JPH06222780A - Active noise erasure device adaptable to cooling control - Google Patents

Abstract

PURPOSE:To rapidly follow the temperature fluctuation being the main cause of the increase of a noise from a blower by controlling the filter coefficient of a digital filter so that a remaining noise signal becomes zero according to a temperature signal detected in the vicinity of a heat source in addition to the remaining noise signal detected in the vicinity of the discharge port of pipings. CONSTITUTION:A remaining noise which remains when no fan noise is erased perfectly as a result of synthesizing a speaker sound and the fan noise, that is, a sound occurring due to a remaining error of the simulation result of the fan noise by a FIR filter 5a is received by an error microphone 3a, and is converted to a digital signal by an analog/digital converter 3b to be inputted as the remaining error. By a coefficient control part 6a, it is controlled so that the remaining error is brought close to zero, and the noise occurring due to the fan 7a is erased by correcting and updating the filter coefficient in a real time so as to minimize the remaining error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active noise canceller compatible with cooling control. In particular, the present invention relates to an active noise canceling device compatible with cooling control that cancels the sound emitted from the cooling device.

Recently, environmental problems have become social problems. Noise also causes social problems in various fields, such as damaging the living environment and working environment and physiologically adversely affecting the human body. In addition, in recent years, not only by eliminating noise by absorbing it, but also by eliminating the noise by generating sound waves of the same amplitude and opposite direction to the noise waveform,
So-called active noise cancellers are drawing attention. Therefore, there is a demand for an active noise canceling device compatible with cooling control that can be applied to all devices and equipment that generate noise, such as home appliances and computer systems, and that can cancel the generated noise efficiently and at low cost. ing.

[0003]

2. Description of the Related Art FIG. 6 is an explanatory diagram of a cooling and silencing control system for a computer system, and particularly shows a silencing control system for a large-sized, high-speed computer system that is cooled by cooling air.

Cooling air is sent from the cooling device to the underfloor of the free access, and the cooling control system draws the cooling air into the duct by the fan and exhausts it through the duct.
As a result, the heat generated from a heat source such as a printed board constituting the computer and guided to the duct is exhausted through the duct, and the computer is cooled. At this time, the cooling control system is configured to cool by changing the rotation speed of the fan according to the temperature rise. In addition, in a small computer, instead of cooling air, room temperature air is cooled by passing it through a heat source such as a printed board. In either case, the active noise canceller (abbreviated as ANCC) drives a sound generator such as a speaker based on the noise from the fan received by the sensor microphone and the residual noise received by the error microphone to drive the fan. Is generated so that sound waves having the same amplitude and opposite directions as the noise and the waveform are generated, and the fan sound and the speaker sound are combined and canceled to actively cancel the fan sound.

FIG. 7 is a block diagram of cooling and silencing control showing a conventional example. Fan noise received by a microphone (hereinafter referred to as sensor microphone) installed near a cooling fan (noise source) such as a printed board is converted from an analog sound signal by an analog / digital converter (ADC). Adaptive FIR (finite impulse response) that represents a transfer function that is converted into a digital signal and simulates the physical propagation path of sound through a duct
Input to the filter. The output of the adaptive FIR filter is converted from a digital signal to an analog signal by a digital / analog converter (DAC), and the speaker is driven by the signal, and the noise generated by the fan has the same amplitude and opposite sound waves. Is generated, the speaker sound is synthesized with the fan sound, and the sound is canceled to cancel the fan sound.

As a result of combining the speaker sound and the fan sound,
The residual noise that remains when the noise cannot be completely eliminated, that is,
The sound generated based on the error (residual error) of the simulation result of the fan sound by the adaptive FIR filter is received by the error microphone, and the analog sound signal is converted into a digital error signal by the analog / digital converter. To be done. Based on this error signal, the filter coefficient (or tap coefficient) of the adaptive FIR filter
By changing, the residual error, that is, the residual noise is brought close to zero, and the noise generated by the fan is controlled to be eliminated.

[0007]

As described above, according to the conventional method, the residual error is changed while changing the filter coefficient of the adaptive FIR filter based on the residual noise (residual error signal) received by the error microphone. Alternatively, the residual noise is controlled to approach zero. At this time, in the conventional method, the filter coefficient is modified, that is, the so-called modification coefficient (or step gain) is fixed and the filter coefficient is changed.
Therefore, there is a problem that the estimated time related to the impulse response of the transfer function becomes indefinite with respect to changes in the environment, for example, changes in temperature, resulting in a significant convergence time. Further, when a temperature rise is detected in the cooling control system, cooling is performed by increasing the number of rotations of the fan, so noise from the fan increases. However, in the conventional method, the silencing control system and the cooling control system are controlled independently of each other, and the factors of the cooling control system are not taken into consideration, so the silencing control cannot easily follow the increase in noise due to temperature rise. There was a problem.

It is an object of the present invention to provide an active noise canceling device compatible with cooling control, which can cancel noise generated from a noise source efficiently and economically.

[0009]

FIG. 1 shows a block diagram of the principle of the present invention. In the figure, 7 is a blower, 8 is a conduit, and 9
Is a heat source, 2 is a sound generating means for generating a sound, 1 is a first sound receiving means for receiving a noise generated by the blower 7, and 5 is a
The noise signal from the first sound receiving means 1 is input, the noise transmitted through the conduit 8 is simulated, and a signal for canceling the noise is output to the sound generating means 2. Second sound receiving means for receiving sound, 4 is a sensing means for sensing the temperature of heat generated from the heat source 9, and 6 is a residual noise signal from the second sound receiving means 3 and a temperature signal from the sensing means 4. The control means controls the pseudo means 5 so that the residual noise signal becomes zero based on the above.

[0010]

According to the present invention, the noise generated from the blower 7 of the cooling system for cooling the heat source 9 is canceled by the air blown from the blower 7 and discharged to the outlet through the conduit 8. In the active noise canceling device corresponding to the cooling control, in which the sound is emitted from the sounding means 2, the first sound receiving means 1 receives the noise generated from the blower 7, and the dummy means 5 receives the noise. The noise signal from the sound means 1 is input to simulate the noise transmitted in the conduit 8,
A signal for canceling the noise is output to the sound producing means 2. The second sound receiving means 3 receives the residual noise, and the sensing means 4
Detects the temperature of heat generated from the heat source 9, and the control means 6 controls the residual noise signal to zero based on the residual noise signal from the second sound receiving means 3 and the temperature signal from the sensing means 4. The pseudo means 5 is controlled. Therefore, the pseudo error by the pseudo means 5 is fed back to the pseudo means 5 by the control means 6 to eliminate the noise.

[0011]

FIG. 2 is a block diagram of cooling and silencing control showing an embodiment of the present invention. Throughout the drawings, the same reference numerals indicate the same or similar components.

A fan 7a for cooling a heat source 9a such as a printed board
The noise of the fan 7a received by the sensor microphone 1a installed near the (noise source) is converted from an analog sound signal to a digital signal by the analog / digital converter (called ADC) 1b, and the sound from the duct 8a is generated. Is input to an adaptive FIR (finite impulse response) filter 5a representing a transfer function for simulating the physical propagation path of

FIG. 3 is a block diagram of the FIR filter 5a, showing an example constituted by N stages of elements (or N taps). The adaptive FIR filter 5a is composed of an adder, a multiplier and a delay element, and if the discrete input and output signal sequences on the time axis are {x _i } and {y _i }, respectively, the output at time n y _n is the next convolution operation,

[0014]

[Equation 1]

Is given by Here, h _i is a filter coefficient, the coefficient control unit 6a to be described later, outputs y _n
It is automatically updated to minimize the error of. FIR
The output y _{n of the} filter 5a is converted from a digital signal to an analog signal by a digital / analog converter (referred to as a DAC) 2b, and the speaker 2a is driven by the signal, so that the noise and the waveform generated by the fan 7a have the same amplitude and reverse. Directional sound waves are generated, the speaker sound is combined with the fan sound, and the sound is canceled to cancel the fan sound.

As a result of combining the speaker sound and the fan sound,
The residual noise remaining when the fan sound cannot be completely eliminated, that is, the sound generated based on the residual error of the simulation result of the fan sound by the FIR filter 5a is an error microphone.
3a is sound receiving by being converted into a digital signal by an analog / digital converter 3b, it is inputted as the residual error E _n.

The coefficient control unit 6a sets the filter coefficients h _i (h ₀ , h ₁ , h ₂ , ...) In real time so as to minimize the residual error E _n , that is, for each discrete time period. corrected by updating, the residual error E _n, that is, closer to the residual noise to zero, control to erase noise fan 7a occurs. According to the learning identification method, the filter coefficient h _{i that} is corrected to bring the error E _n close to zero is calculated by using the squared value of the residual error E _n as an evaluation function, and Equation 2,

[0018]

[Equation 2]

It is represented by That is, the filter coefficient h _i (left side) to be updated in the time period n−1 and used in the next time period n is given by the calculation of the right side in the time period n−1. Here, α is a correction coefficient (or loop gain) for correcting the filter coefficient h _i, and is obtained by the method described later. The noise elimination amount and the convergence time depend on the correction coefficient α. When α = 1, the convergence time becomes minimum, and α
It is known that the noise cancellation amount is improved as the value is reduced.

The temperature of the heat source detected by the temperature sensor 4a provided in the vicinity of the heat source 9a such as a printed board is converted into a digital signal by the analog / digital converter 4b, and the PID (proportional / integral / derivative) control unit 4c. Entered in. The PID control unit 4c performs a known operation on the input so that the output is proportional to the input (digitally converted temperature signal), the temporal integration of the input, and the linear combination of the temporal change rate of the input. The resulting PID output is controlled to quickly approach the target value.

The output of the PID control unit 4c is input to the motor control unit 7b of the fan 7a, the rotation speed of the fan 7a is changed according to the output value, and the air volume passing through the duct 8a is increased or decreased to control the heat source 9a. Cooling control is performed to keep the temperature within the required temperature range. Further, it is input to the coefficient control unit 6a and is used as one factor for updating the filter coefficient h _i , that is, as a means for obtaining the correction coefficient α, as described below.

FIG. 4 is an explanatory diagram of how to obtain the correction coefficient according to the present invention. FIG. 4 (a) shows the relationship between the temperature T of the heat source 9a, the rotation speed F (rpm) of the fan, the noise N (db), and the correction coefficient α. Experiments have confirmed that if the temperature of the heat source 9a rises, the number of rotations of the fan increases and noise increases. Further, the characteristic of FIG. 4 (a) is unique to a given cooling system, and the value of the correction coefficient α with respect to the temperature T is
As shown in the figure, it is obtained by empirical trial and error through experiments. The value of the correction coefficient α obtained in this way is
As shown in FIG. 4 (b), a read-only memory (RO) corresponding to the relative value (relative temperature) of the output value of the PID controller 4c.
M) Store in 4m storage location. Therefore, in each period, the ROM 4m uses the output value of the PID control unit 4c as an address.
By reading the value of α from, the filter coefficient h _i
Is configured to fix and update.

FIG. 5 is a flow chart of an embodiment of the present invention. Δt = 1 / f _S (f _S = Analog / digital converter
The active noise canceller updates the time limit and starts processing each time a sampling pulse that occurs at a period of 1b) is detected. When the time limit is n,
Previous results y _n-1 of the convolution operation in timed n-1 and output via the digital / analog converter 2b speaker
The noise generated by the fan 7a is controlled by driving the 2a.

The noise of the fan 7a is received by the sensor microphone 1a, the noise signal is converted into a digital signal x _n via the analog / digital converter 1b, and the digital signal x _n is input to the FIR filter 5a.

The PID control unit 4c performs a known calculation based on the temperature signal from the temperature sensor 4a, and PI of the calculation result.
The D output is supplied to the coefficient control unit 6a and the motor control unit
The heat source 9a is cooled and controlled by supplying it to 8b to control the rotation speed of the fan 7a.

The coefficient control unit 6a is the PI of the PID control unit 4c.
The ROM 4m is accessed by using the D output (temperature signal T) as a relative address, and the correction coefficient α is read. To calculate the ² | from the formula 2 | Xj.

The convolution operation of Expression 1 is performed to obtain y _n . Calculate K _n in Equation 2. The filter coefficient h _i is obtained by Equation 2 and updated.

Therefore, according to the present invention, the cooling control and the adaptive control of the active noise canceller are combined in the same control loop, and a correction coefficient for correcting the filter coefficient of the FIR filter 5a necessary for the adaptive control of the active noise canceller is provided. , Is automatically generated based on the temperature of the heat source 9a as a cooling control input.

[0029]

As described above, according to the present invention, the noise generated from the blower that blows air into the conduit to cool the heat source and the digital filter that simulates the noise transmitted inside the conduit are used. In an active noise eliminator for cooling control that eliminates noise by canceling the noise, it is based on the temperature signal detected near the heat source in addition to the residual noise signal detected near the outlet of the pipe. Since the filter coefficient of the digital filter is controlled so that the residual noise signal becomes zero, it is possible to quickly follow the temperature fluctuation of the heat source, which causes the noise increase of the blower, and to efficiently and efficiently ， There is an effect that it can be deleted economically.

[Brief description of drawings]

FIG. 1 is a block diagram of the principle of the present invention.

FIG. 2 is a block diagram of cooling and silencing control showing an embodiment of the present invention.

FIG. 3 is a block diagram of the FIR filter 5a

FIG. 4 is an explanatory diagram of how to obtain a correction coefficient according to the present invention.

FIG. 5 is a flowchart of an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a computer organization cooling and silencing control system.

FIG. 7 is a block diagram of cooling and silencing control showing a conventional example.

[Explanation of symbols]

 1 1st sound receiving means 2 Sounding means 3 2nd sound receiving means 4 Sensing means 5 Simulating means 6 Control means 7 Blower 8 Conduit 9,9a Heat source 1a Sensor microphone 1b, 3b, 4b Analog / digital converter 2a Speaker 2b , 7c Digital / analog converter 3a Error microphone 4a Temperature sensor 4c PID controller 5a FIR filter 6a Coefficient controller 7a Fan 7b Motor controller 8a Duct

Claims (6)

[Claims] 1. In a cooling system for cooling a heat source (9) by air blown from a blower (7) and discharged to its outlet through a conduit (8), noise generated by the blower (7) An active noise canceller compatible with cooling control, which cancels a sound that cancels the sound by generating sound from the sounding means (2), the first sound receiving means (sound receiving means to receive the noise generated from the blower (7) ( 1) and the noise signal from the first sound receiving means (1) are input, and a signal for canceling the noise is simulated by imitating the noise transmitted through the conduit (8).
A pseudo means (5) for outputting to (2), a second sound receiving means (3) for receiving residual noise, and a sensing means (4) for sensing the temperature of heat generated from the heat source (9) The dummy means (5) so that the residual noise signal becomes zero based on the residual noise signal from the second sound receiving means (3) and the temperature signal from the sensing means (4)
An active noise canceller compatible with cooling control, which is provided with a control means (6) for controlling. 2. In a cooling system for cooling a heat source by air blown from a blower and discharged through a conduit to its outlet, noise generated by the blower drives a sounder provided near the outlet. An active noise canceling device compatible with cooling control that cancels noise by generating a noise that cancels the noise, and is provided in the vicinity of a blower and receives a noise and a sound receiver. First conversion means for converting the received analog signal into a digital noise signal and the noise signal from the first conversion means are input, and the noise transmitted in the conduit is simulated to cancel the noise. A digital filter that outputs such a signal,
Second converting means for converting a digital signal from the digital filter into an analog signal and outputting the analog signal to the sounding device, a sound receiver provided near the outlet of the conduit for receiving residual noise, and the sound receiving device. Third conversion means for converting an analog signal from the sounder into a digital residual noise signal, a temperature sensor for sensing the temperature of heat generated from the heat source, and a digital signal for converting the analog signal from the temperature sensor. Fourth conversion means for converting into a signal and updating means for updating the filter coefficient of the digital filter based on the residual noise signal from the third conversion means and the temperature signal from the fourth conversion means are provided. An active noise canceller for cooling control, which is characterized in that 3. The updating means is provided with table means for storing a correction coefficient for correcting the filter coefficient of the digital filter in accordance with temperature data and reading the correction coefficient based on a temperature signal from the fourth converting means. 3. The cooling control-compatible device according to claim 2, wherein the means updates the filter coefficient of the digital filter based on the residual noise signal from the third converting means and the correction coefficient from the table means. Active noise canceller. 4. A calculation means for performing a PID calculation based on a temperature signal from the fourth conversion means is provided, and the table means reads out the correction coefficient based on a result of the calculation by the calculation means. The active noise canceller for cooling control according to claim 3. 5. The cooling device according to claim 4, further comprising a blower control device for changing the amount of air from the blower and cooling the heat source based on the result of the calculation by the calculation device. Controlled active noise canceller. 6. The active for cooling control according to claim 5, wherein the noise of the blower and the cooling control of the heat source are performed within the period of the sampling pulse generated in the first conversion means. Noise canceler.