• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.913-914
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• 2017

액체로켓엔진 개발 과정에서 중량을 절감하고 구조 신뢰성을 증가시키기 위해서는 엔진 시스템에 대한 구조 해석이 필요하다. 발사체는 비행 중 자세제어를 위해 엔진의 TVC (thrust vector control) 구동기의 변위를 변화시켜 연소기를 회전하여 추력의 방향을 제어한다. 본 연구에서는 연소기 김발을 하는 75톤급 액체 로켓 엔진에 대하여 TVC 구동 전/후의 정적 구조 해석을 수행하고 비교하였다.

• 대한기계학회논문집A
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• 제26권10호
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• pp.1997-2007
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• 2002

Composite air spindles are appropriate for the high-speed and the high-precision machining as small hole drilling of printed circuit board (PCB) or wafer cutting for manufacturing semiconductors because of the low rotational inertia, the high damping ratio and the high fundamental natural frequency of composite shaft. The axial load and stiffness of composite air spindles fur drilling operation are determined by the thrust ben ring composed of the air supply part mounted on the housing and the rotating part mounted on the rotating shaft. At high-speed rotation, the rotating part of the thrust bearing should be designed considering the stresses induced by centrifugal force as well as the axial stiffness and the natural frequency of the rotating shaft to void the shaft from failure due to the centrifugal force and resonant vibration. In this work, the air supply part of the thrust bearing was designed considering the bending stiffness of the bearing and the applied load. The rotating part of the thrust bearing was designed through finite element analysis considering the cutting forces during manufacturing as well as the static and dynamic characteristics under both the axial and con trifugal forces during high-speed rotation.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.564-569
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• 2012

This paper proposes a hybrid-excited linear synchronous motor (LSM) that has potential applications in a magnetically levitated vehicle. The levitation and thrust force characteristics of the LSM are investigated by means of three-dimensional (3-D) numerical electromagnetic FEM calculations and experimental verification. Compared to a conventional LSM with electromagnets, a hybrid-excited LSM can improve levitation force/weight ratios, and reduce the power consumption of the vehicle. Because the two-dimensional (2-D) FE analysis model describes only the center section of the physical device, it cannot express the complex behavior of leakage flux, which this study is able to predicts along with levitation and thrust force characteristics by 3-D FEM calculations. A static force tester for a hybrid-excited LSM has been manufactured and tested in order to verify these predictions. The experimental results confirm the validity of the 3-D FEM calculation scheme for the description of a hybrid-excited LSM.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.52-54
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• 1998

LOA is the linear electromechanical device that mover is similar to secondary conductor of LIM. The mover reciprocates along stroke by supplying the alternating current to primary coil. LOA is the simpler and more efficient than other linear apparatus using the rotary motor because LOA produce the thrust force without any mechanical converter such as cam, clutch, belt, rack and pinion, etc. This paper deals with the static characteristics of moving coil type LOA by virtual work method, FEM analysis and experiment Results show that thrust force increases when mover travels form center to both ends.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권1호
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• pp.1-8
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• 2003

Generally, thrust force of double-sided LPM is more powerful than that of single-sided LPM. Also, double-sided LMP can be effectively applied to the high-precision position system with its simple control scheme. However, An equality between two airgap lengths Is a necessary condition for its high performance. If a little difference between two airgaps is existed, unbalanced normal force and undesirable vibration will be generated. Additionally, even though two airgap lengths are absolutely same, undesirable vibration can be generated because the direction of instantaneous normal force on mover is changed according to excitation methods. An effect of inequality of two airgap lengths is presented in this paper. Distribution of airgap permeance vs. relative displacement is analyzed by two dimensional finite element method. Excitation From this results, current waveforms to reduce the undesirable vibration is proposed.

• International Journal of Aeronautical and Space Sciences
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• 제12권2호
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• pp.134-148
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• 2011

In general, forces acting on aerospace structures can be divided into two categories-a) conservative forces and b) nonconservative forces. Aeroelastic effects occur due to highly flexible nature of the structure, coupled with the unsteady aerodynamic forces, causing unbounded static deflection (divergence) and dynamic oscillations (flutter). Flexible wing panels subjected to jet thrust and missile type of structures under end rocket thrust are nonconservative systems. Here the structural elements are subjected to follower kind of forces; as the end thrust follow the deformed shape of the flexible structure. When a structure is under a constant follower force whose direction changes according to the deformation of the structure, it may undergo static instability (divergence) where transverse natural frequencies merge into zero and dynamic instability (flutter), where two natural frequencies coincide with each other resulting in the amplitude of vibration growing without bound. However, when the follower forces are pulsating in nature, another kind of dynamic instability is also seen. If certain conditions are satisfied between the driving frequency and the transverse natural frequency, then dynamic instability called 'parametric resonance' occurs and the amplitude of transverse vibration increases without bound. The present review paper will discuss the aeroelastic behaviour of aerospace structures under nonconservative forces.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.182-184
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• 2001

Linear pulse Motor(LPM) are used a field where smooth linear motion is required, and it's position accuracy higher than that of a lead. According to the advantage such as simplicity of mechanical frame, high reliability, precise open_loop operation, low inertia etc LPM is applied largely where it have made motor of this kind more and more attractive in many application areas such as factory automation and high speed positioning. This paper is researched to analyze for thrust force characteristic of hybrid LPM. Both the thrust and normal force are very sensitive to the airgap and tooth pitches of the force and platen. To find the optimal design parameter on the hybrid LPM for the embroidery machine. For the field analysis, the finite element method(FEM) is employed for calculating the force. The reluctance models will be used the magnetic permeance of airgap under static-conditions. The forces between forcer and platen have been calculated using the virtual work mathod.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권2호
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• pp.137-141
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• 2005

A transverse flux, PM-exited linear motor (TFM-LM) with inner mover was designed and built. Its output power density is higher and its weight is lower than those of the conventional PM exited linear synchronous motors (PM LSM). To obtain the maximum thrust force under the given volume, the thrust force density with respect to the ratio of the slot width and the length of pole pitch is analyzed by the 3-dimension finite element method (FEM). Finally, calculated static thrust forces was compared with the experimental values. The calculated and measured performance of the transverse flux, PM-exited linear motor with inner mover revealed great potential for system improvements by reducing the mass of the linear motor. For examples, when this motor was applied to a ropeless elevator, it was possible to increase the power density by more than 400% over the conventional PM-LSM. The results of this study recommend this type of motor for the ropeless elevator or gearless direct linear driving system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.18-21
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• 2001

This paper describes the method of vibration supprssion on a control algorithm using Neuro-Fuzzy Theory in Linear Pulse Motor (LPM). The total thrust force Is distorted by magnetic and coil flux, and we classify the harmonic parts of it. A modulated current from harmonic components of static thrust characteristics of LPM compensates with reference current to total thrust force. Low vibration is obtatained by the method of current compensation using ANFIS.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권1호
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• pp.27-33
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• 2005

The development of modern high-energy magnet materials has allowed the replacement of field coils in many different types of electromagnetic energy conversion machines. As well, the linear synchronous motor has recently been proposed for linear motion with high efficiency and thrust. Thus, this paper presents an analytical solution for the high thrust and cost reduction of the Iron-Cored Permanent Magnet Linear Synchronous Motor (PMLSM) considering magnetization arrays and geometry. Hence, the superior utilization points in each of the magnetization arrays are provided by the height ratio of the magnet/air-gap and magnet/winding coil, etc. In formulation, the space harmonic method in analytical solutions and the generalized 2-D tensor finite element analysis can be used to evaluate force components in magneto static devices including the magnetostrictive phenomenon.