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Obstacle

About: Obstacle is a research topic. Over the lifetime, 9517 publications have been published within this topic receiving 94760 citations. The topic is also known as: impediment & barrier.


Papers
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Proceedings ArticleDOI
20 May 2017
TL;DR: To meet the system's goals under changing conditions, the paper proposes to defer obstacle resolution to system runtime and presents techniques for monitoring goal/obstacle satisfaction rates, and adapting the system on the fly to countermeasures that are more appropriate under the monitored conditions.
Abstract: Software systems are deployed in environments that keep changing over time. They should therefore adapt to changing conditions in order to meet their requirements. The satisfaction rate of these requirements depends on the rate at which adverse conditions prevent their satisfaction. Obstacle analysis is a goal-oriented form of risk analysis for requirements engineering (RE) whereby obstacles to system goals are identified, assessed, and resolved through countermeasures yielding new requirements. The selection of appropriate countermeasures relies on the assessed likelihood and criticality of obstacles together with environmental assumptions. These various factors are estimated at RE time, they may however evolve during software development and at system runtime. To meet the system's goals under changing conditions, the paper proposes to defer obstacle resolution to system runtime. Following Monitor–Analyze–Plan–Execute cycles, techniques are presented for monitoring goal/obstacle satisfaction rates, deciding when adaptation should be triggered, and adapting the system on the fly to countermeasures that are more appropriate under the monitored conditions. The approach relies on a model where goals and obstacles are refined and specified in a probabilistic linear temporal logic. The proposed techniques allow for (a) monitoring the satisfaction rate of probabilistic leaf obstacles, (b) determining the severity of their consequences by up-propagating satisfaction rates through refinement trees from leaf obstacles to high-level probabilistic goals, and (c) dynamically shifting to alternative countermeasures that better meet the required satisfaction rate of the system's high-level goals under imposed cost constraints. Our approach is evaluated on fragments of an ambulance dispatching system.

24 citations

Journal ArticleDOI
TL;DR: In this article, an oscillating continuously stratified flow past an isolated obstacle is investigated using scaling arguments and two-dimensional non-hydrostatic numerical experiments, and a new dynamic scaling is introduced that incorporates the blocking of fluid with insufficient energy to overcome the background stratification and crest the obstacle.
Abstract: An oscillating continuously stratified flow past an isolated obstacle is investigated using scaling arguments and two-dimensional non-hydrostatic numerical experiments. A new dynamic scaling is introduced that incorporates the blocking of fluid with insufficient energy to overcome the background stratification and crest the obstacle. This clarifies the distinction between linear and nonlinear flow regimes near the crest of the obstacle. The flow is decomposed into propagating and non-propagating components. In the linear limit, the non-propagating component is related to the unstratified potential flow past the obstacle and the radiating component exhibits narrow wave beams that are tangent to the obstacle at critical points. When the flow is nonlinear, the near crest flow oscillates between states that include asymmetric, crest-controlled flows. Thin, fast, supercritical layers plunge in the lee, separate from the obstacle and undergo shear instability in the fluid interior. These flow features are localized to the neighbourhood of the crest where the flow transitions from subcriticality to supercriticality and are non-propagating. The nonlinear excitation of energetic non-propagating components reduces the efficiency of topographic radiation in comparison with linear dynamics.

24 citations

Patent
Katsuji Matsuoka1
16 Sep 1999
TL;DR: An alarm device for vehicle operable at a time of changing lanes which does not alert in case of congestion by inputting an obstacle by a scan laser radar is presented in this article.
Abstract: An alarm device for vehicle operable at a time of changing lanes which does not alert in case of congestion by inputting an obstacle by a scan laser radar 1, recognizing the obstacle by a obstacle recognizing means 9 based on thus inputted information, recognizing the congestion by a lane state recognizing means 10 based on thus recognized obstacle and a state of peripheral lane, setting an optimum area for alerting by an alarm determining means 11 based on thus recognized state of lane, and conducting an alarm by an alarm means 7 based on the obstacle within the optimum area for alerting.

24 citations

Patent
07 Aug 2013
TL;DR: In this paper, an intelligent vehicle obstacle avoidance method based on binocular vision and fuzzy recognition is presented, where a fuzzy controller is built according to the three-dimensional information of the obstacle, and the vehicle is guided to avoid the obstacle automatically.
Abstract: The invention discloses an intelligent vehicle obstacle avoiding method based on binocular vision and belongs to the field of computer vision technology and fuzzy recognition. The intelligent vehicle obstacle avoiding method includes that a left video camera and a right video camera are calibrated in a binocular mode, a relation between a video camera image coordinate system and a scene coordinate system is obtained, and the left video camera and the right video camera are used for collecting a scene in front of a vehicle; distortion and epipolar rectification are conducted on two images, feature points of the images are extracted, and feature vector indication is conducted on the feature points of the images; stereo matching is conducted according to the feature vector, an initial matching dot pair is obtained according to the feature vector, false matching dot pairs are removed, and a correct matching dot corresponding relation is built; according to the correct matching dot pairs, a disparity map is obtained through calculation, and three-dimensional real information of an obstacle is recovered according to the disparity map; and a fuzzy controller is built according to the three-dimensional information of the obstacle, and the vehicle is guided to avoid the obstacle automatically. By means of the intelligent vehicle obstacle avoiding method, the shape of the obstacle and the distance between the obstacle and the vehicle can be detected correctly, and experiments show that the method is good in real-time performance and high in obstacle avoiding rate.

24 citations

Journal ArticleDOI
01 Dec 2008
TL;DR: The tangential escape approach is able to guide the robot along trajectories that result in a reduction of the traveling time, thus saving batteries and reducing the motor wearing, allowing concluding that the robot reaches any reachable goal, with or without a prescribed final orientation.
Abstract: An approach to guide a mobile robot from an initial position to a goal position avoiding any obstacle in its path, when navigating in a semi-structured environment, is proposed in this paper. Such an approach, hereinafter referred to as tangential escape, consists in changing the current robot orientation through a suitable combination of the values of the angular and linear velocities (the control actions) whenever an obstacle is detected close to it. Then, the robot starts navigating in parallel to the tangent to the obstacle, regarding the point of the obstacle boundary the robot sensing system identifies as the closest one. The stability of the control system designed according this approach is proven, showing that the robot reaches any reachable goal, with or without a prescribed final orientation. Such a control system is programmed onboard a mobile platform whose sensing system is a laser scanner which provides 181 range measurements, for experimental validation. The results obtained are presented and discussed, allowing concluding that the tangential escape approach is able to guide the robot along trajectories that result in a reduction of the traveling time, thus saving batteries and reducing the motor wearing.

24 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
20231,483
20223,389
2021407
2020817
2019873