• 드라이브 ㆍ 컨트롤
• /
• 제13권3호
• /
• pp.24-31
• /
• 2016

The performance characteristics of a dynamic control system are evaluated according to the transient and steady-state responses. The transient performance is the controllability of the output for the tracking of the reference or the ability to reduce or reject the effects of unwanted disturbances; alternatively, the steady-state performance is represented by the magnitude of the control error at the steady state. As the effects of the two performances on each other are reciprocal, a controller design that shows a zero steady-state error for the ramp input is uncommon because of the challenge regarding the achievement of an acceptable transient response. This paper proposes a PI+double-integral controller for the elimination of the steady-state error for the ramp input while a sound transient performance is maintained. The control-gain design procedure is described by the second-order response for the step input and the response of the error dynamics for the ramp input. The PI+double-integral controller is designed for the first-order transfer function that is derived from a system identification with the open-loop experiment data of the dc-motor. The simple structure of the proposed controller enables the adoption of a low-end microcontroller for the implementation of a real-time control. The experiment results show that the control performance is as effective as that of the simulation analysis for the operating point of linear system; furthermore, the PI+double-integral controller can be conveniently applied to the control system, which is desirable for the improvement of the steady-state error.

• Journal of Communications and Networks
• /
• 제9권4호
• /
• pp.356-367
• /
• 2007

In large networks, maintaining precise global network state information is impossible. The imprecise network state information has significant impacts on Quality-of-Service(QoS) routing and path establishment. In this paper, we develop analytical models for investigating the QoS routing schemes that are designed to tolerate imprecise network state information, and study the performance of various QoS routing schemes, including randomized routing, multi-path routing, and probability based routing, using both the models and simulations. We further propose a new mechanism, called local rerouting, that improves the effectiveness of QoS path establishment in the presence of imprecise global network state information. Local rerouting is orthogonal to existing schemes for dealing with imprecise state information and can be used in conjunction with them to alleviate the impacts of the imprecise information. The results of our performance study indicate that local rerouting is robust and effective.

• Ocean Systems Engineering
• /
• 제4권1호
• /
• pp.1-19
• /
• 2014

Hydrodynamic coefficients strongly affect the dynamic performance of autonomous underwater vehicles (AUVs). A novel kind of underwater vehicle (Heavier-than-water AUV) with higher density than water is presented, which is different from conventional ones. RANS method and overlapping grids are used to simulate the flow field around the vehicle. Lifts, drags and moments of different attack and drift angles in steady state are calculated. The hydrodynamic performances and how the forces change with the attitude are analyzed according to the flow field structure. The steady-state results using overlapping grid method are compared with those of software FLUENT and wind tunnel tests. The calculation results show that the overlapping grid method can well simulate the viscous flow field around the underwater vehicle. Overlapping grid skills have also been used to figure out the planar-motion-mechanism (PMM) problem of Heavier-than-water AUV and forecast its hydrodynamic performance, verifying its effectiveness in dealing with the dynamic problems, which would be quite helpful for design and control of Heavier-than-water AUV and other underwater vehicles.

• 한국지능시스템학회논문지
• /
• 제20권6호
• /
• pp.768-773
• /
• 2010

본 논문에서는 도립진자 시스템을 이용한 최적 상태 되먹임 제어기 설계 및 성능 검증을 소개한다. 제안하고 있는 최적 상태 되먹임 제어기는 최적제어 이론을 기반으로 입력크기와 응답성능의 최적값을 고려하였고 뿐만 아니라, 적분제어기법을 도입함으로써 정상상태오차를 줄이도록 하였다. 실험에 사용된 도립진자 시스템은 (주)셈웨어의 PC기반 CEM-IP-01으로써 제안된 제어기를 적용한다. 마지막으로 제안된 제어기와 일반 상태 되먹임 제어기를 모의실험과 실험을 통하여 비교함으로써 제안된 제어기의 성능을 검증한다.

• Journal of Power Electronics
• /
• 제16권2호
• /
• pp.584-597
• /
• 2016

This paper focuses on an improvement in the transient performance of Boost converters when the load changes abruptly. This is achieved on the basis of the nature trajectory in Boost converters. Three key aspects of the transient performance are analyzed including the storage energy change law in the inductors and capacitors of converters during the transient process, the ideal minimum voltage deviation in the transient process, and the minimum voltage deviation control trajectory. The changing relationship curve between the voltage deviation and the recovery time is depicted through analysis and simulations when the load suddenly increases. In addition, the relationship curve between the current fluctuation and the recovery time is obtained when the load suddenly decreases. Considering the aspects of an increasing and decreasing load, this paper proposes the transient performance synthetic optimized trajectory and control laws. Through simulation and experimental results, the transient performances are compared with the other typical three control methods, and the ability of proposed synthetic trajectory and control law to achieve optimal transient performance is verified.

• Nuclear Engineering and Technology
• /
• 제55권3호
• /
• pp.861-869
• /
• 2023

This article proposes a novel approach to measure the performance of Safety-Critical Systems (SCS). Such systems contain multiple processing nodes that communicate with each other is modeled by a Petri nets (PN). The paper uses the PN for the performance evaluation of SCS. A set of ordinary differential equations (ODEs) is derived from the Petri net model that represent the state of the system, and the solutions can be used to measure the system's performance. The proposed method can avoid the state space explosion problem and also introduces new metrics of performance, along with their measurement: deadlock, liveness, stability, boundedness, and steady state. The proposed technique is applied to Shutdown System (SDS) of Nuclear Power Plant (NPP). We obtained 99.887% accuracy of performance measurement, which proves the effectiveness of our approach.

• 한국정밀공학회지
• /
• 제12권10호
• /
• pp.138-148
• /
• 1995

While Model-based Monitoring systems based on state observer theory have shown much promise in the laboratory, they have not been widely accepted by industry because, inpractice, these systems often have poor performance with respect to accuracy, band-width, reliability(false alarms), and robustness. In this paper, the linitations of the deterministic discrete-time state observer are investigated quantitatively from the machine monitoring viewpoint. The limitations in the transient and steady-state observer performance are quantified as estimation error bounds from which performance indices are selected. Each index represents the conditioning of the corresponding performance. By utilizing matrix norm theory, an unified main index is determined, that dominates all the indices. This index could from the basis for an observer design methodology that should improve the performance of model-based monitoring systems.

• 국제학술발표논문집
• /
• The 5th International Conference on Construction Engineering and Project Management
• /
• pp.332-337
• /
• 2013

Various project delivery methods have been utilized by owners over the years to maximize project performance. The design-build delivery method is being increasingly used due to the advantages it can offer to an engineering construction industry. Numerous studies have advocated the use of design/build over the traditional design/bid/build delivery approach. This study represents comprehensive analysis of 40 projects from the construction industry and shows that design/build method may not provide all the benefits to project performance. This study found timesaving was a definitive advantage of design/build project delivery, but the positive effects of cost changes was not convincing. Based on the results of the study, the project management expertise and experience of the contractor may have a greater impact on project performance outcomes than focusing on project delivery strategy only.

• Journal of the Korean Physical Society
• /
• 제73권10호
• /
• pp.1589-1595
• /
• 2018

Similarity index measures the topological proximity of node pairs in a complex network. Numerous similarity indices have been defined and investigated, but the dependency of structure on the performance of similarity indices has not been sufficiently investigated. In this study, we investigated the relationship between the performance of similarity indices and structural properties of a network by employing a two-state random network. A node in a two-state network has binary types that are initially given, and a connection probability is determined from the state of the node pair. The performances of similarity indices are affected by the number of links and the ratio of intra-connections to inter-connections. Similarity indices have different characteristics depending on their type. Local indices perform well in small-size networks and do not depend on whether the structure is intra-dominant or inter-dominant. In contrast, global indices perform better in large-size networks, and some such indices do not perform well in an inter-dominant structure. We also found that link prediction performance and the performance of similarity are correlated in both model networks and empirical networks. This relationship implies that link prediction performance can be used as an approximation for the performance of the similarity index when information about node type is unavailable. This relationship may help to find the appropriate index for given networks.

• 제어로봇시스템학회논문지
• /
• 제10권2호
• /
• pp.153-163
• /
• 2004

The control objective in hard disk drives is to move head as fast as possible to target track and position the head over the center of target track in the presence of external disturbances. The external shock or disk clamping error in manufacturing process causes the disk center to deviate from the disk rotation center. The disk shift acts on the control system as disturbance and degrades severely the performance of disk drives. In this paper, we present a new controller that compensates for the periodic disturbances very fast. The disturbance compensator is arranged in parallel with the state feedback controller. To avoid the interference with the state feedback controller, the compensator creates compensation signal without the feedback of system output until steady state. The pulse type controller is included additionally for improving the transient performance due to initial state. Finally, in order to demonstrate the superior performance of the proposed compensator. we present some experimental results using a commercially available disk drive.