• Journal of Distribution Science
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• v.14 no.2
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• pp.41-45
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• 2016

Purpose - Finding an optimal path is an essential component for the design and operation of smart transportation or logistics network. Many applications in navigation system assume that travel time of each link is fixed and same. However, in practice, the travel time of each link changes over time. In this paper, we introduce a new transportation problem to find a latest departing time and delivery path between the two nodes, while not violating the appointed time at the destination node. Research design, data, and methodology - To solve the problem, we suggest a mathematical model based on network optimization theory and a backward search method to find an optimal solution. Results - First, we introduce a dynamic transportation problem which is different with traditional shortest path or minimum cost path. Second, we propose an algorithm solution based on backward search to solve the problem in a large-sized network. Conclusions - We proposed a new transportation problem which is different with traditional shortest path or minimum cost path. We analyzed the problem under the conditions that travel time is changing, and proposed an algorithm to solve them. Extending our models for visiting two or more destinations is one of the further research topics.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.2
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• pp.252-260
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• 2016

Unlike terrestrial transportation, marine transportation should consider environment factors in order to optimize path planning. This is because, ship's path planning is greatly influenced by real-time ocean environment-sea currents, wave and wind. Therefore, in this study, we suggest a ship path planning algorithm based on real-time ocean environment using not only $A^*$ algorithm but also path smoothing method. Moreover, in order to improve objective function value, we also consider ship's moving distance based on ship's location and real-time ocean environment data on grid map. The efficiency of the suggested algorithm is proved by comparing with $A^*$ algorithm only. This algorithm can be used as a reasonable automatics control system algorithm for unmaned ship.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.3900-3916
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• 2019

The modern mobile devices are typically equipped with multiple network interfaces, e.g., 4G LTE, Wi-Fi, Bluetooth, but the current implementation of TCP can support only a single path at the same time. The Multipath TCP (MPTCP) leverages the multipath feature and provides (i) robust connection by utilizing another interface if the current connection is lost and (ii) higher throughput than single path TCP by simultaneously leveraging multiple network paths. However, if the performance between the multiple paths are significantly diverse, the receiver may have to wait for packets from the slower path, causing reordering and buffering problems. To solve this problem, previous MPTCP schedulers mainly focused on predicting the latency of the path beforehand. Recent studies, however, have shown that the path latency varies by a large margin over time, thus the MPTCP scheduler may wrongly predict the path latency, causing performance degradation. In this paper, we propose a new MPTCP scheduler called, choose fastest subflow (CFS) scheduler to solve this problem. Rather than predicting the path latency, CFS utilizes the characteristics of these paths to reduce the overall flow completion time by redundantly sending the last part of the flow to both paths. We compare the performance through real testbed experiments that implements CFS. The experimental results on both synthetic packet generation and actual Web page requests, show that CFS consistently outperforms the previous proposals in all cases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.10
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• pp.993-998
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• 2007

To verify the 2D or 3D positioning accuracy of a multi-axes stage is not easy, particularly, in the case the moving path of the stage is not linear. This paper is a study on a measuring method for the curved path accurately. A machine vision technique is used to trace the moving path of two-axes stage. To improve the accuracy of machine vision, a zoom lens is used for the 2D micro moving path. The accuracy of this method depends of the CCD resolution and array align accuracy with the zoom lens system. Also, a further study for software algorithm is required to increase the tracing speed. This technique will be useful to trace a small object in the 2D micro path in real-time accurately.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.7
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• pp.671-678
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• 2006

This article proposes a smooth path generation and time scheduling method for general tasks defined by non-smooth path segments in industrial robotic applications. This method utilizes a simple 3rd order polynomial function for smooth interpolation between non-smooth path segments, so that entire task can effectively maintain constant line speed of operation. A predictor-corrector type numerical mapping technique, which correlates time based speed profile to the smoothed path in Cartesian space, is also provided. Finally simulation results show the feasibility of the proposed algorithm.

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.3
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• pp.499-515
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• 1996

The basic function of on industrial robot system is to move objects in the workspace fast and accurately. One difficulty in performing this function is that the path of robot should be programmed to avoid the collision with obstacles, that is, tools, or facilities. This path planning requires much off-line programming time. In this study, a SOM technique to find the collision-free path of robot in real time is developed. That is, the collision-free map is obtained through SOM learning and a collision-free path is found using the map in real time during the robot operation. A learning procedure to obtain the map and an algorithm to find a short path using the map is developed and simulated. Finally, a path smoothing method to stabilize the motion of robot is suggested.

• Journal of Korean Institute of Industrial Engineers
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• v.27 no.2
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• pp.140-149
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• 2001

The paper discusses the problem of finding the Origin-Destination(O-D) shortest paths in internodal transportation networks with time-schedule constraints. The shortest path problem on the internodal transportation network is concerned with finding a path with minimum distance, time, or cost from an origin to a destination using all possible transportation modalities. The time-schedule constraint requires that the departure time to travel from a transfer station to another node takes place only at one of pre-specified departure times. The scheduled departure times at the transfer station are the times when the passengers are allowed to leave the station to another node using the relative transportation modality. Therefore, the total time of a path in an internodal transportation network subject to time-schedule constraints includes traveling time and transfer waiting time. In this paper, a genetic algorithm (GA) approach is developed to deal with this problem. The effectiveness of the GA approach is evaluated using several test problems.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.6
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• pp.43-49
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• 2001

A reduced machining time and increased accuracy for the sculptured surface are very important when producing complicated parts. The step-size and tool-path interval are essential components in high speed and high resolution machining. If they are small, the machining time will increase, whereas if they are large, rough surfaces will be caused. In particular, the machining time, which is key in high speed machining, is affected by the tool-path interval more than the step-size. The conventional method for calculating the tool=path interval is to select a small parametric increment of a small increment based on the curvature of the surface. However, this approach also has limitations. The first is that the tool-path interval can not be calculated precisely. The second is that a separate tool-path interval needs to be calculated in each of the three cases. The third is that the conversion from Cartesian domain to parametric domain or vice versa must be necessary. Accordingly, the current study proposes a new tool-path interval algorithm that do not involve a curvature and that is not necessary for any conversion and a variable step-size algorithm for NURBS.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.15-28
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• 1998

Recently may investigations have been studied on the high-speed machining by using machine tools. A CNC machine tool makes some tool path errors caused by software acceleration/deceleration. The faster a cutting feedrate is, the bigger the tool path errors are. Some known methods reduce these kinds of errors, but they make the total cutting time increased. This paper presents a feed-forward algorithm that can be generated by distorting the original tool path, and reduces the tool path errors and the total cutting time. The algorithm to generate a new tool path is represented as following; 1)calculating each distance of software acceleration/deceleration between two adjacent blocks, 2) estimating the distorted distance which is the adjacent-ratio-constant(k1, k2) multiply the distance of software acceleration/deceleration, 3) generating a 3-degree Bezier curve approximating the distorted tool path, 4) symmetrically transforming the Bezier curve about the intersection point between two blocks, and 5) connecting the transformed Bezier curve with the original tool path. The algorithm is applied to FANUC 0M. The study is to promote the high-precision machining and to reduce the total cutting time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.8
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• pp.2473-2489
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• 2022

Urban development has brought about the increasing saturation of urban traffic demand, and traffic congestion has become the primary problem in transportation. Roads are in a state of waiting in line or even congestion, which seriously affects people's enthusiasm and efficiency of travel. This paper mainly studies the discrete domain path planning method based on the flow data. Taking the traffic flow data based on the highway network structure as the research object, this paper uses the deep learning theory technology to complete the path weight determination process, optimizes the path planning algorithm, realizes the vehicle path planning application for the expressway, and carries on the deployment operation in the highway company. The path topology is constructed to transform the actual road information into abstract space that the machine can understand. An appropriate data structure is used for storage, and a path topology based on the modeling background of expressway is constructed to realize the mutual mapping between the two. Experiments show that the proposed method can further reduce the interpolation error, and the interpolation error in the case of random missing is smaller than that in the other two missing modes. In order to improve the real-time performance of vehicle path planning, the association features are selected, the path weights are calculated comprehensively, and the traditional path planning algorithm structure is optimized. It is of great significance for the sustainable development of cities.