• 제목/요약/키워드: Chance Constraint

검색결과 16건 처리시간 0.021초

다중 평가지표에 기반한 도로용량 증대 소요예산 추정 (Budget Estimation Problem for Capacity Enhancement based on Various Performance Criteria)

  • 김주영;이상민;조종석
    • 대한교통학회지
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    • 제26권5호
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    • pp.175-184
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    • 2008
  • 도로용량 증대를 위한 소요예산 추정문제는 관련주체인 이용자와 공급자의 입장을 모두 반영할 필요가 있다. 본 연구에서는 총통행시간, 형평성, 환경비용을 평가지표로 설정하고, 3가지 평가지표에 대한 관련주체의 요구사항이 만족되는 대안 중 소요예산을 최소화하는 최적 도로용량 증대 대안을 선정하는 문제를 모형화하였다. 일반적으로 도로용량 증대를 위한 소요예산 추정문제는 Network Design Problem(NDP)로 다루어지며, 이용자와 공급자의 다른 입장을 고려하기 위해 Bi-level 최적화문제로 모형화된다. 본 연구에서는 장래 교통수요의 불확실성을 반영하기 위해 확률모형(Stochastic model)을 적용하고, 평가지표별 신뢰도를 차별화하기 위해 Chance-constrained model(CCM)를 적용하였으며, 3가지 평가지표의 제약식을 만족하면서 소요예산을 최소화하는 목적함수를 만족하는 최적대안을 선정하기 위해 렉시코그라픽(Lexicographic) 최적화문제로 접근하였다. 예제 네트워크를 통하여 분석한 결과, 평가지표별 신뢰도 및 교통수요 변화율이 클수록 더욱 많은 소요예산이 요구되며, 평가지표별 신뢰도가 클수록 장래 교통수요의 변화에 더욱 탄력적으로 대응할 수 있는 대안이 선정되었다. 제안된 모델은 다양한 관련주체의 입장을 모두 고려한 최적 도로용량 증대 대안과 소요예산을 선정함과 동시에, 도로용량 증대량의 변화에 따른 평가지표간 상쇄관계(Tradeoff)와 도로 네트워크 개선을 위한 예산 배분의 포트폴리오를 정책결정자에게 제공 가능하다.

Noisy 한 CFD 결과에 대한 구속조건을 고려한 EGO 방법 연구 (A STUDY ON CONSTRAINED EGO METHOD FOR NOISY CFD DATA)

  • 배효길;권장혁
    • 한국전산유체공학회지
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    • 제17권4호
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    • pp.32-40
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    • 2012
  • Efficient Global Optimization (EGO) method is a global optimization technique which can select the next sample point automatically by infill sampling criteria (ISC) and search for the global minimum with less samples than what the conventional global optimization method needs. ISC function consists of the predictor and mean square error (MSE) provided from the kriging model which is a stochastic metamodel. Also the constrained EGO method can minimize the objective function dealing with the constraints under EGO concept. In this study the constrained EGO method applied to the RAE2822 airfoil shape design formulated with the constraint. But the noisy CFD data caused the kriging model to fail to depict the true function. The distorted kriging model would make the EGO deviate from the correct search. This distortion of kriging model can be handled with the interpolation(p=free) kriging model. With the interpolation(p=free) kriging model, however, the search of EGO solution was stalled in the narrow feasible region without the chance to update the objective and constraint functions. Then the accuracy of EGO solution was not good enough. So the three-step search method was proposed to obtain the accurate global minimum as well as prevent from the distortion of kriging model for the noisy constrained CFD problem.

Compensation for Photovoltaic Generation Fluctuation by Use of Pump System with Consideration for Water Demand

  • Imanaka, Masaki;Sasamoto, Hideki;Baba, Jumpei;Higa, Naoto;Shimabuku, Masanori;Kamizato, Ryota
    • Journal of Electrical Engineering and Technology
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    • 제10권3호
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    • pp.1304-1310
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    • 2015
  • In remote islands, due to expense of existing generation systems, installation of photovoltaic cells (PVs) and wind turbines has a chance of reducing generation costs. However, in island power systems, even short-term power fluctuations change the frequency of grids because of their small inertia constant. In order to compensate power fluctuations, the authors proposed the power consumption control of pumps which send water to tanks. The power control doesn’t affect water users’ convenience as long as tanks hold water. Based on experimental characteristics of a pump system, this paper shows methods to determine reference power consumption of the system with compensation for short-term PV fluctuations while satisfying water demand. One method uses a PI controller and the other method calculates reference power consumption from water flow reference. Simulations with a PV and a pump system are carried out to find optimum parameters and to compare the methods. Results show that both PI control method and water flow calculation method are useful for satisfying the water demand constraint. The water demand constraint has a little impact to suppression of the short-term power fluctuation in this condition.

자기 부상 방식 구동원리를 이용한 다자유도 정밀 위치 시스템의 최적 설계, 모델링 및 제어에 관한 연구 (A Study on the Optimal Design, Modeling and Control of the Multi d.o.f Precision Positioning System Using Magnetic Levitation Actuating Principle)

  • 정광석;백윤수
    • 대한기계학회논문집A
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    • 제25권5호
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    • pp.779-787
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    • 2001
  • The multi degree of freedom system using magnetic levitation has been implemented successfully. Differently from another noncontact systems, the developed system was focused on the maximization of the system stiffness under the constraint of a limited input. The variation of a relative adopting point between the magnetic pair, its location on the fixed base, and the selection of optimal specifications for the main active magnetic elements give us another chance to realize the increased robustness against external disturbances with the less control inputs. In this paper, the overall development procedures are given including the optimal design, the dynamic modeling, the various control tests, and the main issues to be solved.

자율주행 자동차 정지 거동에서의 인지 불확실성을 고려한 확률적 모델 예측 제어 (Stochastic Model Predictive Control for Stop Maneuver of Autonomous Vehicles under Perception Uncertainty)

  • 김상윤;조아라;이경수
    • 자동차안전학회지
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    • 제14권4호
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    • pp.35-42
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    • 2022
  • This paper presents a stochastic model predictive control (SMPC) for stop maneuver of autonomous vehicles considering perception uncertainty of stopped vehicle. The vehicle longitudinal motion should achieve both driving comfortability and safety. The comfortable stop maneuver can be performed by mimicking acceleration profile of human driving pattern. In order to implement human-like stop motion, we propose a reference safe inter-distance and velocity model for the longitudinal control system. The SMPC is used to track the reference model which contains the position uncertainty of preceding vehicle as a chance constraint. We conduct simulation studies of deceleration scenarios against stopped vehicle in urban environment. The test results show that proposed SMPC can execute comfortable stop maneuver and guarantee safety simultaneously.

MPC-based Two-stage Rolling Power Dispatch Approach for Wind-integrated Power System

  • Zhai, Junyi;Zhou, Ming;Dong, Shengxiao;Li, Gengyin;Ren, Jianwen
    • Journal of Electrical Engineering and Technology
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    • 제13권2호
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    • pp.648-658
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    • 2018
  • Regarding the fact that wind power forecast accuracy is gradually improved as time is approaching, this paper proposes a two-stage rolling dispatch approach based on model predictive control (MPC), which contains an intra-day rolling optimal scheme and a real-time rolling base point tracing scheme. The scheduled output of the intra-day rolling scheme is set as the reference output, and the real-time rolling scheme is based on MPC which includes the leading rolling optimization and lagging feedback correction strategy. On the basis of the latest measured thermal unit output feedback, the closed-loop optimization is formed to correct the power deviation timely, making the unit output smoother, thus reducing the costs of power adjustment and promoting wind power accommodation. We adopt chance constraint to describe forecasts uncertainty. Then for reflecting the increasing prediction precision as well as the power dispatcher's rising expected satisfaction degree with reliable system operation, we set the confidence level of reserve constraints at different timescales as the incremental vector. The expectation of up/down reserve shortage is proposed to assess the adequacy of the upward/downward reserve. The studies executed on the modified IEEE RTS system demonstrate the effectiveness of the proposed approach.