• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.46-50
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• 2008

The present status and future prospects of the levitation mass method (LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers, materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing, providing methods for evaluating material viscoelasticity under an oscillating or impact load, evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.590-599
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• 2003

In this study. object transport method based on ultrasonic flexural vibration is presented. Ultrasonic vibration generates ultrasonic traveling waves on the surface of elastic medium. Objects are transported through the interaction with traveling waves propagating in medium. Two types of transport methods are studied： frictional drive and acoustic levitation. With frictional drive, objects are transported in contact with the beam in the opposite direction of wave propagation whereas with acoustic levitation, objects are acoustically levitated above the beam surface and transported in the wave propagation direction. Transport characteristics are experimentally investigated using objects of different shapes and sizes. The transition from acoustic levitation mode to frictional drive mode is also examined. and it is found to occur when the ratio of mass to area of an object exceeds the threshold ratio of mass to area. It is envisaged that this feasibility study will serve as a stepping-stone for ultrasonic vibration to become an effective industrial material handling device in the future.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.355-359
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• 1992

This paper presents a procedure to design a real time control system for a magnetic levitation system based on the state space approach by adopting a control method compensating attractive force according to load variation of maglev vehicle. Also the paper has realized a robust control algorithm for the change of self-inductance parameters and the disturbance such as the change of mass of Maglev vehicles. The theoretical results are applied to the gap control problems of an attractive-type-magnetic levitation system and the effectiveness is proved by the implementation of digital control using 16 bits microcomputer.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.22-25
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• 2008

The dynamic response of the head arm assembly (HAA) of a hard disk drive to an impact load was obtained from a 3D non-linear finite element model using ANSYS/LS-DYNA and from experiments using a modified levitation mass method (LMM). In the finite element model, the impact load was created by modeling the mass as a rigid body and making it collide with the HAA. The velocity, displacement, acceleration, and inertial force of the mass were then obtained from the time history data of the finite element analysis. In the LMM, a mass that was levitated with an aerostatic linear bearing, and hence encountered negligible friction, was made to collide with the actuator arm, resulting in a dynamic bending test for the arm. During the collision, the Doppler frequency shift of the laser beam reflected from the mass was accurately measured with an optical interferometer. The velocity, displacement, acceleration, and inertial force of the mass were accurately calculated from the measured time-varying Doppler frequency shift. A good correlation between the experimental data and FEA results was observed. The FEA was also used to investigate the dynamic response of the HAA to impact by different masses.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.4
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• pp.321-327
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• 2011

This paper proposes an equipment and an algorithm for modeling the magnetic force of electromagnets in magnetic levitation systems. We assume that the magnetic force model is represented in terms of a 2D lookup table. The 2D lookup table is constructed by applying noncausal filtering and interpolation to data measured by the proposed modeling equipment. The proposed modeling equipment is designed such that it can measure the magnetic force exerted on the levitation object while it changes the voltage applied to the electromagnet and position of the levitation object. The algorithm of making a 2D lookup table has two stages. The data measured by the proposed modeling equipment is smoothed by a noncausal filter and then the 2D lookup table is obtained by interpolating filtered data. The proposed modeling method has advantages of time-saving, model consistency, and chance of automation for mass production. We show the validity of proposed method through control experiments.

• Proceedings of the KSR Conference
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• 2006.11a
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• pp.145-159
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• 2006

This paper describes the development of a clustering based fuzzy controller of an electromagnetic suspension vehicle using gain scheduling method and Kalman filter for a simplified single magnet system. Electromagnetic suspension vehicle systems are highly nonlinear and essentially unstable systems For achieving the levitation control of the DC electromagnetic suspension system, we considered a fuzzy system modeling method based on clustering algorithm which a set of input/output data is collected from the well defined Linear Quadratic Gaussian(LQG) controller. Simulation results show that the proposed clustering based fuzzy controller methodology robustly yields uniform performance with adequate gap response over the mass variation range.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.3
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• pp.300-310
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• 1992

This paper deals with the problem of robust pole-assignment control for linear systems with structured uncertainty. It considers two cases whose colsed-loop characteristic equations are presented as a family of interval polynomial and polytopic polynomial family respectively. We propose a method of finding the pole-placement region in which the fixed gain controller guarantees the required damping ratio and stability margin despite parameter perturbation. Some results of Kharitonov like stability and two kinds of transformations are included. As an illustrative example, we show that the proposed method can apply effectivly to the single magnet levitation system including some uncertainties (mass, inductance etc.).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.205-209
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• 2006

A linear motor based transfer vehicle is significantly focused as transportation systems in marine terminals for the future. We propose a control method for the systems to hence mass reduction and propulsion effects at a starting point by using a lift-force mechanism. This method is newly based on a combined levitation-and-propulsion power by a lift and thrust force of a permanent magnet linear synchronous motor (PMLSM), which is carried out by a decoupled control. We exam that our proposed control largely compensates the vehicle weight, reduces friction effect of the system, and increases its velocity. Consequently, this result contributes numerous productivity and economical efficiency for the port systems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1128-1138
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• 2010

One of the typical problems in the precise vibration is resonance characteristics at low frequency disturbance due to a heavy mass. An electro-magnetic(EM) air spring is a kind of vibration control unit and active isolator. The EM air spring in this study aims at removing the low frequency resonance for semiconductor manufacturing. The mechanical and electronic parts in the active isolator are designed to operate under a weight of 2.5 tons. The EM spring is floated using air pressure in a pneumatic elastic chamber and actuated by EM levitation force. The actuator consists of a EM coil and a permanent magnetic plate which are installed inside of the chamber. An air mount was constructed for the experiment with a stone surface plate, 4 active air springs, 4 gap sensors, a DSP controller, and a multi-channel power amp. A PD control method and operating logic was applied to the DSP. Simulation using 1/4 model was carried out and compared with the experiments. The time duration and maximum peak at resonance frequency can be reduced sharply by the proposed system. The results show that the active system can avoid the resonance caused by the natural frequency of the passive system.