• 열처리공학회지
• /
• 제32권3호
• /
• pp.124-130
• /
• 2019

Friction stir welding is one of the interesting welding methods for titanium and its alloy which proceeds with plastic flow due to thermo-mechanical stirring and friction heat. Solid-state welding can solve severe problems such as high-temperature oxidation, interstitial oxygen diffusion and grain coarsening by liquid-state welding. Dynamic recrystallization and grain refinement can vary significantly with the plunging load and rotational speed of tool during friction stir welding, and suitable process conditions must be optimized to obtain microstructure and better mechanical characteristics. Suitable FSW conditions were 1000 kg of plunging load and 200 rpm of rotational speed and it showed YS 270 MPa, UTS 332.1 MPa, and El 17.3%, which were very similar to those of wrought titanium sheet.

• 제어로봇시스템학회논문지
• /
• 제10권12호
• /
• pp.1202-1209
• /
• 2004

This paper presents a design methodology of a Digital Servo Signal Processor for high speed CD-RW drive systems. The proposed Digital Servo Signal Processor enables us to develop CD-related systems for the very high speed applications and is one of the key components of the CD-RW systems. The proposed center compensation servo control is newly built for an actuator shaking due to the fast response of a step motor when it jumps to a long distance. A control method compensating for eccentricity of a disc is implemented for operating robustly at a higher rotational speed. This servo mechanism is more size efficient and less power consumed because it is implemented using a ARM7 embedded processor and hardware digital filters. Furthermore, it is convenient to upgrade firmware for the future required functions. From experimental results, we can see that the performance of the control system is improved greatly. The proposed servo algorithm shows a shorter setting time including a pull-in time and a faster access time. It can be applied easily to the DVD-ROM and the DVD-RAM which have the same optical structure.

• 한국정밀공학회지
• /
• 제19권2호
• /
• pp.213-219
• /
• 2002

A cone-shaped active magnetic healing spindle system for high speed internal grinding with built-in motor that has 7.5kW power and maximum rotational speed of 50,000 rpm is designed and built. Using cone-shaped AMB(Active Magnetic Bearing) system, the axial rotor dick and magnets of conventional 5-axis actuating design can be eliminated. so this concept of design provides a simple magnetic bearing system. In this paper, the cone-shaped electromagnets are designed by magnetic circuit theory, and a de-coupled direct feedback PID controller is applied to control the coupled magnetic bearings. The designed crone-shaped AMB spindle system is built and constructed with a digital control system, which has TMS320C6702 DSP, 16 bit AD/DA, switching power amplifier and gap sensors. As the AMB system provides high damping ratio eliminating overshoot and resonance speed, this spindle runs up to 40,000 rpm stably with about 5${\mu}{\textrm}{m}$ of runout.

• International Journal of Precision Engineering and Manufacturing
• /
• 제7권3호
• /
• pp.3-7
• /
• 2006

For the purpose to improve and to automate designing of high-speed spindle units (SU's), we have developed the mathematical models and software to estimate SU performance characteristics, including the run-out of spindles running on ball bearings. In order to understand better the mechanics of high-speed SUs, the dynamic interaction of ball bearings and SU, and the influence of the bearing imperfections and SU's operational conditions on the run-out, we have carried out computer simulation and experimental studies. Through the study of SU's, we have found out that run-out of SU can vary drastically with variation of rpm. The influences of rotation speed and of accuracy parameters of bearings on the SU accuracy have the greatest importance. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models and software developed to the real SU's.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 전력전자학술대회 논문집
• /
• pp.123-128
• /
• 1998

This paper describes the evaluation of a force-reflecting interface with ultrasonic motors(USMs). The force-reflecting interface allows a human to feel object within virtual environment. To effectively display the mechanical impedance of the human hand we need a haptic device with specific characteristics, such as low inertia, almost zero friction and very high stiffness. USMs have attracted considerable attention as the actuator satisfied these conditions. USMs combine features such as high driving torque at low rotational speed, high holding torque and fast response therefore we studied two degree of freedom force-reflecting haptic system.

• 한국생산제조학회지
• /
• 제5권3호
• /
• pp.40-49
• /
• 1996

The problem related to the rotational vibration at steering wheel end of passenger cars during high speed driving is investigated. to analyze vibration of steering wheel, a steering system of passenger car is modelled in twelve degrees of freedom including backlash effect of rack and pinion gear system. The one degree of freedom system with backlash in investigated by the analytical method. Consequently the skeleton curve and the frequency response curves are computed. The steering system is analyzed by the numerical simulation using the 4th order Runge-Kutta method, the obtained results are compared with the experimental data. Also the effects of the change of rack gear tooth stiffness and backlash on the acceleration level of steering wheel are investigated. As a result, it can be found that the acceleration level of steering wheel becames lower as the rack gear tooth stiffness becames higher, and that acceleration level becames high as the magnitude of backlash between rack and pinion gear increase.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.388-391
• /
• 2006

In the development of sheet-handling machinery, it is important to predict the static and dynamic behavior of the sheets with a high degree of reliability because the sheets are fed and stacked at such a high speed. Flexible media behaves geometric nonlinearity of large displacement and small strain. In this paper, static and dynamic analyses of flexible media are performed by FEM considering geometric nonlinearity. Linear stiffness matrix and geometric nonlinear stiffness matrix based on the Co-rotational(CR) approach are derived and numerical simulations are performed by Updated Newton-Raphson(UNR) method and Newmark integration scheme.

• 한국초전도ㆍ저온공학회논문지
• /
• 제26권1호
• /
• pp.25-30
• /
• 2024

High-temperature superconducting rotors offer advantages in terms of output-to-weight ratio and efficiency compared to conventional phase conduction motors or generators. The rotor can be cooled by conduction cooling, which attaches a cryocooler, and by refrigerant circulation, which uses circulating liquid or gas neon, helium and hydrogen. Recent work has focused on environmental issues and on high-temperature superconducting motors cooled with liquid hydrogen that can be combined with fuel cells. However, to ensure smooth supply and return of the cryogenic cooling fluid, a cryogenic rotational coupling between the rotating and stationary parts is necessary. Additionally, the development of a sealing structure to minimize fluid leakage applicable to the coupling is essential. This study describes the design and performance evaluation of a non-contact sealing method, specifically a labyrinth seal, which avoids power loss and heat load caused by friction in contact sealing structures. The seal design incorporates a spiral flow path to reduce leakage using centrifugal force, and computational fluid dynamics (CFD) simulations were conducted to analyze the flow path and rotational speed. A performance evaluation device was configured and employed to evaluate the designed seal. The results of this study will be used to develop a cryogenic rotational coupling with supply and return flow paths for cryogenic applications.

• 전기학회논문지
• /
• 제62권7호
• /
• pp.1045-1052
• /
• 2013

In this study we deal with design procedures for the flywheel energy storage system that has the capacity to store the regenerative energy produced from the railway vehicles. The flywheel energy storage system (FESS) stores the regenerative electrical energy into the high speed rotational flywheel, by conversion the electrical energy into the mechanical rotational energy. Thus the FESS is composed of the energy conversion components, such as the motor and generator, mechanical support components, such as the rotational rotor, the magnetic bearings to support the rotor, and the digital controller to control the air gap between the rotor and the magnetic bearings. In this paper the design procedures for the rotor operating at the rigid mode and the magnetic bearings to support the rotational rotor without contact are presented.

• 한국전산구조공학회논문집
• /
• 제33권4호
• /
• pp.209-216
• /
• 2020

본 논문에서는 CR 쉘 요소 해석 기법을 활용하여 모터사이클 후방프레임의 해석을 수행하였다. CR 쉘 요소 해석기법은 적은 요소수에서 NASTRAN보다 빠르게 수렴하는 결과를 보여주었다. 후방프레임은 수직 방향에 대해 실 주행 조건 시 엔진 RPM과 근접한 고유진동수를 가짐을 보여주었다. 2가지 설계변수를 반영한 세 가지 경우에 대한 해석이 제시되었으며, 보강용 자재는 동일한 중량 변화 내에서 두께 변화에 비해 더 유용한 수단임을 확인할 수 있었다. 본 연구의 구조 해석은 차후 모터사이클 후방프레임의 내구성을 향상하는 설계 개선 연구에 효과적으로 활용될 수 있다.