• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.899-903
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• 2013

A self-bearing is an electric machine that achieves both rotational actuation and magnetic levitation using a single magnetic structure. To be able to stably levitate the rotor in a self-bearing, one needs to have an inverse of the force-current model. However, the force-current model in a self-bearing motor is typically not square. Furthermore, the elements of the matrix vary with respect to the rotational angle, resulting in singularities of the pseudo-inverse at various angles. In this paper, we propose a new force-current model that eliminates the singularities by adding a constraint in coil currents. This constraint eliminates the flux density in the stator core so that the saturation problem in the previous study is avoided. By implementing this force-current model, we are able to implement a levitation controller for a toroidally-wound self-bearing BLDC motor. The model inversion and levitation are validated experimentally.

• Journal of KSNVE
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• v.8 no.5
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• pp.964-973
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• 1998

In this paper we propose a levitation and imbalance compensation controller design methodology of magnetic bearing system. In order to achieve levitation and elimination of unbalance vibartion in some operation speed we use the discrete-time Q-parameterization control. When rotor speed p = 0 there are no rotor unbalance, with frequency equals to the rotational speed. So in order to make levitatiom we choose the Q-parameterization controller free parameter Q such that the controller has poles on the unit circle at z = 1. However, when rotor speed p $\neq$ 0 there exist sinusoidal disturbance forces, with frequency equals to the rotational speed. So in order to achieve asymptotic rejection of these disturbance forces, the Q-parameterization controller free parameter Q is chosen such that the controller has poles on the unit circle at z = $exp^{ipTs}$ for a certain speed of rotation p ( $T_s$ is the sampling period). First, we introduce the experimental setup employed in this research. Second, we give a mathematical model for the magnetic bearing in difference equation form. Third, we explain the proposed discrete-time Q-parameterization controller design methodology. The controller free parameter Q is assumed to be a proper stable transfer function. Fourth, we show that the controller free parameter which satisfies the design objectives can be obtained by simply solving a set of linear equations rather than solving a complicated optimization problem. Finally, several simulation and experimental results are obtained to evaluate the proposed controller. The results obtained show the effectiveness of the proposed controller in eliminating the unbalance vibrations at the design speed of rotation.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2378-2380
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• 2003

본 연구에서는 각 운동량 보존법칙으로부터 도출되어지는 공중부상체(flying objects)의 제어기법에 대해 논의하고자 한다. 먼저, 공중부상체에 대하여 각 운동량 보존법칙을 적용하여 적분불가능한 구속조건으로부터 비 홀로노믹시스템을 도출하고 상태변환과 입력변환을 행하여 제어가 용이한 체인드 폼(Chained form)을 유도한다. 체인드 폼에 대해서는 백스테핑제어기법을 적용하여 제어기를 설계하고 제어기법의 유용성을 검증하기 위하여 3개의 회전관절로 구성된 공중부상체를 대상으로 하여 초기자세로부터 목적자세까지의 제어를 행하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.41-47
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• 2009

In this paper, authors performed improvement of control characteristics of an attraction type magnetic levitation system. The attraction type magnetic levitation system has an inherent instability in the system, therefore its controller must have not only proportional-integral gain but also differential gain additionally. In this paper, authors were proposed control algorithm using disturbance observer(DOB) on feedback signal. The computer simulation and experiments were performed for its verification.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.3
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• pp.67-73
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• 2002

This paper presents a sliding mode observer and Controller far the state estimation and the dynamic stabilization of the magnetic levitation systems. The proposed striding mode observer is constructed by means of Lyapunov stability theorem to decrease the observer error, and the sliding rode controller is designed by a linear combination of the equivalent and nonlinear control input for the estimated states. The feasibilities of the suggested design method are illustrated with the simulation results.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.2
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• pp.129-135
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• 2014

In the paper, we propose a design method for the logistics transportation system using magnetic levitation that has a good characteristics without mechanical friction, noise and dust. The proposed transportation system consists of a levitation control system and a propulsion control system. Magnetic levitation system is an electromagnetic suspension system in which electromagnet generates magnetic attractive force and the attractive force pulls the rail. We design a PID controller for the current control of electromagnets. We use linear induction motors for propulsion of the proposed logistics transportation system and adapt the space vector PWM method for the propulsion control system. The proposed transportation system using magnetic levitation is verified performances through levitation and propulsion experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.3 s.108
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• pp.283-290
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• 2006

This study is concerned with static and sinusoidal disturbance rejection for a single periodic input disturbance with known period. In the area of active elimination of a disturbance force, the control input should have two different kinds of gains: one is to deliver a stable control and the other is a force component to cancel the external disturbance force. In this paper we employ a simple state feedback control law to make the balance beam stable and employ a linear observer to estimate the states which represent the external disturbance force components. Simulation results verify our proposed control method to reject a static and sinusoidal disturbance force.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.722-726
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• 2007

In this paper we deal with a design of the integral sliding mode controller to suppress the disturbance force acting on the suspension system of the magnetically levitated train system. One of the important factors that cause the disturbance force acting on the suspension system comes from the low propulsion speed of linear induction motor. In this paper integral sliding mode controller is employed to reject the disturbance force produced by the propulsion system of the linear induction motor. In order to show the effectiveness of the designed controller a dynamic simulation is utilized and the sliding mode controller without integral compensator is compared with the proposed integral sliding mode controller to suppress the disturbance force.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.225-229
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• 2019

Magnetic bearings are widely used in vacuum and clean environments or in high-precision applications, because they have no mechanical friction and have stable dynamic characteristics. Despite the aforementioned advantages of magnetic bearings, their applications are generally limited due to the controller complexity. In this paper, we proposed a reduced-complexity digital controller for magnetic bearings. In addition, we analyzed and solved the problems, such as quantization errors in the analog-to-digital conversion and integral windup in a feedback controller, which are known as the main causes of performance degradation. Experiments showed that the proposed digital controller achieves a target magnetic levitation accuracy.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.158-162
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• 2004

The magnetic levitator is the device which can float a magnetic material at the midair by electromagnetic force and it's principle can be applied to the high speed magnetic bearing or magnetic levitation train. There are many difficulties to control, because the magnetic levitator is basically a nonlinear and unstable system. In this paper, this system is modeled assuming that it is a linear system nearby an operating point, and a proportional and derivative(PD) position controller is designed to carry out the variable position control. The performance of position control response is shown through simulation and experiment. A prototype magnetic levitator is constructed using PWM converter and DSP(Digital Signal Processor) based control board.