• International Journal of Automotive Technology
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• 제5권1호
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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 Wood Science and Technology
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• 제19권1호
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• pp.71-80
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• 1991

This study was carried out to investigate replaceable species with the conventional sounding board sitka spruce. by comparing the dynamic properties such as density, dynamic Young's modulus and internal friction Dynamic Young's modulus. internal friction of longitudinal and radial direction measured in free mass-free boundary condition for facile vibration analysis and measured by forced vibration method. Dynamical properties of four species were measured on squared plate specimen that the four edges were hung vertically by threads and driven magnetically through an iron piece glued on the specimen, by the use of condenser microphone as vibration transducer, and analyzed by FFT analyzer. The results obtained were as follows: 1. Chaldni method using aluminum powder was proper to identify the vibration mode in the plate vibration and it was possible to verify the resornance mode. 2. It was considered that it was necessary to investigate the influence of adhesive part on the plate vibration when the sounding board was made by two or three small board adhesion. 3. It was considered that plate vibration method, which was a superior to the vibration test of beam, was suitable for selecting suounding board because dynamic Young's modulus and internal friction show different order according to longitudinal and radial direction. 4. Paulownia tomentosa Thunb.) Steudel has been considered to be replaceable species with sitka spruce because it has high dynamic Young's modulus compared with low density, low internal friction, and K value of Paulownia tomentosa (Thunb.) Steudel is greater than that of sitka spruce.

• 대한기계학회논문집A
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• 제26권6호
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• pp.1060-1068
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• 2002

Compound continuously variable transmission(CVT) mechanisms are proposed, which can offer a backward mode, a geared neutral, an underdrive mode and an overdrive mode. They are composed of a 2K-H I type differential gear unit, a V-belt type continuously variable unit(CVU), a few friction clutches and gears, and not required of a starting device as a torque converter. Compound CVT mechanisms developed here present two distinct operating modes which are a power circulation mode and a power split mode. The transition of two modes takes place at the particular CVU speed ratio. For these CVT mechanisms, performance analysis related to speed ratio, power ratio and efficiency are executed and proven by experimental studies.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권5호
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• pp.271-279
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• 2006

In this paper, a new speed sensorless control based on an adaptive sliding mode observer is proposed lot the interior permanent magnet synchronous motor(IPMSM) drives. With using voltage equation only, the adaptive sliding mode observer was investigated. Since the parameter of the dynamic equation such as machine inertia or viscosity friction coefficient are not well known and these values can be easily changed during normal operation, there are many restrictions in the actual implementation. The proposed adaptive sliding mode observer applied to overcome the problem caused by using the dynamic equation. Furthermore, the Lyapunov function is used to prove the system stability included speed estimate and speed control. The effectiveness of the proposed algorithm is confirmed by the experiments.

• 제어로봇시스템학회논문지
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• 제12권11호
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• pp.1061-1064
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• 2006

In this study, the performance of the tracking control of a pneumatic servo motor driven position control system using sliding mode is investigated. It is usually quite difficult to obtain precise tracking control of a pneumatic servo motor driven position control system because of the nonlinear deadband and stick-slip friction of the proportional valve. Therefore, a continuous sliding mode controller with velocity feedforward gain is proposed. Experimental results show that the tracking accurracy can be remarkably improved by adding a proper velocity feedforward term to continuous sliding mode controller.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권2호
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• pp.83-91
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• 2002

This paper presents a new speed and position sensorless control method of permanent magnet synchronous motors based on the sliding mode observer. Since the parameter of the dynamic equation such as machine inertia or viscosity friction coefficient are not well known and these values can be easily changed generally during normal operation, there are many restrictions in the actual implementation. The proposed adaptive sliding mode observer applies adaptive scheme so that observer may overcome the problem caused by using the dynamic equation. Furthermore, using the Lyapunov Function, the adaptive sliding mode observer can estimate rotor speed as well as stator resistance. The feasibility of the Proposed observer is verified cia the experiments.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.149-157
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• 2002

This paper is to investigate collapse mechanisms of CFRP(Carbon Fiber Reinforced Plastics)composite tubes and to evaluate collapse characteristics on the change of interlaiminar number and ply orientation angle of outer under static and impact axial compression loads. When a CFRP composite tube is crushed, static/impact energy is consumed by friction between the loading plate and the splayed fronds of the tube, by fracture of the fibers, matrix and their interface. These are associated with the energy absorption capability. In general, CFRP tube with 6 interlaminar number(C-type), absorbed more energy than other tubes(A, B, D-types). The maximum collapse load seemed to increase as the interlaminar number of such tubes increases. The collapse mode depended upon orientation angle of outer of CFRP tubes and loading status(static/impact). Typical collapse modes of CFRP tubes are wedge collapse mode, splaying collapse mode and fragmentation collapse mode. The wedge collapse mode was shown in case of CFRP tubes with 0° orientation angle of outer under static and impact loadings. The splaying collapse mode was shown in only case of CFRP tubes with 90°orientation angle of outer under static loadings, however in Impact tests those were collapsed in fragmentation mode .

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.288-292
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• 1997

Positioning accuracy largely depends on the variation of friction force in guide table, geometric accuracy of feed unit like as ballscrew and controllable accrecy of servo unit, in general. This paper deals with improvement of microstep resolution about hydrostatic table. Torque control mode have a advantage in microstep test, and more stable than velocity control mode in low velocity motion. Hydro static table have the elastic behavior within several .mu.m, so different character exist between the elastic motion and rolling motion. Integral gain is dominant than other gain in elastic motion. In order to improve response time in elastic motion,increasing gain is suggested within the stable region.

• Journal of Mechanical Science and Technology
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• 제16권1호
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• pp.39-45
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• 2002

Initiation and propagation of interfacial crack along bimaterial interface are considered in this study. A biaxial loading device for a single specimen is used for obtaining a wide range of mode-mixities. The specimen is an edge-cracked bimaterial strip of glass and epoxy; the biaxial loading device, being capable of controlling displacements in two perpendicular directions, is developed. A series of interfacial crack initiation and Propagation experiments are conducted using the biaxial loading device for various mixed modes. Normal crack opening displacement (NCOD) is measured near crack front by a crack opening interferometry and used for extracting fracture parameters. From mixed mode interfacial crack initiation experiments, large increase in toughness with shear components is observed. The behavior of interfacial crack propagation analyzed as a function of mode-mix shows that initial crack propagation is delayed with increase of mode-mixity, and its velocity is increased with positive mode-mixity but decreased with negative case. However, it is found that crack propagation is less accelerated with positive mode-mixity than the negative mode-mixity, which may be caused by contact and/or effects of friction between far field and near-tip Held along the interfacial crack.

• Tribology and Lubricants
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• 제18권4호
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• pp.260-266
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• 2002

In this study, the effects of oxide layer farmed on the wear tracks of TiN coated silicon wafer on friction and wear characteristics were investigated. Silicon wafer was used for the substrate of coated disk specimens, which were prepared by depositing TiN coating with 1 ${\mu}{\textrm}{m}$ in coating thickness. AISI 52100 steel ball was used fur the counterpart. The tests were performed both in air for forming oxide layer on the wear track and in nitrogen to avoid oxidation. This paper reports characterization of the oxide layer effects on friction and wear characteristics using X-ray diffraction(XRD), Auger electron spectroscopy(AES), scanning electron microscopy (SEM) and multi-mode atomic force microscope(AFM).