• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.293-297
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• 1998

A method for the evaluation and the compensation of the vertical milling machine is presented. The method used a mathmatical model of thermal deformation based on temperatur variations of the machine and the environment. It follows an empirical approach and requires low cost equipment to be applied. According to this study, machine error caused by thermal deformation will be reduced to about 1/6.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제13권2호
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• pp.100-105
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• 2013

In this study, we analyze the balance of quadruped walking robots. For this purpose, a simplified polygonal model of a quadruped walking configuration is considered. A boundary-range-based balance margin is used for determining the system stability of the polygonal walking configuration considered herein. The balance margin enables the estimation of the walking configuration's balance for effective walking. The usefulness of the balance margin is demonstrated through exemplary simulations. Furthermore, balance compensation by means of foot stepping is addressed.

• Journal of Power Electronics
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• 제10권6호
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• pp.749-761
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• 2010

The switching frequency of a power device is a very important parameter in the design of a parallel active power filter (PAPF), but so far, very little discussion has been conducted on it in a quantitative manner in previous publications. In this paper, an extensive analysis on the effects of the switching frequency on the performance of a PAPF is made, and a specification of the switching frequency values with different compensation results is presented. A first-order inertia element and a second-order oscillation element are considered as approximate models of a PAPF, respectively. The compensation characteristic for each order of harmonic current is obtained at different switching frequencies. Then, the THDs of each model for the system loads of a rectifier with resistance and inductance loads are proposed. The compensation results of a PAPF controlled as a first-order inertia element are better than those of a PAPF controlled as a second-order oscillation element. With two types of system loads which are rectifier with resistance and inductance loads and rectifier with resistance, inductance and capacitance loads, the THDs of the source current after compensation are presented with different switching frequencies. The compensation characteristics for the most widely used digital control system are investigated. The situation with an analog control is the theoretical characteristic and it is the best situation. The compensation characteristic of the digital control is worse than the compensation characteristic of the theoretical characteristic. Based on these analyses, the specifications of compensation characteristics with different switching frequencies are quite straightforward. Finally, a practical design example is studied to verify the application.

• 소성∙가공
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• 제29권4호
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• pp.188-193
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• 2020

Piping work of large ships or offshore plants is often done in a narrow and confined space, requiring precise bending and safety. In order to realize an accurate bending angle, it is very important to predict and correct a deformation that may be caused by elasticity in the bending process, that is, an angular deviation due to springback. Therefore, by using CAE analysis to develop a correction angle model for springback based on multiple tube bending angles and using trend line data derived from this correction angle model, at bending the tube as the diameter of the base former and the tube outer diameter change, the springback compensation angle at any angle can be obtained. In this study, the bending mechanism was analyzed to increase the bending precision, and a correction angle model was developed and a trend line was derived in consideration of springback occurring in the bending process. In order to derive a more accurate and reliable trend line, a tube tensile test was performed, and the reliability of the corrected angle trend line was verified by comparing the bending angle measurement and analysis results with a 3D scanner.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1645-1655
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• 2016

A Dynamic Voltage Restorer (DVR) model is proposed to eliminate the short-term voltage disturbances that occur in the grid-connected mode, the switching between grid-connected mode and the stand-alone mode of a Microgrid. The proposed DVR structure is based on a conventional cascaded H-bridge multilevel inverter (MLI) topology; a novel composite control strategy is presented, which could ensure the compensation ability of voltage sag by the DVR. Moreover, the compensation to specified order of harmonic is added to implement effects that zero-steady error compensation to harmonic voltage in specified order of the presented control strategy; utilizing wind turbines-batteries units as DC energy storage components in the Microgrid, the operation cost of the DVR is reduced. When the Microgrid operates under stand-alone mode, the DVR can operate on microsource mode, which could ease the power supply from the main grid (distribution network) and consequently be favorable for energy saving and emission reduction. Simulation results validate the robustness and effective of the proposed DVR system.

• Journal of Power Electronics
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• 제19권3호
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• pp.655-664
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• 2019

In order to analyze the nonlinear phenomena of the bifurcation and chaos caused by the switching of nonlinear switching devices in inductively coupled power transfer (ICPT) systems, a Jacobian matrix model, based on discrete mapping numerical modeling, is established to judge the system stability of the periodic closed orbit and to study the nonlinear behavior of Hopf bifurcation in a system under full resonance. The general flow of the parameter design, based on the stability principle for ICPT systems, is proposed to avoid the chaos and bifurcation phenomena caused by unreasonable parameter selection. Firstly, based on the state equation of SS-type compensation, a three-dimensional bifurcation diagram with the coupling coefficient as the bifurcation parameter is established with a numerical simulation to observe the nonlinear phenomena in the system. Then Filippov's method based on a Jacobian matrix model is adopted to deduce the boundary of stable operation and to judge the type of the bifurcation in the system. Then the general flow of the parameter design based on the stability principle for ICPT systems is proposed through the above analysis to realize stable operation under the conditions of weak coupling. Finally, an experimental platform is built to confirm the correctness of the numerical simulation and modeling.

• 융합경영연구
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• 제5권1호
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• pp.21-26
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• 2017

Purpose - This study extracts performance-reward factors based on the previous studies related to Herzberg's two-factor theory and performance-reward and proposes a research method to identify how these factors have an influence on task performance directly related to production performance and contextual performance that has an indirect influence. Research Design, Data, and Methodology - This study draws performance-reward factors through Focus Group Interview(FGI), classifies them into economic/uneconomic and direct/indirect factors, draws maintenance/improvement factors and unnecessary ones through IPA, and maximizes the effectiveness of performance-reward factors. Results - It also identifies how performance-reward factors have an influence on internal and external motives based on previous studies, classifies performance-reward factors into task performance and contextual performance and identifies the influence relationship between these, and proposes a research model to identify the roles of equity sensitivity based on equity theory. Conclusion - The findings from this study are expected to lay the groundwork for drawing various methods to reduce the turnover rate of employees and be important resources for reinforcing the competitiveness of businesses by classifying the performance -reward factors that may cause internal and external motives from the small and medium-sized manufacturing perspective and presenting methods to identify if these have an influence on task performance and contextual performance.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.272-283
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• 2017

In this paper, an improved predictive functional control (PFC) scheme for permanent magnet synchronous motor (PMSM) control system is proposed, on account of the standard PFC method cannot provides a satisfying disturbance rejection performance in the case of strong disturbances. The PFC-based method is first introduced in the control design of speed loop, since the good tracking and robustness properties of the PFC heavily depend on the accuracy of the internal model of the plant. However, in orthodox design of prediction model based control method, disturbances are not considered in the prediction model as well as the control design. A minimum-order observer (MOO) is introduced to estimate the disturbances, which structure is simple and can be realized at a low computational load. This paper adopted the MOO to observe the load torque, and the observations are then fed back into PFC model to rebuild it when considering the influence of perturbation. Therefore, an improved PFC strategy with torque compensation, called the PFC+MOO method, is presented. The validity of the proposed method was tested via simulation and experiments. Excellent results were obtained with respect to the speed trajectory tracking, stability, and disturbance rejection.

• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.174-180
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• 1996

The friction is one of the nonlinearities to be considered in the precise position control of a system which has electromechanical components. The friction has complicated nonlinear characteristics and depends on the velocity, the position and the time. The conventional fixed friction compensator and the controller based on linear control theory may cause the steady state position error or oscillation. The plant to be controlled in this study is a positioning system with a linear brushless DC motor(LBLDCM). The system behaves like a 4th-order model including the compliance and the friction. In this study, the plant model is simplified to a 2nd-order model to reduce the computation in on- line estimation. Also, to reduce the computation time, only the friction is estimated on-line while the mass and the viscous damping coefficient are fixed to the values obtained from off-line estimation. The validity of the proposed scheme is illustrated with the computer simulation and the experiment where the friction is compensated by using the estimation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.183-186
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• 1999

The Ultra-miniature and low phase noise Colpitts VCO of 0.06㏄ in size has been developed using the high Q resonator and phase compensation technique. This type is one transistor VCO without a buffer. To design and simulate the VCO accurately, nolinear model parameters of a bipolar transistor are extracted using the measured I-V data and S parameters based on the Gummel-Poon model. Design and simulation have been done by Serenade 7.5 design tool using the extracted nonlinear model parameters. The wideband VCO has been designed using two varactor diodes and open loop gain compensation technique to improve the operating frequency range. The ultra-miniature VCO has shown the phase noise of -91㏈c/Hz at 10KHz offset and output power of -3㏈m The wideband VCO has shown the tuning frequency bandwidth of 150MHz phase noise of -95㏈c/Hz at 10KHz offset and output power of 5㏈m.