• Title/Summary/Keyword: admissible control

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A Study on Material Characterization of Semi-Solid Materials(II) -Determination of Flow Stress For Semi-Solid Materials Using Backward Extrusion Experiment with Model Material and Upper Bound Analysis- (반용융 재료의 물성치 평가에 관한 연구(II) -모델재료의 후방압출 실험과 상계해석을 통한 반용융 재료의 유동응력식 결정-)

  • 이주영;김낙수
    • Transactions of Materials Processing
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    • v.8 no.4
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    • pp.374-383
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    • 1999
  • To determine the flow stress of semi-solid materials, a new combined method has been studied by experimental and analytic technique in the current approach. Using backward extrusion experiment and its numerical analysis, the characterization scheme of semi-solid materials according to the change of initial solid volume fraction has been proposed. Because that solid volume fraction is sensitive to temperature change, it is required to precisely control the temperature setting. Model materials can guarantee the establishment of material characterization technique from the noise due to temperature change. Thus, clay mixed with bonded abrasives was used for experiment and the change of initial solid fraction was copied out through the variation of mixing ratio. Upper bound method was adapted to increase in efficiency of the calculation in numerical analysis and new kinematically admissible velocity field was employed to improve the accuracy of numerical solution. It is thought that the material characterization scheme proposed in this study can be applied to not only semi-solid materials, but also other materials that is difficult to obtain the simple stress state.

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A method of minimum-time trajectory planning ensuring collision-free motion for two robot arms

  • Lee, Jihong;Bien, Zeungnam
    • 제어로봇시스템학회:학술대회논문집
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    • 1990.10b
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    • pp.990-995
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    • 1990
  • A minimum-time trajectory planning for two robot arms with designated paths and coordination is proposed. The problem considered in this paper is a subproblem of hierarchically decomposed trajectory planning approach for multiple robots : i) path planning, ii) coordination planning, iii) velocity planning. In coordination planning stage, coordination space, a specific form of configuration space, is constructed to determine collision region and collision-free region, and a collision-free coordination curve (CFCC) passing collision-free region is selected. In velocity planning stage, normal dynamic equations of the robots, described by joint angles, velocities and accelerations, are converted into simpler forms which are described by traveling distance along collision-free coordination curve. By utilizing maximum allowable torques and joint velocity limits, admissible range of velocity and acceleration along CFCC is derived, and a minimum-time velocity planning is calculated in phase plane. Also the planning algorithm itself is converted to simple numerical iterative calculation form based on the concept of neural optimization network, which gives a feasible approximate solution to this planning problem. To show the usefulness of proposed method, an example of trajectory planning for 2 SCARA type robots in common workspace is illustrated.

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An Analysis of Cell Loss Process in an ATM Network Under Partial Buffer Sharing Policy (ATM 전송망에서의 PBS를 이용한 셀 우선 순위 제어 방식의 연구)

  • 곽민곤;성수란;김종권
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.19 no.12
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    • pp.2328-2339
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    • 1994
  • The PBS(Partial Buffer Sharing) space priority mechanism is one of priority control methods which may improve the performance of a single server queueing system when mixed traffic with different performance requirements is applied to the system. This paper analyzes the cell loss behavior of PBS assuming loss sensitive traffic and delay sensitive traffic are applied to the system. To derive the successive cell loss probabilities. which are an important performance measure of realtime traffic, we develop a recursive algorithm. Performance results show the successive cell loss probabilities obtained by our method are lager than the probabilities derived from an independent cell loss assumption. These results may indicate the limitation of PBS for realtime traffic and the increase of the admissible load with the criterion of quality of service.

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A Provable Authenticated Certificateless Group Key Agreement with Constant Rounds

  • Teng, Jikai;Wu, Chuankun
    • Journal of Communications and Networks
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    • v.14 no.1
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    • pp.104-110
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    • 2012
  • Group key agreement protocols allow a group of users, communicating over a public network, to establish a shared secret key to achieve a cryptographic goal. Protocols based on certificateless public key cryptography (CL-PKC) are preferred since CL-PKC does not need certificates to guarantee the authenticity of public keys and does not suffer from key escrow of identity-based cryptography. Most previous certificateless group key agreement protocols deploy signature schemes to achieve authentication and do not have constant rounds. No security model has been presented for group key agreement protocols based on CL-PKC. This paper presents a security model for a certificateless group key agreement protocol and proposes a constant-round group key agreement protocol based on CL-PKC. The proposed protocol does not involve any signature scheme, which increases the efficiency of the protocol. It is formally proven that the proposed protocol provides strong AKE-security and tolerates up to $n$-2 malicious insiders for weak MA-security. The protocol also resists key control attack under a weak corruption model.

Real-time Obstacle Avoidance of Non-holonomic Mobile Robots Using Expanded Guide Circle Method (확장 가이드 서클 방법을 이용한 비홀로노믹 이동로봇의 실시간 장애물 회피)

  • Shim, Young-Bo;Kim, Gon-Woo
    • The Journal of Korea Robotics Society
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    • v.12 no.1
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    • pp.86-93
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    • 2017
  • The Expanded Guide Circle (EGC) method has been originally proposed as the guidance navigation method for improving the efficiency of the remote operation using the sensory information. The previous algorithm is, however, concerned only for the omni-directional mobile robot, so it needs to suggest a suitable one for a mobile robot with non-holonomic constraints. The ego-kinematic transform is a method to map points of $R^2$ into the ego-kinematic space which implicitly represents non-holonomic constraints for admissible paths. Thus, robots with non-holonomic constraints in the ego-kinematic space can be considered as "free-flying object". In this paper, we propose an effective obstacle avoidance method for mobile robots with non-holonomic constraints by applying EGC method in the ego-kinematic space using the ego-kinematic transformation. This proposed method shows that it works better for non-holonomic mobile robots such as differential-drive robot than the original one. The simulation results show its effectiveness of performance.

Fuzzy $H^{\infty}$ Controller Design for Uncertain Nonlinear Systems (불확실성을 갖는 비선형 시스템의 퍼지 $H^{\infty}$ 제어기 설계)

  • Lee, Kap-Rai;Jeung, Eun-Tae;Park, Hong-Bae
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.35S no.6
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    • pp.46-54
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    • 1998
  • This paper presents a method for designing robust fuzzy $H^{\infty}$ controllers which stabilize nonlinear systems with parameter uncertainty adn guarantee an induced $L_{2}$ norm bound constraint on disturbance attenuation for all admissible uncertainties. Takagi and Sugeno's fuzzy models with uncertainty are used as the model for the uncertain nonlinear systems. Fuzzy control systems utilize the concept of so-called parallel distributed compensation(PDC). Using a single quadratic Lyapunov function, the stability condition satisfying decay rate and disturbance attenuation condition for Takagi and Sugeno's fuzzy model with parameter uncertainty are discussed. A sufficient condition for the existence of robust fuzzy $H^{\infty}$ controllers is then presented in terms of linear matrix inequalities(LMIs). Finally, design examples of robust fuzzy $H^{\infty}$ controllers for uncertain nonlinear systems are presented.

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New prototypes of target transfer functions for time domain specification (시간영역 설계명세를 위한 목표전달함수의 새로운 표준형)

  • Kim, Sin-Gu;Kim, Yeong-Cheol
    • Journal of Institute of Control, Robotics and Systems
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    • v.5 no.8
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    • pp.889-897
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    • 1999
  • This paper deals with a problem searching a target transfer function to meet the time-domain specifications for feedback system with given plant transfer function. For the Type I system, we first define three forms of transient response to unit step input, which are named by F, M, S-type. These are charaacterized as follows ; F-type has fast initial response and slow approach to the steady sate after reaching at 90% of the steady state value, S-type has slow initial response but fast approach to the steady state, and M-type is denoted by highly smooth response between F-type and S-type. Three prototypes corresponding to each form are proposed, time. For the order $n{\geq}4$, after determining admissible root structures of target characteristic polynomials empirically and expressing such polynomial coefficients by using special parameters ${\gamma}_i$ and $\epsilon$, the optimal prototypes that minimize the integral of the squared of the modified errors(ISME) have been obtained. Since the step responses of these prototypes have almost same wave forms irrespective to the order, the desired settling time or the rise time can be converted into the equibalent time constant $\tau$ and thus it is easy to obtain a target transfer function. It is shown through a design example that the present prototype is very useful for meeting the time-domain specifications and has been compared with different methods with a viewpoint of pertinence.

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OPF with Environmental Constraints with Multi Shunt Dynamic Controllers using Decomposed Parallel GA: Application to the Algerian Network

  • Mahdad, B.;Bouktir, T.;Srairi, K.
    • Journal of Electrical Engineering and Technology
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    • v.4 no.1
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    • pp.55-65
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    • 2009
  • Due to the rapid increase of electricity demand, consideration of environmental constraints in optimal power flow (OPF) problems is increasingly important. In Algeria, up to 90% of electricity is produced by thermal generators (vapor, gas). In order to keep the emission of gaseous pollutants like sulfur dioxide (SO2) and Nitrogen (NO2) under the admissible ecological limits, many conventional and global optimization methods have been proposed to study the trade-off relation between fuel cost and emissions. This paper presents an efficient decomposed Parallel GA to solve the multi-objective environmental/economic dispatch problem. At the decomposed stage the length of the original chromosome is reduced successively and adapted to the topology of the new partition. Two subproblems are proposed: the first subproblem is related to the active power planning to minimize the total fuel cost, and the second subproblem is a reactive power planning design based in practical rules to make fine corrections to the voltage deviation and reactive power violation using a specified number of shunt dynamic compensators named Static Var Compensators (SVC). To validate the robustness of the proposed approach, the algorithm proposed was tested on the Algerian 59-bus network test and compared with conventional methods and with global optimization methods (GA, FGA, and ACO). The results show that the approach proposed can converge to the near solution and obtain a competitive solution at a critical situation and within a reasonable time.

Construction Process Modelling Method Improving the Traceability of ICT Applications (ICT 적용 추적성 개선을 위한 시공관리 프로세스 모델링)

  • Go, Taeyong;Lim, Taekyung;Lee, Dong-Eun
    • Korean Journal of Construction Engineering and Management
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    • v.20 no.1
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    • pp.114-123
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    • 2019
  • Tracking ICT applications on construction business processes is critical to the success of ICT-applied construction projects. Existing IDEF0 is a representative modeling method for visualizing and analyzing business processes. It defines a construction production process into a visual information model, hence, encouraging the project participant to understand the activities, their deliverable, and control flow of the process. However, IDEF0 dose not lend itself to ICT-applied construction processes, because it does not provide a mean to define how, in what order, by which each and every activity that ICT applied implements. This paper presents a new business modeling method that improves the traceability of ICT application (IAMB: ICT Application tracking Model for Business process) for construction management. The IAMB contributes to handle the sophisticated features of construction management processes to which ICT are applied. The method categorizes the process into three types: management, construction, and information exchange. The validity of IAMB was confirmed by analyzing the performance when it is used for tracking each modeling step of lift reservation process which making use of ICT. The test case provides an admissible evidence that the method encourage to define who, what, how, which order, and by which ICT tools the construction process exchanges production information.