• Journal of Power Electronics
• /
• 제15권5호
• /
• pp.1264-1273
• /
• 2015

An inverter output power control based power factor correction (PFC) strategy is being extensively used for permanent magnet synchronous motor (PMSM) drives in appliances because such a strategy can considerably reduce the cost and size of the inverter. In this strategy, PFC circuits are removed and large electrolytic DC-link capacitors are replaced with small film capacitors. In this application, the PMSM d-q axes currents are controlled to produce ripples, the frequency of which is twice that of the AC main voltage, to obtain a high power factor at the AC mains. This process indicates that the PMSM operates under periodic magnetic saturation conditions. This paper proposes a back electromotive-force (back-EMF) estimator for the high-speed sensorless control of PMSM operating under periodic magnetic saturation conditions. The transfer function of the back-EMF estimator is analyzed to examine the effect of the periodic magnetic saturation on the accuracy of the estimated rotor position. A simple compensation method for the estimated position errors caused by the periodic magnetic saturation is also proposed in this paper. The effectiveness of the proposed method is experimentally verified with the use of a PMSM drive for a vacuum cleaner centrifugal fan, wherein the maximum operating speed reaches 30,000 rpm.

• 전력전자학회논문지
• /
• 제15권4호
• /
• pp.335-341
• /
• 2010

전기제동 시스템(Electric braking system)은 기존 자동차 시스템에서 사용된 유압 브레이크를 대신하여 전동기를 이용하여 제동력을 얻게 된다. 전기제동은 기존 유압식에 비해 부품의 수가 감소되며 ABS, ESC 등의 응답성 향상 및 제동거리 감소효과를 얻을 수 있다. 본 논문에서는 EMB(Electro-Magnetic Brake)용 BLAC 전동기의 제어기를 개발하였다. 제어 시스템은 BLAC 전동기 구동을 위한 전력변환장치와 속도제어를 위한 디지털제어기로 구성되었으며, 빠른 토크 응답특성을 위해 벡터제어 기법을 적용하였다. 또한 Matlab/Simulink를 이용한 시뮬레이션 및 실험 결과를 제시하여 EMB용 BLAC 전동기의 성능을 검증하였다.

• 전기학회논문지
• /
• 제64권12호
• /
• pp.1703-1708
• /
• 2015

This paper deals with the position and torque control of a toroidal type rotor which has a magnetic bearing structure. The proposed magnetic bearing structure supports the rotor by the repulsive forces of permanent magnets, and has a two degree of freedom for rotor position when the rotor is rotating. Permanent magnets and coils in the stator allow for a two degree of freedom control of the rotor position and torque generation by reacting with permanent magnets of the rotor. The executed gyro actuator has a number of poles such as five-phase permanent magnet motors and 10 stator coils for the rotor position control. In this study, the verification of the stability of the magnetic bearing was conducted using the equation of motion when the rotor was rotating, and the coil current commutation method for the position control and torque generation was studied. As a result, the feasibility of the proposed structure and control was verified by simulations of Finite Element Method (FEM) and experiments using the executed gyro actuator.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2018년도 춘계학술대회 논문집
• /
• pp.32.1-32.1
• /
• 2018

Novel soft magnetic materials can be achieved by altering material properties such as morphology, composition, crystallinity, and grain size of soft magnetic alloys. Especially, magnetic properties (i.e., saturation magnetization, coarcivity) of soft magnetics are significantly affected by grain boundaries which act as a control of magnetic domain wall movement. Thus, we herein develop a two-step electroless plating method to control morphology and grain size of FeCo films for excellent magnetic properties. Accordingly, the chemical composition to control the degree of polarization of FeCo alloys was altered by electroless deposition parameters; for example, electrolyte concentration and temperature. The grain size and crystallinity of FeCo alloys was dramatically affected by the reaction temperature because the grain growth mechanism dominantly occurs at $90^{\circ}C$ where as the neucleation only happens at $50^{\circ}C$. By simply controlling the temperature, the micron-sized FeCo grains embedded FeCo film was synthesized where the large grains allow high magnetization originated from larger magnetic domain with low corecivity and the nano-sized grains allow excellent soft magnetic properties due to the magnetic correlation length.

• 대한기계학회논문집A
• /
• 제29권12권
• /
• pp.1567-1573
• /
• 2005

This paper introduces a new active magnetic bearing(AMB) that can provide both radial and axial control functions in one bearing unit without axial disk. It has a structure of double four-pole AMB or a four-pole AMB where each core is split into two axially. The cores have two kinds of coil winding; they independently generate fluxes on the planes perpendicular or parallel to the shaft. For the radial control action, it works just like a conventional four-pole AMB. Meanwhile, for the axial control, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. In this paper, the proposed structure, principle, and design process based on magnetic flux analysis are introduced, and its feasibility is experimentally verified by using a simple PD control algorithm with a feedforward loop to compensate the coupled flux effect.

• 대한기계학회논문집A
• /
• 제29권12권
• /
• pp.1561-1566
• /
• 2005

In this paper, a new compact active magnetic bearing(AMB) is proposed in which radial and axial bearings are integrated in one bearing unit. It consists of four U-shaped cores circumferentially connected by yokes and two-layer coils for radial and axial controls. For the radial control action, it has the same principle as conventional homopolar AMBs, while for the axial control, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. The proposed structure makes it easy to design a compact AMB because it has no disk for axial control. This paper introduces the proposed structure, principle, and design process based on the magnetic flux analysis. By using a control algorithm with feedforward action to compensate the coupled flux effect, the feasibility of the proposed AMB is experimentally verified.

• Transactions on Control, Automation and Systems Engineering
• /
• 제3권2호
• /
• pp.106-110
• /
• 2001

The external force disturbance is the one of the main causes that deteriorate the performance of the magnetic suspension. Thus, this paper develops a fuzzy estimator for gain scheduling control of magnetic suspension system suffering from the unknown disturbance. The propose fuzzy estimator computes the disturbance injected to the plant the gain scheduled controller generates the corresponding stabilizing control input associated with estimated disturbance. In the simulation results we confirm the novelty of the proposed control scheme comparing with the other method using a feedback linearization.

• 제어로봇시스템학회논문지
• /
• 제12권10호
• /
• pp.1029-1034
• /
• 2006

In this paper, the tracking control of an automatic pipe cutting robot, called APCROM, with a magnetic binder is studied. Using magnetic force APCROM, a wheeled robot, binds itself to the pipe and executes unmanned cutting process. The gravity effect on the movement of APCROM varies as it rotates around the pipe laid in the gravitational field. In addition to the varying gravity effect other types of nonlinear disturbances including backlash in the driving system and the slip between the wheels of APCROM and the pipe also cause degradation in the cutting process. To maintain a constant velocity and consistent cutting performance, the authors adopt a repetitive learning controller (MRLC), which learns the required effort to cancel the tracking errors. An angular-position estimation method based on the MEMS-type accelerometer is also used in conjunction with MRLC to compensate the tracking error caused by slip at the wheels. Experimental results verify the effectiveness of the proposed control scheme.

• 한국한의학연구원논문집
• /
• 제9권2호
• /
• pp.121-130
• /
• 2003

The goal of this study is construction and efficacy evaluation of MPC-25 (Magnetic Pain Control-25), a medical device using magnetic stimulation. MPC-25 consists of a main body containing power supply and control module and a bed containing magnetic core and coil. In distinction from electric pain control medical devices, magnetic pain control system is non-contact, so the patients need not take off their clothes to be treated. High amplitude current pulses are applied to a magnetic coil and induce time varying magnetic field generating eddy current in a conductor like human body. Clinical efficacy test was performed in patients suffering from musculoskeletal pain of lumbar, shoulder and joint. Degree of pain before and after treatment for 30 minutes was compared using Visual Analogous Scale. As a result, 14 cases out of 20 showed decreased pain perception, so the rate of efficacy is 70%. Reduction of pain perception was statistically significant (P=0.001 by Wilcoxon Signed Rank Test).

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1997년도 추계학술대회 논문집
• /
• pp.303-306
• /
• 1997

Magnetic bearings have been adopted to support the rotor by electromagnetic force without mechanical contact and have many advantages. The application of the magnetic bearings have become more and more widespread in recent years. But magnetic bearings require feedback control for stable operation because they are inherently open loop unstable systems. In this study, H infinity controller has been applied for rotor-magnetic bearing system for vibration control. The result showed that H infinity controller has better performance than PID controller through simulations.