• Journal of Drive and Control
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• v.15 no.4
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• pp.39-47
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• 2018

Recently, as environmental regulations for earth-moving equipment have been tightening, advanced systems such as electronic control, have been introduced for energy savings. An IMV (Independent Metering Valve) consisting of four 2-way valves, is an electro-hydraulic control systems that provides more flexible controllability, and potential for energy savings in excavators, when compared to the conventional 4-way spool valve system. To fully maximize use of an IMV, the bi-directional flow control valve that can regulate a large amount of flow in both directions, should be adopted. The hydraulic circuit of an IMV applied to an excavator from an overseas construction equipment company, reveals the flow control valve with the compound of proportional solenoid valve for first stage, and 2-way spool valve for the second stage. Moreover, the two spools are interconnected by a feedback spring, presumed to compensate for flow force acting on the second stage spool. This paper addresses the static analysis of flow control valve in an IMV to investigate the improvement of robustness, against flow force by the feedback spring. From the steady-state analysis of flow control valve model, it can be concluded that the feedback spring facilitates maintaining linearity of spool displacement for control input, and relatively constant flow for load disturbance.

• Journal of Drive and Control
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• v.18 no.4
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• pp.52-58
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• 2021

The variable structure controller is designed such that in sliding mode, the system moves along the switching plane in the vicinity of the switching plane, thus it is robust because it is not affected by the parameter fluctuations of the plant. However, a controller based on a variable structure may not meet the desired performance when it is commanded to track any input or is exposed to disturbances. This study proposes a sliding mode controller that follows the IVSC (Integral Variable Structure Control) approach with ELO (Extended Luenberger observer) to solve this problem. The proposed sliding mode control is applied to the velocity control of the hydraulic motor. The sliding plane was determined by the pole placement, and the control input was designed to ensure the existence of the sliding mode. The feasibility of modeling and controller are reviewed by comparing with conventional proportional-integral control through computer simulation using MATLAB software and experimenting on the cases of significant plant parameter fluctuations and disturbances.

• Journal of Power System Engineering
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• v.17 no.3
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• pp.89-98
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• 2013

In this paper, the authors consider control system design problem of barge type surface vessel. It is based on the Dynamic Positioning System(DPS) design problem. The main role of barge ship is to carry and supply the materials to the floating units and other places. To carry out this job, it should be positioned in the specified area. Even though sometimes the thrust systems are installed on it, in general the mooring winch system with the rope is used. It may be difficult to compare the control performances of two types. But, if we consider this problem in point of usefulness, we can easily find out that the winch control system is more useful and applicable to the real field than the thrust control system except a special use. Therefore, in this paper we consider a single type mooring winch system and control system design problem in which accurate position control is needed. Because this result can be extended to the general type mooring system in which a number of winch are installed. At first, a mathematical model of winch is obtained and evaluated to verify the usefulness for control system design by experiment. Also, the disturbance model is extracted from experiment data to evaluate the strength of the uncertainty. Based on this results, the robust control system is designed and control performance is evaluated by simulation.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.45-53
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• 2009

Today, reduction of $CO_2$ exhaustion gas for global-warming prevention becomes important issues in all industrial fields. Hydraulic systems have been widely used in industrial applications due to high power density and so on. However hydraulic pump is always being operated by engine or electric motor in the conventional hydraulic system. Therefore most of the conventional hydraulic system is not efficient system. Recently, an electro-hydraulic hybrid system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. In the electro-hydraulic hybrid system, hydraulic pump is operated by electric motor only when hydraulic power is needed. Therefore the electro-hydraulic system can reduce the energy consumption drastically when compared to the conventional hydraulic systems. This paper presents a new kind of hydraulic load simulator which is composed of electro-hydraulic hybrid system. Disturbances in the real working condition make the control performance decrease or go bad. QFT controller is designed to eliminate or reduce the disturbance and improve the control performance of the electro-hydraulic load simulator. Experimental results show that the proposed controller is verified to apply for electro-hydraulic hybrid system with varied external disturbances.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.6
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• pp.546-553
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• 2002

A control of the body posture and movement is maintained by the vestibular system, vision, and proprioceptors. Especially, vestibular system has a very important function that controls the eye movement through vestibuloocular reflex and contraction of skeletal muscles through vestibulospinal reflex. However, postural disturbance caused by loss of vestibular function results in nausea, vomiting, vertigo and loss of craving for life. Lose of vestibular function leads to abnormal reflex of eye movements named nystagmus. Analysis of the nystagmus is needed to diagnose the vertigo, which is performed by means of electrooculography(EOG). The purpose of this study is to develop a computerized system for data processing and an algorithm for the automatic evaluation of the slow component velocity(SCV) of nystagmus induced by optokinetic(OKN) stimulation system. A new algorithm using recursive least square method(RLSM) to detect SCV of nystagmus is suggested in this paper. This method allows a fast and precise evaluation of the nystagmus, through artifact rejection techniques. The results are depicted in this paper.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1324-1335
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• 2016

This article explores the speed regulation problem of permanent magnet synchronous motor (PMSM) systems subjected to unknown time-varying disturbances. A continuous sliding mode control (CSMC) technique is introduced for the speed loop to enhance the robustness of PMSM systems and eliminate the chattering phenomenon caused by high-frequency switch function in the conventional control law. However, the high control gain of the CSMC law in the presence of strong disturbances leads to large steady-state speed fluctuations for PMSM systems. In many application fields, PMSM systems are affected by time-varying disturbances instead of constant disturbances. For example, electric bicycles are usually affected by changing environmental disturbances, including wind speeds, road conditions, etc. These disturbances may be in the form of constant, ramp, and parabolic disturbances. Hence, a generalized proportional integral (GPI) observer is employed to estimate these types of disturbances. Then, the disturbance estimation method and the aforementioned CSMC method are combined to establish a composite sliding mode control method called the CSMC+GPI method for the speed loop of PMSM systems. Contrary to the conventional sliding mode control technique, the proposed method completely eliminates the chattering phenomenon caused by the switching function in the conventional control law. Moreover, a small control gain for the CSMC+GPI method is chosen by feed-forwarding estimated values to the speed controller. Hence, the steady-state speed fluctuations are small. The effectiveness of the proposed control scheme is verified by simulation and experimental result.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.162-172
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• 2011

This paper proposes embedded System of two wheeled inverted pendulum robot designed by model based design method, using MATLAB/SIMULINK and LEGO NXT Mindstorms. At first, stability and performance of controller is verified through modeling and simulation. After that direct conversion from simulation model to C code is carried and effectiveness of controller is experimentally verified. Two wheeled inverted pendulum robot has basic function about autonomous balancing control using principle of inverted pedulum and it is also possible to arrive at destination. In this paper, state feedback controller designed by quadratic optimal control method is used. And quadratic optimal control uses state feedback control gain K to minimize performance index function J. Because it is easy to find gain, this control method can be used in the controller of two wheeled inverted pendulum robot. This proposed robot system is experimentally verified with following performances - balancing control, disturbance rejection, remote control, line following and obstacle avoidance.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.459-466
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• 2000

A new control method for precision robust speed control of a PMSM(Permanent Magnet Synchronous Motor) using load torque observer is presented. Using this system, we can more precisely evacuate of vestibular function. Until now a rotating chair system, so called 2D-stimulator, which has vertical rotate axis is used to make dizziness. However, an inclined rotating chair system witch is called 3D-stimulator is needed to obtain the precise dizziness data. This 3D-stimulator include unbalanced load caused by unbalanced center of mass. In this case, new compensation method is considered to obtain robust speed control using load torque observer. To reduce the effect of this disturbance, we can use dead-beat observer that has high gain. The application of the load to torque observer is published in for position control. However, there is a problem of using speed information such as amplifying effect of noise. Therefore, we can reduce a noise effect by moving average process. The experimental results are depicted in this paper to show the effect of this proposed algorithm.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.1
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• pp.70-79
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• 2016

This paper proposes a low-power range-scaled 14b 30 MS/s pipeline-SAR composite ADC for high-performance CIS applications. The SAR ADC is employed in the first stage to alleviate a sampling-time mismatch as observed in the conventional SHA-free architecture. A range-scaling technique processes a wide input range of 3.0VP-P without thick-gate-oxide transistors under a 1.8 V supply voltage. The first- and second-stage MDACs share a single amplifier to reduce power consumption and chip area. Moreover, two separate reference voltage drivers for the first-stage SAR ADC and the remaining pipeline stages reduce a reference voltage disturbance caused by the high-speed switching noise from the SAR ADC. The measured DNL and INL of the prototype ADC in a $0.18{\mu}m$ CMOS are within 0.88 LSB and 3.28 LSB, respectively. The ADC shows a maximum SNDR of 65.4 dB and SFDR of 78.9 dB at 30 MS/s, respectively. The ADC with an active die area of $1.43mm^2$ consumes 20.5 mW at a 1.8 V supply voltage and 30 MS/s, which corresponds to a figure-of-merit (FOM) of 0.45 pJ/conversion-step.

• Journal of the Korean Magnetics Society
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• v.3 no.2
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• pp.87-93
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• 1993

Iron nitride (Fe-N) magnetic thin films were deposited using a DC magnetron sputtering system. Microstructures and magnetic properties were examined as a function of deposition power and nitrogen gas input ratio. The nitrogen content in the film was found to be the major factor determining the microstructure and the magnetic properties. The films deposited at low nitrogen input ratios have an $\alpha$-Fe structure of which the lattice is expanded due to the nitrogen atoms incorporated at the interstitial sites. As the nitrogen content in the film increases, the degree of lat-tice expansion increases and the value of saturation magnetization decreases linearly. The films with a high degree of lattice expansion give very low values of coercivity, which is attributed to the disturbance of colunmar growth and the decrease of surface roughness. Further increase in the nitrogen input ratio causes the phase transfonnation from $\alpha$-Fe to $Fe_{2-3}N$, resulting in the marked reduction in the saturation magnetization. The phase transformation occurs when, regardless of deposition conditions, the nitrogen content reaches at 15 at.% and the lattice is expanded by 5%.