• Journal of information and communication convergence engineering
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• v.10 no.1
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• pp.21-26
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• 2012

As the new requirements for wireless sensor networks are emerging, real-time communications is becoming a major research challenge because resource-constrained sensor nodes are not powerful enough to accommodate the complexity of the protocol. In addition, an efficient energy management scheme has naturally been a concern in wireless sensor networks for a long time. However, the existing schemes are limited to meeting one of these two requirements. To address the two factors together, we propose real-time communications with two approaches, a protocol for satisfied conditions and one for unsatisfied. Under the satisfied requirement, existing real-time protocol is employed. On the other hand, for the unsatisfied requirement, the newly developed scheme replaces the existing scheme by adjusting the transmission range of some surplus nodes. By expanding the transmission range, the end-to-end delay is shortened because the number of intermediate nodes decreases. These nodes conserve their energy for real-time communications by avoiding other activities such as sensing, forwarding, and computing. Finally, simulation results are given to demonstrate the feasibility of the proposed scheme in high traffic environments.

• International journal of advanced smart convergence
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• v.8 no.1
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• pp.9-17
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• 2019

In this article, we present a performance enhancement scheme for mobile applications by adopting persistent memory. The proposed scheme supports the deadline guarantee of real-time applications like a video player, and also provides reasonable performances for non-real-time applications. To do so, we analyze the program execution path of mobile software platforms and find two sources of unpredictable time delays that make the deadline-guarantee of real-time applications difficult. The first is the irregular activation of garbage collection in flash storage and the second is the blocking and time-slice based scheduling used in mobile platforms. We resolve these two issues by adopting high performance persistent memory as the storage of real-time applications. By maintaining real-time applications and their data in persistent memory, I/O latency can become predictable because persistent memory does not need garbage collection. Also, we present a new scheduler that exclusively allocates a processor core to a real-time application. Although processor cycles can be wasted while a real-time application performs I/O, we depict that the processor utilization is not degraded significantly due to the acceleration of I/O by adopting persistent memory. Simulation experiments show that the proposed scheme improves the deadline misses of real-time applications by 90% in comparison with the legacy I/O scheme used in mobile systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.352-359
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• 2008

This paper presents a controller implementation using model based controller design programs-System Identification Toolkit, Control Design Toolkit, Simulation module. This method is easier and simpler than conventional controller design method. To implement speed control system of DC motor, a CompactRIO, Real-Time(RT) cntroller provided by NI(National Instruments), is used as hardware equipment. Firstly transfer function of DC motor drive system, which was a control target plant, can be acquired through System Identification Toolkit by using test input signal applied to motor and output signal from motor. And designing of pole-zero compensator satisfying desired control response performance through Control Design Toolkit, designed speed control response can be tested through Simulation Module. Finally LabVIEW program is converted to real-time program and downloaded to CompactRIO real-time controller Through experimental results to real DC motor drive system, designed speed control response is compared to simulation results.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.163-171
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• 2012

Demand Responsive Transit (DRT) services are becoming necessary as part of not only alternative transportation means for elderly and mobility impaired passengers, but also sustainable and flexible transportation options in urban area due to the development of communication technologies and Location Based Services (LBS). It is difficult to investigate the system performance regarding vehicle operational schemes and vehicle routing algorithms due to the lack of commercial software to support door-to-door vehicle simulation for larger area. This study proposes a simulation framework to evaluate innovative and flexible transit systems focusing on various vehicle routing algorithms, which describes data-type requirements for simulating door-to-door service on demand. A simulation framework is applied to compare two vehicle dispatch algorithms, Nearest Vehicle Dispatch (NVD) and Insertion Heuristic (IH) for real-time shared-taxi service in Seoul. System productivity and efficiency of the shared-taxi service are investigated, comparing to the conventional taxi system.

• Smart Structures and Systems
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• v.25 no.6
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• pp.719-732
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• 2020

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

• Proceedings of the Korea Society for Simulation Conference
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• 1997.04a
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• pp.93-99
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• 1997

Most of the past studies on FMS scheduling problems may be classified into two classes, namely off-line scheduling and on-line scheduling approach. The off-line scheduling methods are used mostly for FMS planning purposes and may not be useful real time control of FMSs, because it generates solutions only after a relatively long period of time. The on-line scheduling methods are used extensively for dynamic real-time control of FMSs although the performance of on-line scheduling algorithms tends vary dramatically depending on various configurations of FMS. Current study is about finding a better on-line scheduling rules for FMS operations. In this study, we propose a method to create priority functions that can be used in setting relative priorities among jobs or machines in on-line scheduling. The priority functions reflect the configuration of FMS and the user-defined objective functions. The priority functions are generated from diverse dispatching rules which may be considered a special priority functions by themselves, and used to determine the order of processing and transporting parts. Overall system of our work consists of two modules, the Priority Function Evolution Module (PFEM) and the FMS Simulation Module (FMSSM). The PFEM generates new priority functions using input variables from a terminal set and primitive functions from a function set by genetic programming. And the FMSSM evaluates each priority function by a simulation methodology. Based on these evaluated values, the PFEM creates new priority functions by using crossover, mutation operation and probabilistic selection. These processes are iteratively applied until the termination criteria are satisfied. We considered various configurations and objective functions of FMSs in our study, and we seek a workable solution rather than an optimum or near optimum solution in scheduling FMS operations in real time. To verify the viability of our approach, experimental results of our model on real FMS are included.

• Journal of KIISE
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• v.42 no.7
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• pp.846-851
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• 2015

Seas and swells are basic wave types in ocean surface simulation and are very important elements in the simulation of ocean background. In this paper, we propose a real-time simulation method, for reproducing realistic seas and swells, to be used in real-time simulators such as ship maneuvering simulators. Seas and swells have different visual properties. Swells have relatively longer wavelengths and round crests compared with seas, therefore they are visualized globally with large meshes and procedural methods. Parameters to illustrate swells are extracted from ocean wave spectra. Conversely, seas have shorter wavelengths and their characteristics are only clearly apparent near to the observation point. Here, we present visualization of seas based on a statistical wave model using ocean wave spectra, which provides realistic results in a reactively small area.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.77-88
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• 1997

Fieldbus is the lowest level communication network in factory automation and process control systems. Performance of factory automation and process control systems is directly affected by the data delay induced by network traffic. Data generated from several distributed field devices can be largely divided into three categories: sporadic real-time, periodic real-time and non real-time data. Since these data share one fieldbus network medium, the limited bandwidth of a fieldbus network must be appropriately allocated to the sporadic real-time, periodic real-time and non real-time traffic. This paper introduces a new fieldbus design scheme which allocates the limited bandwidth of fieldbus network to several different kinds of traffic. The design scheme introduced in this study not only satisfies the performance requirements of application systems interconnected into the fieldbus but also fully utilizes the network resources. The design scheme introduced in this study can be applicable to cyclic service protocols operated under single-service discipline. The bandwidth allocation scheme introduced in this study is verified using a discrete-event/continuous-time simulation experiment.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.12
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• pp.1580-1588
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• 1999

This paper evaluates the real-time performance of the Train Communication Network (TCN) that consists of WTB and MVB. A run-time scheduling algorithm for the hard-real time communication was proposed and its performance was evaluated. Also, a new addressing method and the adaptive tree algorithm were suggested to enhance performance. The overall performance was evaluated by computer simulation using Arena.

• Journal of Korean Institute of Industrial Engineers
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• v.25 no.3
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• pp.369-381
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• 1999

Recently, the researches of real-time scheduling that manage flexibly system movement are being progressed by using simulation. But because the existing researches are focused on state change of whole system and selected dispatching with real-time, it could not reflect the state changes of each work center accurately, Therefore, the main core of this paper is to examine the state of workcenter, to select the optimal dispatching dynamically through simulation, and to present the algorithm that can manage actively on state of workcenter. Also, performance measure was used the mean tardiness and mean flow time that are used existing researches.