• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.11
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• pp.664-670
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• 2004

This paper presents a new velocity estimation strategy of a non-salient permanent magnet synchronous motor (PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system that has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to zero. For zero and low speed operation, PI controller gains of rotor position tracking controller have a variable structure according to the estimated rotor velocity. In order to boost the bandwidth of PI controller around zero speed, a loop recovery technique is applied to the control system. The proposed method only requires the flux linkage of permanent magnet and is insensitive to the parameter estimation error and variation. The designers can easily determine the possible operating range with a desired bandwidth and perform the vector control even at low speeds. The experimental results show the satisfactory operation of the proposed sensorless algorithm under rated load conditions.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1079-1082
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• 1996

To automate an excavator the control issues resulting from environmental uncertainties must be solved. In particular the interactions between the excavation tool and the excavation environment are dynamic, unstructured and complex. In addition, operating modes of an excavator depend on working conditions, which makes it difficult to derive the exact mathematical model of excavator. Even after the exact mathematical model is established, it is difficult to design of a controller because the system equations are highly nonlinear and the state variable are coupled. The objective of this study is to design a fuzzy logic controller(FLC) which controls the position of excavator's attachment. This approach enables the transfer of human heuristics and expert knowledge to the controller. Excavation experiments are carried out to check the performance of the FLC.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.52 no.3
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• pp.121-126
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• 2003

In this paper, we propose the haptic system for the real-time virtual environment-control, which controls the sense of sight, hearing and touch. In order to maintain the stable haptic system in this study, we apply the proxy force rendering algorithm and the real-time graphic deformation algorithm based on the FEM. The applied proxy algorithm makes the system possible to be more stable and prompt with a virtual object. Moreover, the haptic rendering algorithm is applied to work out a problem that the tactual transaction-period is different from the graphic transaction- period. The graphic deformation algorithm is developed in the real-time using the deformed FEM. To apply the FEM, a deformed material-model is produced and then the graphic deformation with this model is able to force. Consequently, the graphic rendering algorithm is deduced by the real-time calculation and simplification because the purpose of this system is to transact in the real time. Applying this system to the PC, we prove that it is possible to deform the graphics and transact the haptic. Finally we suggest the variable simulation program to show the efficiency of this system.

• Nuclear Engineering and Technology
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• v.50 no.5
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• pp.654-664
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• 2018

Self-pressurization analysis of the natural circulation integral nuclear reactor through a new dynamic model is studied. Unlike conventional pressurized water reactors, this reactor type controls the system pressure using saturated coolant water in the steam dome at the top of the pressure vessel. Self-pressurization model is developed based on conservation of mass, volume, and energy by predicting the condensation that occurs in the steam dome and the flashing inside the chimney using the partial differential equation. A simple but functional model is adopted for the steam generator. The obtained results indicate that the variable measurement is consistent with design data and that this new model is able to predict the dynamics of the reactor in different situations. It is revealed that flashing and condensation power are in direct relation with the stability of the system pressure, without which pressure convergence cannot be established.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.266-272
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• 2000

The importance of variable displacement piston pump is recently increasing in industrial applications, as it is widely used for raising the energy level of the fluid in hydraulic system. The regulator is the device that controls the pump output flow depending on the machine load and engine speed, and that regulates the discharge flow of the piston pump by controlling the swivel angel. This work deals with constant power control of a regulator system in bent-axis type piston pump. In order to use engine power effectively, it is important to keep the horsepower from the engine to the pump constant. Therefore, optimum power usage is obtained by accurately following the power hyperbola. First, the governing equations of the regulator are derived, and analysis is performed by numerical simulation in which significant parameters of regulator are identified. Also, we designed and manufactured the prototype of the constant power control regulator for experiments. The experimental results show the responsibility and pressure-flowrate characteristics and these are compared with the theoretical analysis. As the result, it is confirmed that the characteristics of the designed regulator correspond to the numerical simulation.

• Horticultural Science & Technology
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• v.33 no.1
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• pp.106-113
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• 2015

Effects of mineral salts (N, P, K, $Ca^{2+}$, $Mg^{2+}$, and $Fe^{3+}$) on the shoot growth and metabolite production of tea tree were studied using in vitro culture techniques. Among mineral s alts, ${H_2PO_4}^-$ was the most important for enhanced growth rate of tea tree, while $Mg^{2+}$ and $Ca^{2+}$ did not affect plant growth. Removal of ${NH_4}^+$ and $NO_3$ from the culture medium enhanced shoot multiplication compared to other treatments. Metabolite production was variable depending on mineral types and concentration. Removal of $Ca^{2+}$ decreased the production of caffeine; however, other treatments did not influence its production. $Ca^{2+}$, ${NH_4}^+$ and $Fe^{3+}$ were important factors for catechin production in tea tree. These results can be used as the basis for development of technical soil controls suitable for tea tree cultivation in the future.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.5
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• pp.679-688
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• 2021

This study aims to verify family ownership's effect on earnings management by using corporate governance as the moderation variable. This study uses data panel regression with the period of 2011-2017. Corporate governance consisted of three dimensions, namely the board of commissioners, share ownership and transparency, and disclosure and auditing. Discretionary accruals measure earnings management with a model that controls company performance. Samples are manufacturing companies listed on Indonesia Stock Exchange. Observations were conducted on 198 firms throughout the year. The results indicated that corporate governance significantly affected earnings management. However, it declined the significance of family ownership toward earnings management. Hence, corporate governance can reduce earnings management. Furthermore, of the three components of corporate governance: the board of commissioners, shareholding, and transparency, the term shareholding precisely encouraged managers to conduct earnings management. Besides, the three core bodies of corporate governance lowered the significance of shareholding toward earnings management. This study's findings suggest that in family firms in Indonesia, earnings management is becoming more intensive than in non-family firms. Additional tests show that there is an entrenchment effect on family firms in Indonesia. Furthermore, corporate governance leads to earnings management.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.72.3-72.3
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• 2019

The observation of transient objects such as supernovae or variable stars requires a survey of the wide sky and quickly extracting the results. In accordance with this purpose, we have been developing an automatic observing software, KAOS (Kyung Hee University Automatic Observing Software) as a series. KAOS30 was the first series of KAOS and it was applied to the 30-inch platform at the McDonald Observatory in the United States of America. KAOS76 controls the 76-cm telescope at Kyung Hee Astronomical Observatory. In this poster, we introduce KAOS10 for controlling a portable telescope with a small aperture size attaching a guiding camera as QHY-5L II. Kyung Hee University auto-guiding package which includes the auto-guiding function for small aperture size telescope was also developed. Additionally, the Telescope Control Package(TCP) can communicate with the main server to do astrometry for pointing and identifying targets efficiently. KAOS10 has a universal interface that will be useful for the research of both amateurs and professionals.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.564-565
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• 2019

The Internet of Things technology is regarded as the next major technology that will be the driving force behind the fourth industrial revolution. The characteristics of entities for Internet of Things application are changing more actively and actively, requiring a more detailed approach, but existing access control technologies are designed around users, requiring access control techniques that maintain efficiency and security with less system load to apply complex and variable content. Therefore, research on role-based access controls that are appropriate for Internet of Things entities is essential. In this study, the relevant research for the study of access control of the Internet of Things entities and the RBAC and AC methods that can define the properties of the various entities within the Internet of Things.

• Korean Journal of Applied Biomechanics
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• v.33 no.3
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• pp.85-93
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• 2023

Objective: This study examined differences in joint kinematics and movement variability of lower extremity between adolescent athletes with and without lateral ankle sprain (LAS) history during drop vertical jump. Method: Fourteen adolescent athletes with LAS history and 14 controls participated in this study. The independent variable was group while dependent variables were 3D joint kinematics and movement variability of hip, knee, and ankle joint. Ensemble curve analyses were conducted to identify differences in movement strategies between two groups. Results: The LAS group showed that greater eversion during jump phase compared with the control group. Additionally, less movement variability was found in the LAS group during the pre-landing and jump phases in ankle and hip joints compared with the control group. Conclusion: The LAS group may adapt the environmental constraints by reducing the movement variability in ankle and hip joints. However, training programs focusing on recovery of ankle function should be emphasized after LAS because excessive pronation for prevention of LAS during the jump phase may result in reduced performance.