• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2196-2208
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• 1997

In this work, a magnetic levitation (maglev) system is developed to transport a wafer between semiconductor fabrication process modules in clean rooms to take advantages of eliminating particle and oil contamination that normally exist in conventional transport systems due to contact motion of mechanical components. A main feature of the maglev system developed in this work is that a controller and power supplying part are not mounted on the moving carrier but on the stationary track, which is defined a controller-free carrier, to reduce carrier's weight. Iron-core electromagnets and irons are used for levitation, and air-core electromagnets and permanent magnets are used for stabilization. Analysis, design, and modeling of the magnetically levitated transport system are presented. The performance of the maglev system is experimentally demonstrated.

• Journal of Power System Engineering
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• v.14 no.1
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• pp.65-70
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• 2010

Magnetic levitation system is nonlinear and inherently unstable, so it is difficult to control. Analog control circuit was widly used as the controller of magnetic levitation system, but digital controller is now substituted for analog controller according to development of digital electronics. In this study, Atmel AVR series, ATmega 128 which is a kind of $\mu$-processor for digital controller is used because the chip is cheap and popular. We designed and made ATmega 128 one-board controller and aimed to verify validity through the experiance of levitation response.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.438-439
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• 2011

Magnetic levitation control system of a metal ball was designed using combined PID and fuzzy logic, in which two electromagnets are used to control the vertical and horizontal position of the ball. Single synchronization coil sensor was used to detect the vertical position. Electric power is differentially supplied to two electromagnets so that the ball can move horizontally. In the experiment 25 cm diameter metal ball was levitated and successfully controlled to move horizontally.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.263-264
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• 2006

A new method for the electrostatic suspension of disk-shaped objects is proposed which is based on a time-optimal control scheme and deploys only high-voltage power supplies that can deliver do voltages of positive and/or negative polarity. This method possesses the unique feature that no high-voltage amplifiers are needed which leads to a remarkable system simplification and objects can be suspended stably even in vacuum environment. Using this scheme, an Aluminium disk employed in a 3.5-inch HDD was suspended stably at an airgap of 0.3mm.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.56-64
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• 2005

A simple and cost-effective method for the electrostatic suspension of thin plates like silicon wafers is proposed which is based on a switched voltage control scheme. It operates according to a relay feedback control and deploys only a single high-voltage power supply that can deliver a DC voltage of positive and/or negative polarity. This method possesses the unique feature that no high-voltage amplifiers are needed which leads to a remarkable system simplification relative to conventional methods. It is shown that despite the inherent limit cycle property of the relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping origination from the air between the electrodes and levitated object. Using this scheme, a 4-inch silicon wafer was levitated stably with airgap variation decreasing down to $1 {\mu}m$ at an airgap of $100{\mu}m$.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.3
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• pp.144-153
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• 1996

The magnetic levitation system has many advantages, such as little friction, no lubrication, no noise and so on. For this reason, the magnetic levitation system is utilized in the magnetic bearing of high-speed rotor. The method to obtain magnetic force is both the repulsive suspension method and the attraction suspension method need a stabilizing controller because it is a unstable system in natural. This paper presents the design of robust stabilizing servo controller in spite of being the model uncertainties in the magnetic levitation system by $\textit{H}_{\infty}$ control theory using the free parameter. And we investigated the validity of a designed controller through results of the simulation and the actual experiment.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.875-880
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• 2016

A new hybrid permanent magnet biased magnetic levitation actuator (maglev) is developed. This new maglev actuator is composed of two C-core electromagnetic cores separated with two permanent magnets. Compared to the conventional hybrid maglev actuators, the new actuator has unique flux paths such that bias flux paths are separated with control flux paths. The control flux paths have minimum reluctances only developed by air gaps, so the currents to produce control fluxes can be minimized. The gravity load can be compensated with the permanent magnet bias fluxes developed at off-centered air gap positions while external disturbances are controlled with control fluxes by currents. The consumed power to operate this levitation system can be minimized. 1-D magnetic circuit model is developed for this model such that the flux densities and magnetic forces are extensively analyzed. 3-D finite element model is also developed to analyze the performances of the maglev actuator.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.922-927
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• 2007

The present urban maglev which has been developed in Korea is controlled by 4-edge control method over each bogie. The control output which is derived from two gap sensors and one vertical acceleration sensor controls magnet to maintain a nominal gap. But, the gap signal acts as a big disturbance in rail joint though two gap sensors are used and finally result in unstable response and poor ride comfort. This paper treats of a method to compensate the gap signal in rail joint for the levitation control of urban maglev. The physically abnormal change of gap is detected when one gap sensor passes a rail joint, the disturbance of gap in rail joint is estimated. Finally the disturbance in gap signal is eliminated by processing the information of vehicle speed and estimated disturbance in when the other gap sensor passes a rail joint.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1126-1127
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• 2006

Being controlled by a pole placement, levitation system should need many sensors such as measure air-gap, velocity, acceleration, and so on. However, these sensors have observational errors by changed temperature. This paper proposed a output compensated command tracking controller for reducing the error and reducing sensors. Simulation results will be provided to show the validity of the proposed scheme.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1024-1031
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• 2008

The performance of magnetic levitation controller is affected from not only levitation control algorithm but also the interaction between compositing system, so it is important to design maglev system considering the character of magnetic levitation controller in order to get the required performance of Maglev. The factors affecting the levitation controller of maglev are the dynamics of levitation magnet, the carrying weight of the overall system, the normal force and lateral force of traction motor and rail condition. In this paper the interaction between magnet and vehicle weight is analysed on side of stability of levitation controller in order to get the required performance of levitation controller.