• Journal of Korean Society of Transportation
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• v.29 no.6
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• pp.129-136
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• 2011

Variable Message Signs have been used for providing information on the current traffic conditions. However, it is considered more important to achieve optimal traffic allocation among the alternative routes by strategic VMS information provision. Fuzzy control is very effective and efficient to deal with such systems that are too complex and uncertain to build mathematical models. In this paper, a fuzzy feedback controller for VMS is proposed, whose goal is to achieve the travel time equilibrium between the two alternative routes. The performance of the suggested controller is implemented and examined using MATLAB/Simulink. More robust controller applicable to a real highway network is suggested for the further research.

• Journal of Korean Society of Transportation
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• v.20 no.7
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• pp.177-183
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• 2002

Current state-of-the-art of VMS control is based upon simple knowledge-based inference engine with message set and each message's priority. And R&Ds of the VMS control are focused on the accurate detection and estimation of traffic condition of the subject roadways. However VMS display itself cannot achieve a desirable traffic allocation among alternative routes in the network In this context, VMS display strategy is the most crucial part in the VMS control. VMS itself has several limitations in its nature. It is generally known that VMS causes overreaction and concentration problems, which may be more serious in urban network than highway network because diversion should be more easily made in urban network. A feedback control algorithm is proposed in this paper to address the above-mentioned issues. It is generally true that feedback control approach requires low computational effort and is less sensitive to models inaccuracy and disturbance uncertainties. Major features of the proposed algorithm are as follows: Firstly, a regulator is designed to attain system optimal traffic allocation among alternative routes for each VMS in the network. Secondly, strategic messages should be prepared to realize the desirable traffic allocation, that is, output of the above regulator. VMS display strategy module is designed in this context. To evaluate Probable control benefit and to detect logical errors of the Proposed feedback algorithm, a offline simulation test is performed using real network in Daejon, Korea.

• Journal of Korean Society of Transportation
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• v.22 no.4 s.75
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• pp.107-116
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• 2004

VMS를 통한 정보제공에는 과도반응과 통행집중의 위험부담이 따른다. 즉 대안경로간에 이루어져야 할 통행배분을 정확히 유도할 수 있는 VMS 메시지란 존재치 않는다. VMS 메시지에 의해 특정 경로가 교통상황이 타 경로에 비해 좋다고 정보가 주어질 때, 그 정보에 대한 과도반응과 그 특정경로에 대한 통행집중 문제가 발생하여 정보제공에 의해 오히려 상황이 악화될 수 있다. 본 연구에서는 대안경로간의 물리적 특성 측면에서 우열이 있는 가상 네트워크를 대상으로 하여, 과도반응과 통행집중 문제를 극복하고 대안경로간의 적절한 통행배분을 달성하기 위한 VMS 운영알고리즘을 개발하는 것을 목표로 한다. VMS정보제공 결과, 즉 VMS를 통해 상황이 좋다고 알려준 경로에 통행이 집중할 경우 문제가 될 것인가 여부를 미리 예측해 보고, 문제가 될 경우 정보제공 전략을 수정하도록 하는, 피드백 제어에 예측적 방식을 접목하였다. 본 연구에서 제안한 알고리즘의 주요 기능은 다음과 같다. 1. 교통량, 속도 등에 대한 실시간 모니터링 시스템이 구축되어 있음을 전제로 한다. 2. 실시간 제어에는 모니터링 결과와 이에 근거한 정보제공전략의 시행사이에는 시간차가 존재한다. 이러한 시간차이로 인하여 단기예측이 필요하고, 이를 수행하는 모듈이 있다. 3. 정보제공 결과로 특정 경로에 과부하가 걸리는지 여부를 예측하기 위하여, 그 판단기준으로 그 경로의 실제 용량 산정이 필요하다. 이에 혼잡의 시공간적 전개에 따라 변하는 동적 용량을 산정하는 모듈이 있다. 4. 대안 경로간 통행배분 목표치를 수리적으로 산정할 수는 있으나, 이를 자동적으로 이루어 주는 메시지는 존재하지 않는다. 아울러 현실적으로 예측 불가능한 외란을 모형에 의존하여 예측하기 보다는, 계속적인 피드백 레귤레이터(Regulator) 작동에 의해 보정하여 목표를 달성해 가는 자동제어 기능을 갖고 있다.

• 한국ITS학회:학술대회논문집
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• 2005.11a
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• pp.203-208
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• 2005

• Journal of Korean Society of Transportation
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• v.24 no.7 s.93
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• pp.65-79
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• 2006

The ATIS(Advance Traveler Information System), as one part of ITS, is a system aiming to disperse traffic volume on transportation networks by providing traffic information to transportation users on pre-trip and en-route trips. One of tools in ATIS is usage of VMS(Variable Message Signs). It provides to the drivers with direct information about state of processing direction. which is considered as the most effective method in ATIS. The purposes of providing VMS information are classified two categories. One is to provide simple information to drivers for their convenience. The other is to manage traffic demand to improve transportation network performance. However, for more effective and reliable VMS information, several strategies should be taken into account. The main VMS management strategy is "Traffic Diversion Strategy for minimum delay" when traffic congestion or incident are occurred. For effective operation. firstly. reasonable diversion traffic volume is determined by network traffic condition Secondly, it is necessary to make providing information strategy which reflects driver response behavior for controling diversion traffic volume. This paper focuses on the providing real-time route guidance information by VMS when congestion is occurred by the incidents. This sturdy estimates time-dependent system optimal diversion rate that inflects travel time and queue lengths using traffic flow simulation model on base Cellular Automata. In addition, route choice behavior models are developed using binary logit model for traffic information variable by traffic system controller. Finally, this study provides time-dependent VMS massage contents and degree of providing information in order to optimize the traffic flow.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.409-416
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• 2006

Real-time traveler information disseminated through Variable Message Signs (VMS) is known to have effects on driver route choice decisions. In the past, many studies have attempted to optimize the system performance using VMS message content as the primary control variable of driver route choice. This research proposes a VMS information provision optimization model which searches the best combination of VMS message contents and display sequence to minimize the total travel time on a highway network considered. The driver route choice models under VMS information provision are developed using a stated preference (SP) survey data in order to realistically capture driver response behavior. The genetic algorithm (GA) is used to find the optimal VMS information provision strategies which consists of the VMS message contents and the sequence of message display. In the process of the GA module, the system performance is measured using micro traffic simulation. The experiment results highlight the capability of the proposed model to search the optimal solution in an efficient way. The results show that the traveler information conveyed via VMS can reduce the total travel time on a highway network. They also suggest that as the frequency of VMS message update gets shorter, a smaller number of VMS message contents performs better to reduce the total travel time, all other things being equal.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.747-754
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• 2006

Real-time traffic information disseminated through VMS is known to have effects not only on driver to plan a route choice, detour the congestion, and cope with incident, but also on VMS operator to manage the traffic volume indirectly. But, the dissemination of traffic information is operated in the side of provider, not of user. Importance-Performance analysis (IPA) offers a simple, useful method for simultaneously considering both the importance and performance dimensions when evaluating or improving strategy. This technique has been successfully used in a variety of settings to define priorities and guide resource optimization decisions. This study uses IPA to evaluate traffic information strategies through VMS to make resource improvement recommendations. It gained 760 samples by field surveys, which are conducted in Korean Thanksgiving Day, weekday and weekend at the service areas of expressways. The results indicate that the motivations in quadrant I (concentrate here) are dissemination of exactly information and quick transmission, while distance of VMS, most drivers are not satisfied with that is located in quadrant III (low priority).

• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.57-71
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• 2005

Precise visual measurement applications, like video measuring system (VMS), use camera systems with motorized zoom lens for fast and efficient measurement. In this paper, we introduce an efficient calibration method for zoom lens of VMS controlled by servo motor. For the automated zoom lens calibration of the VMS, only zoom lens setting needs to be calibrated and parameters calibrated by zoom lens settings are image center and pixel size changed by zoom levels, The extrinsic parameters, like focus and iris, do not need to be calibrated since the parameters are usually fixed, It needs a lot of time and effort to calibrate the camera for ali the different zoom levels. In this paper, we also propose an efficient and fast zoom lens calibration method, which calculates the calibration parameters of the zoom lens settings for the minimum number of zoom levels and estimates other parameters for the uncalculated zoom levels using the interpolation of the calculated parameter values.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.354-357
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• 1996

Virtual Manufacturing System(VMS) is an integrated computer based model which has physical, logical schema and behavior of real manufacturing system. In this paper, an integrated scheduling system is developed to simulate and control a Virtual Factory. A workflow model is constructed to define and analyze the structure of a VMS. On-line dynamic dispatching system is developed using MultiPass algorithm and scheduling system considering dynamic CAPP is carried out. Integrated scheduling system developed in this paper reduces the discrepancies between virtual model and real manufacturing system, and control of real shop floor is possible.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.4
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• pp.25-35
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• 2008

Variable Message Sign(VMS) is one of the subsystem of Intelligent Transportation Systems (ITS), which is useful for providing real-time information on weather, traffic and highway conditions. However, there are various situations such as incidents/accidents, constructions, special events, etc., which would be occurred on segments, it is unable to control traffic with only the VMS. Thus, it is essential to use of PVMS(Portable Variable Message Signs), which can move to the location needed traffic control and provide more active traffic information than VMS. This study developed a legibility distance model for PVMS messages using in-vehicle Differential Global Positioning Data(DGPS). Traffic conditions, drivers' characteristics, weather conditions and characteristics of PVMS message were investigated for establishing the legibility model based on multiple linear regression analysis. The factors such as height of PVMS characters, spot speed, age, gender and day and night were identified as dominants affecting the variation of legibility distances. It is expected that the proposed model would play a significant role in designing PVMS messages for providing more effective real-time traffic information.