• 소성∙가공
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• 제14권1호
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• pp.37-42
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• 2005

In order to invstigate the influence of die design variables on the quality of the sheared surface in cutting of sandwich sheet metals, the cut-off operation is carried out, which is the typical shearing process in sheet metal forming technology. For experiments we made the cut-off die which can be easily adjusted for die design variables such as blankholding force, pad force and clearance. The sandwich sheet metals considered are clad304(STS304-Al1050-STS304) and anti-vibration sheet metal. The shearing process is visualized by the computer vision system installed in front of the cut-off die and the sheared surface is measured and quantitatively compared with the help of the optical microscope after cut-off operation. From test results it is shown that the shearing mechanisms are different according the material of which sandwitch sheet metal is composed. The influence of die design variable is explored and we found optimal conditions for both sandwich sheet metals. It is expected that this investigation can be utilized to get the better sheared surface.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.57-61
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• 2004

in order to improve the quality of the sheared surface in cutting of sandwich sheet metals the cut-off operation is mainly investigated which is the typical shearing process in sheet metal forming technology. For experiments the cut-off die is made which can be easily adjusted by die design variables such as blankholding force, pad force, and clearance. The sheet metals chose as specimen are clad304(STS304-Al1050-STS304) and anti-vibration sheet metal. The shearing process is visualized by the computer vision system installed in front of the cut-off die and the sheared surface before and after cut-off operation is measured and quantitatively compared with the help of the optical microscope. From test results the good sheared surface was shown when the clearance gets small with large blankholding force.

• Journal of Biosystems Engineering
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• 제34권5호
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• pp.305-314
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• 2009

The purpose of this paper was to design an effective control system of 1-axis exciter for a seat vibration test of agricultural tractors using MATLAB simulation. The developed simulation model was composed with a hydraulic pump, a hydraulic servo valve, a hydraulic cylinder and load system. Also it was verified by comparing the simulation results with experimental results of actual control system in order to optimize the control performance. And in order to improve its control performance, the designed PID controller in this research was tuned using Ziegler-Nichols 2nd law and zero's moving method of PID controller's transfer function. As the result of these research, the developed position control system was able to control the system's position accurately within 5% errors.

• Smart Structures and Systems
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• 제14권3호
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• pp.327-345
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• 2014

This paper presents a composite control strategy for the active suppression of vibration due to the unknown disturbances, such as external excitation, harmonic effects and control spillover, as well as high-frequency accelerometer measurement noise in the all-clamped stiffened plate. The proposed composite control action based on the modal approach, consists of two contributions including feedback part and feedforward part. The feedback part is the well-known PID controller, which is widely used to increase the structure damping and improve its dynamic performance close to the resonance frequencies. In order to get better performance for vibration suppression, the weight matrixes is optimized by chaos sequence. Then an improved disturbance observer (IDOB) as the feedforward compensation part is developed to enhance the vibration suppression performance of PID under various disturbances and uncertainties. The proposed IDOB can simultaneously estimate the various disturbances dynamically as well as measurement noise acting on the system and suppress them by feedforward compensation design. A rigorous analysis is also given to show why the IDOB can effectively suppress the unknown disturbances and measurement noise. In order to verify the proposed composite control algorithm (IDOB-PID), the dSPACE real-time simulation platform is used and an experimental platform for the all-clamped stiffened plate active vibration control system is set up. The experimental results demonstrate the effectiveness, practicality and strong anti-disturbances ability of the proposed control strategy.

• Steel and Composite Structures
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• 제31권4호
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• pp.387-396
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• 2019

This paper deals with the effect of ply orientation and control gain on tip transverse displacement of functionally graded beam layer for both active constrained layer damping (ACLD) and passive constrained layer damping (PCLD) system. The functionally graded beam is taken as host beam with a bonded viscoelastic layer in ACLD beam system. Piezoelectric fiber reinforced composite (PFRC) laminate is a constraining layer which acts as actuator through the velocity feedback control system. A finite element model has been developed to study actuation of the smart beam system. Fractional order derivative constitutive model is used for the viscoelastic constitutive equation. The control voltage required for ACLD treatment for various symmetric ply stacking sequences is highest in case of longitudinal orientation of fibers of PFRC laminate over other ply stacking sequences. Performance of symmetric and anti-symmetric ply laminates on damping characteristics has been investigated for smart beam system using time and frequency response plots. Symmetric and anti-symmetric ply laminates significantly reduce the amplitude of the vibration over the longitudinal orientation of fibers of PFRC laminate. The analysis reveals that the PFRC laminate can be used effectively for developing very light weight smart structures.

• 한국재난정보학회 논문집
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• 제11권1호
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• pp.89-96
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• 2015

선하역사 내부에 발생하는 소음을 저감하기 위해서는 진동의 감소가 필요하며, 보다 효과적인 진동 저감 대책 수립을 위해서는 궤도-접속교량-구조물의 상호작용 특성을 감안하여 열차 운행으로 발생하는 진동이 전달되는 경로 및 특성에 대한 명확한 이해가 필요하다. 이 논문에서는 국내 선하역사 현황을 구조적으로 분류하고 대표 선하역사에 대한 진동 측정을 통하여 역사에 발생하는 진동의 전달 특성을 분석하였다. 주파수응답을 통한 분석 결과 궤도의 진동이 역사로 전달되면서 고주파 성분이 큰 감소를 나타냈으며, 일부 역사에서 저주파 대역 내 증폭 구간이 발견되었다. 플로팅궤도가 적용되거나 TPS 구조의 역사는 궤도로부터 전달되는 진동이 비교적 큰 감소를 나타냈다.

• 동력기계공학회지
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• 제12권2호
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• pp.23-28
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• 2008

The primary objective of this study is to truly understand reaction force be due to engine exciting force. Exciting forces of the engine apply a source of the vehicle NVH(Noise, Vibration, Harshness). To understand reaction force was applied MSC.Nastran software. Analyzed frequency response analysis of powertrain mount system. First, engine exciting force was applied field function. Also nonlinear characteristics was applied field function : such as dynamic spring constant and loss factor. And nonlinear characteristics was applied CBUSH. Generally characteristics of rubber mount is constant frequency. But characteristics of hydraulic mount depend to frequency. Therefore nonlinear characteristics was applied. Powertrain mounting system be influenced by powertrain specification, mount position, mount angle and mount characteristics etc. In this study, we was analyzed effects of powertrain mounting system. And we was varied dynamics spring constant and loss factor of mounts.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.483-488
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• 2013

The psychoacoustic quality of ABS is now considered more important than before as the focus of recent ABS function is expanded to basic function from typical emergency function. Thus, the automotive parts manufacturing companies are actively working to improve NVH (Noise, Vibration, and Harshness) in ABS module. In terms of time, test place, and cost, however, it is very inefficient to have all the operating noise validation test in real vehicle configuration especially for partially improved ABS module. To contribute to reducing the development period and to grasping the improvements faster, this research presents the study of a correlation to predict ABS operating noise inside vehicle via HILS rig test. The regression equation in this paper was statistically drawn from using Minitab S/W, and based on that equation, the noise spectrum of vehicle interior was analogized.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.321-324
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• 2007

The actuators of anti-vibration system(AVS) can be separated into several types: piezoelectric actuators, pneumatic springs, cylinders, rotating motor and linear motor. The last one has some advantages, such as low noise, low vibration, simpler configuration and possibility of direct drive. The voice coil motor(VCM) is one type of linear motor, originally used in speaker system. VCM actuators are usually used in occasions that rapid and controlled motion of devices are required. In this paper, a controller which satisfies system specification(e.g. current controller bandwidth) within whole operation range is designed. For that objective, parameters as position were initially obtained with 3D FEM analysis and motor modeling was performed. A current controller in 2-axis VCM drive system was designed and then performance of the proposed controller was verified with simulation using Simplorer and an experimental result.

• 한국소음진동공학회논문집
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• 제20권10호
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• pp.976-982
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• 2010

This paper proposes a novel type of pressure control mechanism which can apply to vehicle ABS (anti-lock braking system) utilizing the piezoactuator based valve system associated with the pressure modulator. As a first step, a flapper-nozzle of a pneumatic valve system is devised by integrating the piezoacuator to the flexible beam structure. The dynamic modeling of the valve system is then undertaken and subsequently the governing equation of pressure control is derived considering the pressure modulator. A sliding mode controller is designed in order to achieve accurate pressure tracking control in the presence of actuator uncertainty as well as input pressure variation. It is shown through computer simulation that an accurate pressure tracking for sinusoidal motion whose magnitude is 40 bar is achieved by utilizing the proposed pressure control mechanism.