JPH08164289A - Noise control device for sewing machine - Google Patents

Abstract

PURPOSE: To provide a sawing machine noise control device capable of actively reducing a noise generated due to the rotation of an arm shaft, the vertical reciprocating motion of a needle bar or the like without causing any drop in the mechanical strength of a sewing machine. CONSTITUTION: A control section 220 controls a control sound generation speaker 203 for minimizing the detection value of a microphone 204 for detecting a noise, on the basis of a vibration signal detected with a vibration sensor 202 for detecting the vibration of a sewing machine body 201, and a signal detected with the microphone 204. Furthermore, a control sound generated with the speaker 203 acts to offset a noise. Thus, the noise can be actively reduced.

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 a sewing machine, which is capable of actively reducing the noise of the sewing machine generated by the rotation of the upper shaft of the sewing machine and the reciprocating movement of the needle bar. Is.

[0002]

2. Description of the Related Art Conventionally, in a sewing machine, in order to reduce the noise generated by the driving of the sewing machine, the weight of the motion system of the sewing machine and the balance of the rotating system are reduced to reduce vibrations and the like. I was trying to reduce noise.

A simple apparatus has also been proposed in which the noise of the sewing machine is detected and accumulated in advance, a waveform having an opposite phase to that is generated, and the noise of the sewing machine is suppressed by using the waveform having the opposite phase.

[0004]

However, reducing the weight of the motion system of the sewing machine lowers the mechanical strength of the motion system as a whole, and this method has a limit, which causes noise. There is a limit to noise reduction.

Further, in the rotating system of the sewing machine, since the respective parts make complicated mutual movements with each other, it is very difficult to balance them so as to reduce noise.

Further, according to the above simple noise suppressing device, it is very difficult to accurately adjust the noise generated by the high speed rotation of the sewing machine to the same amplitude and opposite phase. Further, in practice, the noise of the sewing machine is affected by the influence of disturbance and the time delay of the noise transmission system, so it is considered impossible to suppress the noise while always following the noise.

The present invention has been made in order to solve the above-mentioned problems, and is caused by the rotation of the upper shaft of the sewing machine, the vertical reciprocating motion of the needle bar, etc. without lowering the mechanical strength of the sewing machine. An object of the present invention is to provide a noise control device for a sewing machine that actively reduces the noise of the sewing machine.

[0008]

In order to achieve the above object, a noise control device for a sewing machine according to the present invention comprises a vibration detecting means for detecting a vibration generated by driving the sewing machine, and a noise generated by driving the sewing machine. A noise detecting means for detecting the control noise, a control sound generating means capable of generating a control sound for canceling the noise generated by driving the sewing machine, a signal detected by the vibration detecting means and a signal detected by the noise detecting means. Based on the above, there is provided control means for controlling the control sound generating means so that the noise detected by the noise detecting means is minimized.

The vibration detecting means is preferably provided on the sewing machine main body.

Further, the vibration detecting means may be installed at a plurality of locations on the sewing machine main body, and respective signals of the vibration detecting means may be inputted to the control means at the same time.

Further, there is provided a transfer function setting means for presetting a transfer function indicating a characteristic or a mutual interference characteristic of a mechanical system part or an electric part of the sewing machine, and the control means comprises the vibration detecting means and the noise detecting means. The control sound generating means may be controlled on the basis of the transfer function together with each detection signal.

[0012]

According to the noise control device for a sewing machine of the present invention having the above-mentioned structure, the driving of the sewing machine causes vibration and noise in the main body of the sewing machine. At this time, the vibration detecting means detects the vibration and the noise detecting means detects the noise. Then, based on the signal detected by the vibration detection means and the signal detected by the noise detection means, the control means controls the control sound generation means to minimize the noise detected by the noise detection means. Control.
Therefore, the control sound generated from the control sound generating means works to cancel the noise generated from the sewing machine main body, so that the noise can be actively reduced.

By providing the vibration detecting means on the sewing machine main body, the vibration of the sewing machine main body can be directly detected. In this case, since the signal detected directly is input to the control means, the control of the control sound generation means can be made more reliable.

Further, the vibration detecting means can be installed at a plurality of locations on the sewing machine main body, and respective signals of the respective vibration detecting means can be inputted to the control means at the same time. In this case, by arranging the vibration detecting means at a plurality of places where relatively large vibrations are generated, noise due to the vibrations at a plurality of such places can be efficiently reduced over the entire sewing machine.

Further, by considering the transfer function set by the transfer function setting means in the control by the control means, the control of the control sound generating means can be performed more finely and highly accurately, and The reduction of noise can be further ensured.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, the noise control system of the sewing machine has a vibration for detecting a vibration having a correlation with the noise generated from the sewing machine main body 201 at a position corresponding to the lower side of the needle bar of the sewing machine main body 201. Detection sensor (vibration detection means)
202 is installed. A microphone 204 for detecting the noise of the sewing machine and a speaker 203 for generating a control sound for canceling the noise of the sewing machine are arranged near the periphery of the sewing machine body 201. Preferably, the vicinity of a portion where particularly loud noise is generated or the vibration detection sensor 202
It will be placed near the installation location.

The amplifier 205 and the A / D converter 20 are mainly included in the control section for controlling the noise of the main body 201.
8, D / A converter 209, filter LPF207 for removing high frequency components, filter HPF for removing DC components
206, an adaptive filter 210, and a control unit 220 are provided. The control unit 220 constitutes the control means of the present invention, and detects the noise microphone 204 based on the detection signal of the vibration detection sensor 202, the detection signal of the noise microphone 204, and the transfer function described later. The coefficient of the adaptive filter 210 is adjusted so as to minimize noise, a drive control signal is output to the control sound generation speaker 203 via the adaptive filter 210, and a control sound is generated from the control sound generation speaker 201. .

That is, when the vibration signal generated by driving the sewing machine main body 201 is detected by the vibration sensor 202, the vibration signal is transmitted through the amplifier 205, the filter HPF 206, the filter LPF 207 and the A / D converter 208 to the adaptive filter 210 and control. It is input to each unit 220. On the other hand, the noise of the sewing machine main body 201 is detected by the noise detection microphone 204, and the detection signal is input to the control unit 220 via the amplifier 205, the filter LPF 207, and the A / D conversion unit 208. In the control unit 220, the control sound generation speaker 20 that generates a control sound from the noise detection microphone 204.
3 acoustic paths and electrical components, amplifier 205, A /
D conversion unit 208, D / A conversion unit 209, filter LPF
The transfer functions showing these characteristics are obtained in consideration of the characteristics such as 207, and the damping effect, that is,
The control unit 22 is configured to minimize the detection signal of the noise detection microphone 204 that detects the interference state between the noise generated by the operation of the sewing machine and the control sound generated from the control source speaker 203.
0 determines the transfer function to be given to the adaptive filter 210, and sets the control parameter for specifying the transfer function in the adaptive filter 210.

The control unit 220 modifies the control parameters as needed according to changes in the noise transmission path and changes in the characteristics of the control system. As a result, the vibration signal detected by the vibration sensor 202 is transmitted to the amplifier 205 and the filter H.
PF 206, filter LPF 207, and A / D converter 2
The signal is input to the adaptive filter 210 via 08, and the input signal is converted by the adaptive filter 210 into a digital signal having predetermined amplitude characteristics and phase characteristics based on the transfer function given from the control unit 220. The digital signal is D / A converted and amplified by the D / A converter 209, the filter LPF 207, and the amplifier 205, and applied as a drive signal for the control sound generation speaker 203. The control sound generation speaker 203 produces noise generated by driving the sewing machine. A control sound for canceling is generated. As a result, the noise generated from the sewing machine main body 201 is attenuated near the installation position of the noise detection microphone 204.

In order to synthesize the control sound for driving the control sound generating speaker 203 from the vibration signal detected by the vibration sensor 202, the adaptive filter 210 shown in FIG. It is configured by a finite impulse response filter (also called FIR filter) as shown in FIG. The input signal x (n) 300 is the detection signal of the vibration sensor 202 in FIG. 2, the symbol 301 is the delay element, and the symbols 303 w _{0 n} , w _1n , w _2n , ..., W _Mn are the control units 220 in FIG. From the variable filter coefficient, symbol 302 is an adder, and symbol 306 is the number of filter taps M
Is. That is, the output y (n) 305 of the adaptive filter 210 is given by the following equation.

[0022]

[Equation 1]

The variable filter coefficients w _1n , w _2n , ..., W _Mn are used to follow changes in the transfer characteristics due to disturbances in the noise path and changes in the characteristics of each electric component itself. However, the reason for this is that the value converges to the optimum filter coefficient value.

The control unit 220 of FIG. 2 is configured to sequentially estimate such variable coefficients. FIG. 4 shows the configuration of the control unit 220. Here, FIG.
The vibration signal x (n) detected by the vibration sensor 202 is passed through the delay filter 402 to generate the reference signal c (n). This reference signal c (n) and noise microphone 2
The detection signal e (n) of 04 is input to the adaptive algorithm 401, and the variable filter coefficients w _1n , w _2n , ..., W _Mn are updated using the adaptive formula called LMS algorithm given by the following formula.

[0025]

[Equation 2]

The parameter μ in the above equation is a constant called a step size, which is a parameter that influences the convergence speed and convergence accuracy of the filter coefficient W (n).

That is, in order to pursue the convergence speed, it is necessary to increase the parameter μ within a range in which it can be converged, but in consideration of the accuracy after convergence, it is necessary to comprehensively select the parameter μ. In particular, with respect to noise caused by reciprocating motion or rotary motion of the needle bar of the sewing machine, it is necessary to suppress the noise within a short time, and thus it is considered that a convergence speed is required.

As described above, the estimated filter coefficient w _1n
w _2n ... W _Mn are transmitted to the adaptive filter of FIG. 3 to generate the output digital signal y (n) 305. The digital signal y (n)
Is D / A converted and amplified by the D / A converter 209, the filter LPF 207, and the amplifier 205, and the speaker 203
And a control sound for canceling the noise around the microphone 204 generated by the rotation of the sewing machine is generated from the speaker 203.

The coefficient h _{0 of} the delay filter 402 shown in FIG.
h ₁ , ... H _p are obtained in advance. FIG. 5 shows an identification sequence before noise control for obtaining these. That is, the transfer function from the control sound source speaker including the electric circuit, the noise detection sensor 204, and the control sound generation speaker 203 serving as the control sound source to the noise detection sensor 204 is obtained. LMS is used as the adaptive filter 501.
An adaptive FIR filter using an adaptive algorithm is mainly used. The random noise source 500 is adapted to provide a random signal.

Regarding the overall operation of FIG. 5, a random digital signal is generated from the random noise generation source 500, and this is the D / A conversion unit 209 and the low pass filter LP.
The control sound generation speaker 203 is driven through the F207 and the amplification amplifier 205 to generate a control sound. On the other hand, a random digital signal from the signal source is applied to the adaptive filter 5
Input 01 and generate output. In the adder 503, the noise signal detected by the noise detection microphone 204 and passed through the amplifier 205, the low pass filter LPF 207, and the A / D converter 208 is added to the output of the adaptive filter 501, and the error e (n ) Ask for 504. Adaptive filter 501
Then, the coefficient of the adaptive filter 501 is sequentially corrected so as to minimize the error e (n) 504. Finally, this convergence value is set to the filter coefficients h ₀ , h ₁ , ...
_-Used as h _p .

As described above, in the noise control device for a sewing machine of the above-described embodiment, since it is composed of the components that have been conventionally used, the mechanical strength of the sewing machine is not lowered, and it is generated by driving the sewing machine. It is possible to provide a noise control device that actively reduces the generated noise.

FIG. 6 shows the result of an experiment for a certain sewing machine based on the above noise control device for the sewing machine. A dotted line and a solid line in FIG. 6 indicate the noise detection microphone 2 when the control is OFF and the control is ON at 3000 rpm, respectively.
4 is a frequency characteristic measured in the vicinity of 4 cm in 04. It can be seen that the effect of control was well documented.

In the noise control system of the sewing machine shown in FIG. 2, the vibration sensor 202 for detecting vibration is not limited to the fixed type, but may be any arrangement on the sewing machine main body 201.

Further, in the noise control system of the sewing machine shown in FIG. 2, vibration sensors 202 for detecting vibration are installed at a plurality of locations on the sewing machine main body 201, that is, a plurality of locations where particularly large vibrations are generated, and the outputs of these are provided. The vibration signal may be input to the adaptive filter 210 and the control unit 220 at the same time. In this case, since the noises of a plurality of sound sources can be comprehensively taken into consideration, the effect that the noise of the entire sewing machine can be totally reduced can be obtained.

[0035]

As is apparent from the above description, according to the noise control device for a sewing machine of the present invention, the driving of the sewing machine causes vibration and noise in the sewing machine main body. The vibration detecting means detects the vibration, and the noise detecting means detects the noise. Then, based on the signal detected by the vibration detection means and the signal detected by the noise detection means, the control means,
In order to minimize the noise detected by the noise detecting means,
Since the control sound generation means is controlled, the control sound generated from the control sound generation means works to cancel the noise generated from the sewing machine main body, and thus the noise can be actively reduced. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a configuration diagram of a noise control system of the sewing machine.

FIG. 3 is a configuration diagram of an adaptive filter.

FIG. 4 is a configuration diagram of a control unit of the control system of the sewing machine.

FIG. 5 is a configuration diagram showing an identification sequence of noise control of the sewing machine.

FIG. 6 is a graph showing experimental results of noise control.

[Explanation of symbols]

 201 sewing machine main body 202 vibration sensor 203 control sound source speaker 204 noise detection microphone 210 adaptive filter 220 control unit 502 random noise generation source

Claims (4)

[Claims] 1. A vibration detecting means for detecting vibration generated by driving the sewing machine, a noise detecting means for detecting noise generated by driving the sewing machine, and a control sound for canceling noise generated by driving the sewing machine. Based on the signal detected by the vibration detection means and the signal detected by the noise detection means, the control sound generation means is configured to minimize the noise detected by the noise detection means. A noise control device for a sewing machine, comprising: a control unit for controlling. 2. The noise control device for a sewing machine according to claim 1, wherein the vibration detecting means is provided on the sewing machine main body. 3. The vibration detecting means is installed at a plurality of positions on the main body of the sewing machine, and respective signals of the vibration detecting means are input to the control means at the same time. Sewing machine noise control device. 4. A transfer function setting means for presetting a transfer function indicating a characteristic or a mutual interference characteristic of a mechanical system component, an electrical component or the like of the sewing machine is provided, and the control means comprises the vibration detection means and the noise detection means. 2. The noise control device for a sewing machine according to claim 1, wherein the control sound generating means is controlled based on the transfer function together with each detection signal of.