JP2798843B2 - Active noise control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an active noise control device that cancels noise by generating a secondary sound having an opposite phase, and particularly relates to generation of a reference signal.

[0002]

2. Description of the Related Art Active noise control, in which noise is canceled out by waves of the same amplitude and opposite phase, has been pioneered by Lueg in the 1930s (USP-2043416, 1936).
It can be said that this is an old technology that has been studied by Conver and others, but it has been relatively recently that it has actually been applied to products. This is largely due to the advent of high-speed operation elements for enabling control, such as digital signal processors, but also due to the development of theoretical aspects regarding control algorithms.

[0003] Two recent remarkable examples of research on active noise control technology include those by GBBChaplin (for example, Published Patent Application No. 56-501062) and those by PANelson / SJElliot (for example, Published Patent Application No. 1-501344). Can be mentioned. The difference between the two control methods is that the former uses "repetitive control" that presupposes the periodicity of the target noise, while the latter uses an LMS algorithm, which is a type of steepest descent method. In that the target noise is not necessarily periodic.

[0004] This LMS adaptive control algorithm is based on a method codified by Widrow in the 1960s (for example, B. Widro).
w / PAMantey / BBGoode "Adaptive Antenna Systems,
(PROCEEDINGS OF THE IEEE, Vol.55, NO.12, DEC 1967)
However, most of the recent research on active noise control due to its versatility relies on this control algorithm. In the present invention, basically, it is assumed that the control algorithm is used.
The prior art will be described using 1344 (PANelson / SJElliot) as an example.

FIG. 12 shows an active noise control apparatus 12100 described in the above-mentioned published patent which uses a plurality of loudspeakers and microphones to mute a specific closed space such as a vehicle interior. This means that three microphones 1212 for measuring sound pressure at a predetermined position in the closed space are used.
And the primary sound (noise) at each microphone 1212 position and 2
Two loudspeakers 11 for outputting secondary sounds for reducing noise due to interference of secondary sounds, a reference signal (reference signal) generator 1215 for generating a signal 124 synchronized with the rotation of the engine 122, a reference A control circuit 1213 having a pair of adaptive filters 1214 for driving a loudspeaker 1211 by outputting a signal 123 for driving a speaker by phase-modulating the signal 124 and outputting a signal 123. An engine rotation signal (for example, an ignition timing signal, a signal of a crank angle sensor, etc.) is input to the reference signal generator 1215, and the reference signal generator 1215 is proportional to an integral multiple of the instantaneous engine rotation period. Generates a sine wave signal.

In the LMS adaptive control algorithm, the coefficient of the adaptive filter 1214 is updated every moment so that the square of the sound pressure at each microphone 1212 is minimized, but the primary sound and the secondary sound interfere well. Therefore, in order to achieve noise reduction, the reference signal 124 or the reference signal 1216 which is the basis of the reference signal 124 must include a component having sufficiently high correlation with the primary sound. Usually, a dimensionless quantity that takes a value between 0 and 1 called coherence is defined as an index indicating the degree of correlation between two signals. From the result of the rigorous theoretical analysis, it is known that the noise reduction by the active noise control system based on the LMS adaptive control algorithm is determined by the value of the coherence.

In an active noise control apparatus in a vehicle cabin as shown in FIG. 12, the noise accompanying the rotational vibration of the engine is to be controlled, and the engine rotation signal is supplied as a reference signal and synchronized therewith. By generating a sine wave signal, a reference signal having high coherence with respect to the engine noise component is obtained. For example, if the engine is 4
In the case of a four-cycle cylinder, vibration having a frequency twice as high as that of the engine rotation is large, and is generally called secondary engine vibration. This is due to fluctuations in gas torque due to gas combustion every 1/2 rotation and fluctuations in inertia torque due to imbalance in moment of the crankshaft system.
This becomes the excitation torque and vibrates the vehicle body, which propagates into the vehicle cabin to generate standing wave noise. Therefore, at this time, the active noise control of the secondary vibration noise can be performed by supplying the rotation signal every 180 degrees of the crank angle as the reference signal.

[0008]

Incidentally, the LMS adaptive control algorithm can be applied not only to silencing only a single spectrum noise as shown in FIG. 12, but also to a case where a plurality of noise spectra are included. is there.

For this purpose, it is necessary that the reference signal contains a spectrum component having the same frequency and sufficiently high coherence with respect to each noise spectrum component.

[0010] In the above-mentioned published patent, several methods are proposed as a method of generating the reference sine wave signal.

First, a rotation pulse train synchronized with the engine frequency is passed through a tracking filter whose fundamental frequency is the engine frequency, and the Nth engine speed is calculated.
That is, the signal is converted into a signal that includes harmonics at a fixed rate.

Second, a plurality of rotation pulse trains having different frequencies are generated by dividing a rotation pulse train (for example, 128 pulses per rotation) sufficiently larger than the engine speed, and only the fundamental frequency of each pulse signal is passed. This is a method of passing through a tracking filter and synthesizing signals passing through each filter.

A third method is to measure a time interval of a rotation pulse train using a clock pulse generator and generate a sine wave having a period equal to the pulse interval by a digital oscillator. By including a sine wave signal of a plurality of frequency components in the reference signal or the reference signal, noise spectra of a plurality of rotation order components can be simultaneously silenced.

By the way, in an industrial vehicle, for example, a medium or small truck of several tons or less, a power source of 4 to 4 tons is used.
A diesel engine of about six cylinders is usually used, but in addition to the engine, auxiliary equipment such as a generator and a hydraulic pump and a transmission are built in, all of which rotate in synchronization with the engine. In trucks, the engine is usually mounted slightly behind the cabin, and the vibration of the engine itself propagates through the body and excites the entire cabin to generate standing-wave noise, as well as the rotation of accessories and transmissions. Since all vibrations also excite the cabin and become noise, the cabin room is filled with noise composed of a plurality of spectral components proportional to the engine speed. Further, the magnitude of the noise spectrum is not always large only for a certain component, for example, only a secondary vibration component, and varies depending on various situations.

In such a machine, the reference signal must include, in addition to the engine rotational order component, a spectral component having a frequency proportional to the engine rotational speed but not necessarily an integral multiple of the fundamental order. Yes and again LM
From the viewpoint of the adaptability of the S adaptive control algorithm, it is desirable that the ratio of the magnitude of each spectral component is also variable depending on the situation.

However, as described above, the first and the second
In the method of generating a pulse train having a reference frequency of the engine speed and passing the same through a tracking filter to obtain a reference signal as in the example of the above, there are the following problems.

In order to silence a spectral component having a frequency that is a non-integer multiple of the fundamental order of engine rotation, for example, 7
In order to mute the 成分 times frequency spectrum component, prepare a circuit that generates 28 pulses per rotation, divide the frequency and generate a pulse containing the ／ times frequency spectrum component. I do. As described above, it is difficult to generate a pulse including a frequency of a non-integer multiple because a large number of pulses need to be generated.

No consideration is given to making the ratio of the magnitude of each spectral component included in the reference signal variable. In the above example, the reference signals of multiple frequencies are:
After passing through different tracking filters, they are combined and become the input of the speaker. For this reason, it was difficult to change the ratio of the magnitude of each spectral component included in the reference signal, because the characteristics of the tracking filter had to be changed.

In the method using the digital oscillator from the time interval of the rotation pulse train as in the third method,
In order to generate the trigonometric function, a series-expanded expression representing the trigonometric function is calculated and calculated at high speed inside the processor, so that there is a problem that the amount of calculation is large. For this reason, there is a problem that a load on the processor is increased to simultaneously generate the sine waveforms of a plurality of frequencies.

An object of the present invention is to provide an active noise control device capable of easily silencing a spectral component having a frequency that is a non-integer multiple of the fundamental order.

[0021]

Means for Solving the Problems To solve the above problems,
Therefore, the present invention generates a secondary sound having the same amplitude and opposite phase with respect to noise.
The active noise control device that generates and cancels the noise
There are a noise detecting means for detecting the noise at the evaluation point
Sound output means for outputting a secondary sound that interferes with the noise of the vehicle
And the frequency of the periodic motion (vibration, rotation, etc.) of the noise source
Detection means for detecting a number-dependent speed signal, and a reference waveform
Storage means for storing data, and the detection means
Multiple values with different magnifications for the speed signal value
At the read speed, the waveform data is read from the storage means.
Each read out, a plurality of reference waves having different periods from each other
The shape data is referred to as a reference signal as a reference for the generation of the secondary sound.
A reference signal generating means for outputting the noise and the noise detecting means.
The detected noise and the reference output by the reference signal generating means
The input signal to the secondary sound output means based on the signal
Signal processing means for determining
Provide a mold noise control device.

[0022]

In an active noise control device for generating a secondary sound having the same amplitude and opposite phase with respect to noise and canceling the noise , the noise detecting means detects the noise, and the detecting means detects the noise.
Velocity signal dependent on the frequency of the periodic motion of the source
I do. Then, the reference signal generating means detects the
With different magnifications for the speed signal values
At the readout speed, the reference waveform data is
Each read, a plurality of reference waveforms with different periods from each other
The data is output as a reference signal. And the signal processing hand
The stage includes the noise detected by the noise detection means and the reference signal generation means.
To the secondary sound output means based on the reference signal output by the stage
Is determined. Then, the secondary sound output means
Outputs a secondary sound that interferes with the noise at the valence point.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment in which an active noise control device is applied to reduce noise in a cabin space of a truck which is a typical industrial vehicle.

In the truck 50 shown in the figure, a four-cylinder diesel engine 1 is mounted behind the cabin 2 as a power source, and auxiliary equipment such as a generator and a hydraulic pump driven by the engine 1 to rotate. And a transmission (not shown). And all the vibrations caused by these excite the cabin 2 and become noise,
The cabin is filled with noise composed of a plurality of spectral components proportional to the engine speed.

In the figure, the noise in the cabin is controlled by the operator.
A system is shown in which sound pressure is detected by two microphones 3 and 4 arranged near the ear of the user, and secondary sound is generated by two speakers 5 and 6 to mute the sound. A tach sensor 7 for generating a pulse signal of four pulses per rotation is attached to a rotary shaft that rotates once for every two rotations of the crankshaft of the diesel engine 1, and a signal 1 of two pulses for one rotation of the crank.
01 is obtained. Control for active noise control
Unit 10 is provided with an F
/ V converter 11, A / D converter 12, A / D converter 13 for inputting measured sound pressures 102 and 103 by microphones 3 and 4, and speaker 5 by secondary sound control signals 104 and 105. / D converter 1 for driving, 6
4, a power amplifier 15, and a processor unit 16 for performing LMS adaptive control using these input signals.

Here, the F / V converter 11 receives the instantaneous rotation pulse signal 101 and outputs an analog voltage 107 proportional to the rotation speed of the crankshaft. And
The analog voltage 107 is converted to a digital voltage 106 via the A / D converter 12 and input to the processor 16. FIG. 2 shows an example of a circuit configuration of the F / V converter 11 using a general-purpose linear IC (RC4151). RC4151 is a IC that operates with a single power supply, surrounding the resistor, the input frequency f _IN to set the capacitor appropriately
The output voltage V ₀ which is proportional to can be obtained by the formula shown in FIG.

FIG. 3 shows an example of the configuration of the processor unit 16. Here, the processor unit 16 is a single-chip microcomputer 20 of about 8 bits for creating a reference signal.
And a digital signal processor (DSP) 30 for executing a high-speed product-sum operation for adaptive control. The microcomputer 20 includes a CPU 21, a RAM 22,
The DSP 30 includes a ROM 23, I / O ports 24 and 25, a counter 26, and the like.
AM32, ROM33, I / O ports 34, 35, 36
And so on.

FIG. 4 is a diagram showing the operation of the microcomputer 20 of FIG. The process of generating the digital reference signal will be described with reference to FIGS. 3, 4, and 5. FIG. 4A shows a ROM.
1 cycle of de sine waves written in the 23 - a data X _i. This means that the sine wave amplitude (Y axis) is 8 bits (-1
27 to 127), and the angle (X axis) is 8 bits (0 to 25).
5), and when one cycle of the waveform is 360 degrees, the X axis is every 360 / 256２1.4 degrees. These 256 8-bit data (256 bytes) are sequentially read out to the CPU 21 at a certain timing.

FIG. 4B shows a digital voltage 106 obtained from the A / D converter 12 via the I / O port 25 at the read speed (time interval) of the sine waveform data in the ROM 23.
4 shows a flowchart to be obtained from the above. First, the value V ₀ of the digital voltage 106 is supplied from the I / O port 25 to the CPU.
When the data is loaded to the register 21, the read time interval t _R is calculated by the following equation.

[0030]

[Number 1] t _R = B / V ₀ where, B is stored constants in ROM 23, the value t _R × 256 is set in advance such that one period of the noise spectrum to be silenced. (Since division requires time, if this time is not allowed, the value of t _R corresponding to the digital voltage value V may be stored in the ROM and read out.) FIG. 5 shows a flowchart for controlling the reading of ROM data using the built-in counter 26. That is, the counter 26 operates independently, clocks a clock signal generated by a built-in clock generator, and updates the value every moment (FIG. 5 (a)). When the reading interval t _R is set at a certain point in time, the value t of the counter 26 at that point in time is set.
_C = T _C is loaded to the CPU 21 to calculate ΔT _C = T _C + t _R and temporarily stored in the RAM 22. The value t _{C of the} counter 26 is constantly monitored and compared with ΔT _C. Then, an interrupt signal is generated again when t _C ≧ ΔT _C. Then, the value of the counter 26 at that time is again
B 1 - a new [Delta] T _C is de is repeated the same thing is calculated.

On the other hand, when receiving the interrupt signal, the CPU 2
1 is a digital data X _{0 of} a sine waveform in the ROM 23.
Is loaded and the I / O port 24 of the DSP 30
It is sent to the / O port 34 (FIG. 5B). The following de when the interrupt signal occurs again - data X ₂ is DSP
30. Thus, the sine waveform digital data X ₀ , X ₁ , X ₂ ,..., X ₂₅₅ , X ₀ ,. Then, by changing the reading interval t _R , it is possible to cope with a noise component of an arbitrary frequency.

[0032] Now, de sent towards the DSP30 at a certain time - data X _i is, Russia to CPU31 - is passed, RAM
32 is stored as a reference signal X (n). here,
FIG. 6 is an operation flowchart showing the control sequence of the LMS adaptive control algorithm written in the ROM 33.
It is.

First, the CPU 31 determines the filter coefficients W ₁₁ , W ₁₂ , W ₂₁ , W ₂₂ of the adaptive filter, the reference signal X
(N), X b from (n-1) to RAM 32 - De and output Y ₁ (n), Y ₂ (n) is calculated by the following equation (step 1).

[0034]

(Equation 2)

Here, the number of taps of the adaptive filter is at most 2
The tap is the only one since both the reference signal and the output signal have a single frequency. The value of the adaptive filter is initially set to an appropriate value, for example, 0.

Outputs Y ₁ and Y ₂ of the operation results are output from speakers 5 and 6 via D / A converter 14 and power amplifier 15 as output signals 104 and 105 shown in FIG. A secondary control sound is generated (step 2).

On the other hand, the sound pressures e ₁ and e ₂ (102, 103) measured by the microphones 3, 4 are input to the CPU 31 from the I / O port 35 via the A / D converter 13. (Step 3) At this time, the evaluation function J = e ₁ ² + e ₂ ²
Then, each filter coefficient of the adaptive filter is updated at a constant sampling interval so as to minimize J. This is given by the minimum value when J is differentiated by each filter coefficient.

Here, the sound pressures e ₁ and e ₂ are primary sounds (noise) d.
_It is given by the following equation as the sum of ₁ , d ₂ and the secondary sound.

[0039]

(Equation 3)

Where C _lmj is the sound transfer coefficient between the speaker and the microphone, and is expressed by the number of taps j.
By substituting Equation 2 for Equation 3, the following equation is obtained.

[0041]

(Equation 4)

In general, the update of the filter coefficient in the LMS adaptive control algorithm is given by the following equation using (∂J / ∂W _m ).

[0043]

(Equation 5)

Here, μ is generally called a convergence coefficient and relates to the speed of adaptation.

When J is calculated from Equation (4) and (∂J / ∂W _m ) is calculated, an updating equation for each filter coefficient is expressed by the following equation.

[0046]

(Equation 6)

However, α = 2μ. The CPU 31 accesses the data necessary for the operation from the RAM 32 at any time, and
Is executed at high speed (step 4).

The operations of (Steps 1) to (Step 4) are executed at a fixed sampling interval, and at the next sampling, the operation returns to (Step 1) again to execute the same control sequence. (Here, the sampling time for creating the reference signal by the microcomputer 20 and the sampling time for updating the adaptive filter by the DSP 30 do not necessarily have to be synchronized.) In the embodiment shown in FIGS. For example, this is an active noise control system for only the rotational secondary vibration component. However, in this system, by preparing a plurality of reading speeds for waveform data, a plurality of noise components having different frequency components can be simultaneously silenced. For example, trucks, construction machinery vehicles, and the like are characterized in that the level of noise generated by elements rotating in synchronization with the engine, such as generators, transmissions, and hydraulic pumps, is large. When the rotation speed of the engine changes, the rotation speed of these driven elements also changes, but the rotation speed ratio is constant and the noise frequency ratio is also constant. Therefore, in the equation for calculating the read interval t _R of the waveform data shown in the equation 1, if the value of the constant A is set in accordance with the frequency ratio, an arbitrary frequency-multiplied signal can be obtained with respect to the engine rotation frequency. Can be.

FIG. 7 shows an active noise control system for simultaneously silencing a plurality of noise spectra, the secondary and quaternary rotational components of a four-cylinder diesel engine, and the rotational eighth and seventh-order components provided by driven elements. Fig. 3 shows a system for silencing components simultaneously. The digital voltage value V _* obtained through the A / D converter 12 is loaded to the CPU 21 of the microcomputer 20 (step 11), and the time interval for reading the sine waveform data in the ROM is obtained by the following equation. .

[0050]

(Equation 7)

Here, A ₁ , A ₂ , A ₃ , and A ₄ are constants for generating a sine waveform having a frequency twice, four times, eight times, and 7/2 times the rotation frequency of the engine ( Step 1
2).

[0052] When the reading interval t _R1 was determined by the number 7 at some _{point, t R2, t R3, t} R4 is set, the value T _C of the counter 26 at that time is determined. (Step 1
3) The following formula is calculated from the read interval and the value of the counter to determine the data read timing. (Step 1
4)

[0053]

(Equation 8)

The value t _C of the counter is constantly updated, and the value is constantly compared with ΔT _R1 , ΔT _R2 , ΔT _R3 , ΔT _R4 (in the above case, ΔT _R3 <ΔT _R2 <ΔT _R4 <ΔT _R1 ). ing. When t _C is equal to or larger than ΔT _R3 for the first time, an interrupt signal is generated and data X _i (i = 0... 2)
55) are sequentially loaded, and a signal sequence X3 = {..., X3 _i ,. On the other hand, the value T _C3 of the counter at that time is read, and ΔT _R3 = t _R3 + T _C3 is reset (step 15).

Similarly, the counter value t _C becomes ΔT _R2 ,
The values of ΔT _R4 and ΔT _R1 are also compared in order, and when the values become equal to or larger than each value, an interrupt signal is generated and the data is output.
Data X _i is sequentially Russia - is de. Then, the signal sequence X2 = {.
X2 _i , ...}, X4 = {…, X4 _i , ...}, X1 = {…, X1 _i ,
..} Are stored in the RAM 22. Then, the values T _C2 , T _C4 , and T _C1 of the counter at that time are read and ΔT
_{R2 = t R2 + T C2,} ΔT R4 = t R4 + T C4, ΔT R1 = t R1 +
T _C1 is reset (steps 16 to 18). on the other hand,
Since the digital voltage value V _* is updated every moment according to the change in the rotation speed of the crankshaft, V _* is reloaded at a constant timing and a series of control sequences is performed again.
(Return to step 11) The four signal trains obtained in this way are sent out from the I / O port 24 of the microcomputer 20 and used as reference signals in the DSP 30. Output time intervals are different. Generally, the sampling interval of the digital filter may be twice the input frequency (Nyquist frequency). Therefore, the signal trains # 1, X2, X3, and X4 are sampled for a certain time that is at least twice the maximum frequency X3 (eight times the engine speed), and the reference signal trains S ₁ = ｛... _i ,
,｝, S ₂ = {…, S2 _i ,｝}, S ₃ = {…, S3 _i ,…},
Consider finding S ₄ = {..., S4 _i ,. FIG. 8 is a flowchart showing this constant sampling method. First, a fixed sampling interval t _S is obtained from V _* , and then the counter value T _CS at the time when t _S is set is read, and read timing ΔT _S = T _CS + t _S is calculated.
The counter value t _C and ΔT _{S that} are constantly updated are constantly compared, and when t _C ≧ ΔT _S , an interrupt signal is generated.
The data X1 _i , X stored at that time in the AM 22
2 _i , X 3 _i , X 4 _i are loaded into the CPU 21 and again stored in the RAM 22 as reference signal strings S 1 _i , S 2 _i , S 3 _i , S 4 _i at fixed time intervals.
Stored in Then, the value T of the counter at that time
_CS is read and the same is repeated.

Next, the data stored in the RAM 22 is loaded again to the CPU 21 and transmitted from the I / O port 24 to the DS.
It is sent to the I / O port 34 of P30. Then, the data is temporarily stored in the RAM 32 via the CPU 31. These are loaded into the CPU as predetermined reference signal sequences S _k (k = 1 to 4) at a predetermined sampling time, and each of the two-tap adaptive filter coefficients W _kim (k = 1 to 4, m = 0, 1). Performs a product-sum operation with S _k (n), and outputs y _km (n)
Is obtained as follows:

[0057]

(Equation 9)

However, m = 1, 2 and indicates the speaker number. Each output y _km (n) obtained by the above equation is added for the subscript k for each subscript m.

[0059]

(Equation 10)

The outputs Y ₁ and Y _{2 are} low-pass filters,
It is output as a secondary sound from the speaker via a power amplifier or the like. The LMS adaptive control algorithm for generating the secondary sound so as to minimize the sound pressures e ₁ and e ₂ measured by the microphone is basically the same as the control sequence in FIG. 6 in the first embodiment. Next, in the sampling method shown in FIG. 8, the adaptive filter is operated independently for a plurality of reference signal sequences. On the other hand, FIG. 9 shows a method in which a plurality of generated signal sequences (herein referred to as reference signals) are added to generate one reference signal, and the adaptive filter is operated only for one reference signal. . That is, FIG.
Reference signal S1 obtained by sampling for a fixed time as in
_{From i} , S2 _i , S3 _i , and S4 _i , the addition average of these is calculated every moment by the following equation.

[0061]

[Equation 11]

Then, ｛, SA _i ,...
The data is stored in the AM 22, and thereafter, the data is loaded again to the CPU 21 and transmitted to the DSP 30. Then, the DSP 30 uses the adaptive filter W as a reference signal sequence.
_A1i, W _A2i (the number of taps of this adaptive filter only must be set to the length can all frequency components included in the reference signal representation) is filtered by, spin - output signal to mosquito follows Asked to do so.

[0063]

(Equation 12)

In Equation 11, the sampling signal S
The reference signal has been obtained by simple averaging of 1 _i , S2 _i , S3 _i , and S4 _i . When a reference signal includes a sine wave of a plurality of frequencies, such as noise in a cabin of a truck, the silencing volume of each corresponding noise spectrum is also affected by the ratio of the magnitude of the amplitude of each reference signal component. . Therefore, FIG.
Shows a case where a reference signal is created by weighting and averaging these reference signals, and the ratio of the weights is made variable according to the operating conditions of the engine. In this case, Equation 11 is rewritten as the following equation.

[0065]

(Equation 13)

Here, a ₁ , a ₂ , a ₃ , and a ₄ are weight variables of each reference signal.

The truck 50 is provided with means for detecting a change in the engine rotation speed and a change in the sound transmission characteristic of the control space (in the cabin) (opening and closing of windows, changes in temperature and humidity). The values of a ₁ , a ₂ , a ₃ , and a ₄ corresponding to these are written in the ROM 22 of the microcomputer 20 as a map. Now, when a change in a certain characteristic—for example, when the sound transfer characteristic changes greatly, such as when a cabin door is opened, the composition ratio of each component of the noise spectrum also changes.
In such a case, for example, the open / closed state of the door is detected by some sensor (for example, an infrared sensor) and a signal is sent to the microcomputer 20. Upon receiving the signal, the controller selects the value of the weight variable corresponding to the state from the ROM table,
The values of the variables a ₁ , a ₂ , a ₃ , and a ₄ are changed and the addition operation for creating the reference signal of Expression 13 is performed.

It is to be noted that, unlike the above embodiment, the active noise control device has a plurality of filters, and the waveform output means reads out the waveform data according to the value of the speed signal. At this time, a plurality of readings are performed at a reading speed having different magnifications, a plurality of waveform data are simultaneously output, each is input to a different filter, and a plurality of reference signals having different periods are output and output. May be added.

In the active noise control device, the speed signal is not converted into a voltage signal, but a pulse signal is used as the speed signal, and the reference signal detecting means directly detects the time interval of the pulse signal. Then, the reading speed of the waveform data may be varied according to the time interval.

Further, as an active noise controller unit for canceling noise, reference signal detecting means for inputting a speed signal and outputting a reference signal, and detecting the secondary sound based on the detected noise and the reference signal. Signal processing means for determining the reference signal, the reference signal detecting means storing a reference waveform data, and changing the reading speed of the waveform data according to the value of the speed signal. And a waveform output means for reading out the waveform data and outputting it as a reference signal. A microphone, a speaker, and a sensor can be arbitrarily combined.

By the way, the noise in the cabin of the truck as shown in FIG. 1 is a vibration radiated sound generated by the vibration of the engine transmitting through the body to vibrate a part in the cabin such as a panel. Therefore, as a noise reduction method, instead of using a secondary sound such as a speaker to cancel the generated noise, vibration radiated sound itself is generated by giving vibration of the same amplitude and opposite phase to the vibration transmitted from the engine to the panel. There is also a method of suppressing the noise. FIG. 11 is a diagram illustrating a method of silencing vibration radiation sound by such active excitation. The detection of the engine rotation signal by the tacho sensor 7, the microphone 3,
The detection of the sound pressure signal in the cabin and the configuration of the control unit 10 by the device 4 are the same as those shown in FIG. -Ta 55 and 56 are attached. The actuators 55 and 56 are controlled by the control unit 10 by an LMS adaptive control algorithm so that the sound pressure detected by the microphones 5 and 6 is minimized.

The system for actively silencing noise in the cabin of a truck as a typical example of an industrial vehicle driven by a 4-cylinder diesel engine has been described above with reference to the drawings. This active noise control device is a general-purpose technology due to its characteristics, and is not limited to this.It has a construction machine such as a passenger car, a hydraulic shovel, and other rotary machines such as an engine and a motor. The present invention can be applied at any time when a noise-generating space is muted.

As described above, the present invention relates to the microcomputer R
Since the sine wave data stored in advance in the OM is used as a reference signal with the readout speed varied according to the rotation speed of the engine, active noise control with high speed and high accuracy can be realized with a simple system. .

Further, by preparing a plurality of ROM data read speeds and simultaneously generating a plurality of reference signals,
Noise consisting of multiple spectra can be silenced simultaneously. In addition, by adding these plurality of reference signals into one reference signal, active noise control of a plurality of spectrum noises can be realized with a simple system. In addition, even if the sound transmission characteristics change significantly and the composition ratio of each component of the noise spectrum changes, the system can make the weighting of each signal variable at the time of signal addition, so that the sound can be quickly eliminated. It is.

In the present invention, the sine wave data to be stored is not limited to one cycle, but may be a half cycle, two cycles, or the like.

Further, as for the speaker, it is not necessary to provide a dedicated speaker for noise control. For example, a speaker for audio may be used.

[0077]

According to the present invention, it is possible to provide an active noise control device capable of easily silencing a spectral component having a frequency which is a non-integer multiple of the fundamental order.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an active noise control device.

FIG. 2 is a circuit configuration diagram of an F / V converter.

FIG. 3 is a configuration diagram of a processor unit.

FIG. 4 is an operation diagram of a microcomputer.

FIG. 5 is an explanatory diagram of a method of reading ROM data.

FIG. 6 is a control sequence diagram of adaptive control.

FIG. 7 is an explanatory diagram of a ROM reading method when a plurality of spectra are muted.

FIG. 8 is an explanatory diagram of a constant sampling method when muting multiple spectra.

FIG. 9 is an explanatory diagram of a reference signal creation method by signal addition.

FIG. 10 is an explanatory diagram of a reference signal generation method by weighted addition.

FIG. 11 is an explanatory diagram of silencing control of vibration radiation sound by active excitation.

FIG. 12 is a block diagram of a conventional active noise control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cabin, 3, 4 ... Microphone, 5, 6 ... Speaker 7 ... Tach sensor, 10 ... Control unit, 11 ...
F / V converter, 12, 13 ... A / D converter, 14 ...
D / A converter, 15: power amplifier, 16: processor, 101: crank rotation signal, 102, 103: microphone sound pressure 104, 105: secondary sound control signal, 106: digital voltage

Claims (3)

(57) [Claims] 1. An active noise control device for generating a secondary sound having the same amplitude and opposite phase with respect to noise to cancel the noise, comprising: a noise detecting means for detecting the noise; Secondary sound output means for outputting the secondary sound causing interference with noise, detection means for detecting a speed signal dependent on the frequency of the periodic motion of the noise source, storage means for storing reference waveform data, The values of the speed signal detected by the detection means are different from each other.
A plurality of reading speeds having different magnifications,
Read the reference waveform data from
And a plurality of reference waveform data having different periods
Reference signal generation to output as a reference signal for generation
Means, noise detected by the noise detection means, and reference signal generation
Signal processing means for determining an input signal to the secondary sound output means based on the reference signal output by the means. 2. A secondary sound having the same amplitude and opposite phase to noise is emitted.
An active noise control device for canceling the noise by
I, and noise detection means for detecting the noise, 2 outputs the secondary sound to interfere with the noise at the evaluation point following
Sound output means, and a speed signal dependent on the frequency of the periodic motion of the noise source.
Detection means for detecting the item, storage means for storing reference waveform data, different from each other with respect to the value of the velocity signal detected by the detector
A plurality of reading speeds having different magnifications,
Read the reference waveform data from
To the reference waveform data with different periods.
The calculated waveform data is converted to a reference signal as a reference for the generation of the secondary sound.
A reference signal generating means for outputting the reference signal, a noise detected by the noise detecting means,
Means on the basis of a reference signal which has been output, the secondary sound output
Signal processing means for determining an input signal to the means . 3. The active noise control device according to claim 2, wherein
The reference waveform data is sinusoidal waveform data, and the reference signal generation unit reads out from the storage unit.
By weighting the amplitude of each reference waveform data,
An active noise control device for calculating additional waveform data .