Browsing by Author "Cho, HJ"

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A finite difference method with adaptive time mesh for hyperbolic traffic flow
(2002)
Cho, HJ
;
Hwang, MC
;
Jou, TJ
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
This paper presents a finite difference method with variable time mesh for the hyperbolic traffic flow. The width of each time step is determined by the ratio of uniform space mesh size and maximal characteristic velocity. The proposed adaptive time mesh scheme Is compatible with most of explicit finite difference methods. Numerical examples with different initial and boundary conditions of the Lighthill-Whitham-Richards (LWR) model and Payne-Whitham model are provided to contrast the effects of adaptive time mesh on the Lax-Friedrichs scheme. Simulation results are generally satisfied. The number of time steps of adaptive-Lax method is much less than that of Lax method with no significant difference in solutions of LWR model. Convergence of solution is readily claimed by the Courant-Friedrichs-Lewy (CFL) condition.
A reduction method for local sensitivity analyses of network equilibrium arc flows
(2000-01-01)
Cho, HJ
;
Smith, TE
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Friesz, TL
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運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
A reduction method is proposed which allows standard sensitivity techniques for variational inequalities to applied to equilibrium network flow problems without additional assumptions on either the underlying network or the numbers of active paths. In particular it is shown that under mild regularity conditions, small perturbations of equilibria can be given an explicit are-flow representation which is free of path-flow variables. It is also shown that this reduced form allows the differentiability of perturbations to be studied by standard methods. These results are illustrated by a small numerical example. (C) 1999 Elsevier Science Ltd. All rights reserved.
A self-consistent dynamic traffic flow model part I: modeling and analysis
(2001)
Cho, HJ
;
Lo, SC
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Traffic flow theory can provide real time prediction and evaluation of traffic management strategies. Lightwill, Whitham and Richards applied a fluid mechanism to traffic flow and proposed a dynamic model (LWR model) in 1955 first. However, the LWR model needs to couple with a specific speed-density relation to be solved. Sometimes the assumption of such a relationship is not consistent with the whole model. In this study, we develop a dynamic traffic flow model based on the continuity equation (LWR model) and second-order model. The assumptions of the system equations are consistent with each other. Therefore, a self-consistent system is proposed herein. The existence and uniqueness of the solution is also illustrated in this work. Numerical simulations are left for further studies.
A stimulus-response model of day-to-day network dynamics
(2005-03-01)
Cho, HJ
;
Hwang, MC
;
運輸與物流管理系註：原交通所+運管所
;
運輸研究中心
;
Department of Transportation and Logistics Management
A general structure of stimulus-response formula is presented to specify the interacted network dynamics under the assumption of a daily learning and adaptive travel behavior. By taking the time derivative of system variable as a response term, the evolution is formulated as a dynamic system. Issues of existence, uniqueness, and stability for the proposed differential equations are briefly discussed. Approximation of a time-varying route-choice model is derived from the addressed path-flow dynamics. Threshold effects on path-flow dynamics are encapsulated into the proposed general structure by incorporating a discontinuous stimulus term. Then, the quasi user equilibrium is achieved when all users feel indifferent between the experienced and predicted travel time provided by intelligent transportation systems, i.e., the whole system dynamics stay within a bounded range. The derived quasi user equilibrium is reduced to Wardrop's user equilibrium as the threshold effects of path-flow dynamics vanish.
A stimulus-response model of day-to-day network dynamics
(2003)
Cho, HJ
;
Hwang, MC
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
A general structure of stimulus-response formula is presented to specify the interacted network dynamics in a day-to-day time scale under the assumption of a learning and adaptive behavioral process. By taking the time derivative of system variable as a reaction in stimulus-response equation the evolution of whole system is formulated as a dynamical system. Issue of stability for the proposed differential equations are briefly discussed. Approximation of time dependent route-choice model is derived from the addressed path flow dynamics, The threshold effect on path flow dynamics is developed in term of defining a discontinuous stimulus. Quasi user equilibrium researched to be a steady state when all users feel indifferent between experienced travel time and predicted travel time provided by Advanced Traveler Information Systems. The proposed quasi user equilibrium is reduced to Wardrop's user equilibrium if threshold effect is vanishing.
A System-on-Chip approach to intelligent traffic signal control
(2005)
Cho, HJ
;
Tseng, MT
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運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
This paper briefly describes the key methodology in the design of a System on Chip (SoC) for intelligent traffic signal control application. It will be integrated with an intelligent traffic control algorithm module, a system on chip ARM CPU board, an I/O monitor card, a display panel board, a light control card and lamp drive card. The simulation of the intelligent traffic control algorithm shows that this intelligent system has better traffic performance index than traditional TOD/DOW traffic controller. The sample arterial also proves this system work well.
Chaos and control of discrete dynamic traffic model
(2005-11-01)
Lo, SC
;
Cho, HJ
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
This study discusses chaotic traffic flow. The discrete dynamic model proposed herein is derived from both the flow-density-speed fundamental diagram and Greenshield's model. The model employs occupancy as its variable and the ratio of free flow and average speed as its control parameter. The function form of the model is equal to logistic map that bifurcates when the value of the control parameter increases. Chaotic traffic means that traffic becomes unstable and unpredictable, which is dangerous for driving. Therefore, this study considers the implementation of chaotic control in signal or ramp metering design so as to stabilize the chaotic traffic phenomena. These results are illustrated by numerical examples. (c) 2005 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
Day-to-day vehicular flow dynamics in intelligent transportation network
(2005-02-01)
Cho, HJ
;
Hwang, MC
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
In this paper, a flow evolution model is developed by using the dynamical system approach for a vehicular network equipped with predicted travel information. The concerned system variables, path flow, and predicted minimal travel time of an origin-destination (OD) pair, are measured on the peak-hour-average base for each day. The time change rates of these two variables are formulated as a system of ordinary differential equations under the assumption of daily learning and adaptive processes for commuters. By incorporating the total perceived travel time loss (or saving) into the proposed models, time change rates of path flows are generated with a flow-related manner to prevent path flow dynamics from being insensible to traffic congestion which had been formulated in the existing studies. Heterogeneous models with various user adjusting sensitivities and predicted travel information are also presented. Equilibrium solutions of the proposed network dynamics satisfy the Wardrop user equilibria and are proved to be asymptotically stable by using the stability theorem of Lyapunov. The issue of existence and uniqueness of solutions is proved both on the lemma of Lipschitz condition and the fundamental theorem of ordinary differential equations. In addition, some simple examples are demonstrated to show the asymptotic behaviors of the proposed models numerically. (c) 2005 Elsevier Ltd. All rights reserved.
Generalized honeycomb torus
(2003-05-31)
Cho, HJ
;
Hsu, LY
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Stojmenovic introduced three different honeycomb tori by adding wraparound edges on honeycomb meshes, namely honeycomb rectangular torus, honeycomb rhombic torus, and honeycomb hexagonal torus. These honeycomb tori have been recognized as an attractive alternative to existing torus interconnection networks in parallel and distributed applications. In this paper, we propose generalized honeycomb tori. The three different honeycomb tori proposed by Stojmenovic are proved to be special cases of our proposed generalized honeycomb tori. We also discuss the Hamiltonian property of some generalized honeycomb tori. (C) 2003 Published by Elsevier Science B.V.
Hybrid models toward traffic detector data treatment and data fusion
(2005)
Wen, YH
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Lee, TT
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Cho, HJ
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電控工程研究所
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Institute of Electrical and Control Engineering
This paper develops a data processing with hybrid models toward data treatment and data fusion for traffic detector data on freeways. Hybrid grey-theory-based pseudo-nearest-neighbor method and grey time-series model are developed to recover spatial and temporal data failures. Both spatial and temporal patterns of traffic data are also considered in travel time data fusion. Two travel time data fusion models are presented using a speed-based link travel time extrapolation model for analytical travel time estimation and a recurrent neural network with grey-models for real-time travel time prediction. Field data from the Taiwan national freeway no.1 were used as a case study for testing the proposed models. Study results shown that the data treatment models for faulty data recovery were accurate. The data fusion models were capable of accurately predicting travel times. The results indicated that the proposed hybrid data processing approaches can ensure the accuracy of travel time estimation with incomplete data sets.
Missing data treatment on travel time estimation for ATIS
(2003)
Jon, YJ
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Wen, YH
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Lee, TT
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Cho, HJ
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統計學研究所
This study proposes a missing data recovery method based on grey-relational nearest-neighbor substitution techniques for treating with missing data from dual-loop detectors in estimating travel time and evaluates the effects of the missing data on travel-time estimation performance. Field data from the Taiwan national freeway no. I were used as a case study for testing the proposed model. Study results shown that the travel time estimation with missing data recovery was accurate even the missing data rate zip to 33%. It is indicated that the proposed missing data treatment model can ensure the accuracy of travel time estimation with incomplete data sets.
Modeling and simulation of motorcycle traffic flow
(2004)
Cho, HJ
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Wu, YT
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運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Mixed-traffic that contains motorized and nonmotorized vehicles become more common in urban areas. Compare with motorized traffic, nonmotorized traffic flow theory isn't mature enough. In this study, a motorcycle traffic flow model is proposed It contains longitudinal and lateral movement models. The motorcycle traffic flow is influenced by driver characteristics, vehicle interactions, and the external environment all of which the proposed model will take into account. Finally, a motorcycle traffic flow simulation is presented. The simulation result indicates that the proposed model is reasonable, and it can reflect some motorcycle traffic flow phenomena The behaviors of bicycles and pedestrians are similar to motorcycles; the result of this study could be the basis of bicycle or pedestrian flow model.
Modeling self-consistent multi-class dynamic traffic flow
(2002-09-15)
Cho, HJ
;
Lo, SC
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
In this study, we present a systematic self-consistent multiclass multilane traffic model derived from the vehicular Boltzmann equation and the traffic dispersion model. The multilane domain is considered as a two-dimensional space and the interaction among vehicles in the domain is described by a dispersion model. The reason we consider a multilane domain as a two-dimensional space is that the driving behavior of road users may not be restricted by lanes, especially motorcyclists. The dispersion model, which is a nonlinear Poisson equation, is derived from the car-following theory and the equilibrium assumption. Under the concept that all kinds of users share the finite section, the density is distributed on a road by the dispersion model. In addition, the dynamic evolution of the traffic flow is determined by the systematic gas-kinetic model derived from the Boltzmann equation. Multiplying Boltzmann equation by the zeroth, first- and second-order moment functions, integrating both side of the equation and using chain rules, we can derive continuity, motion and variance equation, respectively. However, the second-order moment function, which is the square of the individual velocity, is employed by previous researches does not have physical meaning in traffic flow. Although the second-order expansion results in the velocity variance equation, additional terms may be generated. The velocity variance equation we propose is derived from multiplying Boltzmann equation by the individual velocity variance. It modifies the previous model and presents a new gas-kinetic traffic flow model. By coupling the gas-kinetic model and the dispersion model, a self-consistent system is presented. (C) 2002 Elsevier Science B.V. All rights reserved.
Monotone iterative simulation of the multilane traffic dispersion model
(2002-11-01)
Cho, HJ
;
Lo, SC
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
In this study, the multilane traffic flow is modeled as a nonlinear Poisson equation in a two-dimensional space. The model is derived from the interaction among vehicles and the assumption that vehicles will tend toward the equilibrium state under a given traffic condition. A monotone iterative scheme for the nonlinear model, which is a finite difference approximation of the model, is presented. The convergency is also discussed herein. At last, a numerical example is employed to explain the model. (C) 2002 Elsevier Science B.V. All rights reserved.
Numerical simulation of a multilane drift-diffusion traffic model
(2003)
Cho, HJ
;
Shih, HH
;
Hwang, NC
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科技管理研究所
;
Institute of Management of Technology
A numerical method based on the decoupling scheme and the time-matching approach for a multilane drift-diffusion traffic model is presented in this paper. The proposed model is a system of partial differential equations that describes the conservation of vehicle numbers and distributes traffic density on a multilane environment. Especially, the model is deduced from the concept of traffic field. The basic structure of numerical algorithm is on the decoupling scheme that treats the system as two independent partial differential equations. The finite difference scheme is implemented for converting the traffic model into difference equations. Besides, the time variant solution of the two-dimensional drift-diffusion traffic model is numerically solved However, solution process of the time variant model takes a long computing time. Therefore, improving computational efficiency is another important issue.
Quasi user equilibrium and its stability
(2004)
Cho, HJ
;
Hwang, MC
;
Chiu, YT
;
科技管理研究所
;
Institute of Management of Technology
In the historical studies of dynamic traffic assignment (or the so-called dynamic route choice modeling), user equilibrium is a fundamental paradigm to guide the final state of flow diversion for a transportation network. However, the user behavior of path selection had been observed and indicated that there exists an adaptive and learning process to adjust the daily travel decision as travel information is provided by Intelligent Transportation Systems in particular. In this paper, a general structure of stimulus-response mechanism to formulate daily path adjustment is reviewed first. Quasi user equilibrium is then introduced in the same modeling framework but replacing a threshold-effect response term. A proof of the stability of quasi user equilibrium in the sense of Lyapunov is presented. Finally, a simple network is illustrated to show the verification of the proposed approach numerically.
Ring embedding in faulty honeycomb rectangular torus
(2002-12-16)
Cho, HJ
;
Hsu, LY
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Assume that m and n are positive even integers with n greater than or equal to 4. The honeycomb rectangular torus HReT(m,n) is recognized as another attractive alternative to existing torus interconnection networks in parallel and distributed applications. It is known that any HReT(m, n) is a 3-regular bipartite graph. We prove that any HReT(m, n) - e is hamiltonian for any edge e is an element of E(HReT(m, n)). Moreover, any HReT(m, n) - F is hamiltonian for any F = {a, b} with a is an element of A and b is an element of B where A and B are the bipartition of HReT(m, n), if n greater than or equal to 6 or m = 2. (C) 2002 Elsevier Science B.V. All rights reserved.