JP3506442B2 - 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 a noise control device for canceling noise by using a speaker, and particularly to the present invention to improve the accuracy of forming a deleted sound for noise.

[0002]

2. Description of the Related Art Conventionally, a passive muffler such as a muffler has been used to reduce noise generated from an internal combustion engine, etc., but improvement has been desired from the viewpoints of size, muffling characteristics and the like. The compensation sound that conventionally the sound source or al the generated noise and antiphase-Tooto pressure to which output from the speaker, the active noise control system for canceling noise have been proposed. However, the frequency characteristics, stability, etc. of the active noise control device itself are not sufficient, and its practical application has been delayed . Recently results practical noise control device frequency range is also expanded can with the signal processing technology using digital circuits has evolved handling cormorants this <br/> have been proposed (e.g., JP-63 over 311
396). This is a feed-forward system that detects noise with a noise source capture microphone installed upstream of the duct and outputs a signal of opposite phase and equal sound pressure to the noise with a signal processing circuit from a speaker installed downstream of the duct, and muffling. This is a so-called two-microphone / one-speaker type active noise control device that combines a feedback system that detects the generated result with a microphone for a muffling point and minimizes the muffling result. Adaptive filter to form a compensating sound antiphase-Tooto pressure in this apparatus DSP (Digital
Signal Processor).

[0003]

By the way, when the conventional noise control device is mounted on an automobile or the like, it is difficult to install a microphone for capturing a noise source, and a simulated signal of noise is generated from the engine speed. It is possible to However, this has the advantage that the response is fast because it is a feedforward system signal, but there is the problem that it is far from the actual signal. On the other hand, it is possible to form a noise reproduction signal by adding the signal from the microphone of the feedback system, which is the difference signal between the muffler and the speaker, to the signal of the opposite phase / isothermal pressure from the noise by the signal processing circuit. However, this is gutter close to the actual signal
There are cormorants advantages but has a problem of poor response <br/> answer of that against the fast signal to include a delay characteristic. It is very difficult to improve the accuracy of noise control if either one of them is used in all driving conditions of the automobile.

Therefore , in view of the above problems, it is an object of the present invention to provide a noise control device mounted on a vehicle, which is close to an actual signal and excellent in responsiveness.

[0005]

In order to solve the above problems, according to the present invention, a characteristic opposite to the characteristic of noise is formed , and the output and the noise of a speaker driven based on a compensation signal are generated.
In a noise control device having an adaptive filter that performs feedback control by updating a coefficient to minimize an error signal indicating a difference between a sound and a sound deadening point , a compensation signal that is an output signal of the adaptive filter is input. The adaptive fill
And transfer <br/> our characteristic forming unit which simulates the transfer characteristics of the system ranging from the output of the data to the error signal, and an adder for combining the output <br/> signal of the error signal and said transfer characteristic formation unit, A switch that selectively selects one of a state signal indicating the engine rotation state and an output signal of the adder as an input signal of the adaptive filter, and a state in which the transmission position does not apply a load to the engine. In the case of, the adaptive filter is provided with a status signal indicating the rotational state of the engine, and when the position of the transmission is in a state of loading the engine, the adaptive filter is provided with the adder of the adder. And a control means for controlling the switch to provide an output signal. Further, according to the present invention, a speaker that forms an inverse characteristic to a characteristic of noise and is driven based on a compensation signal.
In a noise control device having an adaptive filter that performs feedback control by updating the coefficient so as to minimize the error signal indicating the difference between the output and noise at the silencing point , the compensation signal that is the output signal of the adaptive filter is Enter the appropriate
The transfer characteristic of the system from the output of the adaptive filter to the error signal
A transfer characteristic forming section to be simulated, an adder for synthesizing the error signal and an output signal of the transfer characteristic forming section, and a state signal indicating an engine rotation state or an output of the adder as an input signal of the adaptive filter. a switch for alternatively selecting one of the signal, when the rotation change of state of the engine is large, gives a status signal indicating the rotation state of the engine to the adaptive filter, the rotation state change of the engine A noise control device is provided which comprises control means for controlling the switch so as to provide the output signal of the adder to the adaptive filter when the size is small. Furthermore, according to the present invention, to form a characteristic opposite characteristics of the noise, the compensation signal
Based on the output of the speaker driven based on the noise
In the noise control device having an adaptive filter for updating and feedback control coefficient so as to minimize an error signal indicating a definitive difference, harmonics and which forms a harmonic signal of the noise from a state signal indicating the rotational state of the engine Department,
By inputting the compensation signal which is the output signal of the adaptive filter,
The transmission characteristics of the system from the output of the adaptive filter to the error signal
And transfer characteristic forming section to simulate sex, and an adder for combining the output signal of the error signal and said transfer characteristic forming unit, the harmonic signal or the sum of the harmonics forming unit as an input signal of the adaptive filter a switch for alternatively selected one of the output signals of the vessel, giving harmonic signals of the higher harmonic wave forming portion to the adaptive filter if the rotational state change of the engine is large, the rotation of the engine There is provided a noise control device comprising: a control means for controlling the switch so as to give the output signal of the adder to the adaptive filter when the state change is small.

[0006]

According to the noise control device of the present invention, when the vehicle is stopped and the position of the transmission does not load the engine, the switch causes the adaptive filter to rotate the engine. A state signal indicating the state (a signal indicating the number of revolutions of the engine, a signal indicating the ignition timing of the engine, etc.) or an output signal of the higher harmonic wave forming unit is given. At this time, the accelerator is stepped on to rotate the engine. Even if the number suddenly rises, the time delay in forming these signals or the controlled signal by the harmonic wave forming unit is small, and therefore the error due to the time delay is small. Further, when the position of the transmission gives a load to the engine, the output signal of the adder is given to the adaptive filter by the switch. Therefore, the rotation speed of the engine does not suddenly increase. Therefore, a time delay is allowed and a signal as close as possible to the actual signal is input to reduce the error. Further, when the rotational state of the engine changes greatly during traveling or during acceleration (when the rotational speed of the engine changes drastically), a state signal indicating the rotational state of the engine or an output signal of the harmonic wave forming unit. Is provided, the time delay can be prevented, and in the case of constant speed traveling, a signal close to the actual signal is provided from the adder, and the accuracy of noise control can be improved as a whole.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views showing a noise control device according to an embodiment of the present invention, and FIGS. 1 and 2 are different in the presence or absence of a harmonic wave forming unit 71. The overall configuration of the present invention will be described with reference to this figure. The apparatus includes an engine 1 of an automobile or the like, an exhaust gas pipe 2 for releasing exhaust gas of the engine 1 to the atmosphere, and an exhaust gas pipe 2 on the way to the atmosphere for suppressing noise generation. To the sub-muffler 3-1 and 3-2 for gradually reducing the pressure of the exhaust gas and interfering with the noise generated by the pressure reduction due to the reflection of the wall, and for the same purpose as described above, 3-2, a main muffler 4 provided at the latter stage, a tail pipe 5 connected to the main muffler 4 for discharging exhaust gas to the atmosphere, and a transmission automatically based on a rotation speed signal and a speed signal of the engine 1. A transmission control unit 6 for switching a transmission ratio (gear ratio), and a compensation signal type for forming a controlled signal for noise of the feedforward system based on the rotation speed of the engine 1 and forming a compensation signal using the controlled signal. Section 7, a digital / analog converter 8 for converting the digital output signal from the compensation signal forming section 7 into an analog signal, and a low-pass filter 9 connected to the digital / analog converter 8 for removing harmonics. , Power amplifier 1 connected to the low-pass filter 9
0 and a speaker 1 that is driven by a signal from the power amplifier 10 to emit a sound wave and cancel the noise from the tail pipe 5.
1, a microphone 12 that captures the result of the noise from the tail pipe 5 canceled by the speaker 11 and converts the result into an electric signal, a power amplifier 13 connected to the microphone 12, and a power amplifier 13 connected to the power amplifier 13. Low pass filter 14 and an analog / digital connected to the low pass filter 14 for converting an analog signal into a digital signal and using the converted signal as a feedback control signal of the compensation signal forming section 7 or as a controlled signal. The converter 15 and the shift signal output from the transmission control unit 6 indicating the position of the transmission or the rotational speed of the engine 1 are input and a controlled signal for forming a compensation signal is generated based on the degree of change. And a switching control unit 16 for switching.

In the configuration shown in FIG. 1, the compensation signal forming section 7 includes a pre-filter 72 for pre-equalizing the frequency characteristics of the sub-mufflers 3-1 and 3-2 and the main muffler 4, and the pre-filter 72. A coefficient memory 73 for supplying coefficients to the sub-muffler 3 and the coefficient memory 73.
The coefficient obtained by measuring relative -1 and 3-2 and main muffler 4 from the outer section and the initial setting circuit 74 for setting the said coefficient memory 73, the rotational speed of the one (a) is the engine Or a signal S indicating ignition timing
Enter r as a signal of the feedforward system its other (b) inputs the signal of the feedback system described below the switching
A switch 75 provided in the preceding stage of the pre-filter 72 so as to be switched by the exchange control unit 16 and the output of the pre-filter 72 are input as a controlled signal and a compensation signal is output to the digital / analog converter 8. Adaptive filter 76 and the analog / digital converter 15
From the adaptive filter 7 so that the error signal from
A minimization unit 77 for setting a coefficient to 6, and a digital / analog converter 8, the low-pass filter 9, the power amplifier 10, and the speaker, which are connected to the output of the adaptive filter 76. 11, the microphone 1
2, a transfer characteristic forming section 78 simulating the transfer characteristic Hd to the analog / digital converter 15 via the power amplifier 13 and the low pass filter 14, the transfer characteristic forming section 78 and the analog / digital conversion And the output of the adder 15 and the output of the adder 79 are connected to the other input terminal of the switch 75.

A signal indicating the number of revolutions of the engine 1 is taken out from a sensor from a rotary shaft such as a crankshaft, and a signal showing the ignition timing of the engine 1 is taken out from a distributor.
In the embodiment shown in FIG. 2, the harmonic signal of the engine 1 or the signal Sr indicating the ignition timing of the engine 1 is used as a basic signal to form the harmonic signal of the engine 1 in order to simulate the harmonics of noise. The harmonic wave forming unit 71 is provided, and the signal from the harmonic wave forming unit 71 is applied to the terminal of the switch 75.

FIG. 3 is a diagram showing the higher harmonic wave generating section of FIG. The harmonic wave forming unit 71 shown in the figure includes a variable oscillator 711 that forms a noise signal having a frequency corresponding to the rotation speed or ignition timing of the engine 1, and a plurality of multipliers that multiply the frequency of the output signal of the variable oscillator 711. 712 and the output signals of the plurality of multipliers 712 are added to add the pre-filter 72
And an adder 713 for outputting to.

FIG. 4 is a diagram showing the relationship between engine speed and noise frequency of the variable oscillator of FIG. The noise source of the engine 1 is a primary, secondary, tertiary ...
It is an aggregate of the next higher harmonic component, and rises as the rotation speed increases. The variable oscillator 711 shown in FIG. 3 measures the rotational frequency of the engine 1 and the noise frequency from the tail pipe 5 in advance in order to form the above noise, and obtains the relationship shown in this figure. A signal having a frequency corresponding to the rotation speed is formed and output to the multiplier 712 at the next stage. By doing so, the harmonic component included in the noise generated from the engine 1 can be accurately generated, but a pulse waveform or the like indicating the engine speed also contains some harmonics. Some effects can be expected by using directly. It should be noted that the signal indicating the ignition timing is also usually a signal obtained by multiplying the signal indicating the rotational speed.

FIG. 5 is a diagram showing the configuration of the pre-filter and the adaptive filter shown in FIGS. As shown in the figure, the pre-filter 72 and the adaptive filter 76 have the same configuration and different coefficient setting methods. A plurality of delay devices 721 that both delay the input signal by one sampling period, a plurality of variable multipliers 722 connected to the input signal and the output signal of each delay device 721, and a connection to each variable multiplier 722. A plurality of adders 723 to be performed. Each variable multiplier 7
The coefficients a0, a1, a2, ... An of 22 are variable by the supply from the coefficient memory unit 73 and the minimization unit 77.

Here, when the sampling frequency is fs, the sampling period T is T = 1 / fs, and when the input signal is x (t) = exp (jωt), the output signal y
(T) can be expressed as follows. y (t) = a0 · exp (jωt) + a1 · expjω
(T−T) + a2 · expjω (t−2T) + ... +
am · expjω (t−mT) = exp (jωt) · (a0 + a1 · exp (−jω)
T) + a2 · exp (−j2ωT) + ... + am · e
xp (-jmωT)) In the case of the pre-filter 72, the coefficients a0, a1, a2, ... An of the variable multipliers 722 of the above equation are the sub-mufflers 3-1 and 3-2 and the main muffler in advance. The frequency characteristic of No. 4 is measured, and based on this measurement, it is externally set via the initial setting circuit 74 and the coefficient memory 73.

On the other hand, in the case of the adaptive filter 76, the minimization unit 77 which is supplied by the minimization unit 77 and updates the coefficient will be described next. Input signal x by the above formula
(N) = exp (jnωt) and coefficient ak (n)
When expressed as, each coefficient ak (n) is obtained by converging by the following equation.

[0015]

[Equation 1]

In this equation, e (n) is an output signal of the analog / digital converter 15 and represents an error signal, α is a convergence constant, and a predetermined time is required until the coefficient ak (n) converges to a constant value. Requires. Therefore, as described above, the influence of the main muffler 4 and the like is removed from the adaptive filter 76 to reduce the load on the adaptive filter 76, but a constant convergence time is required, so the rotational speed of the engine 1 is reduced. If the change is large, processing within this convergence time may become difficult.

Next, the feedback system reproduction signal SR input to the other of the switches 75 will be described. The noise signal generated by the engine 1 is represented by SN, and the adaptive filter 7
The output signal of 6 is SC, the output signal of the microphone 12 is SM, and the output signal of the adder 79 is SR. Further, the transfer characteristic from the engine 1 to the microphone 12 is HNOISE, the transfer characteristic from the adaptive filter 76 to the microphone 12 is Hd1, and the microphone 1 is
Hd is the transfer characteristic from 2 to the adder 79, and
= Hd1 · HM, the output signal of the microphone 12 is SM = SN · HNOISE + SC · Hd1, and the output signal SR of the adder 79 is SM = SM · HM-SC.
・ Hd = (SN ・ HNOISE + SC ・ Hd1-SC ・
Hd1) .HM = SN.HNOISE.HM and the signal when only noise is detected by the microphone 12 is calculated.

Next, the minimization unit 7 of the adaptive filter 76.
The output signal SE of the analog / digital converter 15 is given as a control signal for changing the coefficient by 7. The adaptive filter 76 changes the coefficient so that the control signal becomes zero. Since SE = SM.HM, when SE = 0, SM = 0. Therefore, the output signal SR from the adder 79 is input to the adaptive filter 76 as a controlled signal and the analog /
By inputting the output signal SE to the digital converter 15, the adaptive filter 76 calculates and outputs the compensation signal SC so that SE = 0.

The above description is similarly applied to the feedforward system. FIG. 6 is a diagram for explaining the operation of switching the switch 75 of FIGS. 1 and 2 from the state of the transmission. The switching control unit 16, which has received the transmission position signal from the transmission control unit 6, when the position of the transmission is in the no-load state of the parking P range and the neutral N range as shown in FIG. The switch 75 is connected to the switching terminal a side. Further, when the position of the transmission is in the R, D, 2, L range of the load state, the switch 75 is connected to the output side (the switching terminal b side) of the adder 79. Therefore, the adaptive filter 76 inputs the controlled signal of the feedforward system in the unloaded state, and inputs the controlled signal of the feedback system in the loaded state. In the no-load state, the rotation speed change of the engine 1 is likely to be large due to the idling, but in this case, since the controlled signal of the feedforward system is input, the delay becomes small and the accuracy deterioration due to the delay of the signal processing can be prevented. On the other hand, in the load state, the rotation speed does not change abruptly as in the air purging operation, so that a delay in signal processing is allowed and rather a controlled signal that is close to reality is used, so that the accuracy can be improved.

FIG. 7 is a graph of FIG. 1 accompanying a change in the engine speed.
FIG. 6 is a diagram for explaining a switching operation of the switches 75 of 2 and 2. The switching control unit 16 shown in FIGS. 1 and 2 obtains a change in the number of revolutions of the engine 1 as dSr / dt as shown in the figure, and when this value is larger than a predetermined value k, the switch 75 Connect the adaptive filter 76 to the a side.
If this value is smaller than k, the switch 75
And the adaptive filter 76 is connected to the adder 79 by connecting to the b side. As a result, when traveling at low speed or high speed at a constant speed, the delay time is allowed for processing and the change in noise is small. Therefore, the adaptive filter 76 inputs the controlled signal of the feedback system and actually Use close ones to improve accuracy. Further, when the speed is variable, the delay time is not allowed due to the processing, but the change in noise is large. Therefore, the adaptive filter 76 uses a controlled signal that is slightly separated from the actual signal but has a small delay to improve the accuracy.

When the switch 75 is connected to the end a, if the convergence constant α in [Equation 1] is made larger than that when it is connected to the end b, the convergence time is further shortened and the time delay is eliminated. When the switch 75 is connected to the end b side, the convergence time can be extended and the accuracy can be further improved. Further, either the switching control of the switch 75 depending on the position of the transmission or the switching control of the switch 75 based on the change in the rotational speed of the engine 1 may be individually performed, and the transmission control unit 6 simply shifts. It is also possible to output a signal indicating the state of the position of the transmission by submitting the position of the lever, and is not particularly limited to the automatic transmission.

[0022]

As described above, according to the present invention, there is provided the adaptive filter (76) which performs feedback control by forming the characteristic opposite to the noise characteristic and updating the coefficient so as to minimize the error signal. In the noise control device which has, in the case where the engine speed changes drastically, a signal with a small time delay but a little away from the actual signal is used as the controlled signal,
When the change of the engine speed is small, the signal having a relatively large time delay but close to the actual signal is used as the controlled signal, so that the processing accuracy of the adaptive filter 76 can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a noise control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a noise control device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a harmonic generation unit of FIG.

4 is a diagram showing a relationship between engine speed and noise frequency of the variable oscillator of FIG.

FIG. 5 is a diagram showing configurations of the pre-filter and the adaptive filter shown in FIGS. 1 and 2;

FIG. 6 is a diagram for explaining the operation of switching the switch 75 of FIGS. 1 and 2 from the state of the transmission.

FIG. 7 is a diagram for explaining a switching operation of a switch 75 shown in FIGS. 1 and 2 according to a change in engine speed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Exhaust gas pipe 3 ... Sub muffler 4 ... Main muffler 5 ... Tail pipe 6 ... Transmission control part 7 ... Compensation signal forming part 11 ... Speaker 12 ... Microphone 15 ... Analog / digital converter 16 ... Switching control part 71 ... Harmonic wave forming unit 72 ... Pre-filter 73 ... Coefficient memory 74 ... Initial setting circuit 75 ... Switch 76 ... Adaptive filter 77 ... Minimizing unit 78 ... Transfer characteristic forming unit 79 ... Adder

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-311396 (JP, A) JP-A-3-178846 (JP, A) JP-A-5-80789 (JP, A) Actual Kaihei 2- 86297 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G10K 11/178 B60R 16/00 F01N 1/06

Claims (3)

(57) [Claims] 1. A compensation signal is formed by forming a characteristic opposite to that of noise.
Of the output and noise of the speaker driven based on the signal
In a noise control device having an adaptive filter that performs feedback control by updating coefficients so as to minimize an error signal indicating a difference at a point , input a compensation signal that is an output signal of the adaptive filter.
The transmission characteristics of the system from the output of the adaptive filter to the error signal
Transfer characteristic forming section for simulating the characteristics, an adder for combining the error signal and the output signal of the transfer characteristic forming section, and a state signal indicating the engine rotation state or the adder as an input signal of the adaptive filter. A switch for selectively selecting one of the output signals of the engine and a state signal indicating the rotational state of the engine to the adaptive filter when the position of the transmission does not load the engine. And a control means for controlling the switch so as to apply the output signal of the adder to the adaptive filter when the position of the transmission applies a load to the engine. apparatus. 2. A compensation signal which forms a characteristic opposite to that of noise and which is a compensation signal.
Point of the noise and the output of the speaker driven based on
In a noise control device having an adaptive filter that performs feedback control by updating the coefficient so as to minimize the error signal indicating the difference in , the compensation signal that is the output signal of the adaptive filter is input.
The transmission characteristics of the system from the output of the adaptive filter to the error signal
Transfer characteristic forming section for simulating the characteristics, an adder for combining the error signal and the output signal of the transfer characteristic forming section, and a state signal indicating the engine rotation state or the adder as an input signal of the adaptive filter. A switch for selectively selecting any one of the output signals of, and a state signal indicating the rotation state of the engine to the adaptive filter when the rotation state change of the engine is large,
A noise control device comprising: a control means for controlling the switch so as to apply the output signal of the adder to the adaptive filter when the change in the rotational state of the engine is small. 3. A compensation signal is formed by forming a characteristic opposite to that of noise.
Of the output and noise of the speaker driven based on the signal
In a noise control device having an adaptive filter that performs feedback control by updating a coefficient so as to minimize an error signal indicating a difference between points, a harmonic signal of a noise is generated from a state signal indicating a rotation state of an engine. a higher harmonic wave forming section for forming an, type a compensation signal which is an output signal of said adaptive filter
The transmission characteristics of the system from the output of the adaptive filter to the error signal
And transfer characteristic forming section to simulate sex, and an adder for combining the output signal of the error signal and said transfer characteristic forming section, the high of the higher harmonic wave forming portion as an input signal of the adaptive filter
A switch for selectively alternatively either harmonic signal or the output signal of said adder, the harmonic signal of the harmonic wave forming portion to the adaptive filter if the rotational state change of the engine is large And a control means for controlling the switch so as to apply the output signal of the adder to the adaptive filter when the change in the rotational state of the engine is small.