector 17.

[0048] The impedance-frequency characteristic calculation unit 50 calculates the impedance-frequency characteristic of the actuator 16 based on the voltage signal Vspk and the current signal Ispk. More specifically, the impedance-frequency characteristic calculation unit 50 calculates the impedance-frequency characteristic of the actuator 16 by performing Fourier transform.

[0049] Figure 5 This is a graph showing an example of the impedance-frequency characteristics of an actuator. Figure 5 The horizontal axis is frequency. Figure 5 The vertical axis in is the impedance of the actuator 16 . Figure 5 The solid line in shows an example of the impedance-frequency characteristic of the actuator 16 in the early stage. Figure 5 The dotted line in shows an example of the impedance frequency characteristic of the actuator 16 after the aging change.

[0050] The peak frequency identification unit 52 identifies the peak frequency f0 by performing a frequency analysis on the impedance-frequency characteristics calculated by the impedance-frequency characteristics calculation unit 50. Specifically, the peak frequency identification unit 52 sweeps the impedance-frequency characteristics calculated by the impedance-frequency characteristics calculation unit 50 and identifies the frequency at which the impedance of the actuator 16 reaches a maximum as the peak frequency f0. In this way, the peak frequency f0 in the impedance-frequency characteristics of the actuator 16 is identified.

[0051] Figure 6This is a block diagram showing another example of the identification unit.

[0052] Figure 6 The illustrated identification unit 24 includes an impedance characteristic identification unit 54 , a Fourier transform unit 56 , and a peak frequency identification unit 52 .

[0053] The impedance characteristic evaluation unit 54 evaluates the impedance characteristics of the actuator 16 .

[0054] Figure 7 This is a block diagram showing an example of an impedance characteristic evaluation unit.

[0055] The impedance characteristic evaluation unit 54 includes an adaptive filter 60 , a filter coefficient update unit 62 , and a calculation unit 64 .

[0056] Adaptive filter (second adaptive filter) 60 outputs an analog voltage signal Vspk′ by filtering current signal Ispk, which is a time waveform signal of the current consumed by actuator 16. The filter coefficient Wspk in adaptive filter 60 differs from the filter coefficient W in adaptive filter 36 described above. Therefore, the filtering process performed in adaptive filter 60 differs from the filtering process performed in adaptive filter 36 described above.

[0057] The operator 64 calculates the difference between the voltage signal Vspk, which is a time waveform signal of the voltage applied to the actuator 16 , and the analog voltage signal Vspk′. The calculation result of the operator 64 is supplied to the filter coefficient update unit 62 .

[0058] The filter coefficient updating unit 62 updates the filter coefficient Wspk in the adaptive filter 60 to minimize the difference between the voltage signal Vspk, which is a time waveform signal of the voltage applied to the actuator 16 , and the analog voltage signal Vspk′.

[0059] In this manner, the filter coefficient Wspk in the adaptive filter 60 becomes a value corresponding to the impedance characteristic of the actuator 16 . That is, the impedance characteristic evaluation unit 54 evaluates the impedance characteristic of the actuator 16 .

[0060] The Fourier transform unit 56 obtains the impedance-frequency characteristic of the actuator 16 by performing Fourier transform on the adaptive filter 60. Specifically, the Fourier transform unit 56 obtains the impedance-frequency characteristic of the actuator 16 by performing Fourier transform on the adaptive filter 60 having the filter coefficient Wspk corresponding to the impedance characteristic of the actuator 16.

[0061] The peak frequency identification unit 52 identifies the peak frequency f0 by performing frequency analysis on the impedance-frequency characteristic obtained by the Fourier transform unit 56. Specifically, the peak frequency identification unit 52 sweeps the impedance-frequency characteristic calculated by the Fourier transform unit 56 and identifies the frequency at which the impedance of the actuator 16 reaches a maximum as the peak frequency f0. This identifies the peak frequency f0 in the impedance-frequency characteristic of the actuator 16. Similarly, the peak frequency f0 in the impedance-frequency characteristic can also be determined using the adaptive filter 60.

[0062] The peak frequency storage unit 70 pre-stores an initial peak frequency f0org, which is a peak frequency in the initial impedance-frequency characteristic. The initial period refers to a period before the actuator 16 undergoes aging changes. Specifically, the initial period may be, for example, when the active noise control device 10 is installed in the vehicle 12, but the present invention is not limited to this period. The initial peak frequency f0org can be measured when the active noise control device 10 is installed in the vehicle 12, but the present invention is not limited to this period.

[0063] The first determination unit 26 determines whether the difference between the peak frequency f0 identified this time by the identification unit 24 and the initial peak frequency f0org stored in the peak frequency storage unit 70 is equal to or greater than the threshold value TH.

[0064] When the first determination unit 26 determines that the difference between the peak frequency f0 identified this time by the identification unit 24 and the initial peak frequency f0org stored in the peak frequency storage unit 70 is greater than or equal to the threshold value TH, the control unit 28 performs the following control. Specifically, in this case, the characteristics of the control signal u generated by the control signal generation unit 34 are changed.

[0065] The characteristics of the control signal u can be obtained by switching the acoustic characteristics Ĉ applied to the acoustic characteristic filter 38 , but the present invention is not limited thereto.

[0066] Figure 8 is a diagram showing an example of a table. Figure 8 As shown, Table 74 stores a plurality of acoustic characteristics C^ corresponding to each peak frequency f0. C^0 is the acoustic characteristic when the peak frequency is f00. C^1 is the acoustic characteristic when the peak frequency is f01. C^n is the acoustic characteristic when the peak frequency is f0n. When describing the peak frequency as a whole, the reference numeral f0 is used, and when describing each peak frequency, the reference numerals f00 to f0n are used. When describing the acoustic characteristics as a whole, the reference numeral C^ is used. When describing each acoustic characteristic, the reference numerals C^0 to C^n are used.

[0067] The control unit 28 can change the characteristics of the control signal u generated by the control signal generator 34 by appropriately switching the acoustic characteristics C^ applied to the acoustic characteristics filter 38 according to the peak frequency f0. Specifically, the control unit 28 reads the acoustic characteristics C^ corresponding to the current peak frequency f0 from the table 74 and applies the acoustic characteristics C^ read from the table 74 to the acoustic characteristics filter 38. This changes the characteristics of the control signal u generated by the control signal generator 34.

[0068] The second determination unit 27 can determine whether the peak frequency f0 is within a predetermined frequency range.

[0069] If the second determination unit 27 determines that the peak frequency f0 is not within the predetermined frequency range, the control unit 28 stops the control signal generator 34 from generating the control signal u. In other words, if the peak frequency f0 changes significantly, the control unit 28 stops the control signal generator 34 from generating the control signal u.

[0070] When the second determination unit 27 determines that the peak frequency f0 is not within the predetermined frequency range, the control unit 28 stores information indicating that an abnormality has occurred in the characteristics of the actuator 16 in the abnormality information storage unit 72 .

[0071] When the second determination unit 27 determines that the peak frequency f0 is not within the predetermined frequency range, the control unit 28 causes the information display 68 included in the vehicle 12 to display a message indicating that an abnormality has occurred in the characteristics of the actuator 16 .

[0072] Output unit 32 notifies fault diagnosis machine 66 of information indicating abnormality in actuator 16 characteristics. When fault diagnosis machine 66 is connected to vehicle 12, control unit 28 notifies fault diagnosis machine 66 of information indicating abnormality in actuator 16 characteristics via output unit 32.

[0073] Figure 9 This is a flowchart showing an example of the operation of the active noise control device according to this embodiment.

[0074] In step S1, the identification unit 24 identifies the peak frequency f0 in the impedance-frequency characteristic of the actuator 16. Thereafter, the process moves to step S2.

[0075] In step S2, the first determination unit 26 determines whether the difference between the peak frequency f0 identified this time by the identification unit 24 and the initial peak frequency f0org stored in the peak frequency storage unit 70 is greater than the threshold value TH. If the difference is greater than the threshold value TH (yes in step S2), the process proceeds to step S3. If the difference is less than the threshold value TH (no in step S2), Figure 9 The indicated processing is completed.

[0076] In step S3, the control unit 28 changes the characteristics of the control signal u. As described above, the characteristics of the control signal u can be changed by switching the acoustic characteristics C ^ applied to the acoustic characteristic filter 38, but the present invention is not limited to this. Figure 9 The indicated processing is completed.

[0077] Figure 10 This is a flowchart showing an example of the operation of the active noise control device according to this embodiment.

[0078] In step S11, the second determination unit 27 determines whether the peak frequency f0 is within a predetermined frequency range. If the peak frequency f0 is not within the predetermined frequency range (No in step S11), the process proceeds to step S12. If the peak frequency f0 is within the predetermined frequency range (Yes in step S11), Figure 10 The indicated processing is completed.

[0079] In step S12, the control unit 28 stops the generation of the control signal u by the control signal generating unit 34. Thereafter, the process moves to step S13.

[0080] In step S13, the control unit 28 stores information indicating that an abnormality has occurred in the characteristics of the actuator 16 in the abnormality information storage unit 72. Thereafter, the process shifts to step S14.

[0081] In step S14, the control unit 28 displays information indicating that the characteristics of the actuator 16 are abnormal on the information display 68 provided in the vehicle 12. Figure 10 The indicated processing is completed.

[0082] Thus, in this embodiment, a determination is made as to whether the difference between the peak frequency f0 currently identified by the identification unit 24 and the initial peak frequency f0org stored in the peak frequency storage unit 70 is greater than or equal to the threshold value TH. Furthermore, if the difference is determined to be greater than or equal to the threshold value TH, the characteristics of the control signal u generated by the control signal generation unit 34 are changed. Therefore, according to this embodiment, an active noise control device 10 can be provided that can effectively cancel out noise within the vehicle cabin 14, thereby effectively reducing noise, even when the characteristics of the actuator 16 change due to aging or the like.

[0083] While preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0084] The above-mentioned embodiments are summarized as follows.

[0085] An active noise control device (10) causes an actuator (16) to output a canceling sound based on a control signal (u) to reduce noise in a vehicle cabin (14) of a vehicle (12). The active noise control device (10) comprises a control signal generating unit (34), an identification unit (24), a peak frequency storage unit (70), a first determination unit (26), and a control unit (28). The control signal generating unit (34) includes a first adaptive filter (36) that generates the control signal by filtering a reference signal (r) corresponding to the noise. The identification unit (24) identifies a peak frequency (f0) in an impedance-frequency characteristic. The impedance-frequency characteristic is the frequency characteristic of the impedance of the actuator; the peak frequency storage unit (70) stores an initial peak frequency (f0org), which is the peak frequency in the initial impedance-frequency characteristic; the first determination unit (26) determines whether the difference between the peak frequency identified by the identification unit and the initial peak frequency stored in the peak frequency storage unit is greater than a threshold value (TH); if the first determination unit determines that the difference is greater than the threshold value, the control unit (28) changes the characteristics of the control signal generated by the control signal generation unit. According to this configuration, when the difference exceeds the threshold value due to aging, the characteristics of the control signal generated by the control signal generation unit are changed. Therefore, according to this configuration, it is possible to provide an active noise control device that can effectively cancel out noise in the vehicle cabin and effectively reduce noise even when the characteristics of the actuator change due to aging.

[0086] Alternatively, the identification unit may include a voltage detection unit (46), a current detection unit (48), an impedance frequency characteristic calculation unit (50), and a peak frequency identification unit (52), wherein the voltage detection unit (46) detects a voltage signal (Vspk) which is a time waveform signal of a voltage applied to the actuator; the current detection unit (48) detects a current signal (Ispk) which is a time waveform signal of a current consumed in the actuator; the impedance frequency characteristic calculation unit (50) calculates the impedance frequency characteristic based on the voltage signal and the current signal; and the peak frequency identification unit (52) identifies the peak frequency by performing frequency analysis on the impedance frequency characteristic. According to this configuration, the peak frequency can be identified based on the impedance frequency characteristic.

[0087] Alternatively, the identification unit may include an impedance characteristic identification unit (54) that calculates the impedance characteristic of the actuator, and the impedance characteristic identification unit may include a second adaptive filter (60) and a second filter coefficient updating unit (62), wherein the second adaptive filter (60) outputs an analog voltage signal (Vspk′) by performing filtering processing different from the filtering processing performed by the first adaptive filter on a current signal, wherein the current signal is a time waveform signal of current consumed in the actuator; and the second filter coefficient updating unit (62) updates the filter coefficient (Wspk) in the second adaptive filter so as to minimize the difference between a voltage signal, which is a time waveform signal of voltage applied to the actuator, and the analog voltage signal. The identification unit may also include a Fourier transform unit (56) and a peak frequency identification unit, wherein the Fourier transform unit (56) obtains the impedance frequency characteristic by performing Fourier transform on the second adaptive filter; and the peak frequency identification unit identifies the peak frequency by performing frequency analysis on the impedance frequency characteristic obtained by the Fourier transform unit.

[0088] The control unit may further include a second determination unit (27) for determining whether the peak frequency is within a predetermined frequency range. If the second determination unit determines that the peak frequency is not within the frequency range, the control unit stops the control signal generation unit from generating the control signal. According to this configuration, the control signal generation unit stops generating the control signal when the peak frequency in the impedance-frequency characteristic of the actuator changes significantly, thereby preventing an increase in noise caused by a malfunction or abnormality of the actuator.

[0089] The apparatus may further include a second determination unit and an abnormality information storage unit (72), wherein the second determination unit determines whether the peak frequency is within a predetermined frequency range; and when the second determination unit determines that the peak frequency is not within the frequency range, the abnormality information storage unit (72) stores information indicating that an abnormality has occurred in the characteristics of the actuator. With this configuration, the information indicating an abnormality in the actuator can be used for fault diagnosis, etc.

[0090] Alternatively, when the second determination unit determines that the peak frequency is not within the frequency range, the control unit (28) causes information indicating that an abnormality has occurred in the characteristics of the actuator to be displayed on an information display (68) provided in the vehicle. According to this configuration, information indicating that an abnormality has occurred in the characteristics of the actuator can be displayed on the information display, so that a user can grasp the abnormality in the characteristics of the actuator based on the display on the information display.

[0091] The apparatus may further include an output unit (32) for notifying the fault diagnosis machine (66) of information indicating that the characteristics of the actuator are abnormal. According to this structure, the information indicating that the characteristics of the actuator are abnormal can be supplied to the fault diagnosis machine, thereby enabling the fault diagnosis machine to perform reliable fault diagnosis.

[0092] The apparatus may further include a table (74), an acoustic characteristic filter (38), and a first filter coefficient updating unit (40), wherein the table (74) includes a plurality of acoustic characteristics (C^) corresponding to each of the peak frequencies; the acoustic characteristic filter (38) corrects the reference signal by performing a filtering process corresponding to any one of the plurality of acoustic characteristics included in the table on the reference signal; the first filter coefficient updating unit (40) updates the filter coefficient (W) in the first adaptive filter based on an error signal (e) and the reference signal corrected by the acoustic characteristic filter, wherein the error signal (e) is a signal obtained by detecting residual noise generated by interference between the noise and the cancellation sound by a microphone (20); and the control unit changes the characteristics of the control signal generated by the control signal generating unit by switching the acoustic characteristics applied to the acoustic characteristic filter according to the peak frequency. According to this configuration, the acoustic characteristics of the acoustic characteristic filter are switched according to the peak frequency, so that the characteristics of the control signal can be reliably changed without complicated signal processing. That is, according to this configuration, it is possible to prevent the control of the vibration of the noise from becoming unstable, thereby effectively reducing the noise.

[0093] The actuator may also be a loudspeaker.

[0094] The vehicle includes the active noise control device as described above.

Claims

1. An active noise control device (10) that causes an actuator (16) to output a canceling sound based on a control signal (u) to reduce noise in a cabin (14) of a vehicle (12), It is characterized by: The invention comprises a control signal generating unit (34), an identification unit (24), a peak frequency storage unit (70), a first determination unit (26) and a control unit (28), wherein: The control signal generating unit (34) includes a first adaptive filter (36) that generates the control signal by filtering a reference signal (r) corresponding to the noise; The identification unit (24) identifies a peak frequency (f0) in an impedance frequency characteristic, wherein the impedance frequency characteristic refers to a frequency characteristic of the impedance of the actuator; The peak frequency storage unit (70) stores an initial peak frequency (f0org), which is the peak frequency in the initial impedance-frequency characteristic. The first determination unit (26) determines whether a difference between the peak frequency identified this time by the identification unit and the initial peak frequency stored in the peak frequency storage unit is greater than a threshold value (TH); When the first determination unit determines that the difference is greater than or equal to the threshold value, the control unit (28) changes the characteristics of the control signal generated by the control signal generation unit.

2. The active noise control device according to claim 1, characterized in that: The identification unit includes a voltage detection unit (46), a current detection unit (48), an impedance frequency characteristic calculation unit (50), and a peak frequency identification unit (52), wherein the voltage detection unit (46) detects a voltage signal (Vspk), which is a time waveform signal of a voltage applied to the actuator; the current detection unit (48) detects a current signal (Ispk), which is a time waveform signal of a current consumed in the actuator; the impedance frequency characteristic calculation unit (50) calculates the impedance frequency characteristic based on the voltage signal and the current signal; and the peak frequency identification unit (52) identifies the peak frequency by performing frequency analysis on the impedance frequency characteristic.

3. The active noise control device according to claim 1, characterized in that: The evaluation unit includes an impedance characteristic evaluation unit (54) that calculates the impedance characteristic of the actuator. The impedance characteristic identification unit includes a second adaptive filter (60) and a second filter coefficient updating unit (62), wherein the second adaptive filter (60) outputs an analog voltage signal (Vspk′) by performing filtering processing different from the filtering processing performed by the first adaptive filter on a current signal, wherein the current signal is a time waveform signal of current consumed in the actuator; and the second filter coefficient updating unit (62) updates the filter coefficient (Wspk) in the second adaptive filter so as to minimize the difference between a voltage signal, which is a time waveform signal of a voltage applied to the actuator, and the analog voltage signal. The identification unit further includes a Fourier transform unit (56) and a peak frequency identification unit, wherein the Fourier transform unit (56) obtains the impedance frequency characteristic by performing Fourier transform on the filter coefficients in the second adaptive filter; and the peak frequency identification unit identifies the peak frequency by performing frequency analysis on the impedance frequency characteristic obtained by the Fourier transform unit.

4. The active noise control device according to claim 1, characterized in that: The invention further comprises a second determination unit (27) for determining whether the peak frequency is within a predetermined frequency range. When the second determination unit determines that the peak frequency is not within the frequency range, the control unit stops the control signal generation unit from generating the control signal.

5. The active noise control device according to claim 1, characterized in that: It also has a second determination unit and an abnormality information storage unit (72), wherein: The second determination unit determines whether the peak frequency is within a predetermined frequency range; When the second determination unit determines that the peak frequency is not within the frequency range, the abnormality information storage unit (72) stores information indicating that an abnormality has occurred in the characteristics of the actuator.

6. The active noise control device according to claim 5, characterized in that: When the second determination unit determines that the peak frequency is not within the frequency range, the control unit displays information indicating that the characteristics of the actuator are abnormal on an information display (68) provided in the vehicle.

7. The active noise control device according to claim 5, characterized in that: An output unit (32) is also provided for notifying a fault diagnosis machine (66) of information indicating that an abnormality has occurred in the characteristics of the actuator.

8. The active noise control device according to claim 1, characterized in that: It also includes a table (74), an acoustic characteristic filter (38), and a first filter coefficient updating unit (40), wherein: The table (74) includes a plurality of acoustic characteristics (C^) corresponding to each of the peak frequencies; The acoustic characteristic filter (38) corrects the reference signal by performing a filtering process corresponding to any one of the plurality of acoustic characteristics included in the table on the reference signal; The first filter coefficient updating unit (40) updates the filter coefficient (W) in the first adaptive filter based on an error signal (e) and the reference signal corrected by the acoustic characteristic filter, wherein the error signal (e) is a signal obtained by detecting residual noise generated by interference between the noise and the canceling sound by a microphone (20), The control unit changes the characteristics of the control signal generated by the control signal generation unit by switching the acoustic characteristics applied to the acoustic characteristic filter according to the peak frequency.

9. The active noise control device according to claim 1, characterized in that: The actuator is a speaker.

10. A vehicle, characterized in that: An active noise control device according to any one of claims 1 to 9.

Images