JP2010208456A - Noise control device and noise control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise control device and a noise control method reducing the power consumption. <P>SOLUTION: A control command value calculating unit 6 sets the frequency band for performing the noise control according to the level of the road noise and the level of the wind whistle, and controls a piezoelectric actuator 2 to reduce the noise in the set frequency band. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a noise control device and a noise control method for reducing noise by superimposing waves such as sound waves and vibrations on noise.

  Conventionally, a noise control device that reduces noise in a vehicle interior by driving an actuator such as a speaker or a vibrator installed in a vehicle based on vibrations of a vehicle body detected by a plurality of vibration sensors is known. ing.

Japanese Patent Laid-Open No. 8-2922771

  In the conventional noise control device, if the control for reducing the noise in the passenger compartment is continuously performed in the frequency region where the wind noise level is higher than the road noise level, the noise caused by the wind noise cannot be reduced. In addition, power is wasted.

  The present invention has been made in view of the above problems, and an object thereof is to provide a noise control device and a noise control method capable of reducing power consumption.

  The present invention

  According to the present invention, since the frequency band for performing noise control is appropriately set, power consumption can be reduced.

It is a conceptual diagram which shows a mode that the vibration and road noise of a vehicle body by the influence of the unevenness | corrugation of a road surface propagate. It is a block diagram which shows the structure of the noise control apparatus used as embodiment of this invention. It is a schematic diagram which shows the propagation path of the sound and vibration at the time of noise control. FIG. 3 is a layout diagram of an acceleration sensor, a piezoelectric actuator, and a control space in the present embodiment. It is a block diagram which shows the internal structure of the control command value calculation part shown in FIG. It is a block diagram which shows the modification of the internal structure of the control command value calculation part shown in FIG. It is a figure which shows the filter characteristic of a band pass filter. It is a figure which shows the frequency characteristic of the road noise in the case where noise control is not performed and when noise control is performed. (A) It is a figure which shows the frequency characteristic of a road noise and a wind noise, and (b) the frequency area | region where a wind noise becomes larger than a road noise. It is a figure which shows the frequency characteristic of the road noise in the case where noise control is not performed, and the case where noise control is performed, and the frequency characteristic of wind noise. It is a figure which shows an example of the threshold level which determines the frequency band which performs noise control. It is a figure which shows the other example of the threshold level which determines the frequency band which performs noise control. It is a figure which shows the other example of the threshold level which determines the frequency band which performs noise control. It is a figure which shows the other example of the threshold level which determines the frequency band which performs noise control. It is a flowchart figure which shows the flow of the noise control process used as embodiment of this invention. It is a figure which shows the frequency characteristic of the road noise and the wind noise in (a) vehicle speed va, (b) vb (> va), (c) vc (> vb). It is a figure which shows the frequency characteristic L1 of road noise and the frequency characteristic L3 of a wind noise in road surface roughness (a) rd, (b) re (> rd), (c) rf (> re).

  Hereinafter, a noise control device according to an embodiment of the present invention will be described with reference to the drawings. The noise control device according to the present embodiment is intended to reduce noise (hereinafter referred to as road noise) caused by unevenness on the road surface on which the vehicle is traveling. However, the present invention can be applied to the reduction of noise other than road noise such as engine noise caused by engine vibration and wind noise generated by air flow during vehicle travel.

[Road noise propagation path]
First, a road noise propagation path will be described with reference to FIGS. In general, as a main component of road noise transmitted to the vehicle body via the tire 50, the vibration of the member 53 (highly rigid beam-like shape) is provided via the mounting portion of the axle 51 and the suspension 52 as shown in FIG. 1 (a), the floor panel 54 is vibrated by transmitting to the floor panel 54 (a plate member having relatively low rigidity) surrounded by the member 53, as shown in FIG. When the floor panel 54 vibrates, the air in the passenger compartment vibrates and a resonance phenomenon occurs in the passenger compartment, so that road noise can be heard in the passenger compartment space (hereinafter referred to as control space) 55.

  The noise is also generated when the roof panel or window glass vibrates in addition to the floor panel 54, but most of the road noise transmitted from the mounting portion of the suspension 52 is highly related to the vibration of the floor panel 54. Are known. Therefore, road noise can be reduced by performing noise control according to the vibration of the floor panel 54. However, the present invention is not limited to the reduction of noise due to vibration of the floor panel 54, and can also be applied to a vehicle interior noise source generated by the same mechanism such as a dash panel, a windshield, and a roof panel.

[Configuration of noise control device]
Next, the configuration of the noise control apparatus according to the embodiment of the present invention will be described with reference to FIG.

  A noise control device according to an embodiment of the present invention is mounted on a vehicle and, as shown in FIG. 2, an acceleration sensor 1 that measures vibration of the floor panel 54 of the vehicle, and a piezo actuator 2 that applies vibration to the floor panel 54. The control device main body 3 that reduces the noise in the control space 55 by controlling the driving of the piezo actuator 2 based on the output signal of the acceleration sensor 1 is provided as a main component.

[Configuration of acceleration sensor and piezo actuator]
The excitation force input to the tire from the road surface on which the vehicle is traveling vibrates the floor panel. As indicated by a broken line A in FIG. 3, vibration due to the excitation force is generated in the acceleration sensor 1 installed on the floor panel. Detected. Further, since the vibration of the floor panel generates vehicle interior noise, noise caused by the excitation force is generated in the control space 55 as indicated by a solid line B in FIG. On the other hand, since the piezo actuator 2 vibrates the floor panel by vibration suppression vibration, vibration caused by the vibration suppression vibration is detected in the acceleration sensor 1 as indicated by a broken line C in FIG. Similarly to the case of the excitation force input to the tire 50, noise caused by vibration suppression vibration is generated in the control space 55 as indicated by a dashed line D in FIG.

  In practice, as shown in FIG. 4, a plurality of tire excitation forces are input from a plurality of tires 50, and noises due to the plurality of tire excitation forces overlap to form road noise. Therefore, in order to perform noise control, it is necessary to extract all the independent noise components included in the noise source, and therefore the number of acceleration sensors 1 needs to be larger than the number of noise components. In addition, a sufficient number of piezoelectric actuators 2 are attached to appropriate positions on the floor panel of the vehicle body in order to reduce noise in the control space 55. In the present embodiment, as shown in FIG. 4, two control spaces 55 (55a, 55b), five acceleration sensors 1 (1a to 1e), and four piezoelectric actuators 2 (2a to 2d) are provided. ing.

When there are a plurality of tire excitation forces, acceleration sensors, piezo actuators, and control spaces in this way, each acceleration sensor detects all tire excitation forces and vibrations generated by the piezo actuators in an overlapping manner. All tire excitation forces and vibrations generated by the piezo actuator are generated in an overlapping manner. Therefore, the number of acceleration sensors arranged on the floor panel and the arrangement positions thereof are determined so that the coherency between each acceleration sensor and the sound pressure of noise in the control space is sufficiently high (for example, 0.9 or more). Is desirable. Note that coherency C _xy (ω) is defined by Equation 1 below, and represents the degree of causal relationship between the signal x and the signal y. In Equation 1, P _xy represents a cross power spectrum between the signal x and the signal y, P _xx represents an auto power spectrum of the signal x, and P _yy represents an auto power spectrum of the signal y. P ^H represents a Hermitian transpose matrix of P.

[Configuration of control unit body]
As shown in FIG. 2, the control device main body 3 converts the acceleration signal α amplified by the amplification unit 4 and the amplification unit 4 to a digital form to amplify the analog form acceleration signal α detected by the acceleration sensor 1. D / A for converting the control command value calculated by the / D conversion unit 5 and the control command value calculation unit 6 for calculating the control command value for controlling the driving of the piezo actuator 2 to the analog form A conversion unit 7 and an amplification unit 8 that amplifies an analog control command value and outputs the amplified control command value to the piezo actuator 2, and the piezo actuator 2 vibrates the floor panel according to the control command value output from the amplification unit 8. When the acceleration sensor 1 is a so-called charge type, the amplification unit 4 converts the electric charge detected by the acceleration sensor 1 into a voltage signal and then outputs the voltage signal to the A / D conversion unit 5.

[Configuration of control command value calculation unit]
The control command value calculation unit 6 is configured by a microcomputer, and calculates a control command value every control cycle (for example, 1 msec). In the present embodiment, as shown in FIG. 5, the control command value calculation unit 6 transfers the transfer function G _d ^SPL (s) from the vibration d at the position of the acceleration sensor 1 caused by the tire excitation force to the control space sound pressure SPL. ), A block representing the transfer function G _u ^SPL (s) from the controller output u to the control space sound pressure SPL, a block representing the controller transfer function C (s), and the piezo actuator 2 Block representing the transfer function G _u ^α (s) from the controller output u to the acceleration signal α. The control command value calculation unit 6 calculates a drive control command value u to the piezo actuator so as to reduce noise in the control space using the controller transfer characteristic C (s) from the acceleration signal α. The relationship between the acceleration signal α and the noise control command value u is expressed by the following formulas 2 and 3. Here in Equation 2, the parameter _{A C, B C, C C} , D D is a parameter representing the controller transfer function C (s), the acceleration noise control command value u is using Equation 2 below Calculated from the signal α.

The controller can be redesigned using, for example, H2 control. Specifically, the controller and the transfer function G _u ^α (s) are first extracted from the noise control system shown in FIG. 5 to be deformed as shown in FIG. Here, Wc (s) is a weight function of the output of the piezoelectric actuator 2, u is an actuator command value, and y is an acceleration signal. The reason for extracting the transfer function G _u ^α (s) is to design the controller C ₀ (s) on the assumption that there is no vibration wraparound from the actuator command value u to the acceleration signal α. If the generalized plant shown in FIG. 6 is used to design with H2 control, the controller ₀ (s) is designed to minimize the H2 norm from d to z1 and z2, so that road noise is reduced. (With regard to H2 control, Active Structural Acoustic Control in a car cabin using a virtual sound sensing method, Mens Remy Shell (Nissan Motor), Yoshiro Takamatsu, Takataka Deguchi, Haruki Yashiro, Dynamics and Design Conference 2006 (D & D2006 )reference).

FIG. 7 shows the filter characteristics of the bandpass filter of the weight function We or the weight function Wc. The bandpass filter shown in FIG. 7 controls the noise in the frequency region between the minimum frequency f _l and a maximum frequency f _u. FIG. 8 shows a road noise frequency characteristic L1 when noise control is not performed and a road noise frequency characteristic L2 when noise control is performed. As shown in FIG. 8, in the case of performing the noise control, noise in the frequency domain between the minimum frequency f _l and a maximum frequency f _u of the band-pass filter is reduced (reduction amount R1).

FIG. 9A shows a frequency characteristic L1 of road noise and a frequency characteristic L3 of wind noise. 9 (b) shows a frequency region R3 which is set in the frequency region between the minimum frequency f _l and a maximum frequency f _u of the band-pass filter. In the frequency region R3, the wind noise is larger than the road noise, and in other frequency regions, the wind noise is smaller than the road noise. The controller controls road noise but not wind noise. For this reason, the road noise reduction effect (region R2) is smaller than the reduction effect (region R1) shown in FIG.

  In the example shown in FIG. 9B, when noise is controlled in all frequency regions, a lot of power is wasted. The wind noise is not reduced in the frequency domain R3, and the wind noise is larger than the road noise in the frequency domain R3. Therefore, it can be said that the frequency region R3 is a frequency region in which power is wasted.

FIG. 10 shows a frequency characteristic L1 of road noise when noise control is not performed, a frequency characteristic L2 of road noise when noise control is performed, and a frequency characteristic L3 of wind noise. In the figure, a region R2 shows a noise reduction effect. In this embodiment, in order not to waste power, a frequency band for controlling noise is set according to the minimum frequency f _l ′ and the maximum frequency f _u ′ of the bandpass filter. The frequency band is set using a threshold level. A method for setting the threshold level will be described later with reference to a flowchart shown in FIG. In the example shown in FIG. 10, the threshold level is a wind noise (see FIG. 11).

Noise is controlled in a frequency region where road noise becomes a threshold level or more. In the example shown in FIG. 9, the minimum frequency f ₁ ′ is the same as the minimum frequency f ₁ , but the maximum frequency f _u ′ is smaller than the maximum frequency f _u . The maximum frequency can be changed by using a threshold value. The frequency band of noise control for which the threshold level is set is narrower than the frequency band of noise control for which the threshold level is not set. By narrowing the frequency band of noise control, the amount of power required for noise control can be reduced and the power consumption can be reduced.

  FIG. 11 shows an example of threshold frequency characteristics. In this example, the threshold level L4 is set to the frequency characteristic of wind noise. FIG. 12 shows another example of the threshold level. In this example, the threshold level L4 is set to a value obtained by adding an arbitrary constant to the frequency characteristic L3 of the wind noise. FIG. 13 shows another example of the threshold level. In this example, the threshold level L4 is set to a value obtained by adding a constant that increases in a high frequency region where road noise is small to the frequency characteristic L3 of the wind noise. FIG. 14 shows another example of the threshold level. In this example, the threshold level L4 is set to the maximum value of the frequency characteristic L3 of the wind noise.

  Hereinafter, with reference to the flowchart shown in FIG. 15, the flow of the noise control process according to the embodiment of the present invention based on the above idea will be described.

  The flowchart shown in FIG. 15 starts at the timing when the frequency characteristics of road noise and wind noise under certain conditions are measured and stored in the ROM, and the noise control process proceeds to step S1.

  In the process of step S1, the control command value calculation unit 6 estimates the frequency characteristics of road noise from the measurement signal of node noise. Thereby, the process of step S1 is completed and the noise control process proceeds to the process of step S2.

  In the process of step S2, the control command value calculation unit 6 measures the frequency characteristics of the wind noise corresponding to the vehicle speed when measuring the frequency characteristics of the wind noise from the table indicating the relationship between the vehicle speed and the frequency characteristics of the wind noise. The frequency characteristics of wind noise are estimated by reading out the data. Thereby, the process of step S2 is completed, and the noise control process proceeds to the process of step S3.

  In the process of step S3, the control command value calculation unit 6 compares the road noise frequency characteristic estimated by the process of step S1 with the wind noise frequency characteristic estimated by the process of step S2, thereby setting the threshold level. decide. Thereby, the process of step S3 is completed and the noise control process proceeds to the process of step S4.

  In the process of step S4, the control command value calculation unit 6 determines a frequency region for performing noise control based on the threshold level determined by the process of step S3. Thereby, the process of step S4 is completed and the noise control process proceeds to the process of step S5.

  In the process of step S5, the control command value calculation unit 6 determines whether there is a controller capable of performing noise control in the frequency region determined by the process of step S4. As a result of the determination, if there is a controller, the control command value calculation unit 6 advances the noise control process to the process of step S7. On the other hand, if there is no controller, the control command value calculation unit 6 advances the noise control process to the process of step S6.

  In the process of step S6, the control command value calculation unit 6 creates a new controller. Thereby, the process of step S6 is completed and the noise control process proceeds to the process of step S7.

  In the process of step S7, the control command value calculation unit 6 calculates an input voltage u to the piezo actuator 2 using a controller, and controls the piezo actuator 2 according to the calculated input voltage u. Thereby, the process of step S7 is completed and a series of noise control processes are complete | finished.

  FIGS. 16A, 16B, and 16C are diagrams showing a road noise frequency characteristic L1 and a wind noise frequency characteristic L3 at vehicle speeds va, vb (> va), and vc (> vb), respectively. As shown in FIG. 16, the level of road noise and wind noise increases as the vehicle speed increases. However, wind noise increases more than road noise. Accordingly, the frequency region where noise control is performed becomes narrower as the vehicle speed increases.

  FIGS. 17A, 17B, and 17C show road noise frequency characteristics L1 and wind noise frequency at road surface roughness rd, re (> rd), and rf (> re), respectively, when the vehicle speed is constant. It is a figure which shows the characteristic L3. As shown in FIG. 17, the road noise level increases as the road surface roughness increases, and the frequency region where noise control is performed becomes narrower. As the road noise level decreases, the frequency region where noise control is performed becomes narrower.

  As is apparent from the above description, according to the noise control device according to the embodiment of the present invention, the frequency at which the control command value calculation unit 6 performs noise control according to the road noise level and the wind noise level. A band is set, and the piezo actuator 2 is controlled to reduce noise within the set frequency band. And according to such a structure, since the frequency band which performs noise control is set appropriately, power consumption can be reduced.

  As mentioned above, although embodiment which applied the invention made by the present inventors was described, this invention is not limited by description and drawing which make a part of indication of this invention by this embodiment. That is, it is needless to say that other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

1: Microphone 2: Speaker 3: Control device body 4, 8: Amplifier 6: Control command value calculator 7: D / A converter 55: Control space

Claims (5)

Noise detection means for detecting or estimating noise in a control space inside the vehicle;
Wave applying means for applying a wave to the control space;
Wind noise estimation means for estimating wind noise generated when the vehicle is running;
Frequency band setting means for setting a frequency band for performing noise control according to the level of noise detected or estimated by the noise detection means and the level of wind noise estimated by the wind noise estimation means;
A noise control device comprising: noise control means for controlling a wave applied by the wave applying means so as to reduce noise within a frequency band set by the frequency band setting means. The noise control device according to claim 1,
The noise control apparatus, wherein the frequency band setting means sets a frequency band in which the noise level is higher than the wind noise level to a frequency band for performing noise control. In the noise control device according to claim 1 or 2,
The noise control apparatus characterized in that the frequency band setting means narrows a frequency band in which noise control is performed as the vehicle speed increases. The noise control device according to any one of claims 1 to 3,
The noise control apparatus, wherein the frequency band setting means narrows a frequency band for performing noise control in accordance with a decrease in noise level. Processing to detect or estimate noise in the control space inside the vehicle;
A process for estimating wind noise generated when the vehicle travels;
A process for setting a frequency band for noise control according to the detected or estimated noise level and the estimated wind noise level;
And a process for controlling a wave applied to the control space so as to reduce noise within a set frequency band.

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