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DESCRIPTION JP2004020714

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DESCRIPTION JP2004020714
The present invention provides an active vibration noise reduction device that can be realized by
an inexpensive microcomputer or the like without using an expensive DSP or the like in order to
reduce vibration noise of a rotational secondary component in a 4-cycle 4-cylinder engine. An
active vibration noise is generated by updating an adaptive notch filter coefficient of an adaptive
notch filter 4 by adaptive processing and canceling vibration noise by a secondary vibration
noise generator 8 driven based on an output of the adaptive notch filter 4. In the reduction
device, a pulse wave synchronized with the rotational secondary component of the 4-cycle 4cylinder engine 21 is generated by the tacho pulse generator 22, and this pulse wave is formed
by an analog circuit with the low pass filter 23 and the first phase shift. The reference cosine
wave signal and the reference sine wave signal are obtained by filtering in the second phase
shifter 25 and the second phase shifter 25. [Selected figure] Figure 1
Active vibration noise reduction device
The present invention relates to an equal phase and an anti-phase to vibration noise such as
unpleasant engine vibration or engine squeaking (noise) generated in a vehicle interior as the
engine rotates. More specifically, the present invention relates to an active vibration noise
reduction device that can be realized by an inexpensive microcomputer or the like without using
an expensive DSP or the like. [0002] Since the engine muddy sound is a vibration radiation sound
generated by transmitting the excitation force generated by the engine rotation to the vehicle
body, the vibration having remarkable periodicity synchronized with the number of rotations of
the engine The noise is noise. For example, in the case of a four-stroke four-cylinder engine, a
large amount of vibration noise, which is called a rotational secondary component having a
frequency twice as high as the engine rotation speed, is generated. [0003] This is because torque
fluctuation due to gas combustion that occurs every half rotation of the engine crank generates
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excitation vibration originating from the engine, and this causes vibration noise in the vehicle
interior. When this rotational secondary component coincides with the cavity resonance
frequency of the vehicle body, a particularly loud noise is generated in the vehicle interior,
causing discomfort to the occupants. Among such engine noises, a method using an adaptive
notch filter as proposed in, for example, Japanese Patent Laid-Open No. 2000-99037 is known as
a method for actively reducing the rotational secondary component most likely to be a problem.
ing. The configuration of the active vibration noise reduction device disclosed therein is shown in
FIG. In FIG. 5, all discrete operations for realizing the active vibration noise reduction device are
processed by the DSP 17. First, noise and the like superimposed on the engine pulse are removed
by the waveform shaper 1 and the waveform is shaped. The output signal of this waveform
shaper 1 is applied to a cosine wave generator 2 and a sine wave generator 3 to produce a cosine
wave and a sine wave as reference signals. The output signal of the coefficient multiplier 5 that
multiplies the reference cosine wave signal that is the output signal of the cosine wave generator
2 and the filter coefficient W0 of the adaptive notch filter 4 is a reference sine wave signal that is
the output signal of the sine wave generator 3 And the filter coefficient W 1 of the adaptive
notch filter 4 are added by the adder 7 at the output signal of the coefficient multiplier 6 and
supplied to the secondary vibration noise generator 8. The secondary vibration noise is
generated by the secondary vibration noise generator 8 and is canceled by interfering with the
vibration noise based on the engine pulse. At this time, the residual signal that can not be
silenced is used as an error signal e in the adaptive control algorithm.
On the other hand, at the notch frequency to be muffled determined from the engine speed, a
reference cosine wave is transferred to the transfer element 9 having C 0 simulating the transfer
characteristic from the output of the adaptive notch filter 4 to the adaptive control algorithm
calculator 15. A reference sine wave signal is supplied to the transfer element 10 which supplies
a signal and has C1 simulating the transfer characteristic from the output of the adaptive notch
filter 4 to the adaptive control algorithm calculator 15 as well, and outputs the transfer element
9 and the transfer element 10 Are added by the adder 13 and the error signal e are supplied to
the adaptive control algorithm computing unit 15, and the filter coefficient W0 of the adaptive
notch filter 4 is updated based on the adaptive control algorithm, for example, the LMS
algorithm. Similarly, a reference sine wave signal is supplied to the transfer element 11 having
C0 simulating the transfer characteristic from the output of the adaptive notch filter 4 to the
adaptive control algorithm computing unit 16 at the notch frequency to be muffled determined
from the engine speed Similarly, the reference cosine wave signal is supplied to the transfer
element 12 having (-C1) simulating the transfer characteristic from the output of the adaptive
notch filter 4 to the adaptive control algorithm computing unit 16, and the outputs of the
transfer element 11 and the transfer element 12 Are added by the adder 14 and the error signal
e to the adaptive control algorithm computing unit 16, and the filter coefficient W1 of the
adaptive notch filter 4 is updated based on the adaptive control algorithm, for example, the LMS
algorithm. In this manner, the filter coefficients W 0 and W 1 of the adaptive notch filter 4
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recursively converge to an optimal value so that the error signal e becomes smaller, in other
words, the vibration noise in the vibration noise suppression unit is reduced. I will. SUMMARY OF
THE INVENTION The above-mentioned active vibration noise reduction device according to the
prior art is realized by discrete signal processing. In order to output a muffling signal as an active
vibration noise reduction device, multiplication of the reference cosine wave signal and the filter
coefficient W0 of the adaptive notch filter 4, multiplication of the reference sine wave signal and
the filter coefficient W1 of the adaptive notch filter 4, and Two multiplications such as addition
and one addition are required. On the other hand, in order to perform adaptive processing, r0
can be obtained by multiplying the reference cosine wave signal and the transfer characteristic
C0, multiplying the reference sine wave signal and the transfer characteristic C1, and performing
addition and two additions such as addition and one addition. Similarly, r1 can be determined by
two multiplications and one addition. In addition, since two multiplications and one addition are
required in the LMS algorithm operation, eventually, eight multiplications and four additions are
required for the adaptive processing alone.
[0010] A total of 10 multiplications and 5 additions must be performed within the discrete
sampling period. This has the advantageous aspect that the amount of calculation is very small
compared to the long tap length adaptive filter used in realizing general non-periodic active noise
and vibration control. On the other hand, although a specific method for generating the reference
cosine wave signal and the reference sine wave signal is not shown, generally, the period of the
vibration noise generated from the engine rotational speed is calculated. For sampling values at
each sampling time of a cosine signal or a sine signal based on a period, a method is used in
which a cosine function or a sine function is calculated with a Taylor-expanded polynomial.
Shown below is a polynomial by Taylor expansion of cosine function and sine function. 【
0011】 cos(x)=1−x<2>/2! +x<4>/4! ……+(−1)<n>・
x<2n>/(2n)! sin(x)=x−x<3>/3! +x<5>/5! ……+(−1)<n>・
x<2n+1>/(2n+1)! The reference cosine wave signal and the reference sine wave
signal are created by obtaining an approximation value by calculation up to a certain constant in
the above-described polynomial which actually goes to infinity. As described above, in the
apparatus for actively reducing vibration noise of engine rotation second-order components
using the conventional adaptive notch filter, a large number of multiplications are required to
generate the reference cosine wave signal and the reference sine wave signal. At the same time
as the addition is required and the merit of a small amount of operation when the adaptive notch
filter is used is reduced, it is indispensable to use an expensive DSP or the like which can perform
high-speed operation. Therefore, it has a problem that it is difficult to realize a low-cost active
vibration noise reduction device using an inexpensive microcomputer or the like although the
calculation speed is low. The present invention solves the above-mentioned conventional
problems, and discrete numerical operation for producing a reference cosine wave signal and a
reference sine wave signal by using a filter and a phase shifter constituted by an analog circuit. It
is an object of the present invention to realize a low-cost active vibration noise reduction device
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by eliminating the need to use a microcomputer. According to the present invention for achieving
the above object, there is provided a synchronous pulse generator for generating an electrical
pulse synchronized with a frequency to be a subject of vibration noise generated from a vibration
noise source, A cosine wave generating means for generating a cosine wave synchronized with
the generated pulse signal from the synchronous pulse generator, and a reference cosine wave
signal and a reference sine wave signal synchronized with the generated cosine wave from the
cosine wave generating means and orthogonal to each other Means for generating a reference
signal, an adaptive notch filter to which the reference cosine wave signal and the reference sine
wave signal from the reference signal generating means are input, and vibration noise driven by
an output signal from the adaptive notch filter A secondary vibration noise generator generating
secondary vibration noise that cancels out the residual noise signal due to the interference
between the vibration noise and the secondary vibration noise, the reference cosine wave signal,
and Coefficient updating means for updating the filter coefficient of the adaptive notch filter by
the correction signal of the reference sine wave signal, the coefficient from the output of the
adaptive notch filter of the reference cosine wave signal and the reference sine wave signal to
form the correction signal In an active vibration noise reduction device comprising simulated
transfer characteristic correction means for simulating transfer characteristics up to the input of
the updating means, the cosine wave generation means is a low pass filter or a band pass filter
constituted by an analog circuit. It is characterized by
The active vibration noise reduction device having the above configuration is characterized in
that the cosine wave generation means is a low pass filter or a band pass filter formed of an
analog circuit, whereby discrete numerical operation is performed. It is possible to generate a
cosine wave as a reference signal for generating the reference cosine wave signal and the
reference sine wave signal without requiring any The effect is obtained that the device can be
used. In the above configuration, the reference signal generating means is a first phase shifter
composed of an analog circuit to which the generated cosine wave as an output signal from the
cosine wave generating means is input, and the same as the cosine wave generating means. And
a second phase shifter composed of an analog circuit to which the generated cosine wave, which
is an output signal from the above, is input, thereby eliminating the need for any discrete
numerical operation. It is possible to generate the reference cosine wave signal and the reference
sine wave signal, and it is possible to obtain an effect that a discrete arithmetic processing unit
having a low calculation speed can be used in realizing the active vibration noise control
apparatus. In addition, the synchronous pulse generator has a feature of outputting a pulse
synchronized with the ignition cycle of the engine, so that it is possible to obtain a pulse
synchronized with the ignition cycle identical to the gas combustion cycle. The advantage is
obtained that it is easy to generate a reference signal synchronized with the vibration caused by
the gas combustion of the engine. The synchronous pulse generator is characterized by being a
tach pulse generator or a TDC sensor, and these are devices that are already equipped in
vehicles, and there are vibrations that become a problem by using them. The effect is obtained
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that it is possible to eliminate the need to separately install a device that generates an electrical
pulse synchronized with the frequency of noise. BEST MODE FOR CARRYING OUT THE
INVENTION Hereinafter, embodiments of the present invention will be described with reference
to the accompanying drawings for understanding of the present invention. The same components
as those of the conventional active vibration noise reduction device shown in the prior art are
designated by the same reference numerals. FIG. 1 is a block diagram showing the configuration
of the active vibration noise reduction device according to the present embodiment, and 21 is a
4-cycle 4-cylinder engine as a vibration noise source. It operates to reduce the rotational
secondary component in the vibration noise generated from the cycle 4 cylinder engine 21.
Generally, among the rotational secondary components in the four-cycle four-cylinder engine,
vibration noise (hereinafter referred to as secondary task vibration noise) in a specific frequency
range is often a problem.
A TDC sensor (top dead center sensor) as a synchronous pulse generator or a tacho pulse
generator 22 (hereinafter referred to as a tacho pulse generator) is used as a rotational
secondary component of a 4-cycle 4-cylinder engine 21 as a vibration noise source. It generates
a tacho pulse signal which is a synchronized signal. In many cases, the tach pulse signal is
already provided on the vehicle side as an input signal of the tachometer, etc. There is no need to
separately install a device for generating an electric pulse synchronized with the frequency of the
vibration noise which is a special problem. The tach pulse signal in the four-stroke four-cylinder
engine 21 is a pulse wave of two cycles per one rotation of the crank, and hence is a signal
synchronized with the rotational secondary component of the four-stroke four-cylinder engine
21. A tacho pulse signal which is an output signal from the tacho pulse generator 22 is input to a
low pass filter 23 as cosine wave generating means constituted by an analog circuit. Since the
tach pulse signal is a pulse signal synchronized with the rotational secondary component of the
4-cycle 4-cylinder engine 21 as described above, the tacho pulse signal is composed of the sum
of a component having the rotational secondary component as a fundamental frequency and its
harmonic components There is. Therefore, by inputting a tacho pulse signal to the low pass filter
23 set so that the pass frequency band is the second-order task vibration noise frequency, only
cosine waves having a frequency equal to the frequency of the second-task vibration noise are
extracted It becomes possible. FIG. 2 is an example of a filter used as the low pass filter 23. This
filter is called a second-order positive feedback low-pass filter, and is composed of terminals 27,
33, resistors 28, 29, capacitors 30, 31 and an operational amplifier 32. The frequency
characteristic of this filter is determined by the values of the resistors 28, 29 and the capacitors
30, 31, and the frequency above the cutoff frequency has a characteristic that the level decreases
with a slope of 12 dB / oct. The cosine wave, which is an output signal from the low pass filter
23, is a reference signal generating means similarly constituted by an analog circuit and a first
phase shifter 24 as a reference signal generating means constituted by an analog circuit. Are
input to the second phase shifter 25. FIG. 3 shows an example of the phase shifter used in the
present embodiment. This phase shifter is called a first-order phase shifter using an operational
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amplifier, and comprises terminals 34 and 40, resistors 35, 36 and 37, a capacitor 38 and an
operational amplifier 39. An example of the phase characteristic of this phase shifter is shown in
FIG. The phase characteristic of this phase shifter is a characteristic in which the phase of the
output signal is delayed with respect to the input signal.
Here, at the secondary task vibration noise frequency, the phase characteristic of the first phase
shifter 24 is set to advance by π / 2 [rad] with respect to the phase characteristic of the second
phase shifter 25. That is, if the output signals of the first phase shifter 24 and the second phase
shifter 25 are relatively viewed, the output signal of the first phase shifter 24 is a cosine wave
having a frequency equal to the secondary task vibration noise frequency. It can be said that the
output signal of the second phase shifter 25 is a sine wave having a frequency equal to that of
the secondary task vibration noise frequency. Therefore, in the active vibration noise reduction
device shown in FIG. 1, the output signal of the first phase shifter 24 is a reference cosine wave
signal, and the output signal of the second phase shifter 25 is a reference sine wave signal. In
this way, the reference cosine wave signal and the reference sine wave signal obtained only by
analog signal processing without performing discrete operation processing are respectively
quantized by the microcomputer 26 that processes the discrete operation, and discrete operation
processing is performed. Used as numerical data for The arithmetic processing after the
reference cosine wave signal and the reference sine wave signal as discrete numerical data are
obtained is the same as that shown in the prior art. That is, the output signal of the coefficient
multiplier 5 that multiplies the reference cosine wave signal by the filter coefficient W 0 of the
adaptive notch filter 4 is the coefficient multiplier 6 of the coefficient multiplier 6 that multiplies
the reference sine wave signal by the filter coefficient W 1 of the adaptive notch filter 4. The
output signal is added by the adder 7 and supplied to the secondary vibration noise generator 8.
The secondary vibration noise is generated by the secondary vibration noise generator 8 and is
canceled by interfering with the subject vibration noise generated from the vibration noise
source. At this time, the residual signal that can not be silenced is used as an error signal e in an
adaptive control algorithm described later. On the other hand, at the notch frequency to be
muffled determined from the engine speed, a simulated transfer having C 0 simulating the
transfer characteristic from the output of the adaptive notch filter 4 to the adaptive control
algorithm computing unit 15 as coefficient updating means A reference cosine wave signal is
supplied to the transfer element 10 having C1 that simulates the transfer characteristic from the
output of the adaptive notch filter 4 to the adaptive control algorithm computing unit 15 by
supplying the reference cosine wave signal to the transfer element 9 as characteristic correction
means. The correction signal r0 and the error signal e obtained by adding the outputs of the
transfer element 9 and the transfer element 10 in the adder 13 are supplied to the adaptive
control algorithm computing unit 15, and adaptation is performed based on the adaptive control
algorithm, for example, LMS algorithm. The filter coefficient W0 of the notch filter 4 is updated.
Similarly, a reference sine wave signal is supplied to the transfer element 11 having C0
simulating the transfer characteristic from the output of the adaptive notch filter 4 to the
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adaptive control algorithm computing unit 16 at the notch frequency to be muffled determined
from the engine speed Similarly, the reference cosine wave signal is supplied to the transfer
element 12 having (-C1) simulating the transfer characteristic from the output of the adaptive
notch filter 4 to the adaptive control algorithm computing unit 16, and the outputs of the
transfer element 11 and the transfer element 12 Are added by the adder 14 and the error signal
e to the adaptive control algorithm computing unit 16, and the filter coefficient W1 of the
adaptive notch filter 4 is updated based on the adaptive control algorithm, for example, the LMS
algorithm. .
At this time, in the case of the LMS algorithm, the filter coefficients W 0 (n + 1) and W 1 (n + 1)
of the adaptive notch filter 4 are obtained by the following equations. W0 (n + 1) = W0 (n) -μ · e
(n) · r0 (n) (1) W1 (n + 1) = W1 (n) −μ · e (n) · r1 (n) (2) where μ is a step size parameter. In
this manner, the filter coefficients W 0 and W 1 of the adaptive notch filter 4 recursively
converge to an optimal value so as to reduce the vibration noise in the vibration noise
suppression unit so that the error signal e becomes smaller. I will. As described above, the active
vibration noise reduction device described in the present embodiment is inexpensive because it
does not require any discrete arithmetic processing at all when generating the reference cosine
wave signal and the reference sine wave signal. A slow microcomputer can be used as a discrete
arithmetic processing device, and an active vibration noise reduction device can be configured at
low cost to reduce the vibration noise of the rotational secondary component of the 4-cycle 4cylinder engine. In this embodiment, the cosine wave generation means is the low pass filter 23
formed of an analog circuit, but may be a band pass filter formed of an analog circuit. Absent.
Also in this case, the band pass filter is set so that the pass frequency band is the secondary task
vibration noise frequency, and the same effect can be obtained by extracting only cosine waves
having a frequency equal to the frequency of the secondary task vibration noise. In the present
embodiment, the reference signal generating means is the first phase shifter 24 and the second
phase shifter 25. However, the differentiator calculated in the microcomputer 26 It does not
matter. In this case, data obtained by quantizing the cosine wave output from the low pass filter
23 by the microcomputer 26 is used as a reference cosine wave signal, and the difference
between this reference cosine wave signal and the reference cosine wave signal one sample
before is The same effect is achieved by using the obtained differential signal as a reference sine
wave signal. In the present embodiment, the output signal of the synchronous pulse generator 22
is a tach pulse signal, which occurs every 180 degrees of crank angle (in the case of a 4-cycle 4cylinder engine). It may be a TDC sensor signal. In this case, the signal input to the low pass filter
23 is synchronized with the rotational secondary component of the four-stroke four-cylinder
engine 21 and is a pulse wave having a duty of 50% with two cycles per one crank rotation. With
this configuration, in addition to the effects of the above embodiment, since the TDC sensor
signal does not include even-order components in the harmonic components having the
rotational secondary component as the fundamental frequency component, the low-pass filter 23
An effect is obtained that low-order ones can be used.
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Further, in the present embodiment, the case where the secondary vibration noise generator is
applied to an engine muffled sound reduction device in which the speaker is a speaker is shown,
but the secondary vibration noise generator is an electronic control mount device and an engine
The present invention is also applicable to vibration reduction devices, commonly known as
Active Engine Mount devices. As described above, according to the present invention, the
reference cosine wave signal and the reference sine wave signal can be generated without
requiring any discrete numerical operation. A cosine wave can be generated, and in realizing an
active vibration noise control device, a discrete arithmetic processing device with a low
calculation speed can be used, and an effect that an inexpensive microcomputer can be used can
be obtained. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a
configuration of an active vibration noise reduction device according to an embodiment. FIG. 2 is
a block diagram showing the configuration of a low pass filter in the above configuration. FIG. 3
is a block diagram showing the configuration of a phase shifter in the above configuration. FIG. 4
is a graph showing phase characteristics of the same phase shifter. FIG. 5 is a block diagram
showing the configuration of a conventional active vibration noise reduction device. [Description
of the code] 4 adaptive notch filters 5, 6 coefficient multipliers 8 secondary vibration noise
generators 9, 10, 11, 12 transfer elements (simulated transfer characteristic correction means)
15, 16 adaptive control algorithm arithmetic unit (coefficient update means ) 21 4-cycle 4cylinder engine 22 Tach pulse generator (synchronous pulse generator) 23 low pass filter (cosine
wave generator) 24 first phase shifter (reference signal generator) 25 second phase shifter
(reference) Signal generation means) 26 microcomputer
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