Electricity: motive power systems – Impact – mechanical shock – or vibration-producing motors
Reexamination Certificate
2000-10-04
2002-07-02
Ramirez, Nestor (Department: 2834)
Electricity: motive power systems
Impact, mechanical shock, or vibration-producing motors
C318S128000
Reexamination Certificate
active
06414452
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention is applicable to a vibrating device equipped with a vibrating table and a waveform control unit, and it relates to a real-time adaptive waveform control device and method which can make target waves and reproduced waves coincide with each other by a single excitation.
Previously, in order to examine the behavior, strength or the like of structures during, for example, earthquakes, various types of vibration tests have been performed, and for the purpose thereof, a vibrating unit has been used.
FIG. 12
schematically shows the configuration of this type of vibrating unit. This vibrating unit has a vibrating table which vibrates with a test piece
223
of a body to be tested is mounted thereon, and a waveform control unit
100
which controls the waveform of the vibration. Furthermore, the above described vibrating table
2
has a vibrating table control section
21
in which an output signal from the waveform control unit
100
is inputted, an exciting machine
221
into which a control signal from this vibrating table control section
21
is inputted, and a test piece mounting table
222
which is excited by this exciting machine
221
. A vibrating table excitation mechanism
22
comprises the exciting machine
221
and the table
222
. Thus, the signal of an excitation wave
90
emitted from the waveform control unit
100
is converted into a servo command for operating the exciting machine
221
at the vibrating table control section
21
, and the table
222
and the test piece
223
mounted thereon are vibrated by the operation of the exciting machine
221
receiving the servo command signal.
Here, the excitation wave
90
means a waveform of a vibration inputted to the vibrating table
2
, and in order to perform a proper vibration test, it is necessary to indicate an excitation wave
90
to the vibrating table
2
so that the test piece
223
may be vibrated by a specific waveform to be realized (target waveform). That is, it is necessary to set the excitation wave
90
to have such a waveform as to make the vibrational waveform (reproduced wave
20
) obtained from an acceleration sensor
224
provided on the table
222
and the target wave coincide with each other. The waveform control unit
100
is a unit provided for the purpose of generating such a proper excitation wave
90
.
Generally, the correlation between the excitation wave
90
and the reproduced wave
20
can be expressed by the following expression (1) as a function of the frequency (&ohgr;):
Y
(&ohgr;)=
G
(&ohgr;)·
X
(&ohgr;) (1)
where Y(&ohgr;) expresses the characteristic of a reproduced wave
20
, and X(&ohgr;) expresses the characteristic of an excitation wave
90
, and G(&ohgr;) expresses the characteristic of a vibrating table
222
including a test piece
223
(hereafter, referred to simply as the characteristic of the vibration table). When this expression (1) is changed into an expression for determining an excitation wave X(&ohgr;), the following expression (2) is found:
X
(&ohgr;)=
G
−1
(&ohgr;)·
Y
(&ohgr;) (2)
where G
−1
(&ohgr;) is the inverse characteristic of the vibrating table. In the above described waveform control unit
100
, an excitation wave X(&ohgr;) is determined using equation (2) so as to make the reproduced wave Y(&ohgr;) coincide with the target wave. Since the reproduced wave Y(&ohgr;) is set to become the target wave, it is known that a proper excitation wave X(&ohgr;) can be calculated if the inverse characteristic G
−1
(&ohgr;) of the vibrating table is determined.
However, it is difficult to directly determine this inverse characteristic G
−1
(&ohgr;) of the vibrating table since it changes with the vibrating table
2
itself, test pieces
223
, and the amplitude level of the vibration or the like. Accordingly, usually, some experimental approach is used, in which estimated values {tilde over (G)}
−1
(&ohgr;) for the inverse characteristic G
−1
(&ohgr;), are calculated on the basis of experimental data concerning excitation waves
90
and reproduced waves
20
obtained when the vibrating unit is actually operated. In a conventional vibrating unit, this determination of the inverse characteristic of the vibrating table is not performed during the actual excitation of the vibrating table
2
, but it has been performed after the excitation in an off-line manner. In other words, conventionally, the inverse characteristic of a vibrating table are estimated in advance from the data obtained by previous vibration tests or preliminary tests, and the estimated values are used as fixed values in subsequent vibration tests.
FIG. 13
shows a conventional vibrating unit in terms of a waveform control unit
100
. In
FIG. 13
, the parts except the vibrating table
2
form the waveform control unit
100
in FIG.
12
. Furthermore, the dotted line in
FIG. 13
expresses operations carried out in an off-line manner. At the time of excitation, a target wave
11
emitted from a target wave generator
1
is transmitted to an off-line compensation wave generator
3
, and the target wave
11
is compensated by the inverse characteristic of the vibrating table calculated in advance. That is, a proper excitation wave
90
is generated on the basis of the above described expression (2) from the target wave
11
and the inverse characteristic of the vibrating table. Actually, in the above described expression (2), the estimated values {tilde over (G)}
−1
(&ohgr;) for the inverse characteristic are used in place of the actual inverse characteristic G
−1
(&ohgr;)of the vibrating table. Using more precise expressions,the waveform obtained as a result of the compensation done in the off-line compensation wave generator
3
is called an (off-line) compensation wave. In this example, this compensation wave is used as an excitation wave
90
to be transmitted to the vibrating table
2
as it is.
The generated excitation wave
90
is transmitted to the vibrating table as mentioned above, and the vibrating table excitation mechanical section
22
is vibrated under the control of the vibrating table control section
21
. Furthermore, the data of the excitation wave
90
during the excitation and the reproduced wave
20
are recorded in an excitation-wave recorder
5
and a reproduced wave recorder
6
, respectively. After the end of the excitation, on the basis of this recorded data, with the vibrating table inverse characteristic calculator
4
, estimated values
40
[{tilde over (G)}
−1
(&ohgr;)] of the inverse characteristic of the vibrating table are determined in an off-line manner as mentioned above, and that such values are utilized for future excitation or the like.
Furthermore, in the off-line compensation wave generator
3
, the calculation based on the above described expression (2) is performed by a computing unit
32
, and a Fourier transform unit
31
and an inverse Fourier transform unit
33
are units which transform the target wave
11
in the time domain into the frequency domain and the compensation wave (excitation wave
90
) in the frequency domain into the time domain, respectively.
FIG. 14
is a flow chart in the case where the waveform control unit
100
sown in
FIG. 13
is used, and it shows the procedure up to the main excitation (main test) from the identification of the inverse characteristic of the vibrating table. First of all, an excitation by a weak random wave is performed, and from the reproduced wave at that moment, the estimated value {tilde over (G)}
−1
(&ohgr;) of the inverse characteristic of in the case where the excitation level (amplitude level of the vibration) is low is determined (step S
1
in FIG.
14
). Next, the initial excitation level is set (step S
2
in FIG.
14
), and an excitation is performed by the off-line compensation wave generated by using the determined inverse characteristic {tilde over (G)}
−1
(&ohgr;) (steps S
3
and S
4
). Usually, the initial excitation level is
Hiroe Takaharu
Maekawa Akihiro
Okuda Yukihito
Sakuno Makoto
Alston & Bird LLP
Jones Judson H.
Mitsubishi Heavy Industries Ltd.
Ramirez Nestor
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