• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.3
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• pp.12-21
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• 1993

In recent years, high efficiency, high performance, and low pollutant emmision engines have been developed. Knock phenomenon has drawn interests because it became an hinderance to engine power and efficiency increase through higher compression ratio. Knock phenomenon is an abnormal combustion originated from autoignition of unburned gas in the end-gas region during the later stage of combustion process and accompanied a high pitched metallic noise. And this phenomenon is characterized by knock occurrence percentage, knock occurrence angle and knock intensity. A four cylinder spark ignition engine is used in our experiment, and its combustion chamber pressure is measured at various engine speeds, ignition timing. The data are analyzed by numerous methods in order to select the optimum methods and to achieve better understanding of knock characteristics. Methods using band-pass filter, third derivative and step method are shown to be the most suitable, while methods using frequency analysis are shown to be unsuitable. Because step method only uses signals above threshold value during knocking condition, pressure signal analyses with this method show good signal-to-noise ratio.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.436-442
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• 2016

This paper presents the torsional vibration isolation performance evaluation of a centrifugal pendulum absorbers (CPAs) that has a continuously varying resonance frequencies proportional to engine firing (excitation) order. CPAs are commonly used to suppress torsional vibrations in rotating machinery and internal combustion engines. In this study, they are employed on the current spring type torsional damper inside a torque converter of automotive vehicle. To evaluate the effectiveness of designed resonance tuning order, the torsional vibration transmissibility based on torque measurements with respect to different engine firing orders is experimentally measured with a lower-inertia dynamometer. The torsional vibration transmissibility with respect to different frequencies with engine order of 2 is also evaluated. It has been demonstrated that the significant vibration reduction over operational frequency range of interest can be achieved by attaching simple pendulums. Future research direction includes the study on theoretical analysis, improved design of pendulum etc.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.457-469
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• 2006

In automotive engineering, the brand sound is one of the important advantage strategies in a car company. For the design of brand sound, the selection of descriptive word for a car sound is one of major works in automotive sound quality research. In this paper, booming and rumbling sound, which are professional words used by sound and vibration engineers are used for the design of brand sound. We employed sound quality metrics, which are used in the psychoacoustics. By most research results, the relationship between subjective evaluations and sound quality metrics has nonlinear characteristics. In order to correlate these subjective evaluations with sound quality metrics, the artificial neural network technology has been applied to two-dimensional sound quality index for a passenger car. These indexes are used for 46 passenger cars, which are samples of the famous cars around the world. Also a preference evaluation for car sound was carried out by sound and vibration engineers. We coupled this preference with booming and rumbling sounds by using artificial neural network. In future, the two dimensional sound and preference index will be very useful to develop brand sound in passenger cars.

• International Journal of Automotive Technology
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• v.5 no.1
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• pp.61-67
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• 2004

This paper suggests two simple two-degree-of-freedom models to describe the dynamical interaction between the pad and the disc of a disc brake system. Separate models for in-plane and out -of-plane vibration are described. Although a brake pad and disc have many modes of vibration, the interaction between a single mode of each component is considered as this is thought to be crucial for brake noise. For both models, the pad and the disc are connected by a sliding friction interface having a velocity dependent friction coefficient. In this paper, it is shown that this friction model acts as negative damping in the system that describes the in-plane vibration, and as negative stiffness in system that describes the out-of-plane vibration. Stability analysis is performed to investigate the conditions under which the systems become unstable. The results of the stability analysis show that the damping is the most important parameter for in-plane vibration, whereas the stiffness is the most important parameter for the out-of-plane vibration.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.5
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• pp.61-68
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• 1988

This paper reports the basic performance of a naturally aspirated DI diesel engine which is used widely in industry and agriculture when vegetable oils are used as fuel substitutes. In this paper, the properties of vegetable oils as diesel fuel were investigated and the load-performance of diesel engine when vegetable oils were used, as tested compared against diesel fuel. The general objective of this investigation is to realize an efficient, clean, and low carbon deposit combustion of the vegetable oils in diesel engines, showing their feasibility as diesel fuel substitutes. The results of this experiment were as follows; (1) Compared with diesel fuel, the droplet size of vegetable oil is very large. (2) Compared with diesel fuel, rapeseed oil, palm oil, and their blend fuels offered lower smoke, lower NOx, ower engine noise, and high thermal efficiency in a D.I. diesel engine However, there were carbon deposit and piston ring sticking problems with long-term operation. (3) For ethanol-rapeseed oil blends, a 10-20% of ethanol content is recommended to enable lower BSHC and less smoke without a remarkable increase in engine noise compared with pure rapeseed oil. (4) A 10% oxygen content in the vegetable oils is contributed to reduced smoke emission.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.242-249
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• 2017

In this study, the relationship between the shape of a passenger airbag and the possibility of injury is analyzed using the Taguchi method. The optimal shape combination is proposed for a design guideline that can reduce the possibility of injury to the dummy. The airbag FE model for analysis is obtained using a CAD system that can change the shape through several independent variables. The widths of the left / right, top / bottom, and back / forth direction of the airbag shape are set as the design factors, and the effect of the combination injury probability according to the shape is analyzed. The minimum geometric combinations are obtained using the orthogonal array method. The signal to noise ratio is calculated and the optimal shape combination is obtained through sensitivity analysis. The obtained optimal shape combination is compared with the possibility of injury of the initial airbag shape to confirm improved airbag performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.915-921
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• 2013

This work presents a 77 GHz low noise amplifier(LNA) for automotive radar systems using 65 nm RF CMOS process. The LNA is composed of three stage common source amplifiers and includes transmission line matching networks. To reduce the time for three dimensional EM simulation, we optimize the transmission line impedance matching network using a pre-built EM library. The proposed compact simulation technique is confirmed by measurement results. The peak gain of the LNA is 10 dB at 77 GHz and input/output return losses are below -10 dB around the design frequency.

• Composites Research
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• v.32 no.5
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• pp.243-248
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• 2019

As demand of light weight in the automotive industry has increased, the cowl cross member has been investigated using various methods to change the material. Conventionally, a cowl cross member has been made of steel and aluminum, but recently researchers tested multi-material such as aluminum and plastic. We studied a new model of the cowl cross member made of composite and non ferrous materials. For products with a high degree of freedom in design, generally, the method of topology optimization is advantageous and for the partial bracket part of the cowl cross member had a degree of freedom in the design, a topology optimization is appropriate. Considering the characteristics of the cowl cross members, we need research to minimize the weight while having the performance of noise, vibration and harshness(NVH). Taking the mounting status of the product into consideration, we used an assembly model to optimize the cowl cross member. But this method took too much time so we considered simple cowl cross member assemble conditions using the direct matrix input method(DMI) with the Craig-Bampton Nodal Method. This method is capable of considering the status of the assembly without assembling the model, which reduced the solving time and increased the accuracy comparison with a cowl cross member without DMI.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.844-850
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• 2016

This study pertains to the extraction of the road noise component of signals from a vehicle's interior noise via the traditional frequency domain and time domain system identification methods. For road noise extraction based on the frequency domain system identification method, the appropriate matrix inversion strategy is investigated and causal and non-causal impulse response filters are compared. Furthermore, appropriate data lengths for the frequency domain system identification method are investigated. In addition to the traditional road noise extraction methods based on frequency domain system identification, a new approach to extract road noise via the time domain system identification method based on a parametric input-output model is proposed and investigated in the present study. In this approach, instead of constructing a higher order model for the full-band road noise, input and output signals are processed in the subband domain and lower order parametric models optimal to each subband are determined. These parametric models are used to extract road noises in each subband; the full band road noise is then reconstructed from the subband road noises. This study shows that both the methods in the frequency domain and the time domain successfully extract the road noise from the vehicle's interior noise.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.259-268
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• 2007

A knock detection circuit that is based on the signal of an accelerometer installed on the engine block of a spark ignition automotive engine has a band-pass filter with a certain frequency as a parameter to be calibrated. A new statistical method for the determination of the frequency which is the most suitable for the knock detection in real-time applications is proposed. The method uses both the cylinder pressure and block vibration signals and is divided into two steps. In both steps, a new recursive trigonometric interpolation method that calculates the frequency contents of the signals is applied. The new trigonometric interpolation method developed in this paper improves the performance of the Discrete Fourier Transformation, allowing a flexible choice of the size of the moving window. In the first step, the frequency contents of the cylinder pressure signal are calculated. The knock is detected in the cylinder of the engine cycle for which at least one value of the maximal amplitudes calculated via the trigonometric interpolation method exceeds a threshold value indicating a considerable amount of oscillations in the pressure signal; this cycle is selected as a knocking cycle. In the second step, the frequency analysis is performed on the block vibration signal for the cycles selected in the previous step. The knock detectability, which is an individual cylinder attribute at a certain frequency, is verified via a statistical hypothesis test for testing the equality of two mean values, i.e. mean values of the amplitudes for knocking and non-knocking cycles. Signal-to-noise ratio is associated in this paper with the value of t-statistic. The frequency with the largest signal-to-noise ratio (the value of t-statistic) is chosen for implementation in the engine knock detection circuit.