• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1999.10a
• /
• pp.411-416
• /
• 1999

The measurement of unsteady flow rate is of vital importance to clarify and improve the dynamic characteristics in pipeline, hydraulic components and system. There is also demand for a real time flow sensor of ability to measure unsteady flow rate with high accuracy and fast response to realize feedback control of flow rate in fluid power systems. In this paper, we propose an approach for estimating unsteady flow rate through a pipeline and components under high pressure condition. In the method, unsteady flow rate is estimated by using hydraulic pipeline dynamics and the measured pressure values at two distant points along the pipeline. The distributed parameter model of hydraulic pipeline is applied with consideration of frequency dependent viscosity friction and unsteady velocity distribution at a cross section of a pipeline. By using the self-checking functions of the method, the validity is investigated by comparison with the measured and estimated pressure waveforms at the halfway section on the pipeline. The results show good agreement between the estimated flow rate waveforms and theroetical those under unsteady laminar flow conditions. the method proposed here is useful in estimating unsteady flow rate through an arbitray cross section in hydraulic pipeline and components without installing an instantaneous flowmeter.

• Korean System Dynamics Review
• /
• v.3 no.1
• /
• pp.43-60
• /
• 2002

This paper describes the forecast of wholesale price in competitive Korean electricity market using the system dynamics approach. The system dynamics concepts have been implemented with the Ithink software. This software facilitates the development of stock and flow model with information feedback. Using this model, the future wholesale electricity price can be computed hour by hour, quarterly, and yearly. This model also gives the energy planner the opportunity to create different scenarios for the future of deregulated wholesale markets in Korea. Also It will lead to increased understanding of competitive wholesale market as a complex, dynamic system. Research results show that the plant construction appeared in waves of boom and bust in Korean electricity market like real estate construction. That is, the Korea wholesale market's new power plants and the market price will appear the Boom and Bust cycle. It is very similar behavior as real estate industry. In case of consideration of DSM program, The DSM savings lead to a somewhat different timing of the booms in construction and of price spikes. But the DSM programs do not eliminated the fundamental dynamics of the boom and bust. And the wholesale price is maintained at the lower level compared to the case of without DSM program. However, the unexpected result is found that due to the lower market price, Investor make significantly less investment in new CCs, which leads to the higher wholesale price after 2010. It suggests that the DSM Policy must be implemented with the dynamics of competitive Electricity Market.

• Journal of the Korean Society of Industry Convergence
• /
• v.19 no.2
• /
• pp.50-61
• /
• 2016

This study proposes a new approach to control the nozzle pressure of homogenizer in refrigerator foam system in the 900L class. Generally, dynamic characteristics of the hydraulic nozzle system is highly nonlinear due to uncertain parameters, and it is very difficult to control of hydraulic dynamics. Firstly, it has been performed to derive a real-time control algorithm based on the mathematical model of hydraulic cylinder, and to estimate the values of the unknown parameter in the hydraulic system. Secondly, the feedback controller was designed to implement the optimal pressure control of the hydraulic nozzle system. Finally the control performance was illustrated by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.14 no.2
• /
• pp.155-163
• /
• 1989

For a one link flexible arm control, quadratic optimal control is applied to the dynamic modilling which is derived from an assumed mode method. For the quadratic optimal control technique, the full state feedback must be obtained for closing the control loop, but because some of the states in the flexible system(e.g. the rate of change of the time dependent variables of the mode shapes) can not be directly measured, state estimator is necessary to achieve the practical implementation of the optimal controller. When disturbances and measurement noise occur, stochastic approach must be applied to estimating the states of the system. Kalman Filter is used as a stste estimator. Through the simulation, the flexible system with state estimator is compared with the flexible system assuming that all the states can be measured.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.6
• /
• pp.2824-2837
• /
• 2019

Container technologies are widely used in infrastructures to deploy and manage applications in cloud computing environment. As containers are light-weight software, the cluster of cloud applications can easily scale up or down to provide Internet-based services. Container-based applications can well deal with fluctuate workloads by dynamically adjusting physical resources. Current works of scheduling applications often construct applications' performance models with collected historical training data, but these works with static models cannot self-adjust physical resources to meet the dynamic requirements of cloud computing. Thus, we propose a self-adaptive automatic container scheduling framework AutoScale for cloud applications, which uses a feedback-based approach to adjust physical resources by extending, contracting and migrating containers. First, a queue-based performance model for cloud applications is proposed to correlate performance and workloads. Second, a fuzzy Kalman filter is used to adjust the performance model's parameters to accurately predict applications' response time. Third, extension, contraction and migration strategies based on predicted response time are designed to schedule containers at runtime. Furthermore, we have implemented a framework AutoScale with container scheduling strategies. By comparing with current approaches in an experiment environment deployed with typical applications, we observe that AutoScale has advantages in predicting response time, and scheduling containers to guarantee that response time keeps stable in fluctuant workloads.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.63 no.4
• /
• pp.65-86
• /
• 2021

This study aims at testing a hypothesis that the resilience of agricultural water systems is characterized by trade-offs and synergies of effects from climate and socioeconomic change. To achieve this, an Agricultural Water System Climate Resilience Assessment (ACRA) framework is established to evaluate comprehensive resilience of an agricultural water system to the combined impacts of the climate and socioeconomic changes with a case study in South Korea. Understanding dynamic behaviors of the agricultural water systems under climate and socioeconomic drivers is not straightforward because the system structure includes complex interactions with multiple feedbacks across components in water and agriculture sectors and climate and socioeconomic factors, which has not been well addressed in the existing decision support models. No consideration of the complex interactions with feedbacks in a decision making process may lead to counterintuitive and untoward evaluation of the coupled impacts of the climate and socioeconomic changes on the system performance. In this regard, the ACRA framework employs a System Dynamics (SD) approach that has been widely used to understand dynamics of the complex systems with the feedback interactions. In the ACRA framework applied to the case study in South Korea, the SD model works along with HOMWRS simulation. The ACRA framework will help to explore resilience-based strategies with infrastructure investment and management options for agricultural water systems.

• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.10
• /
• pp.94-104
• /
• 1996

This paper presents a new approach to the design of adaptive control system using DSPs(TMS320C31) for robotic manpulators to achieve accurate trajectory tracking by the joint angles Digital signal processors are used in implementing real time adaptive control algorithms to provide an enhanced motion control for robotic manipulators. In the proposed contorl scheme, adaptation laws are derived from the improved Lyapunov second stability analysis method based on the adaptive model reference control theory. The adaptive controller consists of an adaptive feedforward controller, feedback controller, and PID type time varying auxillary control elements. The proposed adaptive control scheme is simple in structure, fast in computation, and suitable for implementation of real-time control. Morever, this scheme does not require an accurate dynamic modeling nor values of manpipulator parameters and payload. Performance of the adaptive controller is illustated by simulation and experimental results for a SCARA robot.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.2
• /
• pp.463-477
• /
• 1991

This study proposed a new method to design a robot manipulator control system capable of tracking the trajectories of joint angles in a reasonable accuracy to cover with actual situation of varying payload, uncertain parameters, and time delay. The direct adaptive model following control method has been used to improve existing industrial robot manipulator control system design. The proposed robot manipulator controller is operated by adjusting its gains based on the response of the manipulator in such a way that the manipulator closely matches the reference model trajectories predefined by the designer. The manipulator control system studied has two loops: they are an inner loop on adaptive model following controller to compensate nonlinearity in the manipulator dynamic equation and to decouple the coupling terms and an outer loop of state feedback controller with integral action to guarantee the stability of the adaptive scheme. This adaptation algorithm is based on the hyperstability approach with an improved Lyapunov function. The coupling among joints and the nonlinearity in the dynamic equation are explicitly considered. The designed manipulator controller shows good tracking performance in various cases, load variation, parameter uncertainties. and time delay. Since the proposed adaptive control method requires only a small number of parameters to be estimated, the controller has a relatively simple structure compared to the other adaptive manipulator controllers. Therefore, the method used is expected to be well suited for a high performance robot controller under practical operation environments.

• Proceedings of KOSOMES biannual meeting
• /
• 2004.05b
• /
• pp.29-34
• /
• 2004

Ship is bring operated under a highly dynamic environments and many factors are related whit marine accident and those factors are interacting. An analysis on the marine accident is very important to prepare countermeasures which will ensure the safe navigation This paper aims to build a model of the rouses and improved policy for marine accident using SD(System Dynamics) approach and to measure a effect which is risk control countermeasures of marine accident The methodology of this paper is to perform the causes and improved policy for marine accident using Brainstorming method, and was to changed by quantitutive, qualitative factors and their feedback loops in casual map. This model was performed over 23 years($1997\~2020$) in a standard simulation model and 4 policy simulation models.

• Korean System Dynamics Review
• /
• v.9 no.1
• /
• pp.5-31
• /
• 2008

Korean administrative jurisdiction has changed from separation to integration system, without definite raison d'etre from the effectiveness dimension. It partially comes from the fact that the top priority of most existing documents has given to the behavioral patterns of key variables during specific time periods. As an alternative approach, this study focuses on dynamic analysis on the long-term structural patterns related to urban-rural integration issues. Specifically, it pays attention to unique experiences between two neighboring administrative authorities, namely Cheongju and Cheongwon, all of which have repeated exceptional confrontations between pros and cons over almost two decades. From the theoretical perspectives, this observes structural similarities and differences between separation and integration approaches and compares individual feedback loops in order to examine urban-rural integration effectiveness. Structurally, if the integrated local authority adopts systematic management and balanced territorial development principles, it would gain the highest positive effect of urban-rural integration. After scenario buildings, it analyzes administrative integration dynamics between Cheongju and Cheongwon, highlighting geo-political conditions, key issues, and implementation plans between two administrative authorities. It expects that the integrated jurisdiction as a whole would increase the urban attractiveness as it can facilitate territorial development plans from macro-level. Furthermore, if the integrated authority keeps balanced territorial principles, which would be well reflected in the mutual agreement between two administrative units, it would also guarantee the increased urban attractiveness in the integrated jurisdiction. Nonetheless, compared to Cheongwon, which might be wider open to the location of NIMBY facilities, it would be more difficult for Cheongju to pay attention to territorial development confined to its original jurisdiction in the short run.