....... 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, semi-conductor apparatus. Therefore the developed low noise/vibration technique is expected to be applied in various fields of industry.

....... 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.

....... 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, LMS-CADA 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 epoch-making idea considering characteristics of manufacturing industry, gradual progress based on previous research is expected.