• Journal of the Semiconductor & Display Technology
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• v.4 no.1 s.10
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• pp.35-41
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• 2005

An air levitation type wafer transfer system is composed of control and transfer track. Wafer transfer speed is mainly affected by air velocity of propulsion nozzle. In this study, the propulsion force coefficient was evaluated experimentally for the nozzle with 0.5mm, 0.8mm, and 1.0mm diameter. As a result, the propulsion force was largest in the smallest size of nozzle at same air velocity. The propulsion force coefficient of nozzle increases with reducing diameter of nozzle. This increment of propulsion force coefficient was enlarged remarkably at the 0.5mm diameter of nozzle.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2312-2321
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• 1994

In this work the dynamics of an electromagnetic levitation system is described by a set of three first order nonlinear ordinary differential equations. The objective is to design a digital linear controller which takes the inherent instability of the uncontrolled system and the disturbing force into consideration. The controller is made by employing digital linear quadratic(LQ) design methodology and the unknown state variables are estimated by the kalman filter. The state estimation is performed using not only an air gap sensor but also both an air gap sensor and a piezoelectric accelerometer. The design scheme resulted in a digital linear controller having good stability and performance robustness in spite of various modelling errors. In case of using both a gap sensor and an accelerometer for the state estimation, the control input was rather stable than that in a system with gap sensor only and the controller dealt with the disturbing force more effectively.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1207-1212
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• 2009

The flexible multibody dynamic model of an EMS-type Maglev vehicle is necessary in design stage to predict its behavior, load history and levitation performance. Especially in EMS-type Maglev vehicle, the body flexibility of its bogie with electromagnets affects the levitation performance because its feedback control system is more sensitive to vibration of bogie structure. The flexible multibody dynamic model of a 1/2 Maglev vehicle under test is presented. The basic modeling procedure is almost the same as in other applications. However, the feedback control system model unique in EMS-type maglev vehicle must be included in the model. With the model proposed in this study, the dynamic behavior, load history and levitation performance are more precisely predicted. This model could realize the virtual prototyping in EMS-type Maglev vehicle area.

• Journal of ILASS-Korea
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• v.18 no.3
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• pp.126-131
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• 2013

This paper describes the effect of ultrasonic frequency(f) on the atomization and deformation characteristics of single water droplet in an acoustic levitation field. To achieve this, the ultrasonic levitator that can control sound pressure and velocity amplitude by changing frequency was installed, and visualization of single water droplet was conducted with high resolution ICCD and CCD camera. At the same time, atomization and deformation characteristics of single water droplet was studied in terms of normalized droplet diameter($d/d_0$), droplet diameter(d) variation and droplet volume(V) variation under different ultrasonic frequency(f) conditions. It was revealed that increase of ultrasonic frequency reduces the droplet diameter. Therefore, it is able to levitate with low sound pressure level. It also induces the wide oscillation range, large diameter and volume variation of water droplet. In conclusion, the increase of ultrasonic frequency(f) can enhance the atomization performance of single water droplet.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.76.6-76
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• 2002

Introduction. Modeling. Controller. Simulation. Experiment. Conclusion

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.519-520
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• 2016

BLSRM is a nonlinear, strong coupling and multi-variable system. The conventional control method is vulnerable to uncertain factors such as the load disturbance and satellite parameters change. It is difficult to obtain satisfactory control effect. Basing on a 8/10 BLSRM, whose suspending force control is separated with the torque control, this paper presents adaptive fuzzy PID controller for levitation control, which apply the fuzzy logic control to the conventional PID controller for parameters self-tuning. Both fuzzy and parameters of PID controller are self-tuning on-line, which improve the performance of controller. Finally, simulation and experimental results show the performance of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.327-332
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• 1993

One maglev vehicle is composed of 6 r 8 modules. Each module is composed of 4 staggered magnets attached to an aluminum bogie. In the view point of levitation control except propulsion by LIM, 5 is the maximum degrees of freedo to be controlled. But rolling control of the vehicle depends on the bogie structure. We describe just anti-roll type out of bogie structures and 4 degrees of freedom control is sufficient for levitation quality improvement. Multivariable pole-placement concept and the decentralized control concept are used for controller design. Computer simulation and control experiment are performed on a specially designed test module.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2120-2122
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• 2001

This paper describes a PID controller for an attraction type magnetic levitation system considering $H^{\infty}$ performance. PID controllers are a kind of fixed structure reduced order controllers. Using change of variables a reduced order control problem can be recast into a static output feedback control problem and can be solved efficiently by LMI(Linear Matrix Inequality) method. In this paper, cone complementarity method is adopted and the simulation shows good results.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.12
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• pp.689-697
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• 2005

In this paper, an application of a decentralized $H_{\infty}$ controller(DHC) to multiple controlled-permanent magnet(CMAG) magnetic levitation(Maglev) systems is presented. The designed DHC using two Riccati equations iteratively has simpler structure and needs less computational loads than conventional centralized $H_{\infty}$ controller. A target plant is a hybrid-type CMAG system with permanent magnet and coil, and its mathematical model is firstly derived to design the DHC. To implement the designed algorithm, a real Maglev vehicle system including digital controller, chopper, sensor, etc., is manufactured. To compare the performances of the DHC method with an observer-based state feedback control(OSFC), the input tracking and disturbance rejection characteristics are experimentally tested. As performance indices(PI), integral of squared error(ISE), integral of absolute error(IAE), integral of time multiplied by absolute error(ITAE) and integral of time multiplied by squared error(ITSE) are used. From the experimental results, it can be seen that the input tracking and disturbance rejection performances of the DHC are better than those of the conventional controller.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1184-1191
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• 2009

A bearingless linear motor(BLLM) which consists of two stators and a common mover is able to levitate and move its mover without any linear bearing or even additive windings. In the previous study, BLLM was actively controlled on the translation and pitch motion, while the roll motion is passively stable. In order to control the roll motion, this paper suggests adding active magnetic bearings(AMBs) at bottom of the mover in BLLM. The AMBs control the roll motion and also partially supports the weight of the mover. In this paper, magnetic forces generated by the AMBs are estimated by using an FEM model. Based on the analysis results, the bias current of the AMBs is determined and a PD controller is designed. Through an experimental levitation test, it was verified that roll motion is well controlled by AMB during levitation.