• Elastomers and Composites
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• v.53 no.1
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• pp.13-18
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• 2018

A face seal comprising a metal ring and acrylonitrile butadiene rubber (NBR) was installed in the driving part and suspension unit. The seal serves as a bearing and simultaneously prevents entry of foreign matter from external environment as well as internal oil leakage. Subsequently, the rubber-rod ring generates axial pressure owing to rubber elasticity (hardness), performs static sealing function between housing details and outer diameter of seal, and transmits rotational torque to the rotating support ring. In order to improve the durability of NBR, which performs the above tasks, and to effectively use it in tracked-vehicle applications at extreme temperatures, this study reports a mixing design approach to enhance cold and oil resistances of NBR.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.482-487
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• 2001

This paper introduces a Lorentz force type four-pole self-bearing motor, where the new pole arrangement of a stator is intended to function both as a synchronous PM motor and as a magnetic bearing. The Lorentz force type has some good points such as linearity of control force, freedom from flux saturation, and high efficiency unlike conventional self-bearing motors. Mathematical expressions of torque and radial force are derived to show that they can be separately controlled regardless of rotational speed and time. To verify the proposed theory, a prototype is made, where a ring-shape outer is actively controlled in two radial directions while the other motions are passively stable supposing the radial stability. Through some experiments, it is shown that the proposed scheme can provide high capability and feasibility for a small high-speed self-bearing motor.

• Journal of KSNVE
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• v.8 no.3
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• pp.477-484
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• 1998

An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the prewist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and prewist angles, lead to the coupled motions of the shaft and the bladed disk.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.372-376
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• 1990

This paper represents a control method of improving the performance of direct drive robot. The direct transfer of torque and rotational speed of direct drive motor to the robot body without reduction gear makes the robot speed fast. However, the variation of inertia matrix and low friction cause the control difficult, and one more effort must be in the reducing the acceleration and deceleration time to reduce the cycle time. To fasten the cycle time and to improve the robustness of robot, one control method is developed, and implemented in the Goldstar DD robot. This method does not need to change the conventional PI type control structure, but one additional compensational control law is required. The control law can be obtained via inverse dynamic model of robot, and inverse model of existing control loop. The effects of this control law are shown in this paper.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1950-1953
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• 1996

A $1\;{\times}\;4$ micro mirror array is designed and fabricated. In contrast to other micro mirrors which utilize torsional flexure hinges or cantilevers for restoring torque and supporting purpose, we have placed a substrate hinge structure under each mirror. Each micro mirror consists of address electrode, substrate hinge consisting of pin and staple, supporter post, and mirror plate. Electrical connection between mirror plate and ground electrode is established by substrate hinge. Mirror undergoes a rotational motion due to electrostatic force when voltage difference is applied between address electrode and mirror plate. Micro mirrors with two different types of staple shape and two different pin sizes are designed and fabricated. Each mirror is designed to have ${\pm}\;10^{\circ}$ of deflection angle and have $100\;{\times}\;110\;{\mu}m^2$ of size.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.958-964
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• 2015

This paper implements a model of a double excited three-degree-of-freedom motor (3-DOF) coupled with a PI current controller for position control. The rotational trends of the rotor according to the applied steps are identified using a motion equation. The simulation model is a complete electrical and mechanical model of a 3-DOF motor, which mainly consists of mechanical torque equations, a nonlinear equivalent magnetic circuit, and a PI current controller. This machine is tested using the manufactured control board using the same conditions as in the simulation, where the experimental results also verify the accuracy of the simulation results.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.572-578
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• 2011

The vane type air-motor hand-piece is used widely in the dental services. There are a lot of experimental studies about air-motor but eccentrically off not many numerical studies by using Computational Fluid Dynamics. An air-motor has rotor which rotates at the center of inner housing. The retractable vanes are installed on the rotor. As the rotor of the air-motor rotates, vanes move up and down straightly in the radial direction along the guide. Therefore we have to analyze the unsteady flow field by accurate time dependent marching technique. ANSYS 12.0 CFX is used to analyze unsteady vane-motor flow field Analysis of the changing control volume inside air-motor is implemented by user-defined functions and moving mesh options. Rotational speed of the rotor is approximately 23,000rpm.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.163-172
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• 1998

The design fundamentals of the shaking tables are briefly discussed. In order to understand the recent trends in development of the shaking tables, the characteristics and performances of the major seismic testing facilities are investigated. The international standards related to the vibration tests using shaking table are also overviewed. The newly designed multipurpose biaxial shaking table of Hyundai Heavy Industries, Co., Ltd. is introduced. It has the capabilities to perform the vibration, shock and seismic qualification tests in two simultaneous and independent directions (vertical and horizontal directions). Since the shaking table adapts four extremely stiff torque instead of much more expensive hydraulic actuators, these tubes can restrain two undesired rotational motions. Regarding the manufacturing and maintenance costs, two system is more economical since it has only two hydraulic actuators unlike others.

• Journal of Magnetics
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• v.22 no.2
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• pp.344-351
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• 2017

Wireless magnet pumps are used in medical applications and are particularly useful as artificial heart ventricular assist devices (VADs). To investigate wireless operation of magnetic pumps, we fabricated three types of magnetic impellers using bonded magnets by blending magnetic powders of SmFeN, NdFeB, and Sr-ferrite. We investigated the magnetic properties of the fabricated magnetic impellers, which are driven by the application of magnetic coupling with an external driving magnet or external coil system, without a driving motor, shaft, or mechanical bearings. The use of wireless magnetic pumps is therefore not complicated by critical issues of size, heat, and vibration, which are very important issues for blood pumps. The magnetic properties of the impellers, such as their rotational speed, driving torque and hydrodynamic performance, determine their wireless driving ranges. We conducted performance evaluations of the impeller's magnetic wireless manipulation, heat, and vibration. In addition, we carried out an animal test to confirm the suitability of the wireless magnetic pumps for use as biventricular assist devices (BiVADs).

• Journal of International Academy of Physical Therapy Research
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• v.8 no.2
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• pp.1158-1162
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• 2017

The purpose of the study was to investigate the strength of sokinetic muscle by the position of a volleyball players. Analysis and comparison of shoulder dynamic stability will be conducted according to rotational movement of the shoulder during spiking and serving amongst the various positions. Fifty professional Korean female volleyball players (age: 20~30), all different positions - attacker (left and right), center, setter, and libero were The concentric peak torque, strength ration of the internal and external rotation of the shoulder girdle for both dominant and non-dominant arms. Firstly, there were significant differences found for the strength ratio between the setter and the other positions in the dominant arm. On a second note, there was a significant decrease in shoulder dynamic stabilization for both the attacker and center in the dominant arm. However, there were no significant differences for the setter or the libero. This study suggests that the isokinetic muscle strengths of the volleyball players are different from each other.