.... Structural
Dynamic Modification Technique to Reduce Structure Vibration


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.......
Backgound


The research scope is on the subject of
structure or any kind of product design method which is required to
suppress vibration and achieve quite environment. Recent trend toward
low noise/vibration to get quite and comfort environment becomes more
important designing high function products in the field of from automotive
industry to home appliances. This is not only due to realistic situations
that external factors such as tougher environmental regulation in
vibration and noise than before, but also due to realistic situations
that low noise/vibration products are more profitable in market. As
an example machining tools require high speed to enhance productivity,
but high speed may deteriorate the level of precision. That's why
low noise/vibration design becomes one of the most important factors
to establish high quality machining tools. Low noise/vibration design
is critically necessary in many fields of industry such as looming
machine, printing facility, semiconductor apparatus. Therefore the
developed low noise/vibration technique is expected to be applied
in various fields of industry.


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Objective


The final objective of this research is
to develop about structure design method using structural dynamic
modification technique so as to suppress excessive vibration and construct
quiet environment. In particular, selection of model parameters and
the evaluation of model reliability problem in model updating procedure
will be studied. Also an optimal sensor placement technique for model
updating will be developed. Based on these preliminary works, topology
design, shape or configuration design methods will be studied. In
addition, Evaluation of noise effect caused by redesign will be studied
and the availability of developed design method will be verified through
experimental works.


.......
Research Strategy


Structural Dynamic Modification
is a design technique that is required to acquire desired design quality
by stiffener addition/reduction or shape modification. The following
topics will be studied.
First, inverse design problem requires
precise finite element model. The initial model must be updated because
the dynamic characteristics between ideal and real model are different.
The field of model updating has a long history and almost of the theoretical
background have been completely developed, but still there exist some
problems to be solved before applying to real large structure with
complex shape. Modeling of structure joint or welding spot is still
one of the major problems in model updating theory because the parameter
identification is important to update model quality.
Second, design of optimal experimental
environment which can provide reliable experimental data to identify
dynamic characteristics of structures is needed. Model updating procedure
and design problem require modal testing because experimental data
must be provided. Sensor placement and selection of exciting position
have deep relation to the reliability of modal testing result. Although
commercial softwares have some function to select optimal sensor position,
the level of its algorithm is not up to date thus a more sophisticated
algorithm should be developed.
And lastly, sensitivity analysis
should be studied for redesign. It is the kernel of optimal design
problem and various advanced mathematical theories have been applied.
Eigenvalue/eigenvector or frequency response function sensitivity
analysis are one of basic theories in vibration design. And this laboratory
has studied sensitivity analysis related to vibration design for years,
excellent research capability and database have been already accumulated.


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Strength Technology


This laboratory has accumulated various and rich experience related
to inverse problem through many projects. Thus it is expected to develop
advanced design methodology based on the foundations. Following subjects
is the strength technology and can be used as base to accomplish this
project.
Model updating technique plays a key
role to design some structures. Mathematical or ideal model's quality
must be updated to obtain proper design results through model updating
such as parameter identification or optimization. Model reliability
evaluation is also required technique and indirectly connected to
model identification problem.
Though major part of dynamic property
design is determined by optimal design, it is known as very difficult
procedure. Most difficulty attributes to computation of constraint
or object function sensitivity. This research group has studied shape
or configuration sensitivity including conventional design sensitivity
to the change of thickness or cross section area.


.......
Major Facilities


This research laboratory has many
facilities to accomplish the project such as signal analysers, signal
measurement equipments, signal amplifiers/generators, design softwares,
anechoic chamber etc.. Signal analyser analyses monitored time or frequency
signal. HP analyser, STAR MODAL, and many oscilloscopes are also equipped.
Measurement apparatus such as acceleration meter(1axis, 3axis, laser
accelerometer) measure vibration signal and force signal. B&K charge/voltage
amp. amplify vibration or acoustic signal, and function generator generate
desired signal. ANSYS, LMSCADA X can be used as design tools. Anechoic
chamber presents perfect experimental environment.


.......
Potential Value


Low vibration design is one of
the most important problems confronted in overall manufacturing industries
such as automotive, machining tool industry. It is also expected gradual
progress in this area including advanced modification of commercial
softwares. Though it is seemed to be difficult to derive an epochmaking
idea considering characteristics of manufacturing industry, gradual
progress based on previous research is expected.

