• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.5
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• pp.211-220
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• 2003

The control method of programmable dynamometer for overall test of machine is to load the reference torque which is computed from torque transducer into motor under test. But the torque information detected from torque transducer have a lot of noise when the load torque of meter is a small quantity or changing. Thus, torque transducer must have a low pass filter to detect a definite torque information. But The torque delay generated by filter with torque transducer occur a torque trouble for meter torque of programmable dynamometer. Therefore, this kind of system could not perform dynamic and nonlinear load. In this paper, the control method using the load torque observer without a measure for torque transducer is Proposed. The proposed system improved the problem of the torque measuring delay with torque transducer, and the load torque is estimated by the minimal order state observer based on the torque component of the vector control induction meter. Therefore, the torque controller is not affected by a load torque disturbance. To verify a superiority of the proposed control algorithm, the analysis for a root locus of a conventional control method and the proposed one, and simulation and experiment is performed. Therefore we hope to be extended in industrial application.

• Proceedings of the Korean Reliability Society Conference
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• 2001.06a
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• pp.337-337
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• 2001

High voltage ceramic capacitors are widely applied in power electronic circuits, such as filters, snubbers, and resonant circuits, due to their excellent features of high voltage endurance and low aging. This paper presents a result of failure analysis and reliability evaluation for high voltage ceramic capacitors. The failure nodes and failure mechanisms were identified in order to understand the failure physics in a component. The causes of failure mechanisms for zero resistance phenomena under withstanding voltage test in high voltage ceramic capacitors molded by epoxy resin were studied by establishing an effective closed-loop failure analysis. Also, the condition for dielectric breakdown was investigated. Particular emphasis was placed on breakdown phenomena at the ceramic-epoxy interface. The validity of the results in this study was confirmed by the results of accelerated testing. Thermal shock test as well as pressure cooker test for high voltage ceramic capacitor mounted on a magnetron were implemented. Delamination between ceramic and epoxy, which, might cause electrical short in underlying circuitry, can occur during curing or thermal cycling. The results can be conveniently used to quickly identify defective lots, determine mean time to failure (MTTF) of each lot at the level of Inspection, and detect major changes in the vendors processes.

• Journal of Korean Society for Quality Management
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• v.21 no.2
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• pp.1-16
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• 1993

Early generations of products had little to no inherent capability to test themselves. The technologies involved often required only visual inspection and limited probing to troubleshoot the system once it was turned over to maintenance personnel. However, as the complexity of military and commercial systems grew, symptoms of failure became less noticeable to the operator. Therefore, the procedure to access, inspect, repair and replace a component became complicated, the requirements for personnel skill and testing equipment increased. and it took too long of a time to maintain a system. Meanwhile, the need for availability became more mission-critical and maintenance become very expensive. The obvious solution was to design in-system circuits or devices to self-test the primary system, the Built-In-Test(BIT) was born. This approach has continued right on up through present systems and is an integral part of systems now being designed. The object of this paper is to present a state-of-the-art research for filtering out the BIT diagnosis mistakes using Bayesian analysis and develop the algorithm for Redundant systems with BIT to improve BIT diagnosis.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1110-1118
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• 2011

The recent power add-on drive wheelchairs (PADWs) provide greater physical activity and easier transportability and may be an excellent alternative for the typical manual and powered wheelchairs. The driving system consists of a motor and a motor driver is the most important component of the PADW In this paper, design, implementation, and testing of a driving system for a PADW are presented. To design the output power and torque for the driving system, the equation of motion has been investigated. The motor and driver were fabricated with precise machining and assembled to implement our prototype driving system. The dynamometer test has been carried out using the prototype in order to examine the torque of the system. The experimental results demonstrates that the designed driving system can provide enough output power and efficiency for utilization in a PADW.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2321-2328
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• 2006

Today, SIP standard (The signalling protocol for the Internet phone service) raises to be the standard technique because the expandability is high and complexity is low. It is widely investigated and actively advocated to use Si81a1 ring protocol for SIP in VoIP service. SIP service can be applied even outside the Internet phone service; instance messaging and various multimedia technology are just an example. This paper proposed an embodiment proxy server for rambling support to use JAIN SIP API. It provides standard interface for testing the Proxy server for SIP and embodiment of user agent that transfer instant massaging and voice communication.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.11
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• pp.1885-1895
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• 1997

As track density needs to increase to the order of 10, 000 tpi, the suspension has become a critical component in hard disk drives. One of the main obstacles to attain high track density is the structural resonances of the suspension in lateral direction. We investigate the suspension dynamics through the experimental modal analysis and the finite element method. An LDV (Laser Doppler Vibrometer) is employed to measure the response of the suspension which is excited by a shaker and an inpulse hammer for the free condition and the loaded condition, respectively. After comparing the experimental and numerical results, we study how the initial geometry of the bend region affects the suspension dynamics. It is found that the natural frequency of the sway mode decreases as the bend ratio and the bend angle increase. The shape of torsional mode changes as the mass of a slider increases, resulting in a local decrease in the natural frequency.

• Tribology and Lubricants
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• v.32 no.1
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• pp.32-37
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• 2016

The wear characteristics of metal ball and seat in a metal-seated ball valve significantly affect the performances such as leakage and valve torque. In this work, the wear characteristics of metal ball and seat are experimentally investigated. A stainless steel ball and seat with a high corrosion-resistant coating are prepared and a component level test was performed. The hardness and surface roughness of specimens cut from the metal ball and seat are measured before and after the test using a micro-Vickers hardness tester and confocal microscopy, respectively. In order to assess the wear characteristics, the surfaces of the specimens are carefully examined after the test. The confocal microscope data show that the surface roughness values of both the ball and seat increase by a factor of 3-4, which may lead to an increase in valve torque. However, the wear of the seat is found to be more significant than that of the ball. In addition, a comparison of the surfaces of the ball and seat before and after testing revealed that adhesive and abrasive wear are the major wear mechanisms. The results of this study may aid in the design of metal-seated ball valves from the tribological point of view.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.745-752
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• 2007

In this study, the effects of flexible bodies in vehicle suspension components were investigated to enhance the accuracy of multibody dynamic simulation results. Front and rear suspension components were investigated. Subframes, a stabilizer bar, a tie rod, a front lower control arm, a front knuckle, and front struts were selected. Reverse engineering techniques were used to construct a virtual vehicle model. Hard points and inertia data of the components were measured with surface scanning equipment. The mechanical characteristics of bushings and dampers were obtained from experiments. Reaction forces calculated from the multibody dynamics simulations were compared with test results at the ball joint of the lower control arm in both time-history and range-pair counting plots. Simulation results showed that the flexibility of the strut component had considerable influence on the lateral reaction force. Among the suspension components, the flexibility of the sub-frame, steering knuckle and upper strut resulted in better correlations with test results while the other flexible bodies could be neglected.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.247-249
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• 2007

Urban dynamometer driving schedule(FTP-75 mode) plays very significant role on automotive emission test, due to reference point. The overall system energy efficiency of a HEV(Hybrid Electric Vehicle) is highly dependent on the energy management strategy employed. An energy source is the heart of a HEV. In order to applicable to a vehicle component, it must be need to real world test result. But, the present state of things have numerous problems. In this paper, be studied performed based on HEV simulation software in virtual world and chassis dynamometer test in real world and the result make a comparative. Toyota Prius vehicle was adapted as a modeling and real testing to evaluate the hybrid components and energy balancing management. The point at issue is voltage and current analysis for HEV battery SOC(State of Charge), and verification for energy.

• Journal of Advanced Navigation Technology
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• v.10 no.1
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• pp.26-33
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• 2006

This paper discusses the design and fabrication of a wireless VHF receiver for use in air traffic control. The VHF receiver was designed and tested in three modules: a control module, a receiver module and a power module, all of which were integrated into a single block for final testing. The fundamental performance of the receiver, and in particular, sensitivity, the most important factor, is designed to satisfy existing commercial wireless transmitter specifications for air traffic control. The receiver displays a sensitivity of -113 dBm, which is higher performance than existing commercial products, and is suitable for use as a basic component of CNS/ATM.