Hyoun-Jin Sim

The Design of the Motor Bracket for Reduction of Structure- Borne Noise in Package Air-Conditioner

As the economic power is improved and the customer`s demand is hard to please, the noise and vibration is the most important yardstick that can determine the quality of the product. Especially, as the airconditioner`s demand increase suddenly, the product of quality and the noise is becoming a decisive factor of determining whether purchase the product or not. Therefore, every manufactory is investing a lot of money and research to cut down the unpleasantness induced from noise and vibration. And they are emphasizing their product`s difference by advertising a silence very actively. With these reason, the demand of a silent indoor air-conditioner is the essential research filed when the product is develop(:d. In this study, the noise and vibration is visualized in the space and frequency domain by using experimental methods such as operational deflection shape (ODS), modal testing and sound intensity. Also the location of noise source and its characteristic is analyzed in an acoustical point of view to reduce the structure borne noise that come from the fan motor, and the pertinent control method is suggested. Furthermore, the most suitable shape of the motor bracket is suggested by applying FEM and DOE (Design of experiments) in the noise and vibration point a view.

Sound Quality Evaluation and Grade Construction of the Level D Noise for the Vehicle Using MTS

The reduction of the Vehicle interior noise has been the main interest of NVH engineers. The driver`s perception on the vehicle noise is affected largely by psychoacoustic characteristic of the noise as well as the SPL. The previous methods to evaluation of the SQ about vehicle interior noise are linear regression analysis of subjective SQ metrics by statistics and the estimation of the subjective SQ values by neural network. But these are so depended on jury test very much that they result in many difficulties. So, to reduce jury test weight, we suggested a new method using Mahalanobis distance for SQ evaluation. And, optimal characteristic values influenced on the result of the SQ evaluation were derived by signal to noise ratio(SN ratio) of the Taguchi method. Finally, the new method to evaluate SQ is constructed using Mahalanobis-Taguchi system(MTS). Furthermore, the MTS method for SQ evaluation was compared by the result of SQ grade table at the previous study and their virtues and faults introduced.

Advanced multidimensional spectral analysis and its application for early fault detection

Abstract For the early detection and diagnosis of a machine fault, it is necessary to identify the source that contains a fault signal, and to estimate the magnitude of the fault signal in the case of multiple input systems. However, most conventional research is based on the fast Fourier transform (FFT) method, so it requires entire time data and cannot be used for fault signals occurring instantaneously. Fourier-based methods are not well suited to the analysis of nonlinear or non-stationary systems owing to their time-varying nature. Thus, in this paper, a wavelet packet based technique that calculates the time-varying coherence functions for input/ output relationships is developed. Advanced multidimensional spectral analysis (MDSA) is introduced, and the proposed method analyses the signal instantaneously in both time and frequency domains. Introducing the instantaneous ordinary coherence function (IOCF), which is obtained from the wavelet packet analysis, it shows the possibility of ‘early fault detection’ by analysing signals instantaneously in time. Thus, by examining the trend of coherence functions, it is possible to find which signal contains the major fault signal and the degree to which the system is damaged.

Design of Low Noise Engine Cooling Fan for Automobile using DACE Model

This paper proposes an optimal design scheme to reduce the noise of the engine cooling fan by adapting Kriging with two meta-heuristic techniques. An engineering model has been developed for the prediction of the noise spectrum of the engine cooling fan. The noise of the fan is expressed as the discrete frequency noise peaks at the BPF and its harmonics and line spectrum at the broad band by noise generation mechanisms. The object of this paper is to find the optimal design for noise reduction of the engine cooling fan. We firstly show a comparison of the measured and calculated noise spectra of the fan for the validation of the noise prediction program. Orthogonal array is applied as design of experiments because it is suitable for Kriging. With these simulated data, we can estimate a correlation parameter of Kriging by solving the nonlinear problem with genetic algorithm and find an optimal level for the noise reduction of the cooling fan by optimizing Kriging estimates with simulated annealing. We notice that this optimal design scheme gives noticeable results. Therefore, an optimal design for the cooling fan is proposed by reducing the noise of its system.

The Optimal Design for Noise Reduction of the Intake System in Automobile Using Kriging Model

Recently, the regulations of the government and the concerns of people have rise to the interest in noise pollution levels as compared to other vehicles. In this area, many researchers have studied to reduce this noise in the field of automotive engineering. This paper proposes an optimal design scheme to reduce the noise of the intake system by adapting Kriging with two meta-heuristic techniques. For this, as a measuring tool for the performance of the intake system, the performance prediction software, was used. Then, the length and radius of each component of the current intake system are selected as input variables and the orthogonal arrays is adapted as a space-filling design. With these simulated data, we can estimate a correlation parameter in Kriging by solving the nonlinear problem with a genetic algorithm and find an optimal level for the intake system by optimizing Kriging estimated with simulated annealing. We notice that this optimal design scheme gives noticeable results and is a preferable way to analyze the intake system. Therefore, an optimal design for the intake system is proposed by reducing the noise of its system.

Kriging Optimal Design of an Intake System with Meta-Heuristic Methods for Reducing Noise

Abstract Recently, government regulations and public concern have increased interest in noise pollution levels. Therefore, many researchers have studied to reduce this noise in the field of automotive engineering. The current paper proposes an optimal design scheme to reduce the noise of the intake system by adapting Kriging with two meta-heuristic techniques. This was achieved by using performance prediction software (developed by one of the present authors and his co-workers) as a measuring tool for the performance of the intake system. The length and radius of each component of the current intake system were then selected as input variables and the L18 table of orthogonal arrays was adapted as a space-filling design. With these simulated data, a correlation parameter can be estimated in Kriging by solving the non-linear problem with a genetic algorithm to find an optimal level for the intake system by optimizing Kriging estimated through simulated annealing. This optimal design scheme gives significant results and is a preferable way to analyse the intake system. Therefore, an optimal design for the intake system is proposed for reducing the noise of its system.

The Optimal Design for Noise Reduction of the Intake System in Automobile Using DACE Model

We propose an optimal design to improve the capacity by reducing the noise of the intake system. The length and radius of each component of the current Intake system are selected as control factors. We accept the output from computer simulator with orthogonal arrays. Then, the Kriging estimates are computed. From this, we exploit the optimal design of the intake system by adapting simulated annealing. From the results of this optimal design, we conclude that Kriging method with the orthogonal arrays is the efficient method for Design and Analysis of Computer Experiments and we propose the useful results for the low noise intake system.