• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.244-247
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• 2002

The performance of the precision micro-positioning 4-dof stage is presented. The compact design utilizes the monolithic mechanism to achieve the translation in the Z axis and rotation in the $\theta$ z, $\theta$ x and $\theta$ y axes with high stiffness and high damping. Hysteresis, nonlinearity, and drift of the piezoelectric effects are improved by incorporating the sensors in a feedback control. Experiments demonstrate that the micro-positioning stage is capable of 2nm resolution over the travel range of 25$\mu\textrm$ m in the Z axis, 0.0l7 $\mu\textrm$ rad resolution over the 170$\mu\textrm$ rad in the $\theta$ z and 0.011 $\mu\textrm$ rad resolution over the $\mu\textrm$ rad in the $\theta$ x and $\theta$ y axes. The cross-axis interferences among the axes are at a noise range. This stage is available for positioning error compensation of the XY stage with large stroke.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1355-1366
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• 2016

In the present paper, a speed control algorithm with fast response characteristics is proposed to reduce the shift shock of medium/large-sized electric vehicles equipped with a two-speed AMT. Shift shocks, which are closely related with to the vehicles' ride comfort, occur due to the difference between the speed of the motor shaft and the load shaft when the gear is engaged. The proposed speed control method for shift shock reduction can quickly synchronize speeds occurring due to differences in the gear ratios during speed shifts in AMT systems by speed command feed-forward compensation and a state feedback controller. As a result, efficient shift results without any shift shock can be obtained. The proposed speed control method was applied to a 9 m- long medium- sized electric bus to demonstrate the validity through a simulated analysis and experiments.

• Korean System Dynamics Review
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• v.4 no.2
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• pp.95-130
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• 2003

The purpose of this study is to find what causes make public projects hold off, going beyond the planned deadline and budget. Using System Dynamics(SD) and their derivative Urban Dynamics(UD) models, it intends to analyze major feedback loops based on VENSIM and to simulate them with STELLA software, all of which are interrelated with various causes of project delay. To prevent or ameliorate project delay, first of all it advises to focus on endogenous delaying factors not exogenous ones. These factors either reinforce or balance certain loops in complex causal structure, In the case example on the Cremation Building Project in Cheongju, Residents’ participation demand make negotiation put off and delayed negotiation reinforces administrative-expediency planning in order to observe a time limit, on the other hand, once building consensus, it increase both the level of planning performance and public trust. In the meantime, the real planning process used to neglect residents opinions and manage public grievance only through compensation, he a result of simulation, visible fruit of negotiation in the initial phase seems to be not satisfactory owing to funds and time consumed, but after reaching an mutual agreement among stakeholders, planning performance is effective and strategic than administrative-expediency planning viewed in both financial and time angle. It proposes to devise specific tools schematizing project implementation. In order to upgrade the quality of project management, it recommends for planners to adopt key concepts based on SD/UD diagrams and causal loops, which would contribute to enriching Planning abbots.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.11
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• pp.1447-1454
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• 2018

In this paper, the design of robust DSC-PLL(Delayed Signal Cancellation Phase Locked Loop) is proposed for coping with frequency variation. This method shows significant performance for detection of fundamental positive sequence component voltage when the grid voltage is polluted by grid unbalance and frequency variation. The feedback frequency estimation of DSC-PLL is tracking the drift in the phase by unbalance and frequency variation. The robust DSC PLL is to present the analysis on method and performance under frequency variations. These compensation algorithms can correct for discrepancies of changing the frequency within maximum 193[ms] and improve traditional DSC-PLL. Linear interpolation method is adopted to reduce the discretized errors in the digital implementation of the PLL. For verification of robust characteristic, PLL methods are implemented on FPGA with a discrete fixed point based. The proposed method is validated by both Matlab/Simulink and experimental results based on FPGA(XC7Z030).

• International Journal of Safety
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• v.3 no.1
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• pp.47-52
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• 2004

Current OSH system was analyzed in this paper to explain why high fatal incidents and disasters are continuously repeated for recent years in Korea. It was found that we have Dichotomous Perceptional Misconception of prevention before accident and compensation after accident and there is a significant lack of proper feed­back reward system for OSH performance. It was assumed that no reduction of accident rate and fatality rate have not been achieved recently despite of a great effort and increased resource allocations. Some statistics for proving weak punishment were analyzed. In the current system, the will of administrative agency would have been very limited particularly in the legal aspects. The Industrial Safety and Health Act is not suitable to after-injury punishment for employer and/or corporate since it is based on a framework for enforcement of prevention. Based on these analyses, it was concluded that there was a need to consider a special law for Corporate Accountability for Fatal Accidents. Because it is necessary to consider seriously for introduction of a new legal system for after injury punishment to repair the current system where it was found lack of proper feedback system. Also, there was no proper sanction measures for corporate with the current OSH legal system, and the most urgent problem in OSH area is the high fatality rate. it is necessary to consider seriously for introduction of a new legal system for after injury punishment. Also, there is no proper sanction measures for corporate with the current OSH legal system, and the most urgent problem in OSH area is the high fatality rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.24-33
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• 2004

In this paper, the helicopter flight control system using online adaptive neural networks which have the universal function approximation property is considered. It is not compensation for modeling errors but approximation two functions required for feedback linearization control action from input/output of the system. To guarantee the tracking performance and the stability of the closed loop system replaced two nonlinear functions by two neural networks, weight update laws are provided by Lyapunov function and the simulation results in low speed flight mode verified the performance of the control system with the neural networks.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.8
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• pp.457-466
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• 2002

The speed and position control of SRM(Switched Reluctance Motor) needs the encoder or resolver to obtain the rotor position information. These position sensors can be affected by the EMI, dusty, and high temperature surroundings. Therefore the speed and position sensorless control has been studied widely In this paper, the binary observer of the SRM which has two feedback compensation loops to control the speed of SRM is proposed. One loop reduces the estimation error like the sliding mode observer, and the other removes the estimation error chattering occurred in the sliding mode observer. This observer is constructed on the basis of variable structure control theory and has the inertial term to exclude the chattering. This method has a good estimation performance in spite of nonlinear modeling of SRM. The advantages of the proposed method are verified experimentally.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.12
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• pp.1233-1240
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• 2010

In the flat panel display and semiconductor industries, the visual alignment system is considered as a core technology which determines the productivity of a manufacturing line. It consists of the vision system to extract the centroids of alignment marks and the stage control system to compensate the alignment error. In this paper, we develop a Kalman filter algorithm to estimate the alignment mark postures and propose a coarse-fine alignment control method which utilizes both original fine images and reduced coarse ones in the visual feedback. The error compensation trajectory for the distributed joint servos of the alignment stage is generated in terms of the inverse kinematic solution for the misalignment in task space. In constructing the estimation algorithm, the equation of motion for the alignment marks is given by using the forward kinematics of alignment stage. Secondly, the measurements for the alignment mark centroids are obtained from the reduced images by applying the geometric template matching. As a result, the proposed Kalman filter based coarse-fine alignment control method enables a considerable reduction of alignment time.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.277-280
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• 2000

Reverse Engineering is a procedure where the results of engineering decisions in manufacturing is feedback to the design phase and the knowledge-base is generated from the process know-how to reduce the errors. Since it used to take lots of time and efforts to finalize the machining of dies out of the original CAD design especially for die spotting and try-outs, reverse engineering is important to improve the productivity and quality of the die manufacturing process. In this regard, we developed system to support reverse engineering in machining of stamping dies for auto-body production. They automatically generate the relevant MC programs for a CMM simply with the input of measuring points in CAD environments, and show the CAD model and the results of inspection simultaneously for the ease of comparison. They also help reduce the overall clearance between the lower and upper dies. Applying these systems to the machining process of stamping dies, we could improve the reliability of measuring and get the optimal compensation distance between the two dies. We also analyzed the expected benefits of the system in terms of savings in time and costs.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.9
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• pp.813-820
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• 2014

This paper presents design and performance validation of a method for motion compensation using fast steering mirror. First of all, the schematics of the Electro Optical/Infra-Red (EO/IR) and step-stare image gathering system for an aerial reconnaissance are introduced. Because of the steering mirror with low inertia so called Back scan mechanism (BSM), the fast step-stare image gathering technique that is required for taking a high-definition still image will be realized. After then, the BSM hardware includes motors and feedback sensors are introduced. Also, the motion profile for BSM will be designed to compensate roll scan motion of the gimbals. At the end of this paper, designed profile and tracking performance of the EO/IR system with BSM will be validated through experiments.