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JPH07154899

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DESCRIPTION JPH07154899
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
fluid pressure driven speaker proposed as a speaker dedicated to deep bass reproduction, and
more particularly to a fluid pressure driven speaker having improved frequency characteristics.
[0002]
2. Description of the Related Art A hydraulic servo speaker shown in FIG. 6 has been proposed as
a hydraulic drive speaker. In the hydraulic drive type speaker shown in the figure, the diaphragm
2 as a sound source is attached to the tip of the piston rod 3a of the reciprocating piston 3, and
oil is supplied to the front and rear cylinder chambers 4a and 4b in the hydraulic cylinder 4. The
diaphragm 2 is vibrated to generate a sound by moving the reciprocating piston 3 by flowing in
and out. The inflow and outflow of oil into the hydraulic cylinder 4 is controlled by the servo
valve 5. The control device 6 for controlling the drive of the servo valve 5 receives an audio input
signal from the outside and an acceleration signal from the acceleration sensor 7 attached to the
piston rod 3a. That is, the control system of the fluid pressure drive type speaker aims to
reproduce the sound faithful to the target input by feeding back the acceleration of the
diaphragm 2 displaced together with the piston rod 3a to the input side as the output of the
speaker.
[0003]
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1
Since the diaphragm 2 has an edgeless structure and is driven by the return piston 3, the
displacement of the diaphragm 2 can be increased. In addition, a large sound pressure can be
obtained because a large input can be made using the hydraulic driving force. Due to such
characteristics, the hydraulic drive type speaker can reproduce low frequency sound of about 10
Hz to 100 Hz with a large sound pressure which can not be realized by the conventional voice
coil type speaker. Therefore, by combining the hydraulic drive type speaker and the voice coil
type speaker to constitute a speaker system, it is possible to reproduce powerful sound from the
super low frequency range around 10 Hz to the high frequency range.
[0004]
By the way, when the conventional hydraulic drive type speaker and the voice coil type speaker
are used in combination, since the upper limit of the sound generation range of the hydraulic
drive type speaker is about 100 Hz, the voice coil is used. The crossover point with the speaker is
set to 100 Hz or less. However, at a crossover point of 100 Hz or less, the continuity between the
two reproduced sounds is not always good, and there are cases where it is not possible to flatten
the frequency characteristics of the system from the super low range to the high range.
[0005]
Therefore, it is required to increase the generation range of the hydraulic drive speaker to 100
Hz or more. For that purpose, a control system must be established to flatten the frequency
characteristic of the hydraulic drive speaker from around 10 Hz to a range of 100 Hz or more.
[0006]
However, the control system of the liquid pressure drive type speaker monitors the acceleration
of the diaphragm 2 as the output of the speaker, and the control system of the liquid pressure
drive type speaker simultaneously controls the vibration position of the diaphragm 3 for the
purpose of improving the characteristics of the acceleration. When it is difficult to forcibly extend
the frequency characteristics to a high frequency with such a control system, the vibration
position of the diaphragm 2 is largely shifted in a short time after the start of operation, and
finally, the sound reaches the limit of the cylinder stroke. There is a fatal problem that it can not
be released.
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2
[0007]
The present invention was conceived under such circumstances, and its object is to use a
hydraulic drive capable of improving frequency characteristics up to a desired high range in
which the continuity with the reproduced sound of the voice coil type speaker becomes good. To
provide a type speaker.
[0008]
SUMMARY OF THE INVENTION In order to achieve the above object, according to a first aspect
of the present invention, there is provided a fluid pressure vibration speaker in which pressure
fluid flows into and out of a fluid pressure cylinder to move a reciprocating piston. Based on a
fluid pressure driven speaker that generates sound by vibrating a diaphragm fixed to the tip, a
servo valve that controls the inflow and outflow of pressure fluid into the hydraulic cylinder, and
displacement of the diaphragm Internal feedback means functioning as a spring for feedback to
the internal circuit of the servo valve and for always returning the diaphragm to the home
position.
[0009]
In the hydraulic vibration speaker according to the second aspect of the present invention, the
pressure fluid is caused to flow into and out of the hydraulic cylinder to move the reciprocating
piston, thereby vibrating the diaphragm fixed to the tip of the piston to generate sound. On the
premise of a fluid pressure driven speaker, a servo valve for controlling the inflow and outflow of
pressure fluid into the fluid pressure cylinder and a displacement of the diaphragm are fed back
to the internal circuit of the servo valve, and the diaphragm is always a home Internal feedback
means functioning as a spring for returning to the position, the diaphragm, the reciprocating
piston, the hydraulic cylinder, the servo valve, and the state Xf of the controlled object consisting
of the internal feedback means and voice input from the outside and a controller for outputting a
control input u of the servo valve based on i, the controller having a steady-state deviation e of
the control system, that is, an acceleration d2 x / dt2 of the diaphragm. And an internal model
circuit designed according to the audio input i in order to eliminate the difference between the
above-mentioned audio input i and the internal model circuit obtained by inputting the steady
state deviation e with respect to the audio input i of a predetermined band to this internal model
circuit. From the value obtained by multiplying the feedback gain Kc0 by the state Xc of the
model, a value obtained by multiplying the feedback gain Kf0 by the state Xf to be controlled is
subtracted, and the value obtained by multiplying this by the feedback gain Σ is the control
input u of the servo valve. And the feedback gains Kc0, Kf0 and .SIGMA. Are weighted square
integrals of the steady state deviation e and the control input u.
[0011]
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It is desirable that the ratio be set to minimize.
[0012]
The hydraulic drive speaker according to the first aspect of the invention has internal feedback
means which functions as a spring for feeding back the displacement of the diaphragm to the
internal circuit of the servo valve and returning the diaphragm to the home position all the time.
Therefore, even when the control system for driving the hydraulic drive speaker according to the
target input has a function of controlling the position of the diaphragm, the diaphragm can
always be vibrated at the home position.
Therefore, the position of the diaphragm does not matter, and control can be added to flatten the
acceleration characteristic of the diaphragm up to the high region, and a range of 100 Hz or
more which can not be output by the conventional hydraulic drive type speaker Frequency
characteristics can be improved.
Originally, it is preferable in terms of characteristics that the speaker does not have a spring
effect in terms of characteristics, but the hydraulic drive speaker of the present invention has a
spring effect in a controlled manner, so the spring does not support the frequency
characteristics. It is possible to control the degree of preference appropriately.
[0013]
According to a second aspect of the present invention, there is provided a liquid pressure driven
speaker according to the first aspect of the present invention, the control comprising the
diaphragm, the reciprocating piston, the liquid pressure cylinder, the servo valve and the internal
feedback means. A control device is added to control an object based on the optimal control
theory, and the above-mentioned square integral is applied to the voice input i of a
predetermined frequency band for which the frequency characteristic is to be improved.
[0015]
By setting the gains Kc0 and Kf0 and the parameter Σ so as to minimize the frequency
characteristic and forming a control system, it is possible to flatten the frequency characteristic
of the desired band.
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4
Although this control system does not have a function to control the vibration position of the
diaphragm, since the control object itself is equipped with the above-mentioned internal feedback
means, the diaphragm is always vibrated at the home position, and a desired frequency of 100
Hz or more is desired. The frequency characteristics can be improved up to the treble range of
[0016]
Thus, the fluid pressure drive type speaker of the present invention can improve its frequency
characteristic to a high frequency range of 100 Hz or more where the continuity with the
reproduction sound of the voice coil type speaker becomes good.
Therefore, by simultaneously using two types of speakers, hydraulic drive type and voice coil
type, and superimposing the reproduced sound of both types of speakers in a predetermined
range of 100 Hz or more, the frequency from super low range to high range You can flatten the
characteristics.
[0017]
EXAMPLES Examples of the present invention will now be described.
[0018]
FIG. 1 is a schematic configuration view showing an embodiment of a hydraulic drive speaker
according to the present invention.
[0019]
The hydraulic drive speaker shown in the figure includes an acoustic output unit including the
speaker frame 1 and the diaphragm 2, a hydraulic drive unit including the return piston 3, the
hydraulic cylinder 4 and the servo valve 5, and an external unit. And a controller 6 for
controlling the servo valve 5 according to the voice input i.
[0020]
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5
The speaker frame 1 is fitted in and fixed to the opening of the speaker box 7 so as to surround
the diaphragm 2.
The diaphragm 2 is fixed to the end of the piston rod 3 a of the return piston 3, and a hydraulic
cylinder 4 for supporting the return piston 3 is fixed at the center of the back of the speaker
frame 1.
A piston rod 3b slidably contacting the inner wall of the hydraulic cylinder 4 is provided at an
intermediate portion of the piston rod 3a of the reciprocating piston 3. The inside of the
hydraulic cylinder 4 is provided with the front and rear cylinder chambers 4a and 4b by this
piston head 3b. It is divided into
By adjusting the inflow and outflow of the pressure fluid to the front and rear cylinder chambers
4a and 4b by the servo valve 5, the reciprocating piston 3 is driven back and forth.
That is, under the control of the servo valve 5, when the hydraulic fluid is guided to the front
cylinder chamber 4a, the reciprocating piston 3 is displaced rearward, and when the hydraulic
fluid is guided to the rear cylinder chamber 4b, The reciprocating piston 3 is displaced to the
front side.
[0021]
The servo valve 5 regulates the inflow and outflow of the hydraulic fluid to the front and rear
cylinder chambers 4a and 4b in the hydraulic cylinder 4 by adjusting the displacement of the
spool provided inside thereof. An electromagnetic mechanism (torque motor) for displacement
and an internal circuit for controlling the electromagnetic mechanism in accordance with a
control input signal are provided.
The servo valve 5 is configured such that a displacement signal from a displacement sensor 8
provided on the piston rod 3a is input (internal feedback) to its internal circuit, and displacement
of the diaphragm 2 from the home position (piston rod In order to apply a restoring force
proportional to the displacement 3a) to the return piston 3, the inflow and outflow of the
hydraulic fluid to the front and rear cylinder chambers 4a and 4b are controlled. That is, the fluid
pressure drive part of this fluid pressure drive type speaker is equipped with an internal
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6
feedback means functioning as a spring for always returning the diaphragm 2 to the home
position. The spring function by this internal feedback functions regardless of the presence or
absence of the control input u from the control device 6. Therefore, even when the liquid
pressure drive type speaker stops driving with the diaphragm 2 moved from the home position,
the diaphragm 2 moves to the home position immediately upon activating the speaker, and the
control input from the control device 6 When u is emitted, the servo valve 5 is driven accordingly
to vibrate the diaphragm 2 at the home position.
[0022]
FIG. 2 shows a schematic view of a control system of this hydraulic drive speaker. The control
device 6 is designed with the system consisting of the diaphragm 2, the reciprocating piston 3,
the hydraulic cylinder 4, the servo valve 5 and the internal feedback means as the control object
10, and the steady deviation e, that is, the diaphragm The internal model circuit 9 is designed
according to the voice input i in order to eliminate the difference between the acceleration d2 x /
dt2 of 2 and the voice input i from the outside. Then, a value obtained by multiplying the
feedback gain Kc0 by the state Xc of the internal model obtained by inputting the difference
between the steady-state error e with respect to the audio input i of the predetermined frequency
band and the external audio input i to the internal model circuit 9 Then, a value obtained by
multiplying the feedback gain Kf0 by the state Xf to be controlled is subtracted, and a value
obtained by multiplying the feedback gain Σ by this is output as the control input u of the servo
valve 5. Then, the above-mentioned square integral is applied to the voice input i of the
predetermined frequency band for which the frequency characteristic is to be improved
[0024]
By setting the feedback gains Kc0, Kf0 and Σ so as to minimize the control system, the
frequency characteristic of the desired band can be made flat. Although this control system does
not have a function to control the vibration position of the diaphragm 2, since the control target
10 includes the above-mentioned internal feedback means, the diaphragm 2 is always vibrated at
the home position, and 100 Hz or more The frequency characteristics can be improved up to the
desired treble range of
[0025]
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7
For example, the displacement x of the diaphragm 2, the velocity dx / dt, the differential pressure
Pm between the cylinder chambers 4a and 4b in the hydraulic cylinder 4 and the output flow
rate q of the servo valve 5 are selected as the state Xf to be controlled. be able to. In that case,
the displacement sensor 8 can be used as a means for detecting the displacement x. Further, the
velocity dx / dt can be obtained by differentiating the displacement detected by the displacement
sensor 8. The differential pressure Pm between the cylinder chambers 4a and 4b is obtained by
providing the pressure sensors 11a and 11b in the cylinder chambers 4a and 4b as shown in FIG.
1 and taking the difference between the detection values of the two sensors 11a and 11b. Be
Further, the servo valve output flow rate q is detected by providing the flow rate sensor 12 at the
pressure liquid supply port in the servo valve 5.
[0026]
FIG. 3 is a block diagram showing an example of the control system in that case, and Kf0 (1), Kf0
(2), Kf0 (3) and Kf0 (4) are respectively displacement x and velocity dx / It is a feedback gain
applied to dt, differential pressure Pm and servo valve output flow rate q. Also, in this case, as the
state Xc of the internal model obtained by inputting the steady state deviation e to the internal
model circuit 9, the state Xc (1) corresponding to acceleration and the state Xc (2) corresponding
to the velocity are output. Kc0 (1) and Kc0 (2) are controller gains respectively applied to the
states Xc (1) and Xc (2) of these internal models. Then, this control system multiplies the
feedback gains Kc0 (1) and Kc0 (2) by the state Xc (1) and the state Xc (2) of the internal model,
respectively, and adds the two together to obtain A value obtained by multiplying the
displacement x, speed dx / dt, differential pressure Pm and flow rate q, which are in the state,
with feedback gains Kf0 (1), Kf0 (2), Kf0 (3) and Kf0 (4) respectively and adding them , And a
value obtained by multiplying this by the feedback gain Σ as a control input u.
[0027]
To design this control system, that is, to determine each of the feedback gains Kc0 (1), Kc0 (2),
Kf0 (1), Kf0 (2), Kf0 (3), Kf0 (4) and Σ. Return to
[0028]
The ILQ (Invers Linear Quadratic) design method is suitable for designing this type of control
system.
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The ILQ design method is optimal with regard to some weights Q (> 0) and R (> 0), instead of
specifying the weights first to determine optimal control as in the conventional optimal regulator
(LQ) It is a theory that can simplify the design while maintaining the features of the optimal
regulator (low sensitivity characteristics, robust stability, etc.) by obtaining such state feedback,
and is proposed by one of the present inventors (reference Literature; Fujii and Mizushima. A
new attempt to LQ design. Transactions of Measurement and Control Society Vol. 23, No. 2 (Feb.
1987), Fujii and Shimomura. Generalization of ILQ optimal servo design method. Transactions of
the Institute of Systems, Control and Information Engineers Vol. 1, No. 6, pp 194 to 203, 1988).
[0029]
Therefore, here, the control system of the above-mentioned hydraulic drive loudspeaker is
designed by the ILQ design method, and the effectiveness is shown.
[0030]
First, the equation of motion to be controlled is created based on the physical law.
[0032]
From the equations of motion of these models, x, dx / dt, Pm, and q are taken as states, and they
are converted into state space expressions as follows.
[0034]
From the output y = d2 x / dt2, the following output equation is obtained.
[0036]
Here, each parameter included in the model is selected as follows:
[0038]
Kf0 = [Kf0 (1) Kf0 (2) Kf0 (2) Kf0 (3) Kf0 (4)] and Kc0 = [Kc0 (Kf0) according to ILQ CAD using
the second-order vibration system model represented by the following equation (7) as the
internal model 1) Calculated Kc0 (2)].
[0039]
As a result, the following values were obtained.
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[0041]
Kf0 = [1.1899e-4 -1.8358e-4 -2.5252e-5 4.4796e-5] Kc0 = [1.5813e4 1.3454 el] However, in
the ILQ design method, Σ can be extracted as a gain adjustment parameter, in this case Σ =
2000.
[0042]
FIG. 4 is a state variable diagram showing a control system in which each feedback gain is
determined to the above value.
However, the displacement feedback gain KF is variable in the range of 0 to 10, and the position
of the diaphragm 2 is determined in the range not reaching the stroke limit of the hydraulic
cylinder 4.
[0043]
When the closed loop frequency response of this control system was examined with KF = 10, as
shown in FIG. 5, the frequency characteristics from around 10 Hz to around 400 Hz could be
made flat.
[0044]
Therefore, by using the hydraulic drive speaker and the voice coil speaker at the same time, by
superimposing the reproduced sound of both types of speakers in a predetermined sound range
of 100 Hz to 400 Hz, the vicinity of 10 Hz which can be output by the hydraulic drive speaker A
speaker system having a flat frequency characteristic can be realized from the extremely low
frequency range to the high frequency range which can be output by the voice coil type speaker.
[0045]
In particular, when the control system of the hydraulic drive speaker is designed by the ILQ
design method, since the value of Σ can be adjusted after design, the frequency response of the
hydraulic drive speaker is specified according to the characteristics of the voice coil speaker
used. it can.
[0046]
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As described above, according to the present invention, the following excellent effects can be
exhibited.
[0047]
(1) The fluid pressure driven speaker according to claim 1 comprises internal feedback means
which functions as a spring for feeding back the displacement of the diaphragm to the internal
circuit of the servo valve and always returning the diaphragm to the home position. Therefore,
the diaphragm can be always vibrated at the home position.
Therefore, the position of the diaphragm does not matter, and control can be added to flatten the
acceleration characteristic of the diaphragm up to the high region, and a range of 100 Hz or
more which can not be output by the conventional hydraulic drive type speaker Frequency
characteristics can be improved.
[0048]
(2) In the hydraulic drive speaker according to claim 2, the square integral is applied to the voice
input i of the predetermined frequency band for which it is desired to improve the frequency
characteristic.
[0050]
By setting the feedback gains Kc0, Kf0 and Σ so as to minimize the control system, the
frequency characteristics of the desired band can be made flat.
Since the control target itself is provided with the internal feedback means, the diaphragm can be
always vibrated at the home position, and the frequency characteristic can be improved to a
desired high range of 100 Hz or more.
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