• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.04a
• /
• pp.614-619
• /
• 2012

A LQG/LTR(Linear Quadratic Gaussian/Loop Transfer Recovery) controller with an integrator is designed to control the electro-hydraulic positioning system. Without considering the nonlinearity in the dead-zone, computer simulations are performed and show good performances and tracking abilities with the feedback controller based on the linear system model. However, the performance of the closed loop hydraulic positioning system shows big steady-state error in real system because of the dead-zone. In this paper, the feedback controller with a nonlinear compensator is introduced to overcome the dead-zone phenomenon in hydraulic systems. The inverse dead-zone as a nonlinear compensator is used to cancel out the dead-zone phenomenon. Experimental tests are performed to verify the performance of the controller.

• 제어로봇시스템학회:학술대회논문집
• /
• 1993.10a
• /
• pp.1080-1085
• /
• 1993

A nonlinear control algorithm for the depth control of underwater vehicles is presented. In order to consider the deadzone effect of the flow control valve, a nonlinear fuzzy logic controller (FLC) is synthesized and combined with a linear proportional-derivative-acceleration (PDA) controller, which is called, the PDA/FLC controller. And, to show the effectiveness of the PDA/FLC control system, it is compared with the linear PDA control system through computer simulation. It is found that the PDA/FLC control scheme is a suitable one to maintain the desirable depth of underwater vehicles with deadzone.

• 제어로봇시스템학회:학술대회논문집
• /
• 1993.10a
• /
• pp.179-184
• /
• 1993

In general, for underwater vehicles in low speed, depthkeeping operations are carried out by using the variation of the weight in the seaway tank. The depthkeeping control of underwater vehicles is difficult because of the deadzone effect in the flow rate control valve. In this paper, the nonlinear multivariable QLQG/LTR control system using a seaway tank and bow planes is synthesized in order to improve the performance of the depth control system. The computer simulation results show the multivariable QLQG/LTR control system has good depth control performance under the deadzone effect.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.8
• /
• pp.729-735
• /
• 2012

A LQG/LTR(linear quadratic Gaussian/loop transfer recovery) controller with an integrator is designed to control the electro-hydraulic positioning system. Without considering the nonlinearity in the dead-zone, computer simulations are performed and show good performances and tracking abilities with the feedback controller based on the linear system model. However, the performance of the closed loop hydraulic positioning system shows big steady-state error in real system because of the dead-zone. In this paper, the feedback controller with a nonlinear compensator is introduced to overcome the dead-zone phenomenon in hydraulic systems. The inverse dead-zone as a nonlinear compensator is used to cancel out the dead-zone phenomenon. Experimental tests are performed to verify the performance of the controller.

• Journal of Haehwa Medicine
• /
• v.7 no.1
• /
• pp.435-443
• /
• 1998

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.10 no.4
• /
• pp.40-47
• /
• 2001

In this pater, the QLQG/LTR control method is applied for the position control of the nonlinear timing belt driving sys-tem. Parameters fo the plant are identified by genetic algorithm and nonlinear elements, such as Coulomb friction and dead-zone, and quasi-linearized by RIDE method. Comparing with the LQG/LTR contro. the QLQG/LTR has similar structures of the LQG/LTR, but this method can consider nonlinear effects in designing the controller. Thus, the QLQG/LTR control system is robust to hard nonlinearities such as Coulomb friction, dead-zone, etc. Forma given hard non-linear system through experiments, it is shown that the tracking performance of the QLQG/LTR control system can be very improved that the LQF/LTR control system.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.3
• /
• pp.93-101
• /
• 2016

This study presents a simple genetic algorithm to systematically design a PID controller for a hydraulic positioning system operated by a proportional solenoid valve. The inverse dead-zone compensator with nonlinear characteristics is used to cancel out the dead-zone phenomenon in the hydraulic system. The object function considering overshoot, settling time, and control input is adopted to search for optimal PID gains. The designed PID controller is compared with the LQG/LTR controller to check the performance of the hydraulic positioning system in the time and frequency domains. The experimental results show that the hydraulic servo system with the proposed PID controller responds effectively to the various types of reference input.

• Journal of Christian Education in Korea
• /
• v.66
• /
• pp.273-307
• /
• 2021

The purpose of this study is to explore the inner perceptions and dilemmas of young people about the church. To achieve the purpose of the study, this study sampled the research subjects, and conducted in-depth interviews and FGI. The sample in this study was 21 young adults who met the study criteria. Some of these people are not currently attending church or have thought of moving to another church. In this study, research was conducted based on the analysis procedure of Riessman (1993). Focusing on the procedures of 'telling,' 'recording,' and 'analyzing,' the experience and life situation of the study participants are to be grasped. Through this process, we analyzed the situation and context of why young people leave the church. It consisted of 5 areas and 15 sub-themes. Based on the research results, it was found that young adults need a church and are looking for a church. The church is a mystical space, but from an pedagogical point of view, the church is a space for teaching and learning faith. As experts in theology and education, the minister must create a space so that the church can become a space of transcendence, a space of intimacy, a space of understanding, a space of change, a space of service, and a space of reflection.

• The Journal of the Korea Contents Association
• /
• v.20 no.10
• /
• pp.233-246
• /
• 2020

After the COVID-19 crisis, the world's terrain has changed completely to the extent that it has been divided before and after Corona. We are living in the era of new normals, things we never thought of before Corona19, such as wearing masks everywhere, maintaining social distance, sitting on one side in the cafeteria, and online face-to-face classes. Perhaps the most seriously affected by the COVID-19 incident is the church. How should the church respond to the various problems caused by COVID-19? This study intends to re-examine the five essential missions of the church in the post-Corona19 era. The five essences are the three essential functions of the intangible church: didake (teaching), kerygma (declaration), diakonia (service), and the two essential functions of the tangible church: koinonia (association) and leiturgia (worship). Of these, koinonia and leiturgia are the most seriously threatened by the restraint of face-to-face worship in the incident of COVID-19. In times of crisis, the church needs to strengthen its vertical koinonia with God in order to perform its didake function well and increase the efficiency of the horizontal koinonia among believers. However, in the situation where face-to-face worship is desired due to social distance, teaching and proclaiming the Bible is the most important part. For this, it is considered that a specialized ministry is needed to produce high quality contents.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.14 no.4
• /
• pp.1-18
• /
• 2019

Venture capitalists (VCs) play an important role in finding and growing innovative venture companies with high growth potential but high risk. Venture capital investment does not depend on the system, unlike the investment for listed companies. Korea's venture capital industry has entered a period of growth, but lack of data has led to a lack of research on venture capital. Based on this background, this study attempts to analyze various factors affecting investment decision criteria of Korea VCs. In this study, I examined the major factors that VCs consider in decision making of investment through literature review, and I have drawn the research question accordingly. I will focus on the characteristics of founders, products / services, markets, financials, and networks that scholars share common investment decision criteria in Korean VCs. For the purpose of this study, the data were collected through the questionnaire surveyed by investment vetters working in current venture capital and analyzed using AHP analysis. Through this study, I tried to understand the Korean venture capital which has been poorly studied and what criteria and priorities Korean VCs make investment decisions in the Korean venture investment environment. The results of this research will contribute to the vitalization of venture investment, which is important for the upbringing of companies, by providing guidelines for establishing investment attraction strategies of venture companies.