• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1685-1691
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• 2004

The objective of this study is aimed at reducing the contour error of AC Servo derives by improving the interpolation error of each axis through variable structure control system. The errors in machining process by AC Servo motor are due to many elements, such as the delay of the servo drivers, friction and the gain mismatch between x axis and y axis motors and so on. Sliding mode control system is applied to a AC servo drive as a numerical example in this paper. The experiment results which are compared with those of typical PI scheme show the validity of improvement in circular interpolation error of the system.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.129-130
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• 2007

Self servo track writing(SSTW)은 servo track writer(STW)를 이용하지 않고 hard disk drive의 내부 VCM을 이용하여 servo track을 기록하는 방식이다. SSTW는 이전 servo track을 상대적인 reference로 하여 기록하게 되므로 초기에 발생된 error와 외부의 disturbance의 영향으로 error는 급속하게 증가된다. 이것을 radial error propagation 이라 한다. 본 논문에서는 radial error propagation을 억제하기 위한 correction signal을 설계하고 servo writing 과정에서 발생하는 disturbance의 영향을 제거하기 위하여 disturbance observer(DOB)를 add-on type으로 구성하여 tracking 제어기를 설계하였다. 또한 DOB를 적용한 경우와 유사한 gain margin, phase margin과 sensitivity function을 갖는 제어기를 설계하여 그 성능을 비교하였다. 제안된 방식은 radial error propagation을 억제 하였을 뿐만 아니라 disturbance의 최소화하여 쓰여진 track의 DC track spacing과 AC track Squeeze가 개선된 것을 모의실험을 통하여 검증하였다.

• Journal of Drive and Control
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• v.16 no.3
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• pp.86-93
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• 2019

• Journal of Drive and Control
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• v.17 no.4
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• pp.176-180
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• 2020

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2438-2440
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• 2003

This thesis presents a design methodology of a Digital Servo Signal Processor for high speed CD-ROM drive systems. The proposed Digital Servo Signal Processor enables us to develop CD-related systems for the very high speed applications and is one of the key components of the CD-ROM systems. The proposed center compensation servo control is newly built for a actuator shaking due to the fast response of a step motor when it jumps to a long distance. From experimental results, we can see that the performance of the control system is improved greatly. The proposed servo algorithm shows a shorter setting time including a pull-in time and a faster access time.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.348-353
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• 1994

Magnetic Servo Levitation (MSL) has been proposed as a method to drive a fast-tool servo system. This paper discusses some fundamental control and modeling issues in the development of a long-range high-bandwidth fast-tool servo based on MSL. A resursive linear model is developed to describe the system's dynamics linear model is developed to describe the system's dynamics, and further used to discuss controller design. For a given controller architecture, the performance of two controllers is then compared, one based on an approximation to the inverse plant dynamics, the second based on a adaptive neural network.

• Journal of Drive and Control
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• v.15 no.1
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• pp.16-27
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• 2018

Hydraulic torque load simulator is essential to test and qualify the performance of various angle control systems. Typically a flapper-type second stage servovalve is applied to the load simulator, but here the direct drive servovalve, which is a kind of one-stage valve and affected by the large flow force, is applied. Since the torque load is applied not to the stationary shaft but to the rotating shaft of the angle control system, the controlled torque of load simulator is not accurate due to the rotating speed of the angle control system. A feedforward compensator is designed and applied to minimize the disturbance-like effect. A mathematical model is derived and linearized to analyze the stability, accuracy and responsiveness of the torque load simulator. The parameter effects of a controller, servovalve, hydraulic motor, rotating spring shaft are analyzed and summarized. The goodness of the linear analysis is verified by the digital computer simulations using both the linear and nonlinear mathematical models.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.5
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• pp.131-138
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• 1996

This paper suggests a servo control algorithm to reduce the repeatable tracking error which is not explicitly taken into account in the design of a conventional PID controller of a computer hard disk drive. The robust stability of the repetitive control system with multiplicative modelling error is analyzed, and the controller was implemented using a fixed point DSP(Digital Signal Processor). Experimental results show that the repetitive errors are suppressed effectively by the proposed controller.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.3
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• pp.129-135
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• 2007

This paper deals with speed-sensorless control of DC servo motor using Neuro-Fuzzy Observer. DC servo motor has very low rotor inertia and excellent response characteristic and it is very useful to control torque and speed. It is easy to detect the voltage and current and resolver or encoder is used to measure a rotor speed. But it has a limit as a driving speed to detect speed precisely. So it is problem to improve the performance of the driving system. To solve this problem, it is studied to detect a speed of DC servo motor without sensor. In particular, study on the method to estimate the speed using the observer is performed a lot. In this paper, the gain of the observer is properly set up using the Neuro-Fuzzy control and Neuro-Fuzzy Observer that have a superior transient characteristic and is easy to implement compared the existing method is designed. It calculates the differentiation of the rotor current directly using the rotor current measured in the DC servo motor and estimates the speed of the rotor using the differentiation. Proposed speed sensorless control method is performed using the estimated speed. Also, it is proved feasibility of the proposed observer from the comparison tested a case with a speed sensor and a case without a speed sensor which used a highly efficient drive and 200[w] DC servo motor starting system.

• Journal of the Semiconductor & Display Technology
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• v.3 no.1
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• pp.21-26
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• 2004

Recently with the development of power switching device and DSP which has peripheral devices to control AC servo system, the servo technology has met a new development opportunity. Those things make it possible to reduce the time of developing a AC servo system. Fixed point DSP such as TMS320F240x, and TMS320F28x series have a disadvantage in calculating floating number where TMS320C32 or TMS320C31 are floating point DSP. However they usually become a complex hardware system to implement the AC servo system and it increases the cost. In this study, a DSP based AC servo system with a 3-phase PMSM is proposed. The newly produced DSP TMX320F28l2-version C which has the performance of fast speed, 150MIPS, and a rich peripheral interface such as a 12bit high speed AD converter, QEP(Quadrature Encoder Pulse) circuit, PDPINT(Power Drive Protect Interrupt), SVPWM module and dead time module are used. This paper presents a method to overcome fixed point calculating using scaling all parameters. Also space vector pulse width modulation (SVPWM) using off-set voltage and a digital PI control are implemented to the servo system.