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Zhang, Wenle. „Scalable deadlock avoidance algorithms for flexible manufacturing systems“. Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1179862449.
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2
Chua, Kee Koon 1965. „Deadlock avoidance: Improved algorithms for centralized and distributed systems“. Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/291335.
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A deadlock avoidance algorithm for a centralized resource allocation system is presented. Unlike the Banker's algorithm, this proposed algorithm makes use of the state of the previous safe sequence to construct a new safe sequence. The performance of this proposed algorithm is compared to that of both the Banker's algorithm and an efficient algorithm proposed by Belik. The simulation results show that our algorithm's execution time is significantly better than the Banker's algorithm and is very competitive with Belik's algorithm. In addition, our Modified Banker's Algorithm produces optimal results unlike Belik's approach which sometimes deems a safe allocation request unsafe. This centralized algorithm combined with an algorithm by Moser, is extended for use in distributed systems. Compared with Moser's algorithm, this algorithm is less restrictive in acquiring resources from other processes and allowing increase in its maximum resource requirement as confirmed by our analysis and simulation results.
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Liu, Xintong. „Different techniques for congestion avoidance algorithms in bottleneck networks“. Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/26961.
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In this thesis, we systematically examine the ECN (Explicit Congestion Notification) mechanism to be applied to some AQM (Active Queue Management) techniques developed in recent years, namely, RED (Random Early Detection), BLUE, ARED (Adaptive RED) and PI-RED (Proportional and Integral RED). We use packet marking as the indication of network congestion, instead of the strategy of dropping packet currently adopted by these AQM algorithms. The performance comparison of ECN-AQM with AQM has been conducted in not only a single bottleneck network but also a multi-bottleneck network environment. The simulation results have shown that ECN-AQM algorithms can greatly decrease unnecessary packet loss, one of the main shortcomings of RED and some other AQM algorithms. They can also reduce average queue size in most cases, but the queue size oscillation problem remains.
We therefore investigate the application of the head dropping policy to AQM techniques, as a simple solution to the problem of queue oscillation, another shortcoming of RED and its variants. With this method, instead of tail dropping, which is currently used by RED and many other AQM schemes, the TCP source can be informed of the congestion occurring in the bottleneck router earlier by getting rid of time to wait through the queuing delay. We have compared DH-RED (Drop Head RED) and DH-BLUE (Drop Head BLUE) with the current RED and BLUE in both of the single bottleneck and the multi-bottleneck networks. We found the performance of queue size stability can be greatly improved by DH-RED and DH-BLUE.
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Rushall, David Aaron 1964. „Efficient heuristics for collision avoidance in three dimensions“. Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277041.
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This thesis represents a relatively new aspect of computing with regard to robotics. The need for fast, efficient collision avoidance algorithms is growing rapidly. Because conventional methods are complex and require vast amounts of computation, heuristic algorithms are more appealing. The focus of this thesis is the problem of moving a point through three dimensional space while avoiding known polyhedral obstacles. A heuristic algorithm to find shortest (near-optimal) collision-free paths in the presence of polyhedral obstacles, given initial and final positions, is presented. Previous methods for the problem rely on an a priori discretization of the space. The points in the discretization form nodes of a graph, and the collision avoidance problem is then solved by using some shortest path algorithm on the graph. The heuristic suggested here successively adds nodes to a graph, thus keeping the size of the graph manageable. The computational results are extremely encouraging.
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Conkur, Erdinc Sahin. „Real time path planning and obstacle avoidance algorithms for redundant manipulators“. Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389131.
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Pai, Arun S. „Development of deterministic collision-avoidance algorithms for routing automated guided vehicles /“. Online version of thesis, 2008. http://hdl.handle.net/1850/7289.
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Ringdahl, Ola. „Techniques and Algorithms for Autonomous Vehicles in Forest Environment“. Licentiate thesis, Umeå : Department of Computing Science, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1314.
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Conrad, Jeremy (Jeremy A. ). „An educational tool to assist students in the evaluation of object avoidance algorithms“. Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36302.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 21).
Autonomous robots are becoming a part of everyday life. One difficulty in the creation of autonomous robots is having the robots avoid objects. In particular once one has chosen an algorithm difficulty arises in perfecting the parameters involved. Presented here is an implementation of an algorithm and an education support tool add-on to MOOS that allows the end user to quickly vary the parameters to test the performance of the system.
by Jeremy Conrad.
S.B.
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Lee, Hua. „High-Precision Geolocation Algorithms for UAV and UUV Applications in Navigation and Collision Avoidance“. International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606155.
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ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, CaliforniaUUV homing and docking and UAV collision avoidance are two seemingly separate research topics for different applications. Upon close examination, these two are a pair of dual problems, with interesting correspondences and commonality. In this paper, we present the theoretical analysis, signal processing, and the field experiments of these two algorithms in UAV and UUV applications in homing and docking as well as collision avoidance.
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Call, Brandon R. „Obstacle Avoidance for Small Unmanned Air Vehicles“. Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1556.pdf.
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Edwan, Talal A. „Improved algorithms for TCP congestion control“. Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7141.
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Reliable and efficient data transfer on the Internet is an important issue. Since late 70's the protocol responsible for that has been the de facto standard TCP, which has proven to be successful through out the years, its self-managed congestion control algorithms have retained the stability of the Internet for decades. However, the variety of existing new technologies such as high-speed networks (e.g. fibre optics) with high-speed long-delay set-up (e.g. cross-Atlantic links) and wireless technologies have posed lots of challenges to TCP congestion control algorithms. The congestion control research community proposed solutions to most of these challenges. This dissertation adds to the existing work by: firstly tackling the highspeed long-delay problem of TCP, we propose enhancements to one of the existing TCP variants (part of Linux kernel stack). We then propose our own variant: TCP-Gentle. Secondly, tackling the challenge of differentiating the wireless loss from congestive loss in a passive way and we propose a novel loss differentiation algorithm which quantifies the noise in packet inter arrival times and use this information together with the span (ratio of maximum to minimum packet inter arrival times) to adapt the multiplicative decrease factor according to a predefined logical formula. Finally, extending the well-known drift model of TCP to account for wireless loss and some hypothetical cases (e.g. variable multiplicative decrease), we have undertaken stability analysis for the new version of the model.
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Dutra, Teófilo Bezerra. „Gradient-Based Steering for Vision-Based Crowd Simulation Algorithms“. reponame:Repositório Institucional da UFC, 2015. http://www.repositorio.ufc.br/handle/riufc/19859.
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DUTRA, Teófilo Bezerra. Gradient-Based Steering for Vision-Based Crowd Simulation Algorithms. 2015. 122 f. Tese (Doutorado em Ciência da Computação)-Universidade Federal do Ceará, Fortaleza, 2015.Submitted by Vitor Campos (vitband@gmail.com) on 2016-09-28T21:38:15Z No. of bitstreams: 1 2015_tese_tfdutra.pdf: 18611468 bytes, checksum: efc5f80ee6b8df68191af2bca394a07a (MD5)
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Most recent crowd simulation algorithms equip agents with a synthetic vision component for steering. They offer promising perspectives by more realistically imitating the way humans navigate according to what they perceive of their environment. In this thesis, it is proposed a new perception/motion loop to steer agents along collision free trajectories that significantly improves the quality of vision-based crowd simulators. In contrast with previous solutions - which make agents avoid collisions in a purely reactive way - it is suggested exploring the full range of possible adaptations and to retain the locally optimal one. To this end, it is introduced a cost function, based on perceptual variables, which estimates an agent’s situation considering both the risks of future collision and a desired destination. It is then computed the partial derivatives of that function with respect to all possible motion adaptations. The agent adapts its motion to follow the steepest gradient. This thesis has thus two main contributions: the definition of a general purpose control scheme for steering synthetic vision-based agents; and the proposition of cost functions for evaluating the dangerousness of the current situation. Improvements are demonstrated in several cases.
Alguns dos algoritmos mais recentes para simulação de multidão equipam agentes com um sistema visual sintético para auxiliá-los em sua locomoção. Eles oferecem perspectivas promissoras ao imitarem de forma mais realista a forma como os humanos navegam de acordo com o que eles percebem do seu ambiente. Nesta tese, é proposto um novo laço de percepção/ação para dirigir agentes ao longo de trajetórias livres de colisões que melhoram significativamente a qualidade dos simuladores de multidão baseados em visão. Em contraste com abordagens anteriores - que fazem agentes evitarem colisões de maneira puramente reativa - é sugerida a exploração de toda gama de adaptações possíveis e a retenção da que for ótima localmente. Para isto, é introduzida uma função de custo, baseada em variáveis de percepção, que estima a situação atual do agente considerando tanto os riscos de futuras colisões como o destino desejado. São então computadas as derivadas parciais dessa função com respeito a todas adaptações de movimento possíveis. O agente adapta seu movimento de forma a seguir o gradiente descendente. Esta tese possui assim duas principais contribuições: a definição de um esquema de controle de propósito geral para a orientação de agentes baseados em visão sintética; e a proposição de funções de custo para avaliar o perigo da situação atual. As melhorias obtidas com o modelo são demonstradas em diversos casos.
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Kivrikis, Andreas, und Johan Tjernström. „Development and Evaluation of Multiple Objects Collision Mitigation by Braking Algorithms“. Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2676.
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A CMbB system is a system that with the help of sensors in the front of a car detects when a collision in unavoidable. When a situation like that is detected, the brakes are activated. The decision of whether to activate the brakes or not is taken by a piece of software called a decision maker. This software continuously checks for routes that would avoid an object in front of the car and as long as a path is found nothing is done. Volvo has been investigating several different CMbB-systems, and the research done by Volvo has previously focused on decision makers that only consider one object in front of the car. By instead taking all present objects in consideration, it should be possible to detect an imminent collision earlier. Volvo has developed some prototypes but needed help evaluating their performance.
As part of this thesis a testing method was developed. The idea was to test as many cases as possible but as the objects’ possible states increase, the number of test cases quickly becomes huge. Different ways of removing irrelevant test cases were developed and when these ideas were realized in a test bench, it showed that about 98 % of the test cases could be removed.
The test results showed that there is clearly an advantage to consider many objects if the cost of increased complexity in the decision maker is not too big. However, the risk of false alarms is high with the current decision makers and several possible improvements have therefore been suggested.
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Dutra, TeÃfilo Bezerra. „Gradient-Based Steering for Vision-Based Crowd Simulation Algorithms“. Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14967.
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nÃo hÃMost recent crowd simulation algorithms equip agents with a synthetic vision component for steering. They offer promising perspectives by more realistically imitating the way humans navigate according to what they perceive of their environment. In this thesis, it is proposed a new perception/motion loop to steer agents along collision free trajectories that significantly improves the quality of vision-based crowd simulators. In contrast with previous solutions - which make agents avoid collisions in a purely reactive way - it is suggested exploring the full range of possible adaptations and to retain the locally optimal one. To this end, it is introduced a cost function, based on perceptual variables, which estimates an agentâs situation considering both the risks of future collision and a desired destination. It is then computed the partial derivatives of that function with respect to all possible motion adaptations. The agent adapts its motion to follow the steepest gradient. This thesis has thus two main contributions: the definition of a general purpose control scheme for steering synthetic vision-based agents; and the proposition of cost functions for evaluating the dangerousness of the current situation. Improvements are demonstrated in several cases.
Alguns dos algoritmos mais recentes para simulaÃÃo de multidÃo equipam agentes com um sistema visual sintÃtico para auxiliÃ-los em sua locomoÃÃo. Eles oferecem perspectivas promissoras ao imitarem de forma mais realista a forma como os humanos navegam de acordo com o que eles percebem do seu ambiente. Nesta tese, Ã proposto um novo laÃo de percepÃÃo/aÃÃo para dirigir agentes ao longo de trajetÃrias livres de colisÃes que melhoram significativamente a qualidade dos simuladores de multidÃo baseados em visÃo. Em contraste com abordagens anteriores - que fazem agentes evitarem colisÃes de maneira puramente reativa - Ã sugerida a exploraÃÃo de toda gama de adaptaÃÃes possÃveis e a retenÃÃo da que for Ãtima localmente. Para isto, Ã introduzida uma funÃÃo de custo, baseada em variÃveis de percepÃÃo, que estima a situaÃÃo atual do agente considerando tanto os riscos de futuras colisÃes como o destino desejado. SÃo entÃo computadas as derivadas parciais dessa funÃÃo com respeito a todas adaptaÃÃes de movimento possÃveis. O agente adapta seu movimento de forma a seguir o gradiente descendente. Esta tese possui assim duas principais contribuiÃÃes: a definiÃÃo de um esquema de controle de propÃsito geral para a orientaÃÃo de agentes baseados em visÃo sintÃtica; e a proposiÃÃo de funÃÃes de custo para avaliar o perigo da situaÃÃo atual. As melhorias obtidas com o modelo sÃo demonstradas em diversos casos.
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Wolinski, David. „Microscopic crowd simulation : evaluation and development of algorithms“. Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S036/document.
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Dû au grand intérêt porté à la simulation de foules, beaucoup d'algorithmes ont été et sont encore proposés. Toutefois, (1) il n'existe pas de méthode standard pour évaluer le réalisme et la flexibilité de ces algorithmes, et (2) même les algorithmes les plus récents produisent encore des artéfacts évidents. Abordant la première question, nous proposons une méthode visant à évaluer le réalisme des algorithmes de simulation de foules d'une manière objective et impartiale. ''Objective'' grâce à des métriques quantifiant la similitude entre les simulations et des données acquises en situation réelle. ''Impartiale'' grâce à l'estimation de paramètres permettant d'étalonner automatiquement les algorithmes en vue de décrire au mieux les données (par rapport aux métriques), permettant de comparer les algorithmes au mieux de leur capacité. Nous explorons aussi comment ce processus permet d'augmenter le niveau de contrôle d'un utilisateur sur la simulation tout en réduisant son implication. Abordant la deuxième question, nous proposons un nouvel algorithme d'évitement de collisions. Alors que les algorithmes existants prédisent les collisions en extrapolant linéairement les trajectoires des agents, nous allons au-delà grâce à une approche probabiliste et non-linéaire, prenant en compte entre autres la configuration de l'environnement, les trajectoires passées et les interactions avec les obstacles. Nous éliminons ainsi des simulations résultantes des artefacts tels que : les ralentissements et les agglomérats dérangeants d'agents, les mouvements oscillatoires non naturels, ou encore les manœuvres d'évitement exagérées/fausses/de dernière minute. Dans une troisième contribution, nous abordons aussi l'utilisation de notre travail sur l'évaluation et l'estimation de paramètres dans le cadre de systèmes plus larges. Dans un premier temps, nous l'appliquons à la simulation d'insectes, prenant en charge leur comportement local. Après avoir complété le système aux niveaux intermédiaire et global, cette approche basée-données est capable de simuler correctement des essaims d'insectes. Dans un second temps, nous appliquons notre travail au suivi de piétons, construisant un ''méta-algorithme'' servant à calculer la probabilité de transition d'un filtre particulaire, et surpassant les systèmes existantsWith the considerable attention crowd simulation has received, many algorithms have been and are being proposed. Yet, (1) there exists no standard scheme to evaluate the accuracy and flexibility of these algorithms, and (2) even the most recent algorithms produce noticeable simulation artifacts. Addressing the first issue, we propose a framework aiming to provide an objective and fair evaluation of the realism of crowd simulation algorithms. ''Objective'' here means the use of various metrics quantifying the similarity between simulations and ground-truth data acquired with real pedestrians. ''Fair'' here means the use of parameter estimation to automatically tune the tested algorithms to match the ground-truth data as closely as possible (with respect to the metrics), effectively allowing to compare algorithms at the best of their capability. We also explore how this process can increase a user's control on the simulation while reducing the amount of necessary intervention. Addressing the second issue, we propose a new collision-avoidance algorithm. Where current algorithms predict collisions by linearly extrapolating agents' trajectories, we better predict agents' future motions in a probabilistic, non-linear way, taking into account environment layout, agent's past trajectories and interactions with other obstacles among other cues. Resulting simulations do away with common artifacts such as: slowdowns and visually erroneous agent agglutinations, unnatural oscillation motions, or exaggerated/last-minute/false-positive avoidance manoeuvres. In a third contribution, we also explore how evaluation and parameter estimation can be used as part of wider systems. First, we apply it to insect simulation, taking care of local insect behavior. After completing it at the intermediate and global levels, the resulting data-driven system is able to correctly simulate insect swarms. Second, we apply our work to pedestrian tracking, constructing a ''meta-algorithm'', more accurately computing motion priors for a particle-filter-based tracker, outperforming existing systems
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Edmonds, Kendy Elizabeth. „Demonstrating an Equivalent Level of Safety for sUAS in Shielded Environments“. Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/103964.
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The current proposed unmanned aircraft system (UAS) detect and avoid standards require the same safety metrics, even when in close proximity to the ground or structures. This requirement has the potential to hinder low altitude small unmanned aircraft operations, such as local package delivery and utility inspection. One of the main safety metrics for UASs to adhere to is a ``well clear" volume that quantifies the vertical and horizontal separation UASs are required to maintain from manned aircraft. The current volume of 2000 feet horizontal and +/- 250 feet vertical does not provide credit for the safety benefit of being close to an obstacle where manned aircraft do not fly and could prove to be too restricting for low-level flight operations (i.e., under 400 feet above ground level). This thesis suggests using smaller safety metric volumes than the well clear volume to demonstrate that operations at lower altitudes can still be proven to be just as safe as if they were held to the larger well clear volume standard by using obstacle and terrain shielding. The research leverages simulation to analyze different safety metrics and provides an example use case in which the methodology of shielded operations is applied to demonstrate how this methodology can be applied for a safety case.Master of Science
With the development of small unmanned aircraft system (sUAS) technologies have come many practical and regulatory challenges, especially in low altitude airspaces. At lower altitudes, manned aircraft are likely to be operating at lower velocities and restricting standards require UASs to maneuver against aircraft that may not present a significant risk of collision. The excessive avoidance maneuvering can cause the successful execution of even simple operations such as package delivery or survey operations to become difficult. The strict requirements have the potential to specifically inhibit sUAS beyond visual line-of-sight commercial operations, which are of great interest to the industry. This thesis describes a method for demonstrating an equivalent level of safety of small UAS operations when utilizing avoidance algorithms that leverage obstacle and terrain awareness. The purpose of this research is to demonstrate that by remaining close to obstacles, which pose a hazard to other aircraft, an unmanned aircraft can lower the risk of a mid-air collision and to demonstrate an equivalent level of safety for operations using a reduced safety metrics.
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Bridgeman, M. „Algorithms for on-line measurement of harmonic damping and avoidance of harmonic resonances due to power factor capacitor switching in distribution systems“. Thesis, Staffordshire University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272760.
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Schwienbacher, Markus [Verfasser], Heinz [Akademischer Betreuer] Ulbrich und Carlo L. [Akademischer Betreuer] Bottasso. „Efficient Algorithms for Biped Robots - Simulation, Collision Avoidance and Angular Momentum Tracking / Markus Schwienbacher. Gutachter: Heinz Ulbrich ; Carlo L. Bottasso. Betreuer: Heinz Ulbrich“. München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1055040285/34.
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Ledet, Jeffrey H. „Simulation and Performance Evaluation of Algorithms for Unmanned Aircraft Conflict Detection and Resolution“. ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2168.
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The problem of aircraft conflict detection and resolution (CDR) in uncertainty is addressed in this thesis. The main goal in CDR is to provide safety for the aircraft while minimizing their fuel consumption and flight delays. In reality, a high degree of uncertainty can exist in certain aircraft-aircraft encounters especially in cases where aircraft do not have the capabilities to communicate with each other. Through the use of a probabilistic approach and a multiple model (MM) trajectory information processing framework, this uncertainty can be effectively handled. For conflict detection, a randomized Monte Carlo (MC) algorithm is used to accurately detect conflicts, and, if a conflict is detected, a conflict resolution algorithm is run that utilizes a sequential list Viterbi algorithm. This thesis presents the MM CDR method and a comprehensive MC simulation and performance evaluation study that demonstrates its capabilities and efficiency.
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Abas, Ashardi B. „Non-intrusive driver drowsiness detection system“. Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5521.
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The development of technologies for preventing drowsiness at the wheel is a major challenge in the field of accident avoidance systems. Preventing drowsiness during driving requires a method for accurately detecting a decline in driver alertness and a method for alerting and refreshing the driver. As a detection method, the authors have developed a system that uses image processing technology to analyse images of the road lane with a video camera integrated with steering wheel angle data collection from a car simulation system. The main contribution of this study is a novel algorithm for drowsiness detection and tracking, which is based on the incorporation of information from a road vision system and vehicle performance parameters. Refinement of the algorithm is more precisely detected the level of drowsiness by the implementation of a support vector machine classification for robust and accurate drowsiness warning system. The Support Vector Machine (SVM) classification technique diminished drowsiness level by using non intrusive systems, using standard equipment sensors, aim to reduce these road accidents caused by drowsiness drivers. This detection system provides a non-contact technique for judging various levels of driver alertness and facilitates early detection of a decline in alertness during driving. The presented results are based on a selection of drowsiness database, which covers almost 60 hours of driving data collection measurements. All the parameters extracted from vehicle parameter data are collected in a driving simulator. With all the features from a real vehicle, a SVM drowsiness detection model is constructed. After several improvements, the classification results showed a very good indication of drowsiness by using those systems.
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Alam, Sameer Information Technology & Electrical Engineering Australian Defence Force Academy UNSW. „Evolving complexity towards risk : a massive scenario generation approach for evaluating advanced air traffic management concepts“. Awarded by:University of New South Wales - Australian Defence Force Academy, 2008. http://handle.unsw.edu.au/1959.4/38966.
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Present day air traffc control is reaching its operational limits and accommodating future traffic growth will be a challenging task for air traffic service providers and airline operators. Free Flight is a proposed transition from a highly-structured and centrally-controlled air traffic system to a self-optimized and highly-distributed system. In Free Flight, pilots will have the flexibility of real-time trajectory planning and dynamic route optimization given airspace constraints (traffic, weather etc.). A variety of advanced air traffc management (ATM) concepts are proposed as enabling technologies for the realization of Free Flight. Since these concepts can be exposed to unforeseen and challenging scenarios in Free Flight, they need to be validated and evaluated in order to implement the most effective systems in the field. Evaluation of advanced ATM concepts is a challenging task due to the limitations in the existing scenario generation methodologies and limited availability of a common platform (air traffic simulator) where diverse ATM concepts can be modeled and evaluated. Their rigorous evaluation on safety metrics, in a variety of complex scenarios, can provide an insight into their performance, which can help improve upon them while developing new ones. In this thesis, I propose a non-propriety, non-commercial air traffic simulation system, with a novel representation of airspace, which can prototype advanced ATM concepts such as conflict detection and resolution, airborne weather avoidance and cockpit display of traffic information. I then propose a novel evolutionary computation methodology to algorithmically generate a massive number of conflict scenarios of increasing complexity in order to evaluate conflict detection algorithms. I illustrate the methodology in detail by quantitative evaluation of three conflict detection algorithms, from the literature, on safety metrics. I then propose the use of data mining techniques for the discovery of interesting relationships, that may exist implicitly, in the algorithm's performance data. The data mining techniques formulate the conflict characteristics, which may lead to algorithm failure, using if-then rules. Using the rule sets for each algorithm, I propose an ensemble of conflict detection algorithms which uses a switch mechanism to direct the subsequent conflict probes to an algorithm which is less vulnerable to failure in a given conflict scenario. The objective is to form a predictive model for algorithm's vulnerability which can then be included in an ensemble that can minimize the overall vulnerability of the system. In summary, the contributions of this thesis are: 1. A non-propriety, non-commercial air traffic simulation system with a novel representation of airspace for efficient modeling of advanced ATM concepts. 2. An Ant-based dynamic weather avoidance algorithm for traffic-constrained enroute airspace. 3. A novel representation of 4D air traffic scenario that allows the use of an evolutionary computation methodology to evolve complex conflict scenarios for the evaluation of conflict detection algorithms. 4. An evaluation framework where scenario generation, scenario evaluation and scenario evolution processes can be carried out in an integrated manner for rigorous evaluation of advanced ATM concepts. 5. A methodology for forming an intelligent ensemble of conflict detection algorithms by data mining the scenario space.
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Cowley, Edwe Gerrit. „Kinodynamic planning for a fixed-wing aircraft in dynamic, cluttered environments : a local planning method using implicitly-defined motion primitives“. Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80077.
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Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: In order to navigate dynamic, cluttered environments safely, fully autonomous Unmanned Aerial Vehicles (UAVs) are required to plan conflict-free trajectories between two states in position-time space efficiently and reliably. Kinodynamic planning for vehicles with non-holonomic dynamic constraints is an NP-hard problem which is usually addressed using sampling-based, probabilistically complete motion planning algorithms. These algorithms are often applied in conjunction with a finite set of simple geometric motion primitives which encapsulate the dynamic constraints of the vehicle. This ensures that composite trajectories generated by the planning algorithm adhere to the vehicle dynamics. For many vehicles, accurate tracking of position-based trajectories is a non-trivial problem which demands complicated control techniques with high energy requirements. In an effort to reduce control complexity and thus also energy consumption, a generic Local Planning Method (LPM), able to plan trajectories based on implicitly-defined motion primitives, is developed in this project. This allows the planning algorithm to construct trajectories which are based on simulated results of vehicle motion under the control of a rudimentary auto-pilot, as opposed to a more complicated position-tracking system. The LPM abstracts motion primitives in such a way that it may theoretically be made applicable to various vehicles and control systems through simple substitution of the motion primitive set. The LPM, which is based on a variation of the Levenberg-Marquardt Algorithm (LMA), is integrated into a well-known Probabilistic Roadmap (PRM) kinodynamic planning algorithm which is known to work well in dynamic and cluttered environments. The complete motion planning algorithm is tested thoroughly in various simulated environments, using a vehicle model and controllers which have been previously verified against a real UAV during practical flight tests.
AFRIKAANSE OPSOMMING: Ten einde dinamiese, voorwerpryke omgewings veilig te navigeer, word daar vereis dat volledig-outonome onbemande lugvoertuie konflikvrye trajekte tussen twee posisie-tydtoestande doeltreffend en betroubaar kan beplan. Kinodinamiese beplanning is ’n NPmoeilike probleem wat gewoonlik deur middel van probabilisties-volledige beplanningsalgoritmes aangespreek word . Hierdie algoritmes word dikwels in kombinasie met ’n eindige stel eenvoudige geometriese maneuvers, wat die dinamiese beperkings van die voertuig omvat, ingespan. Sodanig word daar verseker dat trajekte wat deur die beplaningsalgoritme saamgestel is aan die dinamiese beperkings van die voertuig voldoen. Vir baie voertuie, is die akkurate volging van posisie-gebaseerde trajekte ’n nie-triviale probleem wat die gebruik van ingewikkelde, energie-intensiewe beheertegnieke vereis. In ’n poging om beheer-kompleksiteit, en dus energie-verbruik, te verminder, word ’n generiese plaaslike-beplanner voorgestel. Hierdie algoritme stel die groter kinodinamiese beplanner in staat daartoe om trajekte saam te stel wat op empiriese waarnemings van voertuig-trajekte gebaseer is. ’n Eenvoudige beheerstelsel kan dus gebruik word, in teenstelling met die meer ingewikkelde padvolgingsbeheerders wat benodig word om eenvoudige geometriese trajekte akkuraat te volg. Die plaaslike-beplanner abstraeer maneuvers in so ’n mate dat dit teoreties op verskeie voertuie en beheerstelsels van toepassing gemaak kan word deur eenvoudig die maneuver-stel te vervang. Die plaaslike-beplanner, wat afgelei is van die Levenberg-Marquardt-Algoritme (LMA), word in ’n welbekende “Probabilistic Roadmap” (PRM) kinodinamiese-beplanningsalgoritme geïntegreer. Dit word algemeen aanvaar dat die PRM effektief werk in dinamiese, voorwerpryke omgewings. Die volledige beplanningsalgoritme word deeglik in verskeie, gesimuleerde omgewings getoets op ’n voertuig-model en -beheerders wat voorheen vir akkuraatheid teenoor ’n werklike voertuig gekontroleer is tydens praktiese vlugtoetse.
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Durusu, Deniz. „Camera Controlled Pick And Place Application With Puma 760 Robot“. Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606759/index.pdf.
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This thesis analyzes the kinematical structure of Puma 760 arm and introduces the implementation of image based pick and place application by taking care of the obstacles in the environment. Forward and inverse kinematical solutions of PUMA 760 are carried out. A control software has been developed to calculate both the forward and inverse kinematics solution of this manipulator. The control program enables user to perform both offline programming and real time realization by transmitting the VAL commands (Variable Assembly Language) to the control computer.
Using the proposed inverse kinematics solutions, an interactive application is generated on PUMA 760 arm. The picture of the workspace is taken using a fixed camera attached above the robot workspace. The captured image is then processed to find the position and the distribution of all objects in the workspace. The target is differentiated from the obstacles by analyzing some specific properties of all objects, i.e. roundness. After determining the configuration of the workspace, a clustering based search algorithm is executed to find a path to pick the target object and places it to the desired place. The trajectory points in pixel coordinates, are mapped into the robot workspace coordinates by using the camera calibration matrix obtained in the calibration procedure of the robot arm with respect to the attached camera. The required joint angles, to get the end effector of the robot arm to the desired location, are calculated using the Jacobian type inverse kinematics algorithm. The VAL commands are generated and sent to the control computer of PUMA 760 to pick the object and places it to a user defined location.
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Jalel, Sawssen. „Optimisation de la navigation robotique“. Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17515/1/Jalel.pdf.
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La robotique mobile autonome est un axe de recherche qui vise à donner à une machine la capacité de se mouvoir dans un environnement sans assistance ni intervention humaine. Cette thèse s’intéresse à la partie décisionnelle de la navigation robotique à savoir la planification de mouvement pour un robot mobile non-holonome, pour lequel, la prise en compte des contraintes cinématiques et non-holonomes est primordiale. Aussi, la nécessité de considérer la géométrie propre du robot et la bonne maîtrise de l’environnement dans lequel il évolue constituent des contraintes à assurer. En effet la planification de mouvement consiste à calculer un mouvement réalisable que doit accomplir le robot entre une position initiale et une position finale données. Selon la nature de l’environnement, notamment les obstacles qui s’y présentent, deux instances du problème se distinguent : la planification de chemin et la planification de trajectoire. L’objectif de cette thèse est de proposer de nouveaux algorithmes pour contribuer aux deux instances du problème de planification de mouvement. La méthodologie suivie repose sur des solutions génériques qui s’appliquent à une classe de systèmes robotiques plutôt qu’à une architecture particulière. Les approches proposées intègrent les B-splines Rationnelles non uniformes (NURBS) dans le processus de modélisation des solutions générées tout en s’appuyant sur la propriété de contrôle local, et utilisent les algorithmes génétiques pour une meilleure exploration de l’espace de recherche.
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Guo, Yixuan. „Hexapod Gait Planning and Obstacle Avoidance Algorithm“. University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1461868607.
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Naik, Ankur. „Arc Path Collision Avoidance Algorithm for Autonomous Ground Vehicles“. Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/30969.
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Presented in this thesis is a collision avoidance algorithm designed around an arc path model. The algorithm was designed for use on Virginia Tech robots entered in the 2003 and 2004 Intelligent Ground Vehicle Competition (IGVC) and on our 2004 entry into the DARPA Grand Challenge. The arc path model was used because of the simplicity of the calculations and because it can accurately represent the base kinematics for Ackerman or differentially steered vehicles.
Clothoid curves have been used in the past to create smooth paths with continuously varying curvature, but clothoids are computationally intensive. The circular arc algorithm proposed here is designed with simplicity and versatility in mind. It is readily adaptable to ground vehicles of any size and shape. The algorithm is also designed to run with minimal tuning. The algorithm can be used as a stand alone reactive collision avoidance algorithm in simple scenarios, but it can be better optimized for speed and safety when guided by a global path planner. A complete navigation architecture is presented as an example of how obstacle avoidance can be incorporated in the algorithm.Master of Science
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Yucel, Gizem. „A Reactionary Obstacle Avoidance Algorithm For Autonomous Vehicles“. Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614480/index.pdf.
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This thesis focuses on the development of guidance algorithms in order to avoid a
prescribed obstacle primarily using the Collision Cone Method (CCM). The
Collision Cone Method is a geometric approach to obstacle avoidance, which forms
an avoidance zone around the obstacles for the vehicle to pass the obstacle around
this zone. The method is reactive as it helps to avoid the pop-up obstacles as well as
the known obstacles and local as it passes the obstacles and continue to the
prescribed trajectory. The algorithm is first developed for a 2D (planar) avoidance
in 3D environment and then extended for 3D scenarios. The algorithm is formed for
the optimized CCM as well. The avoidance zone radius and velocity are optimized
using constraint optimization, Lagrange multipliers with Karush-Kuhn-Tucker
conditions and direct experimentation.
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Chafye, Nemri. „A collision avoidance algorithm for a cylindrical robot manipulator /“. Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61719.
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Doe, Julien Albert. „Sensor Fusion Algorithm for Airborne Autonomous Vehicle Collision Avoidance Applications“. DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/2004.
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A critical ability of any aircraft is to be able to detect potential collisions with other airborne objects, and maneuver to avoid these collisions. This can be done by utilizing sensors on the aircraft to monitor the sky for collision threats. However, several problems face a system which aims to use multiple sensors for target tracking. The data collected from sensors needs to be clustered, fused, and otherwise processed such that the flight control system can make accurate decisions based on it. Raw sensor data, while filled with useful information, is tainted with inaccuracies due to limitations and imperfections of the sensor. Combined use of different sensors presents further issues in how to handle disagreements between sensor data. This thesis project tackles the problem of processing data from multiple sensors (in this application, a radar and an infrared sensor) on an airborne platform in order to allow the aircraft to make flight corrections to avoid collisions.
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Doerzaph, Zachary R. „Development of a Threat Assessment Algorithm for Intersection Collision Avoidance Systems“. Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/30013.
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Relative to other roadway segments, intersections occupy a small portion of the overall infrastructure; however, they represent the location for nearly 41 % of the annual automotive crashes in the United States. Thus, intersections are an inherently dangerous roadway element and a prime location for vehicle conflicts. Traditional safety treatments are effective at addressing certain types of intersection safety deficiencies; however, cumulative traffic data suggests these treatments do not address a large portion of the crashes that occur each year.
Intersection Collision Avoidance Systems (ICAS) represent a new breed of countermeasures that focus on the types of crashes that have not been reduced with the application of traditional methods. Incursion systems, a subset of ICAS, are designed to specifically undertake crashes that are a result of the violation of a traffic control device. Intersection Collision Avoidance Systems to address Violations (ICAS-V) monitor traffic as it approaches the intersection through a network of in-vehicle sensors, infrastructure- mounted sensors, and communication equipment. A threat-assessment algorithm performs computations to predict the driver's intended intersection maneuver, based on these sensor inputs. If the system predicts a violation, it delivers a timely warning to the driver with the aim of compelling the driver to stop. This warning helps the driver to avoid a potential crash with adjacent traffic.
The following dissertation describes an investigation of intersection approach behavior aimed at developing a threat assessment algorithm for stop-sign intersections. Data were collected at live intersections to gather infrastructure-based naturalistic vehicle approach trajectories. This data were compiled and analyzed with the goal of understanding how drivers approach intersections under various speeds and environmental conditions. Six stop-controlled intersection approaches across five intersections in the New River Valley, Virginia area were selected as the test sites. Data were collected from each site for at least two months, resulting in over sixteen total months of data.
A series of statistical analysis techniques were applied to construct a set of threat assessment algorithms for stop-controlled intersections. These analyses identified characteristics of intersection approaches that suggested driver intent at the stop sign. Models were constructed to predict driver stopping intent based on measured vehicle kinematics. These models were thoroughly tested using simulation and evaluated with signal detection theory. The overall output of this work is a set of algorithms that may be integrated into an ICAS-V for on-road testing.Ph. D.
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Gonzalez-Carrascosa, Partida Ricardo. „Optimizing manoeuvres for long collision avoidance active system of a car“. Thesis, Högskolan i Skövde, Institutionen för teknik och samhälle, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-8502.
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This project presents the development of a collision avoidance active system for cars.There is a large interest in developing avoidance system in the automotive industry since the accidents are of such nature that can be avoided if the system works as desirable e.g., in animal crossing or having the car in front stopping without the driver noticing. A control system is designed to avoid collisions by acting on the steer and brakes of a car. An algorithm is developed to optimize a fuzzy logic controller which actuates on the steer and brakes of the car. The algorithm optimizes the inputs of the car, i.e. steer and brake, to avoid the collision with the object. The optimization of the trajectory implies that the car returns to the original lane and it is the minimum time possible inthe other lane. The object is situated at different distances and the initial speed of the car also varies depending on the situations. The results are obtained by using a car model that is developed in this project in conjunction with the tyre model, [1]. Simulations show that it performs collision avoidance manoeuvres in different conditions. Furthermore, improvements of the present work are suggested that are believed to further enhance the presented algorithm.
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Cherrak, Omar. „Séparation aveugle de mélanges linéaires de sources : application à la surveillance maritime“. Thesis, Toulon, 2016. http://www.theses.fr/2016TOUL0008/document.
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Dans cette thèse, nous nous intéressons au système d’identification automatique spatial lequel est dédié à la surveillancemaritime par satellite. Ce système couvre une zone bien plus large que le système standard à terre correspondant àplusieurs cellules traditionnelles ce qui peut entraîner des risques de collision des données envoyées par des navireslocalisés dans des cellules différentes et reçues au niveau de l’antenne du satellite. Nous présentons différentes approchesafin de répondre au problème de collision considéré. Elles ne reposent pas toujours sur les mêmes hypothèses en ce quiconcerne les signaux reçus, et ne s’appliquent donc pas toutes dans les mêmes contextes (nombre de capteurs utilisés,mode semi-supervisé avec utilisation de trames d’apprentissage et information a priori ou mode aveugle, problèmes liés àla synchronisation des signaux, etc...).Dans un premier temps, nous proposons des méthodes permettant la séparation/dé-collision des messages en modèle surdéterminé(plus de capteurs que de messages). Elles sont fondées sur des algorithmes de décompositions matriciellesconjointes combinés à des détecteurs de points temps-fréquence (retard-fréquence Doppler) particuliers permettant laconstruction d’ensembles de matrices devant être (bloc) ou zéro (bloc) diagonalisées conjointement. En ce qui concerneles algorithmes de décompositions matricielles conjointes, nous proposons quatre nouveaux algorithmes de blocdiagonalisation conjointe (de même que leur version à pas optimal) fondés respectivement sur des algorithmesd’optimisation de type gradient conjugué, gradient conjugué pré-conditionné, Levenberg-Marquardt et Quasi-Newton. Lecalcul exact du gradient matriciel complexe et des matrices Hessiennes complexes est mené. Nous introduisonségalement un nouveau problème dénommé zéro-bloc diagonalisation conjointe non-unitaire lequel généralise le problèmedésormais classique de la zéro-diagonalisation conjointe non-unitaire. Il implique le choix d’une fonction de coût adaptéeet à nouveau le calcul de quantités telles que gradient matriciel complexe et les matrices Hessiennes complexes. Nousproposons ensuite trois nouveaux algorithmes à pas optimal fondés sur des algorithmes d’optimisation de type gradientconjugué, gradient conjugué pré-conditionné et Levenberg-Marquardt.Finalement, nous terminons par des approches à base de techniques de détection multi-utilisateurs conjointe susceptiblesde fonctionner en contexte sous-déterminé dans lequel nous ne disposons plus que d’un seul capteur recevantsimultanément plusieurs signaux sources. Nous commençons par développer une première approche par déflationconsistant à supprimer successivement les interférences. Nous proposons ensuite un deuxième mode opératoire fondéquant à lui sur l’estimateur du maximum de vraisemblance conjoint qui est une variante de l’algorithme de VITERBIThis PHD thesis concerns the spatial automatic identification system dedicated to marine surveillance by satellite. Thissystem covers a larger area than the traditional system corresponding to several satellite cells. In such a system, there arerisks of collision of the messages sent by vessels located in different cells and received at the antenna of the samesatellite. We present different approaches to address the considered problem. They are not always based on the sameassumptions regarding the received signals and are not all applied in the same contexts (they depend on the number ofused sensors, semi-supervised mode with use of training sequences and a priori information versus blind mode, problemswith synchronization of signals, etc.). Firstly, we develop several approaches for the source separation/de-collision in theover-determined case (more sensors than messages) using joint matrix decomposition algorithms combined withdetectors of particular time-frequency (delay-Doppler frequency) points to build matrix sets to be joint (block) or zero(block) diagonalized. Concerning joint matrix decomposition algorithms, four new joint block-diagonalization algorithms(with optimal step-size) are introduced based respectively on conjugate gradient, preconditioned conjugate gradient,Levenberg-Marquardt and Quasi-Newton optimization schemes. Secondly, a new problem called non-unitary joint zeroblockdiagonalization is introduced. It encompasses the classical joint zero diagonalization problem. It involves thechoice of a well-chosen cost function and the calculation of quantities such as the complex gradient matrix and thecomplex Hessian matrices. We have therefore proposed three new algorithms (and their optimal step-size version) basedrespectively on conjugate gradient, preconditioned conjugate gradient and Levenberg-Marquardt optimization schemes.Finally, we suggest other approaches based on multi-user joint detection techniques in an underdetermined context wherewe have only one sensor receiving simultaneously several signals. First, we have developed an approach by deflationbased on a successive interferences cancelation technique. Then, we have proposed a second method based on the jointmaximum likelihood sequence estimator which is a variant of the VITERBI algorithm
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Toku, Hadi Alper. „A New Feedback-based Contention Avoidance Algorithm For Optical Burst Switching Networks“. Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610165/index.pdf.
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In this thesis, a feedback-based contention avoidance technique based on weighted Dijkstra algorithm is proposed to address the contention avoidance problem for Optical Burst Switching networks.
Optical Burst Switching (OBS) has been proposed as a promising technique to support high-bandwidth, bursty data traffic in the next-generation optical Internet. Nevertheless, there are still some challenging issues that need to be solved to achieve an effective implementation of OBS. Contention problem occurs when two or more bursts are destined for the same wavelength. To solve this problem, various reactive contention resolution methods have been proposed in the
literature. However, many of them are very vulnerable to network load and may suffer severe loss in case of heavy traffic. By proactively controlling the overall traffic, network is able to update itself in case of high congestion and by means of this methodcontention avoidance can be achieved efficiently. The performance analysis of the proposed algorithm is presented through network simulation results provided by OMNET++ simulation environment. The simulation results show that the proposed contention avoidance technique significantly reduces the burst loss probability as compared to networks without any contention avoidance techniques.
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Balan, Lucian Bone Gary M. „Real-time 3D collision avoidance algorithm for safe human and robot coexistence“. *McMaster only, 2006.
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Avnaïm, Francis. „Placement et déplacement de formes rigides ou articulées“. Besançon, 1989. http://www.theses.fr/1989BESA2018.
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Woolley, Eileen K. „Implementation and evaluation of a collision-avoidance navigational algorithm on a mobile robot“. Full text, Acrobat Reader required, 1998. http://viva.lib.virginia.edu/etd/theses/woolley98.pdf.
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Viquez, Rojas Oscar Alberto. „Evaluation of an acoustic detection algorithm for reactive collision avoidance in underwater applications“. Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83753.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (page 33).
This thesis sought to evaluate a vehicle detection algorithm based on a passive acoustic sensor, intended for autonomous collision avoidance in Unmanned Underwater Vehicles. By placing a hydrophone at a safe distance from a dock, it was possible to record the acoustic signature generated by a small motor boat as it navigated towards, and then away from the sensor. The time-varying sound intensity was estimated by Root Mean Square of the sound amplitude in discrete samples. The time-derivative of the sound intensity was then used to estimate the time to arrival, or collision, of the acoustic source. The algorithm was found to provide a good estimate of the time to collision, with a small standard deviation for the projected collision time, when the acoustic source was moving at approximately constant speed, providing validation of the model at the proof-of-concept level.
by Oscar Alberto Viquez Rojas.
S.B.
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Andrianirina, Heriniaina Philibert. „PF-OBS: A proportionally fair congestion avoidance algorithm for Optical Burst Switching networks“. Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27953.
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Optical Burst Switching (OBS) is an optical switching technique which eliminates the electronic bottleneck by keeping transmitted data in the optical domain. Therefore, it can effectively utilize the large bandwidth available in optical fibres. For these reasons, OBS is considered the future of optical networks. However, burst loss caused by congestion is a significant problem in OBS because flexible, practical optical buffers currently do not exist.
This thesis proposes a rate-based congestion control method, called PF-OBS, which limits the blocking probability in OBS networks. PF-OBS uses a utility maximization approach to congestion control. The method assigns prices to congested links. Ingress nodes receive bandwidth proportionally to the price they are willing to pay. The resulting rate allocation is proportionally fair.
The method can keep the traffic load on all links under a predefined level. Simulations show that PF-OBS maintains the overall blocking probability at lower levels as compared with plain OBS. In addition, PF-OBS achieves higher total throughput than existing OBS flow control methods. The method remains stable in the presence of propagation delays.
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Lee, Jaehwan. „Hardware/Software Deadlock Avoidance for Multiprocessor Multiresource System-on-a-Chip“. Diss., Also available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-11222004-083429/unrestricted/lee%5Fjaehwan%5F200412%5Fphd.pdf.
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Hetrick, Shannon. „Examination of Driver Lane Change Behavior and the Potential Effectiveness of Warning Onset Rules for Lane Change or "Side" Crash Avoidance Systems“. Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36654.
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Lane change or "Side" Crash Avoidance Systems (SCAS) technologies are becoming available to help alleviate the lane change crash problem. They detect lane change crash hazards and warn the driver of the presence of such hazards. This thesis examines driver lane change behavior and evaluates the potential effectiveness of five warning onset rules for lane change or "side" crash avoidance system (SCAS) technologies.
The ideal SCAS should warn the driver only when two conditions are met: (1) positive indication of lane change intent and (2) positive detection of a proximal vehicle in the adjacent lane of concern. Together, these two conditions create a crash hazard. The development of SCAS technologies depends largely on an understanding of driver behavior and performance during lane change maneuvers. By quantifying lane change behavior, real world crash hazard scenarios can be simulated. This provides an opportunity to evaluate potential warning onset rules or algorithms of driver intent to change lanes.
Five warning onset rules for SCAS were evaluated: turn-signal onset (TSO), minimum separation (MS), line crossing (LC), time-to-line crossing (TLC), and tolerance limit (TL). The effectiveness of each rule was measured by the maximum response time available (tavailable) to avoid a crash for a particular lane change crash scenario, and by the crash outcome, crashed or crash avoided, of a particular lane change crash scenario.Master of Science
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Tong, Peter, und mail@petertong com. „Application of Genetic Algorithm to a Forced Landing Manoeuvre on Transfer of Training Analysis“. RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080528.114140.
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This study raises some issues for training pilots to fly forced landings and examines the impact that these issues may have on the design of simulators for such training. It focuses on flight trajectories that a pilot of a single-engine general aviation aircraft should fly after engine failure and how pilots can be better simulator trained for this forced landing manoeuvre. A sensitivity study on the effects of errors and an investigation on the effect of tolerances in the aerodynamic parameters as prescribed in the Manual of Criteria for the Qualification of Flight Simulators have on the performance of flight simulators used for pilot training was carried out. It uses a simplified analytical model for the Beech Bonanza model E33A aircraft and a vertical atmospheric turbulence based on the MIL-F-8785C specifications. It was found that the effect of the tolerances is highly sensitive on the nature of the manoeuvre flown and that in some cases, negative transfe r of training may be induced by the tolerances. A forced landing trajectory optimisation was carried out using Genetic Algorithm. The forced landing manoeuvre analyses with pre-selected touchdown locations and pre-selected final headings were carried out for an engine failure at 650 ft AGL for bank angles varying from banking left at 45° to banking right at 45°, and with an aircraft's speed varying from 75.6 mph to 208 mph, corresponding to 5% above airplane's stall speed and airplane's maximum speed respectively. The results show that certain pre-selected touchdown locations are more susceptible to horizontal wind. The results for the forced landing manoeuvre with a pre-selected location show minimal distance error while the quality of the results for the forced landing manoeuvre with a pre-selected location and a final heading show that the results depend on the end constraints. For certain pre-selected touchdown locations and final headings, the airplane may either touchdown very close to the pre-selected touchdown location but with greater final h eading error from the pre-selected final heading or touchdown with minimal final heading error from the pre-selected final heading but further away from the pre-selected touchdown location. Analyses for an obstacle avoidance forced landing manoeuvre were also carried out where an obstacle was intentionally placed in the flight path as found by the GA program developed for without obstacle. The methodology developed successfully found flight paths that will avoid the obstacle and touchdown near the pre-selected location. In some cases, there exist more than one ensemble grouping of flight paths. The distance error depends on both the pre-selected touchdown location and where the obstacle was placed. The distance error tends to increase with the addition of a specific final heading requirement for an obstacle avoidance forced landing manoeuvre. As with the case without specific final heading requirement, there is a trade off between touching down nearer to the pre-selected location and touching down with a smaller final heading error.
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Wallace, Shane Alan. „DEVELOPMENT OF A SMALL AND INEXPENSIVE TERRAIN AVOIDANCE SYSTEM FOR AN UNMANNED AERIAL VEHICLE VIA POTENTIAL FUNCTION GUIDANCE ALGORITHM“. DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/380.
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Despite the first unmanned aerial vehicle (UAV) mission being flown on Aug 22 1849 to bomb Venice UAVs have only recently began to modernize into sophisticated tools beyond simple aerial vehicles. With an increasing number of potential applications, such as cargo delivery, communications, search and rescue, law enforcement, and homeland security, the need for appropriate UAV technology advancement also arose. Here, the development of a low-cost collision avoidance system is described. Hardware was tested and selected based on predetermined constraints and goals. Additionally, a variety of potential functions were explored and assessed at their effectiveness in preventing a collision of a UAV with mountainous terrain. Simulations were conducted using Cloud Cap’s Piccolo autopilot in conjunction with Matlab. Based on these simulations, a set of potential functions was selected to be used with the chosen hardware on subsequent UAV-development-related projects.
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McLaughlin, Shane Brendan. „Analytic Assessment of Collision Avoidance Systems and Driver Dynamic Performance in Rear-End Crashes and Near-Crashes“. Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29561.
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Collision avoidance systems (CASs) are being developed and fielded to reduce the number and severity of rear-end crashes. Kinematic algorithms within CASs evaluate sensor input and apply assumptions describing human-response timing and deceleration to determine when an alert should be presented. This dissertation presents an analytic assessment of dynamic function and performance CASs and associated driver performance for preventing automotive rear-end crashes. A method for using naturalistic data in the evaluation of CAS algorithms is described and applied to three algorithms. Time-series parametric data collected during 13 rear-end crashes and 70 near-crashes are input into models of collision avoidance algorithms to determine when the alerts would have occurred. Algorithm performance is measured by estimating how much of the driving population would be able to respond in the time available between when an alert would occur and when braking was needed. A sensitivity analysis was performed to consider the effect of alternative inputs into the assessment method. The algorithms were found to warn in sufficient time to permit 50â 70% of the population to avoid collision in similar scenarios. However, the accuracy of this estimate was limited because the tested algorithms were found to alert too frequently to be feasible. The response of the assessment method was most sensitive to differences in assumed response-time distributions and assumed driver braking levels. Low-speed crashes were not addressed by two of the algorithms. Analysis of the events revealed that the necessary avoidance deceleration based on kinematics was generally less than 2 s in duration. At the time of driver response, the time remaining to avoid collision using a 0.5g average deceleration ranged from â 1.1 s to 2.1 s. In 10 of 13 crashes, no driver response deceleration was present. Mean deceleration for the 70 near-crashes was 0.37g and maximum was 0.72g. A set of the events was developed to measure driver response time. The mean driver response time was 0.7 s to begin braking and 1.1 s to reach maximum deceleration. Implications for collision countermeasures are considered, response-time results are compared to previous distributions and future work is discussed.Ph. D.
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Calliess, Jan-Peter. „Conservative decision-making and inference in uncertain dynamical systems“. Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:b7206c3a-8d76-4454-a258-ea1e5bd1c63e.
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The demand for automated decision making, learning and inference in uncertain, risk sensitive and dynamically changing situations presents a challenge: to design computational approaches that promise to be widely deployable and flexible to adapt on the one hand, while offering reliable guarantees on safety on the other. The tension between these desiderata has created a gap that, in spite of intensive research and contributions made from a wide range of communities, remains to be filled. This represents an intriguing challenge that provided motivation for much of the work presented in this thesis. With these desiderata in mind, this thesis makes a number of contributions towards the development of algorithms for automated decision-making and inference under uncertainty. To facilitate inference over unobserved effects of actions, we develop machine learning approaches that are suitable for the construction of models over dynamical laws that provide uncertainty bounds around their predictions. As an example application for conservative decision-making, we apply our learning and inference methods to control in uncertain dynamical systems. Owing to the uncertainty bounds, we can derive performance guarantees of the resulting learning-based controllers. Furthermore, our simulations demonstrate that the resulting decision-making algorithms are effective in learning and controlling under uncertain dynamics and can outperform alternative methods. Another set of contributions is made in multi-agent decision-making which we cast in the general framework of optimisation with interaction constraints. The constraints necessitate coordination, for which we develop several methods. As a particularly challenging application domain, our exposition focusses on collision avoidance. Here we consider coordination both in discrete-time and continuous-time dynamical systems. In the continuous-time case, inference is required to ensure that decisions are made that avoid collisions with adjustably high certainty even when computation is inevitably finite. In both discrete-time and finite-time settings, we introduce conservative decision-making. That is, even with finite computation, a coordination outcome is guaranteed to satisfy collision-avoidance constraints with adjustably high confidence relative to the current uncertain model. Our methods are illustrated in simulations in the context of collision avoidance in graphs, multi-commodity flow problems, distributed stochastic model-predictive control, as well as in collision-prediction and avoidance in stochastic differential systems. Finally, we provide an example of how to combine some of our different methods into a multi-agent predictive controller that coordinates learning agents with uncertain beliefs over their dynamics. Utilising the guarantees established for our learning algorithms, the resulting mechanism can provide collision avoidance guarantees relative to the a posteriori epistemic beliefs over the agents' dynamics.
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Safeea, Mohammad. „Des robots manipulateurs collaboratifs sûrs“. Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE036.
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Les manipulateurs industriels collaboratifs ouvrent une nouvelle ère dans la fabrication flexible, où les robots et les humains sont capables de coexister et de travailler ensemble. Cependant, divers défis persistent pour parvenir à une collaboration complète entre les robots et les humains en milieu industriel. Dans cette thèse, deux défis principaux - la sécurité et la collaboration - sont abordés pour atteindre cet objectif. Concernant la sécurité, la thèse présente une méthode d'évitement des collisions en temps réel qui permet au robot d'ajuster les chemins générés hors ligne pour une tâche industrielle, tout en évitant les collisions avec les humains à proximité. En outre, la thèse a présenté une nouvelle méthode pour effectuer un mouvement d'évitement de collision réactif, en utilisant la méthode de Newton du second ordre qui offre divers avantages par rapport aux méthodes traditionnelles utilisées dans la littérature. Sur la collaboration, la thèse présente un mode de guidage manuel précis comme alternative au mode de guidage actuel pour effectuer des opérations de positionnement précis de l'effecteur terminal du robot d’une manière simple et intuitive. La thèse présente également de nouvelles contributions à la formulation mathématique de la dynamique des robots, y compris un algorithme récursif pour calculer la matrice de masse des robots sériels avec un coût minimal du second ordre et un algorithme récursif pour calculer efficacement les symboles de Christoffel. Tous les algorithmes présentés sont validés soit en simulation, soit dans un scénario réelCollaborative industrial manipulators are ushering a new era in flexible manufacturing, where robots and humans are allowed to coexist and work side by side. However, various challenges still persist in achieving full human robot collaboration on the factory floor. In this thesis two main challenges - safety and collaboration - for achieving that goal are addressed. On safety, the thesis presents a real-time collision avoidance method which allows the robot to adjust the offline generated paths of the industrial task in real-time for avoiding collisions with humans nearby. In addition, the thesis presented a new method for performing the reactive collision avoidance motion using second order Newton method which offers various advantages over the traditional methods in the literature. On collaboration, the thesis presents the precision hand-guiding as an alternative to the teach-pendant for performing precise positioning operations of the robot’s end-effector in a simple and intuitive manner. The thesis also presents new contributions into the mathematical formulation of robot dynamics, including a recursive algorithm for calculating the mass matrix of serially linked robots with a minimal second order cost, and a recursive algorithm for calculating Christoffel symbols efficiently. All the presented algorithms are validated either in simulation or in a real-world scenario
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Stevens, Thomas F. „A LiDAR Based Semi-Autonomous Collision Avoidance System and the Development of a Hardware-in-the-Loop Simulator to Aid in Algorithm Development and Human Studies“. DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1521.
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In this paper, the architecture and implementation of an embedded controller for a steering based semi-autonomous collision avoidance system on a 1/10th scale model is presented. In addition, the development of a 2D hardware-in-the-loop simulator with vehicle dynamics based on the bicycle model is described. The semi-autonomous collision avoidance software is fully contained onboard a single-board computer running embedded GNU/Linux. To eliminate any wired tethers that limit the system’s abilities, the driver operates the vehicle at a user-control-station through a wireless Bluetooth interface. The user-control-station is outfitted with a game-controller that provides standard steering wheel and pedal controls along with a television monitor equipped with a wireless video receiver in order to provide a real-time driver’s perspective video feed. The hardware-in-the-loop simulator was developed in order to aid in the evaluation and further development of the semi-autonomous collision avoidance algorithms. In addition, a post analysis tool was created to numerically and visually inspect the controller’s responses. The ultimate goal of this project was to create a wireless 1/10th scale collision avoidance research platform to facilitate human studies surrounding driver assistance and active safety systems in automobiles. This thesis is a continuation of work done by numerous Cal Poly undergraduate and graduate students.
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Dicheva, Svetlana. „Planification de mission pour un système de lancement aéroporté autonome“. Phd thesis, Université d'Evry-Val d'Essonne, 2012. http://tel.archives-ouvertes.fr/tel-00878784.
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Cette thèse de doctorat s'inscrit dans le cadre des activités de recherche sur les systèmes de lancement aéroporté autonome. L'originalité du travail est basée sur la planification de mission effectuée par un algorithme de type A*(A-étoile). Cet algorithme a été amélioré pour répondre aux besoins de la mission de largage d'un lanceur. Il effectue la planification du chemin le plus court dans un espace tridimensionnel. Le meilleur chemin est choisi à partir de plusieurs points de passage générés dans la région de mission. Une région peut être une phase du vol ou une partie du profil de vol. Le chemin le plus court est identifié par rapport à la présence de différents obstacles dans l'espace de recherche et son objectif consiste à atteindre un point désiré. Les obstacles ont différentes dimensions et orientations dans l'espace. L'étude de leur comportement est associée aux incertitudes en provenance de l'environnement. Ils peuvent représenter des régions interdites au vol ou des conditions atmosphériques défavorables. L'évolution de ces derniers n'est pas prévisible à l'avance, ce qui impose l'addition d'une fonctionnalité dans l'algorithme. Il est possible de replanifier le chemin à partir d'un point de passage appartenant à un chemin généré en fonction de la position détectée récemment de l'obstacle en déplacement pour arriver dans la configuration finale désirée. Cette détection est possible grâce aux capteurs positionnés sur le premier étage de ce système de lancement représenté par un avion-porteur. Les points de passage que le véhicule aérien doit suivre pour atteindre les objectifs importants ne sont pas choisis d'une manière aléatoire. Leur génération dans l'espace de recherche du chemin est définie en rapport aux limitations dynamiques de l'avion. Les modèles cinématique et dynamique du véhicule aérien qui décrivent son évolution sont aussi développés dans cette thèse. Ces modèles sont étudiés dans un système de coordonnées aérodynamiques. Le référentiel traite la présence du vent qui influe sur le comportement du véhicule. Cela nous permet de considérer d'une manière prédictive plusieurs incertitudes en provenance de l'environnement ou internes pour le véhicule. Les perturbations internes sont provoquées par le largage du lanceur. Le régime transitoire est relié à la perte de masse qui pour certaines missions peut atteindre le tiers de la masse totale du système de lancement. L'algorithme de planification traite une autre prévision - la possibilité que le largage ne soit pas réalisé. Cela peut arriver dans le cas où une tempête s'est installée dans la région de lancement ou il y a plusieurs obstacles dont l'évitement risque de consommer trop de carburant et d'empêcher le retour sur le site d'atterrissage. Les connexions entre les différents points de passage peuvent être souvent brutes et difficiles à réaliser par le véhicule aérien. Pour résoudre cette problématique dans le deuxième module développé sur la génération de trajectoire réalisable, nous utilisons l'approche des polynômes de troisième ordre. Ces polynômes par rapport aux autres techniques diminuent le temps du calcul pour générer une trajectoire réalisable entre deux points de passage consécutifs. Le chemin réalisable est facile à suivre par le système. Pour le suivi de la trajectoire, nous avons introduit dans un troisième module - la commande par mode glissant. Le principe de cette commande consiste le choix de la surface de commutation entre la trajectoire actuelle suivie par le véhicule et la trajectoire désirée déterminée par l'algorithme de planification A-étoile et générée par les polynômes cartésiens de troisième ordre.
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Abell, Stephen W. „Parallel acceleration of deadlock detection and avoidance algorithms on GPUs“. Thesis, 2013. http://hdl.handle.net/1805/3653.
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Indiana University-Purdue University Indianapolis (IUPUI)Current mainstream computing systems have become increasingly complex. Most of which have Central Processing Units (CPUs) that invoke multiple threads for their computing tasks. The growing issue with these systems is resource contention and with resource contention comes the risk of encountering a deadlock status in the system. Various software and hardware approaches exist that implement deadlock detection/avoidance techniques; however, they lack either the speed or problem size capability needed for real-time systems. The research conducted for this thesis aims to resolve issues present in past approaches by converging the two platforms (software and hardware) by means of the Graphics Processing Unit (GPU). Presented in this thesis are two GPU-based deadlock detection algorithms and one GPU-based deadlock avoidance algorithm. These GPU-based algorithms are: (i) GPU-OSDDA: A GPU-based Single Unit Resource Deadlock Detection Algorithm, (ii) GPU-LMDDA: A GPU-based Multi-Unit Resource Deadlock Detection Algorithm, and (iii) GPU-PBA: A GPU-based Deadlock Avoidance Algorithm. Both GPU-OSDDA and GPU-LMDDA utilize the Resource Allocation Graph (RAG) to represent resource allocation status in the system. However, the RAG is represented using integer-length bit-vectors. The advantages brought forth by this approach are plenty: (i) less memory required for algorithm matrices, (ii) 32 computations performed per instruction (in most cases), and (iii) allows our algorithms to handle large numbers of processes and resources. The deadlock detection algorithms also require minimal interaction with the CPU by implementing matrix storage and algorithm computations on the GPU, thus providing an interactive service type of behavior. As a result of this approach, both algorithms were able to achieve speedups over two orders of magnitude higher than their serial CPU implementations (3.17-317.42x for GPU-OSDDA and 37.17-812.50x for GPU-LMDDA). Lastly, GPU-PBA is the first parallel deadlock avoidance algorithm implemented on the GPU. While it does not achieve two orders of magnitude speedup over its CPU implementation, it does provide a platform for future deadlock avoidance research for the GPU.
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wang, Ji-shiu, und 王基旭. „Application of multisensor fusion algorithms in collision avoidance of mobile robots“. Thesis, 2009. http://ndltd.ncl.edu.tw/handle/94281980797508607606.
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碩士國立雲林科技大學
電機工程系碩士班
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The thesis develops an intelligent mobile robot system that has uniform interface. The control unit of these detection modules is HOLTEK microchip. The mobile robot system contains many modules, and uses the ultrasonic sensor module and infrared sensor module to avoid obstacle, and uses electronic compass and inclinometer module to detect posture. The master module communicates with main controller of the mobile robot via RS232 interface. Mobile robots can execute obstacle, and tracking, and wall following on the unknown environment using ultrasonic sensors and infrared sensors, and cooperate with electronic compass module to build environment map on the unknown environment.
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Chiu, Ji-Feng, und 邱基峰. „Preemption Avoidance and Traffic Prediction Algorithms for DiffServ-aware Traffic Engineering“. Thesis, 2003. http://ndltd.ncl.edu.tw/handle/95989932858209237108.
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碩士國立成功大學
電機工程學系碩博士班
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The DiffServ-aware traffic engineering incorporates two ideas: DiffServ and traffic engineering. The DiffServ improves the network scalability through aggregating a large number of traffic flows into a set of traffic classes. The traffic engineering primarily deals with constraint-based routing that routing tables are now built not only on the topology basis but also on the basis of resource availability and QoS requirements. Obviously, the traffic engineering requires a resource management mechanism at each network node to reserve resources for satisfying flow QoS requirements, and to flood network information with resource availability. Designing a resource management scheme for supporting the DiffServ-aware traffic engineering framework is what we focus on in this thesis. Resource management is, in fact, the key to achieve the end-to-end quantitative QoS guarantees and the optimization utilization of transmission resources. These drive us to the topic about how to manage resource to meet QoS requirements efficiently. The question resolves itself into the following two points for the DiffServ-aware traffic engineering in a MPLS network. It comprises of LSPs (Label Switching Paths) preemption and capacity allocation. We first point out the automatical setting of QoS parameters to allocate LSP capacity and how to avoid the preemption to achieve QoS guarantees and then discuss the distributing of traffic to achieve load balancing in this thesis.