• International Journal of Precision Engineering and Manufacturing
• /
• 제1권1호
• /
• pp.42-48
• /
• 2000

Friction in bearing exerts an important effect upon power dissipation and heat generation of spindle system. This paper presents frictional moments derived from rotational axis coordinate system of spindle and frictional characteristics to spindle speed A frictional moment of spindle bearings is derived by work-energy method. Differential sliding moments in outer raceway has a major effect upon frictional resistance; spin sliding moments in inner raceway has a secondary effect. As spindle speed increases, also the frictional moments increase. In high-speed region, ceramic ball bearing 몬 smaller frictional moment than steel ball bearing.

• Journal of Electrical Engineering and information Science
• /
• 제3권1호
• /
• pp.86-93
• /
• 1998

In this paper, we propose an effective on-line identification method for rotor resistance, which is useful in making speed control of induction motors without rotational transducers robust with respect to the variation in rotor resistance. Our identification method for rotor resistance is based on the linearly perturbed equations of the closed-loop system for sensorless speed control about th operating point. Our identification method for rotor resistance uses only the information of stator currents and voltages. In can provide fairly good identification accuracy regardless of load conditions. Some experimental results are presented to demonstrate the practical use of our identification method. For our experimental work, we have built a sensorless control system, in which all algorithms are implemented on a DSP. Our experimental results confirm that our on-line identification method allows for high precision speed control of commercially available induction motors without rotational transducers.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2003년도 추계학술대회
• /
• pp.385-389
• /
• 2003

To make high speed spindle system work properly, sensors with outstanding resolution and dynamic characteristics are essential. An optical fiber displacement sensor is based on simple principles. Electrical signal responds to the optical flux change due to the displacement change between a target and a sensor probe. In this paper, the performance of optical fiber displacement sensor has been investigated according to properties of optical fiber Firstly, optical loss has been measured before and after polishing optical fiber endface. Secondly, allowance of optical fiber bending has been tested. thirdly sensitivity and linear range of the sensor has been found out according to the shape of cross section of optical fiber.

• 전자공학회논문지
• /
• 제50권10호
• /
• pp.199-203
• /
• 2013

In this paper, a fast algorithm of discrete cosine transform-based interpolation filter (DCT-IF) for HEVC (high efficiency video coding) encoder is proposed. DCT-IF filter accounts for around 30% of encoder complexity, according to the computational complexity analysis with the HEVC reference software. In this work, the proposed DCT-IF is optimized by applying frame-level interpolation, SIMD optimization, and task-level parallelization via OpenMP on a developed C-based HEVC encoder. Performance analysis is conducted by measuring speed-up factor of the proposed optimization technique on the developed encoder. The results show that speed-up factors by frame-level interpolation, SIMD, and OpenMP are approximately 38-46, 3.6-4.4, and 3.0-3.7, respectively. In the end, we achieved the speed-up factor of 498.4 with the proposed fast algorithm.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 춘계학술대회 논문집
• /
• pp.45-57
• /
• 2007

During the design phase of a system, which requires high reliability and safety such as aircraft, high speed train and nuclear power plant, reliability engineer must set up the target system reliability. To meet a reliability goal for the system, reliability allocation should be done gradually from the system to its element. For this end, first of all, we need to construct functional block diagram based on the design output and PWBS(Project Work Breakdown System). Another important input data for reliability allocation is the relationship between the cost and the reliability. In this study we investigate various reliability allocation models, which can be applicable to aircraft, vehicle, and power plant, and etc. And we suggest a proper reliability allocation model which can be effectively applicable to KTX-II high speed train to achieve the target system reliability.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
• /
• pp.262-271
• /
• 1999

This work was intended to modify the solidification structure of high speed steel roll material for hot strip mill, by the introduction of alloying elements designed to form primary carbide dispersions via melt treatment procedure. Solidification structure was modified by the melt treatment with titanium and distribution. This modifying effect could be attributed to the fact that the nuclie formed at high temperature upon inoculation induce the formation of fine equiaxed grain and primary carbide during solification, which is also likely to be responsible for the fact that TiC acts as effective nuclie for primary VC solidification.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
• /
• pp.441-446
• /
• 2000

Although the net-shape molding of composites is generally recommended, molded composites frequently required cutting or grinding due to the dimensional inaccuracy for precision machine elements. During the composite machining operations such as cutting and grinding, the temperature at the grinding area may increase beyond the allowed limit due to the low thermal conductivity of composites, which might degrade the matrix of composite. Therefore, in this work, the temperature at the grinding point during surface grinding of carbon fiber epoxy composite was measured. The grinding temperature and surface roughness were also measured to investigate the surface grinding characteristics of the composited. The experiments were performed both under dry and wet grinding conditions with respect to cutting speed, feed speed, depth of cut and stacking angle. From the experimental investigation, the optimal conditions for the composite plain grinding were suggested.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2003년도 추계종합학술대회
• /
• pp.31-34
• /
• 2003

In recent, the rapid convergence of telecommunication and broadcasting has been considered as one of the hot issues in the IT industry. This convergence will provide telecom operators with both opportunities and threatens. This is because that telecom operators can enter the broadcasting industry, whereas broadcasters will also have a chance to provide telecom services. This work aims to discuss the business strategy for telecom operators to provide a TV VOD service, one of the convergence services between telecommunication and broadcasting, through the high-speed internet which is so much served in Korea. It seems that this service will achieve two business goals, namely "to minimise an additional investment" and "to find out a new benefit source", by fully utilising a current high-speed internet infrastructure. Finally, this paper mainly contains the market overview of in telecom and broadcasting service, the definition of TV VOD service and the necessity for this service, a market forecasting and the provision strategy of major telecom operators, and key success factors and a benefit model.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권5호
• /
• pp.97-102
• /
• 2000

In this paper, a methodology for designing a controller based on inverse dynamics for speed control of DC motors is presented. The proposed controller consists of a prefilter, the inverse dynamic model of a system and the PI controller. The prefilter prevents high frequency effects from the inverse dynamic model. The model of the system in characterized by a nonlinear equation with coulomb friction. The PI controller regulates the error between the set-point and the system output which may be caused by modeling error, variations of parameters and disturbances. The output which may be caused by modeling error, variations of parameters and disturbances. The parameters of the model and the PI controller are adjusted offlinely by a genetic algorithm. An experimental work on a DC motor system is carried out to illustrate the performance of the proposed controller.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1858-1863
• /
• 2003

The properties of a machine tool greatly affect machining quality since a machine tool has large variance in its features. Machine tool makers want to find best machining condition with the one that they have built. Machine builders need to develop test specimen since it helps finding characteristics of machine tools when the machining properties of the specimen are analyzed. This paper develops test specimen to identify features of the main spindle, the feeding device, and the frame of a machine tool. The specimen is machined with a high speed machine and the features of the machine are analyzed with test items. They are surface roughness, overshoot in axial movement, errors in circular movement, feeding with small movement, and compensational error. This work can improve usability for a machine tool in machining practice.