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Daejeon, South Korea

Chung S.-C.,Hanyang University | Park C.-H.,KIMM
Proceedings - ASPE 2011 Annual Meeting | Year: 2011

To verify previously developed nut stiffness model of a ballscrew, an experimental setup measuring the axial deformation and the stiffness of a ballscrew has been devised. Single-nut and double-nut ballscrews are tested under several load and assembly conditions. It is confirmed that experimental values are around 80% of the mathematical nut stiffness. Source

Kim K.-J.,Chungnam National University | Han J.-B.,Chungnam National University | Han H.-S.,KIMM | Yang S.-J.,Chungnam National University
Vehicle System Dynamics | Year: 2015

Dynamic instability, that is, resonance, may occur on an electromagnetic suspension-type Maglev that runs over the elevated guideway, particularly at very low speeds, due to the flexibility of the guideway. An analysis of the dynamic interaction between the vehicle and guideway is required at the design stage to investigate such instability, setting slender guideway in design direction for reducing construction costs. In addition, it is essential to design an effective control algorithm to solve the problem of instability. In this article, a more detailed model for the dynamic interaction of vehicle/guideway is proposed. The proposed model incorporates a 3D full vehicle model based on virtual prototyping, flexible guideway by a modal superposition method and levitation electromagnets including feedback controller into an integrated model. By applying the proposed model to an urban Maglev vehicle newly developed for commercial application, an analysis of the instability phenomenon and an investigation of air gap control performance are carried out through a simulation. © 2015 Taylor & Francis. Source

International Journal of Advanced Robotic Systems | Year: 2015

This paper proposes a new robot controller for motor-system rehabilitation. The proposed controller simultaneously realizes rehabilitation motion tracking and force generation, as predefined through a musculoskeletal model-based optimization process. We introduce control parameters of weighted control action priorities for the motion-tracking and force-generation tasks, based on the position-tracking error. With the weighted control action priorities, the robot accords higher priority to motion tracking at the robot end point when the position-tracking error is larger than a threshold value, and to force generation when the position-tracking error is smaller than a threshold value. Smooth motion trajectory has to be designed and applied in robot-based rehabilitation. Through simulations and experimental results, we show the usefulness of the proposed control method. © 2015 Author(s). Licensee InTech. Source

Jeong I.H.,University of Seoul | Jeong I.H.,Defense Agency for Technology and Quality | Jung D.H.,University of Seoul | Shin K.S.,University of Seoul | And 2 more authors.
Electronic Materials Letters | Year: 2013

The electrical characteristics and thermal shock properties of a Through Silicon Via (TSV) for the three dimensional (3D) stacking of a Si wafer were investigated. The TSVs were fabricated on a Si wafer by a laser drilling process. The via had a diameter of 75 μm at the via opening and a depth of 150 μm. A daisy chain was made for testing electrical characteristics, such as Rsh (sheet resistance), Rc (contact resistance) and Z 0 (characteristic impedance). After Cu filling, a cross section of the via was observed by Field Emission-Scanning Electron Microscopy. The electrical characteristics were measured using a commercial impedance analyzer and probe station, which revealed the values of Rsh, Rc and Z 0 as 35.5 mΩ/sq, 25.4 mΩ and 48.5 Ω, respectively. After a thermal shock test of 500 cycles, no cracks were observed between the TSV and Si wafer. This study confirms that the laser drilling process is an effective method for via formation on a Si wafer for 3D integration technology. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht. Source

Chung S.-C.,Hanyang University | Park C.-H.,KIMM
Proceedings - ASPE 2010 Annual Meeting | Year: 2010

Positioning error of ballscrew driven feeddrives depends upon stiffness of leadscrew systems. Total axial stiffness of the leadscrew system consists of stiffnesses of the nut, the screw shaft, the support bearings, and the nut bracket. The nut stiffness depends upon screw characteristics, preload and operating conditions. This should be thoroughly studied according to the contact deformation between balls and grooves. In this paper, ballscrew nut stiffness due to contact deformation between balls and grooves according to the preload and operating conditions is studied. Positioning accuracy estimation method is also proposed. Source

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