U.S. patent application number 13/626041 was filed with the patent office on 2014-03-27 for method for an equivalent circuit parameter estimation of a transducer and a sonar system using thereof.
The applicant listed for this patent is Byung Hwa LEE, Jeong Min LEE. Invention is credited to Byung Hwa LEE, Jeong Min LEE.
Application Number | 20140086013 13/626041 |
Document ID | / |
Family ID | 50338723 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140086013 |
Kind Code |
A1 |
LEE; Jeong Min ; et
al. |
March 27, 2014 |
METHOD FOR AN EQUIVALENT CIRCUIT PARAMETER ESTIMATION OF A
TRANSDUCER AND A SONAR SYSTEM USING THEREOF
Abstract
The present disclosure relates to an active sonar system
including a transmitter; a transducer; and an impedance matching
circuit, and a method of estimating an equivalent model parameter
of a multi-mode transducer, wherein an electrical equivalent model
parameter having a plurality of stages corresponding to each mode
is estimated by estimating an individual mode impedance and a total
mode impedance from multi-mode impedance data and obtaining an
interference amount of adjacent modes, and an equivalent model
modeled thereby for which an interference effect by a multi-mode is
taken into consideration is used for the design of an impedance
matching circuit to minimize actual model fabrication and
effectively derive detailed design elements and the like, thereby
allowing an integrated circuit design with peripheral electronic
units for interfacing the sonar system.
Inventors: |
LEE; Jeong Min;
(Gyeongsangnam-Do, KR) ; LEE; Byung Hwa;
(Gyeongsangbuk-Do, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LEE; Jeong Min
LEE; Byung Hwa |
Gyeongsangnam-Do
Gyeongsangbuk-Do |
|
KR
KR |
|
|
Family ID: |
50338723 |
Appl. No.: |
13/626041 |
Filed: |
September 25, 2012 |
Current U.S.
Class: |
367/87 ;
703/2 |
Current CPC
Class: |
G01S 7/524 20130101;
G01S 7/52004 20130101 |
Class at
Publication: |
367/87 ;
703/2 |
International
Class: |
G01S 15/00 20060101
G01S015/00; G06F 17/10 20060101 G06F017/10 |
Claims
1. A method of estimating an equivalent model parameter of a
multi-mode transducer, wherein an electrical equivalent model
parameter having a plurality of stages corresponding to each mode
is estimated by estimating an individual mode impedance and a total
mode impedance from multi-mode impedance data and considering an
interference amount of adjacent modes.
2. The method of claim 1, comprising: a resonant frequency
derivation process of dividing a frequency section for divisions
between resonant modes and obtaining a resonant frequency
corresponding to each mode; an individual mode impedance estimation
process of removing an interference effect of adjacent modes within
the divided mode section to obtain an impedance for each mode; and
a multi-mode impedance estimation process of considering even a
multi-mode impedance characteristic in which individual modes are
combined to have an effect on one another.
3. The method of claim 2, further comprising: an interference
amount derivation process of quantitatively deriving an
interference effect between adjacent modes; and a resonant
frequency failure correction process of correcting a failure of the
resonant frequency from the interference amount.
4. The method of claim 2, wherein the resonant frequency derivation
process divides a frequency section for each mode by a minimum
point of the conductance from impedance data, and derives a maximum
point as a resonant frequency of the relevant mode.
5. The method of claim 2, wherein the individual mode impedance
estimation process comprises: an individual mode impedance
computation process of removing an interference component combined
with a k-th resonant mode from a measured total admittance and
computing a k-th individual mode impedance; and a fitness function
generation process of displaying an error average between the
computed k-th individual mode impedance and a k-th resonant mode
impedance to be estimated as a fitness function (B.sub.k) to be
minimized in the relevant mode section.
6. The method of claim 2, wherein the multi-mode impedance
estimation process estimates a total impedance for which impedance
estimation values of individual modes for a multi-mode equivalent
model are combined, and generates it as another fitness function
(A) to minimize an error from the measured impedance.
7. The method of claim 3, wherein the resonant frequency failure
correction process corrects a resonant frequency in the direction
of its differential values being the same when a differential value
of a total measured conductance is different from a sum of
differential values for interfered adjacent mode conductances at
the computed resonant frequency.
8. The method of claim 5, wherein a resultant fitness function (F)
is expressed as: F = C 1 A + C 2 k = 1 N B k ##EQU00004## by
applying weight constants (C.sub.1, C.sub.2) to take an item for
minimizing the individual mode estimation error and an item for
minimizing an total mode estimation error into consideration at the
same time.
9. An active sonar system, comprising: a transmitter modeled as an
input power source and an input impedance; a transducer configured
to convert an electrical signal of the transmitter into an acoustic
wave or convert an acoustic wave of the outside into an electrical
signal; and an impedance matching circuit configured to transmit
the electric power of the transmitter to the transducer between the
transmitter and transducer, wherein the transducer is modeled as an
electrical equivalent model parameter having a plurality of stages
corresponding to each mode by estimating an individual mode
impedance and a total mode impedance from multi-mode impedance data
and considering an interference amount of adjacent modes.
10. The active sonar system of claim 9, wherein the transducer is
modeled to estimate a multi-mode impedance by dividing a frequency
section for divisions between resonant modes and obtaining a
resonant frequency corresponding to each mode, and removing an
interference effect of adjacent modes within the divided mode
section to obtain an impedance for each mode, and considering even
a multi-mode impedance characteristic in which individual modes are
combined to have an effect on one another in an integrated
manner.
11. The active sonar system of claim 9, wherein the transducer is
modeled by quantifying an interference effect between adjacent
modes and correcting a failure of the resonant frequency.
12. The active sonar system of claim 10, wherein the transducer is
modeled by dividing a frequency section for each mode by a minimum
point of the conductance from impedance data, and deriving a
maximum point as a resonant frequency of the relevant mode.
13. The active sonar system of claim 10, wherein the transducer is
modeled by removing an interference component combined with a k-th
resonant mode from a measured total admittance and computing a k-th
individual mode impedance, and generating an error average between
the computed k-th individual mode impedance and a k-th resonant
mode impedance to be estimated as a fitness function (B.sub.k) to
be minimized in the relevant mode section
14. The active sonar system of claim 10, wherein the transducer is
modeled by estimating a total impedance for which impedance
estimation values of individual modes for a multi-mode equivalent
model are combined, and generating it as another fitness function
(A) to minimize an error from the measured impedance.
15. The active sonar system of claim 11, wherein the transducer is
modeled by correcting a resonant frequency in the direction of its
differential values being the same when a differential value of a
total measured conductance is different from a sum of differential
values for interfered adjacent mode conductances.
16. The method of claim 6, wherein a resultant fitness function (F)
is expressed as: F = C 1 A + C 2 k = 1 N B k ##EQU00005## by
applying weight constants (C.sub.1, C.sub.2) to take an item for
minimizing the individual mode estimation error and an item for
minimizing an total mode estimation error into consideration at the
same time.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present disclosure relates to a method of estimating an
equivalent model parameter of a transducer and a sonar system using
the same, and more particularly, to a method of estimating an
equivalent model parameter of a transducer in which a case where a
mutual impedance interference effect between adjacent resonant
modes of a multi-mode transducer is large and the interference
contributions thereof are different is taken into consideration,
and a sonar system using the same.
[0003] 2. Description of the Related Art
[0004] An active sonar system is a system for transmitting
underwater acoustic waves and detecting signals reflected from a
target, and the detection performance may be dependent upon how
large acoustic output power is transmitted in a desired direction.
Accordingly, the characteristic of an electrical impedance of the
transducer which is a load should be first correctly specified for
the purpose of the design of a high output power transmitter
constituting an active sonar. Furthermore, an impedance matching
circuit corresponding to an interfacing circuit between
transmitter-transducer is very important to effectively transmit
the maximum power from the transmitter to the load. If the
impedance characteristic of a transducer is expressed as an
electrical equivalent model, then it may be possible to obtain
integrated model for a transmitter-matching circuit-transducer
which is a primary constituent element of the active sonar, thereby
allowing an effective design and analysis.
[0005] Equivalent modeling for a transducer in the related art has
been primarily limited to a narrow-band single-mode transducer with
no interference of adjacent resonant modes but equivalent modeling
for a multi-mode transducer in which there exist several resonant
modes within a broadband has been difficult to obtain correct
estimation with an analytical method due to a mutual effect of
adjacent resonant modes. As an equivalent modeling method for the
multi-mode transducer, there have been proposed a method of
deriving an approximate equation from the slope of measured
admittance and resonant frequency information for each resonant
mode and obtaining an equivalent model parameter from it, and the
like, but it has a disadvantage that an interference effect between
adjacent resonant modes is not taken into consideration and thus
the estimation error is very large. In order to overcome the
foregoing problem, an optimization method has been applied thereto,
but in case of a resonant mode having a relatively small impedance
contribution among adjacent resonant modes, it has a problem that
the estimation of a resonant mode is impossible or there occurs a
failure for the resonant frequency of the estimated mode.
Furthermore, it has a problem that a complex calculation is
required to derive an initial value during the process of
estimating an equivalent model parameter from impedance data, and
the estimation result is largely dependent upon the initial
value.
SUMMARY OF THE INVENTION
[0006] A task to be solved by the present disclosure is to solve
the foregoing problem, and there is provided a new method of
equivalent model parameter for which an interference effect for
each resonant mode is taken into consideration for a multi-mode
transducer in which there exist an interference effect between
adjacent resonant modes.
[0007] Another task to be solved by the present disclosure is to
solve the foregoing problem, and there is provided a sonar system
including a transducer modeled as the above equivalent model, in a
transmitting unit of an active sonar system including a
transmitter, an impedance matching circuit, and a transducer.
[0008] The objective of the present disclosure may be accomplished
by providing a method of estimating an equivalent model parameter
of a multi-mode transducer, wherein an electrical equivalent model
parameter having a plurality of stages corresponding to each mode
is estimated by estimating an individual mode impedance and a total
mode impedance from multi-mode impedance data and considering an
interference amount of adjacent modes.
[0009] The equivalent model parameter estimation method may include
a resonant frequency derivation process of dividing a frequency
section for divisions between resonant modes and obtaining a
resonant frequency corresponding to each mode; an individual mode
impedance estimation process of removing an interference effect of
adjacent modes within the divided mode section to obtain an
impedance for each mode (S300); and a multi-mode impedance
estimation process of considering even a multi-mode impedance
characteristic in which individual modes are combined to have an
effect on one another.
[0010] The equivalent model parameter estimation method may further
include an interference amount derivation process of quantitatively
deriving an interference effect between adjacent modes; and a
resonant frequency failure correction process of correcting a
failure of the resonant frequency from the interference amount.
[0011] The resonant frequency derivation process may divide a
frequency section for each mode by a minimum point of the
conductance from impedance data, and derive a maximum point as a
resonant frequency of the relevant mode. The individual mode
impedance estimation process may include an individual mode
impedance computation process of removing an interference component
combined with a k-th resonant mode from a measured total admittance
and computing a k-th individual mode impedance; and a fitness
function display process of displaying an error average between the
computed k-th individual mode impedance and a k-th resonant mode
impedance to be estimated as a fitness function (B.sub.k) to be
minimized in the relevant mode section.
[0012] The multi-mode impedance estimation process may estimate a
total impedance for which impedance estimation values of individual
modes for a multi-mode equivalent model are combined, and display
it as another fitness function (A) to minimize an error from the
measured impedance.
[0013] The resonant frequency failure correction process may
correct a resonant frequency in the direction of its differential
values being the same when a differential value of a total measured
conductance is different from a sum of differential values for
interfered adjacent mode conductances at the computed resonant
frequency.
[0014] A resultant fitness function (F) may be expressed as:
F = C 1 A + C 2 k = 1 N B k ##EQU00001##
by applying weight constants (C.sub.1, C.sub.2).
[0015] Furthermore, the objective of the present disclosure may be
accomplished by an active sonar system, including a transmitter
modeled as an input power source and an input impedance; a
transducer configured to convert an electrical signal of the
transmitter into an acoustic wave or convert an acoustic wave of
the outside into an electrical signal; and an impedance matching
circuit configured to transmit the electric power of the
transmitter to the transducer between the transmitter and
transducer, wherein the transducer is modeled as an electrical
equivalent model parameter having a plurality of stages
corresponding to each mode by estimating an individual mode
impedance and a total mode impedance from multi-mode impedance data
and considering an interference amount of adjacent modes.
[0016] The transducer may be modeled to estimate a multi-mode
impedance by dividing a frequency section for divisions between
resonant modes and obtaining a resonant frequency corresponding to
each mode, and removing an interference effect of adjacent modes
within the divided mode section to obtain an impedance for each
mode, and considering even a multi-mode impedance characteristic in
which individual modes are combined to have an effect on one
another in an integrated manner.
[0017] The transducer may be modeled by quantifying an interference
effect between adjacent modes and correcting a failure of the
resonant frequency.
[0018] The transducer may be modeled by dividing a frequency
section for each mode by a minimum point of the conductance from
impedance data, and deriving a maximum point as a resonant
frequency of the relevant mode.
[0019] The transducer is modeled by removing an interference
component combined with a k-th resonant mode from a measured total
admittance and computing a k-th individual mode impedance, and
displaying an error average between the computed k-th individual
mode impedance and a k-th resonant mode impedance to be estimated
as a fitness function (B.sub.k) to be minimized in the relevant
mode section
[0020] The transducer may be modeled by estimating a total
impedance for which impedance estimation values of individual modes
for a multi-mode equivalent model are combined, and displaying it
as another fitness function (A) to minimize an error from the
measured impedance.
[0021] The transducer may be modeled by correcting a resonant
frequency in the direction of its differential values being the
same when a differential value of a total measured conductance is
different from a sum of differential values for interfered adjacent
mode conductances.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
[0023] In the drawings:
[0024] FIG. 1A and FIG. 1B are a view illustrating an impedance
characteristic according to the frequency of the acoustic and
ultrasonic wave bands in a multi-mode transducer according to the
present disclosure;
[0025] FIG. 2A and FIG. 2B are a circuit diagram illustrating an
impedance characteristic of the multi-mode transducer according to
the present disclosure as an electrical equivalent model using an
electrical lumped element;
[0026] FIG. 3 is an exemplary view illustrating a measured
conductance and an estimated conductance for each mode when there
exist mutual interference by adjacent modes;
[0027] FIG. 4 is a flow chart illustrating the process of
performing a broadband equivalent model parameter estimation method
of the multi-mode transducer 220 in which there exists an
interference effect between adjacent modes within a broadband
contrived by the present disclosure;
[0028] FIG. 5A and FIG. 5B are a view illustrating a conductance of
the transducer having three resonant modes according to the present
disclosure, a frequency section for each mode divided through
differentiating the frequency of the conductance, and a resonant
frequency of the relevant mode;
[0029] FIG. 6A, FIG. 6B and FIG. 6C are a comparison chart in which
an estimated value and a measured value of the conductance
component for each resonant mode are compared with each other on an
impedance characteristic from which the interference effect of
adjacent resonant modes is removed; and
[0030] FIG. 7 is a circuit diagram illustrating a transmitting unit
of the active sonar system modeled as a transmitter, an impedance
matching circuit, and a transducer according to the present
disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Hereinafter, a method of estimating an equivalent model
parameter of a transducer according to an embodiment of the present
disclosure and a sonar system using the same will be described in
detail.
[0032] FIG. 1A and FIG. 1B are a view illustrating an impedance
characteristic according to the frequency of the acoustic and
ultrasonic wave bands in a multi-mode transducer 220 according to
the present disclosure. FIG. 1A illustrates a magnitude value of
the impedance according to the frequency, and FIG. 1B illustrates a
phase value of the impedance according to the frequency. It is seen
that resonance occurs at a frequency adjacent to the phase peak
value, and the number of resonances corresponds to the number of
modes.
[0033] FIG. 2A and FIG. 2B are a circuit diagram illustrating an
impedance characteristic of the multi-mode transducer 220 according
to the present disclosure as an electrical equivalent model using
electrical lumped elements. In other words, a transducer made of an
electrical-mechanical-acoustic structure is formulated into an
electrical equivalent model as illustrated in FIG. 2A and FIG. 2B
using the impedance data of the multi-mode transducer in which
there exist several resonant modes in FIG. 1A and FIG. 1B, and the
equivalent model may be used in an integrated design together with
the transmitter and impedance matching circuit of the active sonar
system. The electrical characteristic impedance 225 in FIG. 2A is a
portion indicating an electrical characteristic of the transducer,
and a first through a third resonant circuit 221-223 illustrate
mechanical-acoustic characteristics, and the individual resonant
circuits are regarded as portions expressing one resonant mode,
respectively. Furthermore, FIG. 2B is an example of an actually
configured circuit using R-L-C lumped elements, and the electrical
characteristic impedance 225 may be expressed as an electrical
capacitance, and the first through the third resonant circuit
221-223 as R-L-C series resonant circuits.
[0034] FIG. 3 is an exemplary view illustrating a measured
conductance and an estimated conductance for each mode when there
exist mutual interference by adjacent modes.
[0035] However, the multi-mode impedance characteristic in FIG. 1A
and FIG. 1B may include a mutual interference effect of adjacent
resonant modes without being configured with a simple sum of
individual resonant modes. For example, taking two resonant modes
in which there exist an interference effect between adjacent modes
into consideration, the characteristic of a measured total resonant
mode conductance (the real part of admittance corresponding to a
reciprocal number of the impedance 31) is different from that of
pure individual mode conductances (first mode conductance 32,
second mode conductance 33) and thus it is seen that they are
different from each other in the aspect of the resonant frequency
and magnitude of conductance.
[0036] Though the first mode conductance 32 by only an estimated
individual mode has a maximum value G.sub.1max at a resonant
frequency f'.sub.s1 and the second mode conductance 33 has a
maximum value G.sub.2max at a resonant frequency f'.sub.s2, the
total resonant mode conductance 31 by a measured total resonant
mode has maximum values G.sub.T1 and G.sub.T2, respectively, at
resonant frequencies f.sub.s1 and f.sub.s2. It is caused by
interference by a mutual effect between the first and second modes
which are resonant modes.
[0037] Referring to FIG. 3, the resonant frequency f'.sub.s1 of the
first mode conductance 32 and the resonant frequency f.sub.s1 of
the measured total resonant mode conductance 31 have different
values because a value of the second mode conductance 33 is not an
ignorable small value compared to the maximum value G.sub.1max of
the first mode conductance 32 at the resonant frequency f'.sub.s1'
of the first mode conductance 32. Similarly, for the second mode
conductance 33, the resonant frequency f'.sub.s2 of the second mode
conductance 33 and the resonant frequency f.sub.s2 of the measured
total resonant mode conductance 31 may have different values.
[0038] The following multi-mode transducer equivalent modeling
method considers an adjacent interference effect between resonant
modes, and thus it may be possible to minimize an error between the
measured total impedance characteristic and the estimated impedance
characteristic by an individual mode parameter, and an equivalent
model parameter estimation scheme of the multi-mode transducer 220
is as follows.
[0039] In this aspect, FIG. 4 is a flow chart illustrating the
process of performing a broadband equivalent model parameter
estimation method of the multi-mode transducer 220 in which there
exists an interference effect between adjacent modes within a
broadband contrived by the present disclosure.
[0040] The equivalent model parameter estimation method may be
carried out by an initial value generation process (S100), a
resonant frequency derivation process (S200), an individual mode
impedance estimation process (S300), a total mode impedance
estimation process (S400), an inter-mode interference amount
determination process (S500), a resonant frequency correction
process (S600), and an equivalent model parameter derivation
process (S700).
[0041] As illustrated in the drawing, an initial value is randomly
generated (S100) by acquiring the measured impedance information of
the object transducer and applying a probability optimization
algorithm using a solution set which is not one solution without a
computation process for deriving an initial value of the equivalent
model parameter. A frequency section is divided for divisions
between resonant modes, and a resonant frequency corresponding to
each mode is derived (S200). An interference effect of adjacent
modes within the divided mode section is removed and an equivalent
model parameter expressing an independent impedance characteristic
for the relevant individual mode is estimated (S300). It is
estimated (S400) by considering even a multi-mode impedance
characteristic combined with independent individual modes to have
an effect on one another in an integrated manner. An interference
amount between adjacent modes is quantitatively determined (S500)
to correct a resonant frequency of the relevant mode (S600), and
when the interference amount is large, the resonant frequency of
the relevant mode is corrected (S600), and as a result, an
equivalent circuit parameter of the multi-mode transducer is
derived (S700).
[0042] For an optimization method for deriving an equivalent
circuit parameter for the multi-mode transducer, there are
algorithms such as a gene, a least square method, and the like, but
an operation for deriving an initial value should be is carried out
in advance for most of the algorithms in the optimization process.
During this process, parameter initial values are derived through a
complex calculation from characteristic information on an impedance
or property value of the transducer, and in most cases, the derived
initial values are closely related to the accuracy of a finally
estimated parameter. Accordingly, in order to solve the problem,
according to the present disclosure, initial values of the
equivalent model parameter are randomly generated (S100) by
applying a probability optimization algorithm using a solution set
which is not one solution to use them in the optimization
process.
[0043] For divisions between resonant modes and resonant frequency
derivation from the measured transducer impedance data, a maximum
point and a minimum point of the conductance corresponding to the
real part of the transducer admittance are obtained as illustrated
in FIG. 5A. The maximum point of conductance is derived by resonant
frequencies (fr1, fr2, fr3) of the relevant mode, and the minimum
point of the conductance is determined by references (fd1, fd2,
fd3) for dividing the frequency section for each mode. For an
example of the method of deriving a maximum point and a minimum
point of the transducer conductance, there is a method of obtaining
the extreme point from differentiation for a frequency of the
conductance component illustrated in FIG. 5A similarly to FIG. 5B.
Accordingly, divisions between modes and derivation of a resonant
frequency (S200) can be implemented even for a multi-mode with a
different mutual interference amount between resonant modes.
[0044] As illustrated in FIG. 3, a total impedance characteristic
31 measured within the relevant divided resonant mode section
includes an effect 33 caused by adjacent resonant modes as well as
an effect 32 by the relevant mode, and thus if it can be shown only
with a single mode characteristic by removing the mutually
interfered effect, then an equivalent model for the multi-mode
transducer in which there exists an interference effect of adjacent
modes may be expressed as a sum of individual mode characteristics.
By taking this point into consideration, the impedance
characteristic of each resonant mode is calculated from theoretical
parameter values derived from the estimation process, and the
calculated impedance effect of adjacent modes is subtracted from
the relevant resonant mode to be estimated, thereby sequentially
estimating impedance characteristics for individual modes.
[0045] FIG. 6A, FIG. 6B and FIG. 6C are a comparison chart in which
an estimated value and a measured value of the conductance
component for each mode are compared with each other on an
impedance characteristic from which the interference effect between
adjacent modes is removed. In case where there exist three resonant
modes as illustrated in FIG. 5A, a value in case where an adjacent
resonant mode effect is removed from a total measured value, an
estimated value of the conductance component for each mode, and a
measured value of the conductance component by a total resonant
mode are shown with reference to FIGS. 6A through 6C.
[0046] Referring to FIGS. 6A through 6C, the measured value
(conductance in FIG. 5A) of a total conductance by the first
through the third mode is commonly shown (single dotted line), and
individual conductances (values for which an effect of adjacent
resonant modes is removed from a total measured value; dotted line)
and estimated values (solid lines) for the first mode, the second
mode, and the third mode, respectively, are shown.
[0047] In FIG. 6A, it is seen that the individual conductance
(dotted line) corresponds to a value for which an estimated value
of the second mode and the third mode is subtracted from a measured
value of the total conductance, and a resonant frequency of the
estimated value (solid line) by only the first mode is
substantially identical to a resonant frequency of the measured
value. It is because an interference effect caused by the second
mode and the third mode is small since the first mode is separated
compared to the second and the third mode. On the contrary, in
FIGS. 6B and 6C, it is seen that a resonant frequency of the
estimated value (solid line) only by the second and the third mode,
respectively, has an error compared to a resonant frequency of the
measured value, and it is because the second and the third mode are
close to each other and thus there is interference between them.
Accordingly, an impedance estimation method by taking an
interference effect between adjacent modes into consideration is
required.
[0048] As a method for obtaining an estimated value only for
individual modes from which an interference effect between adjacent
modes is removed, an error average for an arbitrary k-th resonant
mode impedance of the multi-mode transducer is as shown in the
following equation 1.
B k = 1 Xk Q m = 1 xk [ 1 Y real ( .omega. m ) - { Y 0 ( .omega. m
) + Q i = 1 , i @ k N Y i ( .omega. m ) } - Z k ( .omega. m ) ] [
Equation 1 ] ##EQU00002##
[0049] Here, .DELTA.k is the number of measured impedance data
within the k-th resonant mode section, and Z.sub.k is an estimated
theoretical impedance of the equivalent model for the k-th resonant
mode.
[0050] The first term of the denominator is a measure total
admittance component, and the second and third terms are a sum of
admittance components other than the k-th resonant mode.
[0051] Accordingly, the computation of a whole fraction purely
produces only the k-th individual mode impedance characteristic
excluding an interference component combined with the k-th resonant
mode from the measured admittance. A fitness function (B.sub.k) is
shown as Equation 1 to minimize an error average between a result
of the computed k-th individual mode impedance and a k-th resonant
mode impedance (Z.sub.k(.omega.m)) to be theoretically estimated in
the relevant mode section.
[0052] However, when an equivalent model parameter of the
multi-mode transducer is estimated only using this method, an
inclination to estimate only a single mode characteristic excluding
a mutual interference effect of adjacent resonant modes is strong,
and thus when individual modes are combined with one another, it
has a high probability that an estimated error occurs in the aspect
of a total mode. Accordingly, an additional portion of fitness
function to be estimated (S400) by taking a portion having a mutual
effect on the total resonant mode into consideration in an
integrated manner is required. In other words, a theoretical total
impedance for a multi-mode equivalent model is obtained using
parameter information for each resonant mode that are estimated for
individual modes, and another fitness function (A) is configured to
minimize an error from the measured impedance. A resultant fitness
function for an equivalent modeling of the multi-mode transducer in
which there exists an interference effect between adjacent modes is
configured using two fitness functions at the same time by taking
both an estimation method for the individual modes and a total
multi-mode estimation method combined therewith into consideration.
The resultant fitness function (F) is is determined as shown in the
following equation 2 by applying weight constants (C.sub.1,
C.sub.2) to the multi-mode fitness function, and the resultant
fitness function (F) is minimized to minimize each estimated error
for the individual mode and total mode, respectively.
F = C 1 A + C 2 k = 1 N B k [ Equation 2 ] ##EQU00003##
[0053] On the other hand, as illustrated in the first resonant mode
in FIG. 3, a resonant frequency by a parameter computed during the
equivalent model estimation process may be different from a
resonant frequency derived from the measured total impedance due to
an interference effect of adjacent modes, and thus it should be
corrected. As a result, it is required to quantitatively derive an
interference effect between adjacent modes (S500) to determine
whether to correct the resonant frequency. To this end, a total
conductance characteristic including the interference effect and
independent conductance characteristics for individual modes are
compared at a resonant frequency of the relevant mode, and the
difference thereof is defined as an interference amount.
[0054] When there is a mutual interference effect between resonant
modes, correction for the resonant frequency is required during the
equivalent model estimation process. An error or non-error of the
resonant frequency is determined through a comparison of
differential values for the measured and estimated conductances by
using the foregoing interference amount determination (S500), and
applying a differentiation method for conductance data as
illustrated in FIG. 5B.
[0055] Accordingly, when there exists a mutual interference by
adjacent modes, the measured conductance and the estimated
conductance for each mode are differentiated to determine whether
the resonant frequencies are identical to each other, and when a
failure of the resonant frequency is confirmed, it is required to
have the process of compensating this.
[0056] A differential value is always zero at a resonant frequency
of the relevant estimated individual mode, and thus a differential
value of the measured total conductance at this frequency should be
identical to a sum of differential values for interfered adjacent
mode conductances excluding the relevant individual mode.
[0057] However, a case of the two values being different is a case
that an error is included in the estimated resonant frequency, and
thus the resonant frequency is corrected in the direction of the
two differential values being the same (S600).
[0058] An equivalent circuit parameter of the multi-mode transducer
is finally derived (S700) while the interference effect removal and
individual mode estimation process (S300) is repeated again within
the divided mode section by reflecting the corrected resonant
frequency.
[0059] FIG. 7 is a circuit diagram illustrating a transmitting unit
200 of the active sonar system modeled as a transmitter 110, an
impedance matching circuit 230, and a transducer 220 according to
the present disclosure. When the transducer is equalized to an
equivalent model using the equivalent model parameter estimation
method, the transmitting unit 200 of the active sonar system may
include the transmitter 110, the impedance matching circuit 230,
and the transducer 220, and the impedance matching circuit can be
designed according to a desired condition from them.
[0060] The transmitter 110 is modeled as an input power source 111
supplying power and an input impedance 112 corresponding to an
internal resistor of the input power source.
[0061] The impedance matching circuit 230 is a circuit located
between the transmitter 110 and the transducer 220 to transmit
electric power from the transmitter 110 to the transducer 220 at
high efficiency.
[0062] The transducer 220 is a device configured to convert an
electrical signal of the transmitter into an acoustic wave or
convert an acoustic wave of the outside into an electrical signal,
which is modeled as an electrical equivalent model parameter having
a plurality of stages corresponding to each mode by estimating an
individual mode impedance and a total mode impedance from
multi-mode impedance data and considering an interference amount of
adjacent modes.
[0063] The transducer 220 is modeled to estimate a multi-mode
impedance by generating an initial value in a random manner without
a computation process for deriving an initial value of the
equivalent model parameter, dividing a frequency section for
divisions between resonant modes, obtaining a resonant frequency
corresponding to each mode, removing an interference effect of
adjacent modes within the divided mode section to estimate an
impedance for each individual mode, and considering even a
multi-mode impedance characteristic combined with independent
individual modes to have an effect on one another in an integrated
manner.
[0064] More specifically, the transducer divides a frequency
section for each mode by a minimum point of the conductance from
the impedance data of the transducer 220, and derives a maximum
point of the conductance as a resonant frequency of the relevant
mode.
[0065] More specifically, the transducer 220 is modeled by removing
an interference component combined with a k-th resonant mode from a
measured total admittance and computing a k-th individual mode
impedance, and displaying an error average between the computed
k-th individual mode impedance and a k-th resonant mode impedance
to be estimated as a fitness function (B.sub.k) to be minimized in
the relevant mode section.
[0066] More specifically the transducer 220 is modeled by
estimating a total impedance for which impedance estimation values
of individual modes for a multi-mode equivalent model are combined,
and displaying it as another fitness function (A) to minimize an
error from the measured impedance.
[0067] Furthermore, the transducer 220 is modeled by quantifying an
interference effect between adjacent modes and correcting a failure
of the resonant frequency when the interference amount is larger
than a predetermined reference value.
[0068] More specifically, the transducer 220 is modeled by
correcting a resonant frequency in the direction of its
differential values being the same when a differential value of a
total measured conductance is different from a sum of differential
values for interfered adjacent mode conductances excluding the
relevant individual modes at a resonant frequency of the relevant
individual mode.
[0069] As described above, according to the present disclosure, it
may be possible to estimate an equivalent model parameter that can
be correctly modeled by considering even an interference effect
between resonant modes in the acoustic and ultrasonic wave bands in
a multi-mode transducer.
[0070] According to the present disclosure, a multi-mode transducer
operated as a load of the sonar system transmitter may be correctly
estimated in the acoustic and ultrasonic wave bands, and thus the
estimated multi-mode equivalent model may be used for the design of
an impedance matching circuit to minimize unnecessary actual model
fabrication and effectively derive detailed design is elements and
the like, thereby allowing an integrated circuit design with
peripheral electronic units for interfacing the sonar system.
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