Torque Control

This book is the result of inspirations and contributions from many researchers, a collection of 9 works, which are, in majority, focalised around the Direct Torque Control and may be comprised of three sections: different techniques for the control of asynchronous motors and double feed or double star induction machines, oriented approach of recent developments relating to the control of the Permanent Magnet Synchronous Motors, and special controller design and torque control of switched reluctance machine

Planification de trajectoire sous contraintes d'aéronef

The focus of this PhD thesis is on the trajectory planning module as a part of autonomous aircraft system. Feasible trajectories for aircraft flying in environment cluttered by obstacles are studied. Since aircraft dynamics are complex, nonlinear and nonholonomic; trajectory planning for such systems is very difficult and challenging.Rapidly-exploring Random Tree or RRT path planner is used as a basis to find a feasible trajectory. The advantage of this algorithm is that it does not consider only the complete vehicle model but also the environment. Two algorithms are developed to find a feasible and optimal solution. The RRT algorithm, combined with a preprocessing of the exploration space, is used for a complete realistic model of the system. However, this approach does not consider any optimal criteria. In order to consider performance criteria, the RRT* algorithm is used based on a simplified model with the help of the artificial potential field as a heuristic to improve the convergence rate to the solution.The algorithms are simulated in an application of hypersonic aerial vehicles, for example, interceptor missiles flying in high altitude. This makes the aerodynamically controlled aircraft have less maneuverability since the air density decreases exponentially with altitude. 3D shortest paths are developed and used as a metric. Therefore, a feasible and optimal trajectory is obtained efficiently. With these results, real-time constraints will be easier to verify if the algorithm is implemented on board the vehicle. In future work, replanning will be considered to improve the performance of the algorithm in case of dynamic environment or changes in the mission.Le sujet de cette thèse porte sur la planification de trajectoire pour un aéronef autonome. Les trajectoires d'aéronefs se déplaçant dans un environnement encombré par des obstacles sont étudiées. La dynamique des aéronefs étant complexe, non linéaire, et non holonome, la planification de trajectoire de ce type de systèmes est un problème très difficile.L'algorithme Rapidly-exploring Random Tree, ou RRT, est utilisé comme planificateur de base. L'avantage de cet algorithme est qu'il permet de considérer des modèles d'aéronefs complets dans un environnement complexe. Deux algorithmes sont développés pour trouver une solution faisable et optimale. Pour un modèle complet, L'algorithme RRT avec un prétraitement de l'espace d'état est utilisé dans le cas d'une prise en compte du modèle complet du système. Cependant, cette méthode ne considère pas de critères optimaux. Pour y remédier, l'algorithme RRT* est utilisé pour un modèle simplifié du système avec l'aide de champs de potentiels artificiels comme heuristique pour améliorer le taux de convergence vers la solution.Les algorithmes sont simulés pour une application d'aéronefs hypersoniques, comme par exemple des missiles intercepteurs volants à haute altitude. Les aéronefs ont donc moins de manœuvrabilité parce que la densité de l'air diminue exponentiellement avec l'altitude. Les chemins les plus courts en 3D sont développés et utilisés comme une métrique. Des trajectoires réalisables et optimales sont obtenues efficacement. A partir de ces résultats, les contraintes de temps réel à bord du véhicule seront plus faciles à vérifier. Dans les travaux futurs, la replanification sera considérée pour améliorer la performance de l'algorithme en cas d'environnement dynamique ou de changements dans la mission

Modelling and Control of Small-Scale Helicopter on a Test Platform

The helicopter is a Multiple-Input Multiple-Output (MIMO) system with highly coupled characteristics, which increases the complexity of the system dynamics. In addition, the system dynamics of the helicopter are unstable, referring to its tendency to deviate from an equilibrium when disturbed. Despite the complexity in its modelling and control, the benefit of using a helicopter for unmanned, autonomous applications can be tremendous. One particular application that motivates this research is the use of an unmanned small-scale helicopter in an autonomous survey mission over an area struck by disaster, such as an earthquake. The work presented in this thesis provides a framework for utilizing a platform system for research and development of small-scale helicopter systems. A platform system enables testing and analysis to be performed indoor in a controlled environment. This can provide a more convenient mean for helicopter research since the system is not affected by environmental elements, such as wind, rain or snow condition. However, the presence of the platform linkages poses challenges for analysis and controller design as it alters the helicopter system flight dynamics. Through a six degree-of-freedom (6 DOF) platform model derived in this research, the criteria for matching the trim conditions between the platform system and a stand alone helicopter have been identified. With the matched trim conditions, linearization is applied to perform analysis on the effects that the platform has on the system dynamics. The results of the analysis provide insights into both the limitations and benefits of utilizing the platform system for helicopter research. Finally, a Virtual Joint Control scheme is proposed as an unified control strategy for both the platform and the stand alone helicopter systems. Having a consistent control scheme between the two systems allows for comparisons between simulation and experimental results for the two systems to be made more readily. Furthermore, the Virtual Joint Control scheme represents a novel flight control strategy for stand alone helicopter systems

Development of a transparent knowledge-based spatial decision support system for decentralised stormwater management planning : case study: selection of on-site stormwater management measures for urban catchments: Chemnitz and Emscher Region, Germany

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Modelling based framework for the management of emergency departments.

In the twenty-first century, the healthcare industry faces ever-changing economic, social, political and technology challenges. Costs are rising, funding is diminishing, human and fiscal resources are becoming scarcer, customer-expectations are rising, the complexity of disease is increasing and technology is becoming more complex. These trends have a massive impact on every aspect of hospital operations and the Emergency Department is no exception. Overcrowding in the Emergency Department (ED) in hospitals has become a growing problem in many developed countries around the world. ED overcrowding has a direct effect on patient-care, including compromised patient-safety, increased length-of-stay, increased mortality and morbidity-rates and increased costs. Healthcare policy-makers and hospital and ED administrators are being forced to search for ways to improve the capacity of EDs by better utilisation of existing resources and creating more efficient systems to overcome this problem.Throughout the past few decades, there has been an increasing trend of using numerous systems-analysis tools and techniques which have come from manufacturing and other service industries to address the various issues in healthcare and EDs. Among those tools Discrete-Event Simulation (DES) is a powerful tool to improve the efficiency and capacity in dynamic and complex systems. Use of these tools to address the overcrowding problem in EDs has been patchy; specific aspects of issues have been studied but no attempt has been made to deploy DES or any other systems-analysis tool in a strategic and holistic manner.The aim of this research is to develop a modelling-based framework to manage the overcrowding problem in EDs. The research identified the causes of overcrowding in EDs and developed a decisions-framework with the long-term, medium-term and short-tem decisions in EDs that related to the overcrowding problem. Finally, it identified the best possible systems-analysis tools to support those decisions to overcome the overcrowding problem in EDs. This research could help the healthcare policy-makers, managers, systems-engineers as well as the researchers and consultants who are interesting in the Emergency Department operational management

Challenges for engineering students working with authentic complex problems

Engineers are important participants in solving societal, environmental and technical problems. However, due to an increasing complexity in relation to these problems new interdisciplinary competences are needed in engineering. Instead of students working with monodisciplinary problems, a situation where students work with authentic complex problems in interdisciplinary teams together with a company may scaffold development of new competences. The question is: What are the challenges for students structuring the work on authentic interdisciplinary problems? This study explores a three-day event where 7 students from Aalborg University (AAU) from four different faculties and one student from University College North Denmark (UCN), (6th-10th semester), worked in two groups at a large Danish company, solving authentic complex problems. The event was structured as a Hackathon where the students for three days worked with problem identification, problem analysis and finalizing with a pitch competition presenting their findings. During the event the students had workshops to support the work and they had the opportunity to use employees from the company as facilitators. It was an extracurricular activity during the summer holiday season. The methodology used for data collection was qualitative both in terms of observations and participants’ reflection reports. The students were observed during the whole event. Findings from this part of a larger study indicated, that students experience inability to transfer and transform project competences from their previous disciplinary experiences to an interdisciplinary setting