• 수산경영론집
• /
• 제33권2호
• /
• pp.31-48
• /
• 2002

This paper is aimed to analyze how to evaluate the choice of optimal management measures and level of control in fisheries management under the costly and imperfect management system by comparing with costless and perfect management system that is commonly assumed in the analysis of fisheries regulations. Fishermen would set the level of fishing efforts at the point where the marginal fishing profit for fishing effort is equal to the marginal level of fine under costly and imperfect management system. Therefore, under the case where the marginal fishing profit is higher than the marginal level of fine, the level of fishing efforts would be made at the point which is higher than the level of fishing efforts made under costless and perfect management system and is not a point where the economic profit is maximized in regulated fisheries. From this conclusion, the fishermens avoidance activities against regulations as well as the level of control in fisheries management substantially have an influence on the choice of fisheries management instruments. According to the analysis of optimal fisheries management policy, the economic profits in regulated fisheries are determined by the level of fisheries enforcement costs and total fishing profits, in which as enforcement costs increase the economic profits decrease. In addition, the economic profits vary in response to the level of control in avoidance activities. That is, as avoidance costs decrease, the economic profits increase. The determination of optimal level of control in fisheries management should be made at the point where the marginal regulation costs are equal to the marginal profits from regulated fisheries, in which marginal regulation costs are different according to the type of management measures. And the level of profits changes in response to different levels of avoidance activities. The management measure that can maximize the difference between the marginal regulation costs and marginal profits from regulated fisheries should be chosen as an optimal fisheries management instrument.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2001년도 ICCAS
• /
• pp.85.1-85
• /
• 2001

A phase lock loop (PLL) circuit is a wellknown electronic circuit in communication engineering and other areas. In this paper, we present application of the PLL and fuzzy logic for DC motor control which are mixed well to be more effective for motor control. With this scheme, the control system can reach the set point rapidly, especially, it can eliminate noises. In addition, the PLL makes the system to have more stability; whereas, fuzzy logic controls helping PLL to be able to lock rapidly for a good response. The experiment result shows that the proposed control system works more efficacious. By performance comparison between the pure PLL control and the hybrid architecture of PLL with the fuzzy control, the result reveals the hybrid control ...

• Journal of Biosystems Engineering
• /
• 제23권3호
• /
• pp.291-304
• /
• 1998

A control algorithm fir the unmanned vehicles was developed using image information received through a CCD camera that acquires more powerful information over the wide range of wave-length comparing with other sensors and was applied to a speed-sprayer. The algorithm consisted of straight mode for passing along with middle of two tree-rows and turning mode for changing from a row to another row. In case of turning mode, two marks of colored papers were employed to indicate turning point and to decide turning direction for various orchard situations. The method of analysis and image would be differed according to camera's tilt-angle and position that is set on the speed-sprayer. Hence, it analyzed the point of difference by making camera's up and downward tilt-angle.

• 한국정밀공학회지
• /
• 제12권6호
• /
• pp.128-136
• /
• 1995

The problem addressed in this paper is that of the on-line computational burden of time-optimal control laws for quick, strongly nonlinear systems like revolute robots. It will be demonstrated that a large amount of off-line computation can be substituted for most of the on-line burden in cases of time optimization with constrained inputs if differential point-to- point specifications can be relaxed to cell-to-cell transitions. These cells result from a coarse discretization of likely swaths of state space into a set of nonuniform, contiguous volumes of relatively simple shapes. The cell boundaries approximate stream surfaces of the phase fluid and surfaces of equal transit times. Once the cells have been designed, the bang- bang schedules for the inputs are determined for all likely starting cells and terminating cells. The scheduling process is completed by treating all cells into which the trajectories might unex- pectedly stray as additional starting cells. Then an efficient-to-compute control law can be based on the resulting table of optimal strategies.

• Korean Chemical Engineering Research
• /
• 제52권5호
• /
• pp.581-586
• /
• 2014

하수처리장을 운영함에 있어 안정적인 방류수질 확보와 이에 따른 처리 비용을 최소화하는 것이 주요 목적이다. 하지만 유입수 유량 및 성분 농도의 변화와 미생물의 비선형적인 동특성, 기타 환경 요인에 의해서 최적의 운전 제어를 하기가 쉽지 않기 때문에, 기존의 하수처리장에서는 필요한 양 이상의 폭기 및 화학물질을 과량 주입하는 방법 등을 사용하였다. 본 연구에서는 포기조에서 미생물에 필요한 용존산소농도는 유지하면서 과폭기로 인한 전력 비용을 감소하는 최적 제어 방법을 제안하였다. 하수조성와 포기조 미생물의 호흡률은 실시간 미생물 호흡률 측정기(Oxygen uptake rate, OUR)를 이용하여 측정하였고, 실시간 호흡률 측정값을 바탕으로 현재 미생물에 필요한 최적 DO 농도를 제안하였다. 유입수 부하변동에 따라 변화하는 미생물 호흡에 필요한 산소량 만큼만 폭기하도록 구성함으로써, 방류수 수질기준을 만족함과 동시에 전력 비용을 최소화할 수 있는 방안을 제시하였다.

• 원예과학기술지
• /
• 제30권5호
• /
• pp.501-508
• /
• 2012

Reducing carbon dioxide ($CO_2$) exhaust has become a major issue for society in the last few years, especially since the initial release of the Kyoto Protocol in 1997 that strictly limited the emissions of greenhouse gas for each country. One of the primary sectors affecting the levels of atmospheric greenhouse gases is agriculture where $CO_2$ is not only consumed by plants but also produced from various types of soil and agricultural ecosystems including greenhouses. In greenhouse cultivation, $CO_2$ concentration plays an essential role in the photosynthesis process of crops. Optimum control of greenhouse $CO_2$ enrichment based on accurate monitoring of the added $CO_2$ can improve profitability through efficient crop production and reduce environmental impact, compared to traditional management practices. In this study, a sensor-based control system that could estimate the required $CO_2$ concentration considering emission from soil for cucumber greenhouses was developed and evaluated. The relative profitability index (RPI) was defined by the ratio of growth rate to supplied $CO_2$. RPI for a greenhouse controlled at lower set point of $CO_2$ concentration (500 ${\mu}mol{\cdot}mol^{-1}$) was greater than that of greenhouse at higher set point (800 ${\mu}mol{\cdot}mol^{-1}$). Evaluation tests to optimize $CO_2$ enrichment concluded that the developed control system would be applicable not only to minimize over-exhaust of $CO_2$ but also to maintain the crop profitability.

• Journal of Power Electronics
• /
• 제16권3호
• /
• pp.946-959
• /
• 2016

A novel Virtual Space Vector (VSV) modulation strategy for complete control of potential neutral point (NP) issues is proposed in this paper. The neutral point potential balancing problems of multi-level converters, which include elimination of low frequency oscillations and self-balancing for NP dc unbalance, are investigated first. Then a set of improved virtual space vectors with dynamic adjustment factors are introduced and a multi-objective optimization algorithm which aims to optimize these adjustment factors is presented in this paper. The improved virtual space vectors and the multi-objective optimization algorithm constitute the novel Virtual Space Vector modulation. The proposed novel Virtual Space Vector modulation can simultaneously recover NP dc unbalance and eliminate low frequency oscillations of the neutral point. Experiment results show that the proposed strategy has excellent performance, and that both of the neutral point potential issues can be solved.

• International Journal of CAD/CAM
• /
• 제7권1호
• /
• pp.51-60
• /
• 2007

This paper presents an algorithm of optimal cutting tool selection for machining of the point-based surface that is defined by a set of surface points rather than parametric polynomial surface equations. As the ball-end and fillet-end mills are generally used for finish machining in a 3-axis computer numerical control machine, the algorithm is applicable for both cutters. The optimum tool would be as large as possible in terms of the cutter radius and/or corner radius which maximise (s) the material removal rate (i.e., minimise (s) the machining time), while still being able to machine the entire point-based surface without gouging any surface point. The gouging are two types: local and global. In this paper, the distance between the cutter bottom and surface points is used to check the local gouging whereas the shortest distance between the surface points and cutter axis is effectively used to check the global gouging. The selection procedure begins with a cutter from the tool library, which has the largest cutter radius and/or corner radius, and then adequacy of the point-density is checked to limit the accuracy of the cutter selection for the point-based surface within tolerance prior to the gouge checking. When the entire surface is gouge-free with a chosen cutting tool then the tool becomes the optimum cutting tool for a list of cutters available in the tool library. The effectiveness of the algorithm is demonstrated considering two examples.

• 전기학회논문지
• /
• 제65권4호
• /
• pp.533-538
• /
• 2016

In a power grid that has a high penetration of wind power, the highly-fluctuating output power of wind turbine generators (WTGs) adversely impacts the power quality in terms of the system frequency. This paper proposes a power smoothing scheme of a variable-speed WTG that can smooth its fluctuating output power caused by varying wind speeds, thereby improving system frequency regulation. To achieve this, an additional loop relying on the frequency deviation that operates in association with the maximum power point tracking control loop, is proposed; its control gain is modified with the rotor speed. For a low rotor speed, to ensure the stable operation of a WTG, the gain is set to be proportional to the square of the rotor speed. For a high rotor speed, to improve the power smoothing capability, the control gain is set to be proportional to the cube of the rotor speed. The performance of the proposed scheme is investigated under varying wind speeds for the IEEE 14-bus system using an EMTP-RV simulator. The simulation results indicate that the proposed scheme can mitigate the output power fluctuation of WTGs caused by varying wind speeds by adjusting the control gain depending on the rotor speed, thereby supporting system frequency regulation.

• 제어로봇시스템학회논문지
• /
• 제10권12호
• /
• pp.1181-1188
• /
• 2004

This paper reviews the main aspects of cardiovascular system dynamics with emphasis on modeling hemodynamic characteristics using a lumped parameter approach. Methodological and physiological aspects of the circulation dynamics are summarized with the help of existing mathematical models: The main characteristics of the hemodynamic elements, such as the heart and arterial and venous systems, are first described. Lumped models of micro-circulation and pulmonary circulation are introduced. We also discuss the feedback control of cardiovascular system. The control pathways that participate in feedback mechanisms (baroreceptors and cardiopulmonary receptors) are described to explain the interaction between hemodynamics and autonomic nerve control in the circulation. Based on a set-point model, the computational aspects of reflex control are explained. In final chapter we present the present research trend in this field and discuss the future studies of cardiovascular system modeling.