• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.1 no.1
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• pp.35-53
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• 1997

This paper analyzes the time complexity of Genetic Algorithm based Task Scheduling (GATS) which is designed for the scheduling of parallel programs with diverse embedded parallelism types in a heterogeneous network systems. The analysis of time complexity is performed based on two representation methods (REIA, REIS) which are proposed in this paper to encode the scheduling information. And the heterogeneous network systems consist of a set of loosely coupled parallel and vector machines connected via a high-speed network. The objective of heterogeneous network computing is to solve computationally intensive problems that have several types of parallelism, on a suite of high performance and parallel machines in a manner that best utilizes the capabilities of each machine. Therefore, when scheduling in heterogeneous network systems, the matching of the parallelism characteristics between tasks and parallel machines should be carefully handled in order to obtain more speedup. This paper shows how the parallelism type matching affects the time complexity of GATS.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.4
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• pp.140-146
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• 2002

High speed rotating machines can be very sensitive to rotating mass unbalance that is a major source of harmful vibration for many types of rotating machinery. So, the balancing procedure is needed for all high-speed rotating system. To save the time and cost of off-line balancing, many researchers have developed the on-line balancing devices and methods. In this paper, an active balancing device, which is an electro-magnetic type, is developed and the active balancing algorithm using influence coefficient method is also proposed. The active balancing experiment for flexible rotors during operation is performed by an active balancing device. As a result, controlled unbalance responses are below the vibration limit at all rotating speed ranges with critical speed.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.81-89
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• 2009

Dancer systems are typical equipment for attenuation of tension disturbances. Lately, demands for high speed roll-to-roll machines are rising but it is prior to attenuate the tension variation on the web entering into the printing zone to achieve the speed increment. Maintaining a constant tension before the first printing cylinder is the key of high speed, high quality printing. Dancer has been researched in two ways, whether it is controlled or not. The first one is active dancer and the other one is passive dancer. In the active dancer, a position of idle roll of dancer is measured and the roll is moved by external hydraulic cylinder to control tension disturbances. While the passive one composed with spring, damper and idle roll has no external actuator to position the idle roll. The tension disturbance causes movement of dancer roll and the displacement of the roll regulates the tension variation. On the other hand a composite type of dancer is applied for roll-to-roll printing machines. It has same apparatus as passive dancer. The displacement of roll is measured and front(or rear) driven roller is controlled to position the roll. In this paper, it is presented an analysis of pendulum dancer including position feedback PI control and logic for PI gain tuning in roll-to-roll machines. Pole-zero map and root locus with varying system parameters gives a design method for control of the dancer.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1042-1044
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• 2003

High speed PM machines are being developed as motor/generators for gas-turbine generator sets in smaller power sizes, and as motors for number of applications including gas compressors, machine tools and turbo molecular pumps. Due to the high peripheral speed of the rotor and the relatively high conductivity of the magnets used, rotor eddy current loss can be substantial. This paper deals with the calculation of rotor eddy-current losse in permanent magnet(PM) high speed motor using the analysis of harmonics.

• Journal of Biosystems Engineering
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• v.18 no.3
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• pp.230-238
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• 1993

The parte(I) of this paper deals with the motion analysis of a gear type high speed planting mechanism of rice transplanters. Following that this part(II) contains force analysis of the mechanism. Forces and moments acting on the mechanism were determined analytically and computer coded for the simulation of them on any IBM PC compatiable machines. The simulation program developed in this study can be used as a design tool and also for a sensitivity analysis.

• 유체기계공업학회:학술대회논문집
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• 1997.02a
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• pp.188-195
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• 1997

The application of PIV to the studies of fluid-machines, especially focused on turbo-machinery is reviewed by scrutinizing the previous investigation. Owing to the inevitable high-speed analysis of turbo-machinery consisting of rotating impellers, the importance of optical setups to cope with illumination problem is frequently mentioned as main ingredient affecting the PIV performance. And the acquisition of the relative velocity and absolute velocity is determined mainly by the optical recording conditions. A few studies cast satisfactory extension of the PIV data to quantitative pressure estimation and related noise assessment.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.51-57
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• 1998

In order to minimize vibration problems of rotating machinery rotors have been assembled through balancing machines. Since perfect balancing is impossible, residual unbalances cause serious vibration while the rotor is in high speed region. To minimize unbalance effects of magnetic bearing systems (AMB) during rotation on-line balancing methodology was studied. Unbalances were considered as disturbances of the system. The disturbance observer was used to estimate unbalance force from measurable state and input variables. Balancing inputs computed according to LQR and outputs of the observer were applied to eliminate unbalances during high speed rotation of the AMB. the effectiveness of the on-line balancing was verified through numerical simulations.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.668-678
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• 2003

For the purpose to facilitate development of high-speed spindle units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found out that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.306-310
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• 2010

On account of small size and light weight, a high-speed machine is regarded as a key technology for many future applications of drive systems. In high-speed applications, permanent magnet synchronous motors have a number of merits such as high efficiency and high power density. Therefore, they are suitable for driving the air-blower of a fuel cell electric vehicle (FCEV) where space and energy savings are critical. Particularly, a surface-mounted permanent magnet synchronous motor (SPMSM) of them is mainly used as a high-speed machine. However, the motor has a fatal flaw due to a retaining can to maintain the mechanical integrity of a rotor assembly. The can results in the increase of magnetic air-gap length in the SPMSM. Thus, in this paper, an interior permanent magnet synchronous motor (IPMSM) is applied in order to drive the air-blower of FCEV instead of the SPMSM, and the experimental results of two models are compared to verify the capability of the IPMSM for high-speed applications.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1172-1172
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• 2001

Compact Near Infrared Diode Array Spectrometers offer new possibilities for on line quality assurance in the agricultural sector. Due to their speed and complete robustness towards temperature fluctuations and mechanical shock Diode Array Spectrometers are suitable for the use on Agricultural Harvest Machines. The growing consumer consciousness of food quality in combination with falling manufacturing prices demands procedures for an effective quality control system. The various conventional types of NIR instruments which have so far been used in laboratories are unsuitable for mobile applications under the rough conditions of field cropping not only because of their slow speed of measurement but also because of their shock sensitive filter wheels and monochromators necessary for fractionating polychromatic light. Another advantage of the on line use is the reduction of the sampling error because of the continuously measurement of the whole product. Considering the large economic importance of the dry matter content on agricultural products it is of particular advantage that water belongs to those constituents which are most easily assessed in the near infrared. While other constituents of economic importance such as starch, oil and protein in grains and seeds have a much lesser effect on NIR signals, their contents can nonetheless be assessed with high analytical precision on freshly harvested grains and seeds. In the last years several applications for on line quality assessment on harvesting machines were developed and tested. The talk will give an overview and outlook on existing and future possibilities of this new field of NIR applications.