• 제목/요약/키워드: dynamic constraints

검색결과 686건 처리시간 0.029초

Transient Characteristics and Physical Constraints of Grid-Tied Virtual Synchronous Machines

  • Yuan, Chang;Liu, Chang;Yang, Dan;Zhou, Ruibing;Tang, Niang
    • Journal of Power Electronics
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    • 제18권4호
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    • pp.1111-1126
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    • 2018
  • In modern power systems, distributed generators (DGs) result in high stress on system frequency stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method referred to as a virtual synchronous machine (VSM) has been proposed, which brought new characteristics to inverters such as synchronous machines (SM). DGs employing an energy storage system (ESS) provide inertia and damping through VSM control. Meanwhile, energy storage presents some physical constraints in the VSM implementation level. In this paper, a VSM mathematical model is built and analyzed. The dynamic responses of the output active power are presented when a step change in the frequency occurs. The influences of the inertia constant, damping factor and operating point on the ESS volume margins are investigated. In addition, physical constraints are proposed based on these analyses. The proposed physical constraints are simulated using PSCAD/EMTDC software and tested through RTDS experiment. Both simulation and RTDS test results verify the analysis.

초공동 수중운동체의 설계 제약조건에 관한 연구 (A Study on Design Constraints of a Supercavitating Underwater Vehicle)

  • 김선홍;김낙완
    • 대한조선학회논문집
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    • 제53권1호
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    • pp.54-61
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    • 2016
  • This paper defines the design constraint in consideration of the dynamic characteristics and stability in the longitudinal direction of a supercavitating vehicle. Available range of the design variables is calculated by numerical simulation and the cavity modeling of vehicle dynamics is performed first. Configuration parameters of the supercavitating vehicle to determine the vehicle dynamics and characteristics of the cavity are defined as design variables. Design constraints are supercavitation, trim velocity, stability and vehicle dynamics in transition phase. Numerical results show that in accordance with the change of the design variables, the proposed design constraints reflect the physical characteristics of the supercavitating vehicle. This research finds the design region where the constraints of supercavity and the trim velocity are satisfied, and the stability analysis refines the design results by excluding the region where the stability is not guaranteed. The stability analysis is particularly important for a vehicle with the short fin span.

Performance Improvement of an INS by using a Magnetometer with Pedestrian Dynamic Constraints

  • Woyano, Feyissa;Park, Aangjoon;Lee, Soyeon
    • IEIE Transactions on Smart Processing and Computing
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    • 제6권1호
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    • pp.1-9
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    • 2017
  • This paper proposes to improve the performance of a strap down inertial navigation system using a foot-mounted low-cost inertial measurement unit/magnetometer by configuring an attitude and heading reference system. To track position accurately and for attitude estimations, considering different dynamic constraints, magnetic measurement and a zero velocity update technique is used. A conventional strap down method based on integrating angular rate to determine attitude will inevitably induce long-term drift, while magnetometers are subject to short-term orientation errors. To eliminate this accumulative error, and thus, use the navigation system for a long-duration mission, a hybrid configuration by integrating a miniature micro electromechanical system (MEMS)-based attitude and heading detector with the conventional navigation system is proposed in this paper. The attitude and heading detector is composed of three-axis MEMS accelerometers and three-axis MEMS magnetometers. With an absolute algorithm based on gravity and Earth's magnetic field, rather than an integral algorithm, the attitude detector can obtain an absolute attitude and heading estimation without drift errors, so it can be used to adjust the attitude and orientation of the strap down system. Finally, we verify (by both formula analysis and from test results) that the accumulative errors are effectively eliminated via this hybrid scheme.

듀얼-핑거의 안정적 파지 운동 제어에 관한 연구 (A Study on Stable Grasping Motion Control of Dual-Finger)

  • 엄혁;최종환;김승수;한현용;양순용;이진걸
    • 한국공작기계학회논문집
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    • 제14권4호
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    • pp.81-88
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    • 2005
  • This paper attempts to derive the dynamic model of handling tasks in finger robot which grasps stable and manipulates a rigid object with some dexterity. Firstly, a set of differential equation describing dynamics of the manipulators and object together with geometric constraint of tight area-contacts is formulated by Lagrange's equation. Secondly, the roblems of controlling both the forces of pressing object and the rotation angle of the object under the geometric constraints are discussed. The effect of geometric constraints of area-contacts between the link's end-effector and the object is analyzed and the model based on the differential-algebraic equations is presented. In this paper, the control method for dynamic stable grasping and enhancing dexterity in manipulating things is proposed. It is illustrated by computer simulation and the experiment that the control system gives the performance improvement in the dynamic stable grasping and nimble manipulating of the dual fingers robot with soft tips.

접촉 마찰을 고려한 다중 로봇 시스템의 조작도 해석 (Dynamic Manipulability for Cooperating Multiple Robot Systems with Frictional Contacts)

  • 변재민;이지홍
    • 전자공학회논문지SC
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    • 제43권5호
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    • pp.10-18
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    • 2006
  • 본 논문에서는 다중 로봇 시스템에서 물체와 로봇 팔끝 간에 접촉 마찰이 존재할 때 이 로봇 시스템의 조작도를 해석하는 새로운 방법을 제안한다. 로봇이 물체를 떨어뜨리지 않고 잡고 있으려면, 로봇이 물체에 가하는 힘 벡터가 friction cone 내부에 존재 해야만 한다. 이러한 friction cone 내부를 나타내는 식은 일반적으로 비선형 형태로 되어 있기 때문에 기존의 조작도 분석 방법에 이 식을 구속 조건으로 적용하기가 쉽지 않다. 따라서 본 논문에서는 이러한 friction cone 내부를 다각뿔로 근사함으로써 선형적인 구속 조건으로 표현하였다. 또한 선행 연구에서 찾지 못했던 부분을 새롭게 찾아내었다. 그리고 다중 로봇 시스템에 조작도를 나타내는 물체 중심의 가속도를 구하기 위해서, 먼저 선형계획법을 통해서 허용 가능한 토크의 영역을 구하였다. 이 토크의 영역을 선형 변환을 통해 최종적으로 물체의 최대 가속도의 영역을 구하였다. 본 방법의 타당성을 입증하기 위해서 두 대로 구성 된 다중 로봇 시스템과 PUMA560 로봇 시스템에 적용하였다.

다물체 동역학을 이용한 파력발전기의 동적거동 분석 (Dynamic Analysis of Wave Energy Generation System by Using Multibody Dynamics)

  • 장진석;손정현
    • 대한기계학회논문집A
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    • 제35권12호
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    • pp.1579-1584
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    • 2011
  • 본 논문에서는 파도의 에너지를 전기에너지로 변환하는 파력발전시스템에 대해 다루며, 발전기 및 12개의 암을 가진 가동물체형 파력발전기를 기구학적 구속조건을 이용하여 다물체 동역학 모델링 하였다. 새롭게 제안하는 파력발전기의 기어 메커니즘과 구속방정식 및 전달되는 힘요소에 대해 동역학적으로 모델링하였다. 파력은 시간영역에서 모리슨 방정식을 이용하여 수치적으로 계산하여 모델에 적용하였다. 시스템 거동해석을 위해 상용 다물체동역학 해석프로그램인 MSC/ADAMS를 이용하였다. 파력발전시스템의 파도에 대한 안정성을 검토하고 동적 거동 특성을 분석하였다. 하중에 따라 거동 특성을 분석한 결과 Yaw 운동은 상대적으로 적게 나타났으며 파고 1 m 이상일 경우 충분한 운동에너지가 발생함을 알 수 있다.

Multiple dynamic programming에 관한 연구 (A Study of Multiple Dynamic Programming)

  • 박영문
    • 전기의세계
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    • 제21권1호
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    • pp.13-16
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    • 1972
  • Dynamic Programming is regarded as a very powerful tool for solving nonlinear optimization problem subject to a number of constraints of state and control variables, but has definite disadvantages that it requires much more computing time and consumes much more memory spaces than other technigues. In order to eliminate the above-mentioned demerits, this paper suggests a news technique called Multiple Dynamic Programming. The underlying principles are based on the concept of multiple passes that, instead of forming fin lattices in time-state plane as adopted in the conventional Dynamic Programming, the Multiple Dynamic Programming constitutes, at the first pass, coarse lattices in the feasible domain of time-state plane and determines the optimal state trajectory by the usual method of Dynamic Programming, and at the second pass again constitutes finer lattices in the narrower domain surrounded by both the upperand lower edges next to the lattice edges through which the first pass optimal trajectory passes and determines the more accurate optimal trajectory of state, and then at the third pass repeats the same processes, and so on. The suggested technique insures remarkable curtailment in amounts of computer memory spaces and conputing time, and its applicability has been demonstrated by a case study on the hydro-thermal power coordination in Korean power system.

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차입제약과 한계소비성향 (Borrowing Constraints and the Marginal Propensity to Consume)

  • 토마스 비숍;박철범
    • KDI Journal of Economic Policy
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    • 제33권4호
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    • pp.1-25
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    • 2011
  • 실증연구들은 2001년 미국의 세금 환급에서 나타난 평균적인 한계소비성향이 이전의 조세 감축에서 보여진 한계소비성향보다 감소되었음을 암시하고 있다. 우리는 이와 같은 현상이 신용카드의 광범위한 사용으로 대부분의 미국 가계에서 차입이 쉬워짐으로써 발생하였다는 것을 차입제약 완화의 동태적 효과를 분석하는 시뮬레이션을 통하여 고찰한다. 우리 모형은 위험 기피도와 시점 간 대체탄력성을 독립적으로 결정하는 Kreps-Porteus 선호를 사용하여 차입제약이 완화된 직후 한계소비성향이 크게 하락하였음을 보여주고 있다. 우리 모형은 또한 차입제약이 완화된 후, 소비자들이 자산을 감소시켜 완화된 차입제약의 구속력이 서서히 커져서 한계소비성향이 이전보다 약간 낮은 새로운 정상상태로 서서히 상승됨을 보여주고 있다. 이러한 한계소비성향의 동태적 패턴은 신용카드 사용으로 인한 차입제약 완화가 2001년 세금환급에서 이전보다 낮은 한계소비성향을 야기하였음을 의미한다. 그리고 우리의 모형은 차입제약이 완화되었을 때 소비자들이 예비적 유동자산을 낮은 수준에서 유지한다는 것을 보여주고 있다.

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Energy Optimization of a Biped Robot for Walking a Staircase Using Genetic Algorithms

  • Jeon, Kweon-Soo;Park, Jong-Hyeon
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2003년도 ICCAS
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    • pp.215-219
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    • 2003
  • In this paper, we generate a trajectory minimized the energy gait of a biped robot for walking a staircase using genetic algorithms and apply to the computed torque controller for the stable dynamic biped locomotion. In the saggital plane, a 6 degree of freedom biped robot that model consists of seven links is used. In order to minimize the total energy efficiency, the Real-Coded Genetic Algorithm (RCGA) is used. Operators of genetic algorithms are composed of a reproduction, crossover and mutation. In order to approximate the walking gait, the each joint angle is defined as a 4-th order polynomial of which coefficients are chromosomes. Constraints are divided into equality and inequality. Firstly, equality constraints consist of position conditions at the end of stride period and each joint angle and angular velocity condition for periodic walking. On the other hand, inequality constraints include the knee joint conditions, the zero moment point conditions for the x-direction and the tip conditions of swing leg during the period of a stride for walking a staircase.

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Trust and Risk based Access Control and Access Control Constraints

  • Helil, Nurmamat;Kim, Mu-Cheol;Han, Sang-Yong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제5권11호
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    • pp.2254-2271
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    • 2011
  • Access control in dynamic environments needs the ability to provide more access opportunities of information to users, while also ensuring protection information from malicious users. Trust and risk are essential factors and can be combined together in access control decision-making to meet the above requirement. In this paper, we propose the combination of the trust and risk in access control to balance information accessibility and protection. Access control decision is made on the basis of trustworthiness of users and risk value of permissions. We use potential relations between users and relations between permissions in access control. Our approach not only provides more access opportunities for trustworthy users in accessing permissions, but also enforces traditional access control constraints such as Chinese Wall policy and Separation of Duty (SoD) of Role-Based Access Control (RBAC) model in an effective way.