• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.12
• /
• pp.1173-1179
• /
• 2007

In recent years, research to machine large-surface micro-features has become important because of the light guide panel of a large-scale liquid crystal display and the bipolar plate of a high-capacity proton exchange membrane fuel cell. In this study, in order to realize the systematic design technology and performance improvements of an ultra-precision machine for machining the large-surface micro-features, a structural characteristic analysis was performed using its virtual prototype. The prototype consisted of gantry-type frame, hydrostatic feed mechanisms, linear motors, brushless DC servo motor, counterbalance mechanism, and so on. The loop stiffness was estimated from the relative displacement between the tool post and C-axis table, which was caused by a cutting force. Especially, the causes of structural stiffness deterioration were identified through the structural deformation analysis of sub-models.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.840-846
• /
• 2007

This paper investigates the dynamic behavior of a HDD spindle system due to the imperfect roundness of a rotating shaft. The shaft of a spindle motor rotates with eccentricity by the unbalanced mass of the rotating part. The eccentricity generates the run-out of a spindle motor which results in the eccentric motion of a rotating part. Roundness of a shaft affects this motion which limits the memory capacity of a HDD. This research proposes a modified Reynolds equation for the coupled journal and thrust FDBs to include the variable film thickness due to the roundness. Finite element method is used to solve the Reynolds equation for the pressure distribution. Reaction forces and friction torque are obtained by integrating the pressure and shear stress, respectively. The dynamic behavior is determined by solving the equations of a motion of a HDD spindle system in six degrees of freedom with the Runge-Kutta method to characterize the motion of a rotating part. This research shows that the roundness of a rotating shaft causes the excitation frequency with integer multiple of a rotating frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.514-520
• /
• 2001

A 300Wh class flywheel energy storage system using high Tc superconductor bearings(HTC SFES) is being developed by KIMM and KEPRI. HTC SFES consists of a flywheel rotor, superconductor bearings, a motor/generator and its controller, touch-down bearings, vacuum chamber, etc. Stiffness and damping values of superconductor bearings were experimentally estimated to be 67,700N/m and 29Ns/m respectively. The present HTC SFES was designed to have maximum operating speed of 33000 rpm, which is far above 2 rigid body mode critical speeds of 645rpm and 1,275rpm. Leaf-spring type touch-down bearing were utilized to have the system pass safely through the system critical speeds. It has been experimentally verified that the system can run stably up to 28,000 rpm so that HTC SFES is now expected to reach up to its maximum design speed of 33,000rpm without any difficulties. The Halbach array motor & generator has also been proven its effectiveness on transferring electrical energy to a rotaing composite flywheel in kinetic form.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.3
• /
• pp.261-267
• /
• 2009

The spindle with a built-in motor can be used to simplify the structure of machine tool system, while the rotor has unbalance mass inevitably. Therefore, it is important to recognize the effect of unbalance mass. This paper presents analysis of dynamic behavior of a high speed spindle with a built-in motor. The spindle is supported by the angular contact ball bearings and the rotor is fixed at the middle of spindle. The spindle used in CNC automatic lathe has been investigated using combined methodologies of finite elements and transfer matrices. The Houbolt method is used for the integration of the system equations and the dynamic behavior of spindle is obtained considering unbalance mass of rotor. Results show that increasing rotational speed of spindle magnifies the whirl responses of spindle seriously. Also the whirl responses of spindle are affected by the other factors such as unbalance mass and bearing stiffness.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.10a
• /
• pp.26-31
• /
• 2002

The recent machine tools are requested so high-quality processing and productivity increasing. Therefore, it is so necessary to develop technology fur high-speed and high-precision. This thesis touches on the development of high speed and intellectual line center. At first, the line center is necessary that strong structure, compact structure and light weight design for high-speed processing and transfer. So, it is necessary that examination of new materials and structures for light-weight and control devices for precision processing. So. it is going to make mention of the process of 1st model production for the above-mentioned based on test model production and evaluation.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.9
• /
• pp.1341-1349
• /
• 2001

In this paper, 3 D.O.F. actuator, which has three degrees of freedom in one joint, is proposed. The proposed 3 D.O.F. spherical actuator is composed of the rotor and atator. The upper plate of the stator supports the rotor and five electromagnets are located at the base of the stator. The rotor has two permanent magnets, and each rotational axis of the rotor gimbal system is supported by the bearing. To find out the governing equations for the torque generation, Coulombs law and Lorentz force with respect to magnetism is applied. As the experimental results, if the distance between electromagnet and permanent maget is far enough, the force between these magnets can be expressed from current of coils and z-axial distance. For the purpose of control 3 D.O.F. actuator, PID control law is applied. The experimental results are presented to show the validity of the proposed 3 D.O.F. actuator.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.1
• /
• pp.585-591
• /
• 2017

Turbocharging is widely used in diesel and gasoline engines as an effective way to reduce fuel consumption. But turbochargers have turbo-lag due to mechanical friction losses. Bearing friction losses are a major cause of mechanical friction losses and are particularly intensified in the lower speed range of the engine. Current turbochargers mostly use oil bearings (two journal bearings and one thrust bearing). In this study, we focus on the bearing friction in the lower speed range. Experimental equipment was made using a drive motor, load cell, magnetic coupling, and oil control system. We measured the friction losses of the turbocharger while considering the influence of the rotation speed, oil temperature, and pressure. The friction power losses increased exponentially when the turbocharger speed increased.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.14 no.2
• /
• pp.168-175
• /
• 2009

This paper proposes an enhanced algorithm for sensorless control of 45,000rpm/22kw type Permanent Magnetic Synchronous Motor (PMSM) with air-foil bearing. The proposed algorithm is based on iterative adaptive flux observer for sensorless control of the motor in wide speed range by on-line estimating angle and velocity of rotor. Simulation error between actual and estimated angle of rotor is analyzed to enhance characteristics of frequency response of conventional adaptive flux observer, which results in stable response in wide range of speed. Using the iteration number for stable phase-delay characteristics, the observer enhances the dynamic characteristics of the observer within current control period. The experiment results show the reliable performance of the proposed algorithm through starting to high speed operating range.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.2
• /
• pp.164-170
• /
• 2016

The initial urban railway was only required to perform its role as means of transportation. As the time of staying in an underground platform was extended, it has been faced with the issues of environmental improvement as a living space. Therefore, the sliding automatic door, which is the basis of the screen door, is used widely for large distribution stores, hospitals, restaurants, and public offices for customers' convenience and as a convenient method to control access. Therefore, screen doors are required for the purpose of customers' convenience, securing safety, establishing pleasant station buildings, and energy savings. It would be also necessary to develop the optimal design technology for a screen door system through the design of element parts and to ensure reliability. Therefore, this paper calculated, interpreted, and verified the theoretical weight of the composition parts to verify the design drive hardness of the motor for screen doors necessary for the safety of subways.

• Proceedings of the KIEE Conference
• /
• 2006.04b
• /
• pp.182-184
• /
• 2006

A down-scaled simulator is developed to simulate typical faults in induction motor such as short-turn stator winding, broken rotor bar, dynamic and static air-gap eccentricity, bearing trouble, and mechanical unbalance. The simulator is used as an initial builder to develop design algorithm for real-time faults detecting system by processing an abnormal signal and characteristics in each fault.