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Robust algorithms for the identification and control of Android-powered quadcopters
Get PDFThe focus of this thesis is on modeling and control of a non-real time, Android operated quadcopter of type dji F450 Flame Wheel without having a concrete knowledge about the system's dynamics and parameters. The quadcopter is equipped with an onboard non-rooted Android smartphone, which serves as both the controller and the IMU in the system. The reference command signals are generated by another user-held Android smartphone which defines the desired orientation of the quadcopter. Due to the fact that default Android implementation is not real-time, the measurements of both Android phones are subject to significant latencies resulting in asynchronous data. To obtain a model of the system, a comprehensive system identification study of the quadcopter's rotation dynamics using grey box model and Euler's equations of rigid body is introduced in the thesis. It also introduces two novel algorithms for obtaining an initial guess for the inertia matrix using convex optimization despite the presence of large number of local minimizers in the original prediction error problem. It shows how sensitive the process is to the initial guess of the model's parameters. A detailed comparison of the relevant estimates is also shown. The control laws were implemented on the onboard Android device, which reads the asynchronous built-in sensors measurements and generates the control signals required to steer the quadcopter and obtain the desired orientation defined by the user-held device. Two control laws were developed, an advanced model-free PID controller that accounts for the non-uniformly distributed data, the windup effect, and the derivative kick, and a model-based LQI controller. Both control approaches were able to stabilize the quadcopter despite the data asynchronousity and model uncertainty, and were validated and tested empirically and through simulation. The thesis also introduces a novel approach of optimizing the PID controllers gains based on the jacobian matrix. The optimization problem tends to be poorly conditioned for such systems. Hence, the novel scaling technique improves the conditioning of the optimization problem and obtains better minimizers. The efficiency of the proposed algorithm is evaluated through simulation. Furthermore, a detailed study on the effect of the cost function selection and model uncertainty on the optimization process is shown
A Survey of Time and Space Partitioning for Space Avionics
Get PDFWe present a survey of the current state of the reseach on time and space partitioning for space avionics. The availability of ever more powerful computers allows to assign many control tasks to a single computer easily, in principle. But in its naive form, this would mean too much effort and thus cost for demonstrating dependability. For aircraft, there is already an approach to solve this problem, the Integrated Modular Avionics (IMA) architecture. For spacecraft, the basic problem is similar. But in detail, the setting is different, though. This report compiles a survey and identifies relevant research challenges. Based on some of them, we propose to design a multi-core processor architecture that avoids fundamental problems of the current architectures with respect to time partitioning, and that can be used in the space domain
Simulation-Oriented Methodology for Distortion Minimisation during Laser Beam Welding
Get PDFDistortion is one of the drawbacks of any welding process, most of the time needed to be suppressed. One doubtful factor that could affect welding deformation is the shape of the liquid melt pool, which can be modified via variation of process parameters. The aim of this work was to numerically study the dynamics of the weld pool and its geometrical influence on welding distortion during laser beam welding. To achieve such a goal, a promising novel process simulation model, employed in investigating the keyhole and weld pool dynamics, has successfully been invented. The model incorporated all distinctive behaviours of the laser beam welding process. Moreover, identification of the correlation between the weld pool geometry and welding distortion as well as, eventually, weld pool shapes that favour distortion minimisation has also been simulatively demonstrated
Mechanical and tribological characterization of self-lubricating (Cr1-xAlx)N coatings for deposition on complex-shaped forging tools
Get PDFCold forging processes in production engineering enable a high material utilization with a considerable energy and resource efficiency. In such processes, liquid and solid lubricants are commonly used to reduce the friction between forming tools and workpieces. However, using of lubricants in tribological cold forging processes is unfavorable to economic, ecological and legislative perspectives. To overcome disadvantages of lubricants and conduct lubricant-free cold forging, the physical vapor deposition (PVD) technology for coating of metal forming tools can be applied. Such coatings contain soft and hard constituents. Self-lubricating systems such as MoS2 will be applied as soft constituents. Furthermore, incorporation of MoS2 into the hard matrixes such as (Cr1-xAlx)N is required, in order to increase the life time of coated tools under high tribological loads in dry cold forging. In the presented work, self-lubricating coatings in system (Cr1-xAlx)N MoSy with two different nitrogen contents for the application in dry cold forging of steel were investigated. The coatings were deposited on tool steel X155CrMoV12 (DIN 1.2379, AISI D2) using a hybrid technology, consisting of direct current and high power pulse magnetron sputtering dcMS/HPPMS in an industrial scale PVD unit. In order to investigate the distribution of coating thickness s along the length of complex-shaped forging tools Ltool, an experimental tool was designed and the aspect ratio s/Ltool was determined. The coating and substrate/coating compound properties were investigated. Tribological model tests were conducted using a pin-on-disc (PoD) tribometer, which simulates dry contacts in cold forging. The analyses were performed using pins made of 16MnCr5 (DIN 1.7131, AISI 5115) and included the determination of friction coefficients. Furthermore, contact region was studied by Raman spectroscopy after the tribological tests. Based on the results, the coating system (Cr1-xAlx)N MoSy exhibits a high potential for application in dry cold forging of steel. Moreover, an increase of nitrogen content in the coatings leads to an enhancement of adhesion strength between substrate and coating and the tribological behavior of the coated tools against 1.7131
Schwingfestigkeit laserauftraggeschweißter legierter Stähle
Get PDFLaser cladding is an established, sustainable and value-adding process. So far, merely statically loaded parts profit from its application as its impact on part properties under cyclic loads was not investigated systematically, yet. It is shown that residual stresses are the driving factor determining fatigue strength. These can neither be manipulated by process parameters nor by thermal post-processing so as to influencing fatigue strength significantly positive. Either the material combination is to be chosen so that thermal expansion of the substrate material is higher than of the coating or mechanical post-processing, i.e. by deep rolling is to be applied. Compressive residual stresses are to be induced to the interface of substrate and coating as this area is most prone to failure. Within the representative example of laser cladding of high and low alloy steel with a cobalt-based alloy higher fatigue strength could be realised as for the latter in as-cast condition
Investitionen in die Qualität und ihre Auswirkungen auf den Unternehmenserfolg ambulanter Pflegedienste
Get PDFOver the past decade, long-term care providers have had to face mounting requirements in terms of quality and cost-effectiveness as well as several new legislative regulations to improve patient-centred care. The introduction of public quality reports was one major step towards measuring the quality of care. To meet the quality criteria, long-term care providers have enhanced their efforts in quality improvement. Though already subject to strict budgetary constraints, the care services have had to finance these improvements without any additional remuneration. In this context, the study looks into level and scope of investments made by providers in quality improvement. It examines whether long-term care providers have measurably benefited from such quality investments. In the light of a burgeoning need for care coupled with a growing shortage of qualified carers, company growth alone is seen as a sign of success. The thesis comprises three studies focusing on these questions from different angles. First, data from the Federal Office of Statistics are analyzed in terms of the relation between the proportion of trained staff and company growth. Second, quality reports are examined with respect to the correlation between good grades and an increasing number of people in need of care. In a third step, a survey of long-term care providers was conducted to obtain more information about quality management representatives and quality investments. Multivariate regression analysis shows little correlation between quality investment and company growth. No relation could be found between quality investments and customer growth. But the results show significant correlations in terms of attracting professional staff. There is clear evidence that excellent public quality reports and a greater involvement of staff in quality improvement activities enhance a companya s success. Therefore, after the Second Bill to Strengthen Long-Term Care, it is essential to develop measures enabling better pay for nurses and to secure the proportion of trained staff
Qualitätsorientiertes Artikelstammdatenmanagement und dessen wirtschaftliche Effekte auf die Prozesskette aus Sicht eines globalen Artikelstammdatenpools
Get PDFIn essence, this dissertation is the proof that both the quality of item master data and the management of this data in daily work processes on both retailer and supplier side arena t sufficiently considered. In order to investigate this aspect, the first step is to lay down the theoretical foundations for the terms data quality, item master data and their management. It also classifies the benefits of a better data quality such as cost savings, faster flow of goods and increased customer satisfaction from the supplier perspective with respect to the use of data in retail trade. Furthermore, it takes the difficulty of capturing such benefits in terms of concrete profitability into account. In the second step, the item master data quality will be defined through six distinct data quality dimensions and operationalized for usage in the field. These are correctness, consistency, completeness, standard conformity, trustworthiness and authorized accessibility. All six dimensions were measured and evaluated in eleven supplier case studies of the German consumer goods market, all customers of the item master data pool 1WorldSync, in the years 2014 to 2015. Additionally, two dimensions, correctness and trustworthiness, were measured in the sense of a data crunch on the data pool side and in five retailers of the German food and drugstore trade. The main focus of the data quality measurement is therefore on the interoperable item master data exchange via the Global Data Synchronization Network (GDSN) as standard of Global Standard 1 (GS1). The case studies were evaluated in a multi-case design. The results of the individual cases are compared in terms of pattern recognition. In addition to a comparison between the achieved versus self-assessed data quality of the suppliers, the extent of the Item Master Data Quality Management (IMDQM) related to the areas of knowledge and organization - determined with the help of a scoring model at the sup-pliers -were measured. Based on the findings of the case studies and the consistency check recommendations for the optimization of the data quality for suppliers, retailers and their used data pool were derived. The data crunch was aimed at gathering information on how data quality initiatives on the supplier side affect the data pool and retailers. This is achieved by investigating if and how supplier data changes on the way to a retailera s IT system. The critical debate and evaluation related to the economic effects of an improved data quality is also part of the results. The discussion focuses on the extent to which it is worth investing in improved data quality for suppliers. An attempt is made to answer the question whether the improvement across the value chain really pays off. This dissertation is aimed at professionals in the scientific and business communities, who deal with the topics item master data and their quality optimization
Verbesserung der Lebensqualität und Gesundheit durch Versorgungsoptimierung mittels einer intensiveren Integration und Kooperation von Zahnmedizin und Medizin
Get PDFThe following dissertation illustrates, from various professional perspectives, how our public health care could be optimised through more intensive cooperation and integration of dentistry and medicine. The foundation and starting point for this work is presented on the basis of relevant literature, from a public health care perspective. In addition to the theoretical literature elaboration, qualitative, guided expert interviews were also conducted. The methodical evaluation of these discussions took place, following the qualitative content analysis, according to Mayring, using the evaluation MAXQDA 12 programme. The results of the expert interviews provide an insight into the organisation and handling of the individual professions. Six dentists, six general practitioners, six representatives of care facilities, six institutions and six diabetes patients were interviewed. The results of the expert surveys provide an exciting impression of their respective daily work, from a large number of different perspectives. In addition to these anticipated results, experiences could also be gathered, which had not been considered at the outset. This thesis represents interdisciplinary findings and enriches the basis for discussion of possible action that could be taken within health services research on the above-mentioned topic. The dissertation is of interest to readers from the public health care sector as well as those from the dental, medical and nursing sectors
How to Classify the Chinese Welfare State
Get PDFDespite its remarkable socio-economic transformations, very little has been done to classify China from a welfare-typological perspective. This scholarly project represents a case study of China in which the contemporary Chinese welfare state is analyzed by means of key welfare-regime indicators and analytical criteria in accordance with Esping-Andersen's theoretical framework (1990) for his Three Worlds typology. Analyzing China's welfare system raises interesting questions about how the Chinese welfare state evolves in the transition from a socialist to an open-market economy and, what is more, about what kind of welfare regime is emerging in China. The welfare typological analysis of the Chinese welfare state identified that the contemporary Chinese welfare state is most likely a hybrid of the Three Worlds: liberal in the sphere of healthcare, conservative-corporatist in the sphere of social insurance and social-democratic in the sphere of universal population coverage - albeit with Chinese deficiencies. Prospects of the Chinese welfare system remain an issue of great interest. The findings of this thesis offer a fertile ground for further comparative welfare state studies
