• Journal of Applied Reliability
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• v.15 no.4
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• pp.233-240
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• 2015

We analyse reliability of multi-state UH-60 helicopter hydraulic pump system with a multi-functional standby component using Markov analysis method. The system consists of seven components: 2 main pumps, 1 standby pump, 2 primary servos, and 2 tail rotor servos. The standby pump can take over when one more than components fail. Therefore the standby pump is multi-functional standby component. The system has four states: good, deteriorated, dangerous, and failed. The components have 2 states: working and failed. We assume the system is unrepairable when the components fail. We estimate failure distributions and rates using collected failure time data in field. And we classify multi-state of the system according to emergency procedure of UH-60A student handout. We obtain the reliabilities of multi-state system using Visual Basic program because the differential equations is extremely complicated and tedious to solve.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.6
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• pp.557-567
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• 2015

The most decisive factor of major sources of a helicopter is the main rotor system and the rotor-induced vibration is one of the technical challenges which should be resolved to ensure comfort for crews and passengers. Passive vibration reduction devices are adopted in conventional helicopters and several types of passive devices are also used in Surion. In recent years, foreign helicopter manufactures have increasingly applied the application of AVCS (active vibration control system) because of their superior performance with lower weight compared to passive device. In addition to weight reduction, AVCS has advantages maintaining its performance over aircraft configuration changes and flight condition changes. The technology demonstration program was performed in order to validate the performance of AVCS when applied to Surion, and optimization process for finding optimal configuration of sensors and actuators. Optimal configuration was produced using ground and flight test data, and its performance was evaluated and compared with flight test result.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.499-505
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• 2004

A Propulsion System of the CRW(Canard Rotor Wing) type UAV(Unmanned Aerial Vehicle) was composed of the turbojet engine to generate the propulsive exhaust gas, and the duct system including straight bent ducts, tip-jet nozzles, a master valve and a variable main nozzle for three flight modes such as lift/landing mode, low speed transition flight mode and high speed forward flight mode. In this study, in order to operate safely the propulsion system, the dynamic Performance behavior of the system was modeled and simulated using the SIMULIN $K^{ }$, which is the user-friendly GUI type dynamic analysis tool provided by MATLA $B^{ }$. In the transient performance model, the inter-component volume model was used. The performance analysis using the developed models was performed at various flight condition, valve angle positions and fuel flow schedules, and these results could set the safe flight mode transition region to satisfy the inlet temperature overshoot limitation as well as the compressor surge margin. Performance analysis results using the SIMULIN $K^{ }$ performance program were compared with them using the commercial program GSP.m GSP.

• Progress in Superconductivity
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• v.12 no.1
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• pp.27-31
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• 2010

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. Many aspects of the quasi-static behavior of flywheel rotors still need to be studied closely, and the rotors require a stable and highly efficient supporting system such as high temperature superconductor (HTS) bearings, which offer dynamic stability without the use of active control. Quasi-static properties of HTS bearings in the radial direction provide data to solve problems which may occur in a running system. Since stiffness in countering rotor vibration is the main parameter for designing an HTS bearing system, we investigated the quasi-static properties of the magnetic force between permanent magnets(PMs) and HTS bulks in the radial direction. We measured radial stiffness, and discovered that bearing stiffness varied greatly depending on the number of active HTS bulks. This is valuable data for predicting the change in stiffness during partial HTS bearing failure. The quasi-static test results are used for optimal design and performance prediction for the 100 kWh class superconductor bearing.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.170-172
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• 2003

Among low power servo applications, classical DC motors are very popular because they are reasonably cheap and easy to control. The main disadvantage is the mechanical collector which has only a limited life period. Also, brush sparking can destroy the rotor coil, generate EMC problems. So permanent magnet brushless do motors and drives are being used increasingly in a wide range of applications. This has been made possible with the advantages of high performance permanent magnets with high coercively and residual magnetic, which make it possible for the PM to have superior power density, torque to inertia ratio and efficiency, when compared to an induction or conventional dc machine. This paper presents the design of a PM brushless dc motor drive simplistically operates as a classical dc motor. The BLDC motor drive system for this paper composes to the power integrated circuits, the one chip device. And several simple semiconductors add to drive system for a motor drive system simplistically operates as a conventional dc motor. Test results confirmed the feasibility of the proposed motor drive system design.

• Journal of information and communication convergence engineering
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• v.7 no.2
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• pp.209-214
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• 2009

The employment of the induction generator is preferable in the natural energy utilization by the minimum maintenance and the mechanical robustness, Another merit is also expected when it is connected to the power network system, because constant-voltage and constant frequency (CVCF) power generation is easily realized in spite of the variation of the rotor speed. However the induction generator needs much amount of the reactive power that reduces power factor in the primary side. The improvement of power factor in the primary side requires large VAR compensator, this point is solved, the merit of the induction machine as a main generator will become more established. This paper proposes a novel approach where the secondary is controlled by a PWM inverter not only to get CVCF power but also to improve the primary power factor. Basically the inverter is controlled so that the field current is supplied from the secondary side in this approach. The required capacity of the inverter is small, because only the slip power is controlled in the secondary side. In the experimental system where the sea wave torque simulator is used, the power factor is well improved by the microcomputer controlled PWM inverter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2225-2229
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• 2011

Squirrel cage induction motor is the main driving system of industrial field and familiar with its use in a large variety of applications. However, many engineer are unfamiliar with the induction generator, even though no difference exists between both machines except for the mode of operation. But an induction generator is commonly used for micro & small hydro power applications due to its simplicity, reliability, low cost and robustness. Input and output of induction motor has turned against at the induction generator operation. Rotation speed of induction generator is small faster than induction motor. As output of induction machines increases with the increasement of speed, so loss is same. Actually, generator efficiency is lower than motor at this condition. If induction generator is connected with mechanical load, total efficiency is decreased. In this paper, we analyzed that input, output, torque and efficiency is different from each other above and below synchronous speed.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.756-760
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• 2001

Two different designs of permanent magnet motors as direct wheel-set drive for the German high speed train ICE 3 are designed, one with surface mounted magnets (SM) and one with buried rotor magnets (BM). The surface magnet motor has $17\%$ less mass and a slightly higher efficiency and was therefore chosen for further investigations. Compared with the conventional drive system of the ICE 3, consisting of geared inverter fed induction machines, the gearless permanent magnet direct drive yields about $16\%$ lower losses. This calculation is based on the route parameters of the high speed track between Frankfurt/Main and Cologne in Germany, which is currently under construction.

• Smart Structures and Systems
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• v.6 no.4
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• pp.389-403
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• 2010

By using image recognition technology, this paper presents a new fault diagnosis method for rotating machinery with artificial immune algorithm. This method focuses on the vibration state parameter image. The main contribution of this paper is as follows: firstly, 3-D spectrum is created with raw vibrating signals. Secondly, feature information in the state parameter image of rotating machinery is extracted by using Wavelet Packet transformation. Finally, artificial immune algorithm is adopted to diagnose rotating machinery fault. On the modeling of 600MW turbine experimental bench, rotor's normal rate, fault of unbalance, misalignment and bearing pedestal looseness are being examined. It's demonstrated from the diagnosis example of rotating machinery that the proposed method can improve the accuracy rate and diagnosis system robust quality effectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.368-373
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• 2001

A major concern on high-energy centrifugal pump is the potential for interaction of two-phase flow phenomena with mechanical response of the pumping elements. The other concern is the pressure pulsations created from trailing edge of the impeller blade and flow separation and recirculation at partial load in centrifugal pumps. These interactions generating between rotor and casing cause dynamic pulsation on pump and exciting pipeline vibration. The higher severity responses, the more lead to failure of pump and system components. Finally, it cause severe axial vibration of single stage pump due to the hydraulic instability in flow condition below BEP.