Hardware design of a multiconverter for hybrid vehicle applications

Hybridiajoneuvosovellukset vaativat usein sekä korkea- että matalajännitejärjestelmän. Korkeajännitejärjestelmä sisältää yleensä energiavaraston, joka on joko superkondansaattori tai korkeajänniteakusto, dieselgeneraattorin tai range extenderin ja ajokäytön. Korkeajännitejärjestelmään liitetään usein myös erilaisia apukäyttöjä kuten kompressoreita ja hydraulipumppuja. Matalajännitejärjelmä koostuu yleensä ohjausyksiköistä, ajovaloista, yms. laitteista. Perinteisesti matalajännitejärjestelmää on syötetty dieselmoottorin laturista, mutta korkeajännitejärjestelmien myötä DC/DC-hakkurin käyttäminen korkea- ja matalajännitejärjestelmien välillä on herättänyt kiinnostusta, koska tällöin laturin voisi poistaa ja matalajänniteakustoa pienentää. Tässä työssä kuvatun monilähöisen tehonmuokkaimen invertterisilta soveltuu apukäyttöjen ajamiseen, ja erotettu DC/DC-hakkuri matalajännitejärjestelmän syöttämiseen. Tässä työssä käydään läpi edellä mainitun tehonmuokkaimen suunnittelu, keskittyen eritoten laitteen korkeajänniteosien mitoitukseen ja termiseen suunniteluun. DC/DC-hakkurin osalta perinteisiä piistä valmistettuja IGBT transistoreja vertaillaan piikarbidi MOSFET transistoreihin. Lämpömallilaskujen paikkaansapitävyyttä tutkitaan suorittamalla prototyyppilaitteelle hyötysuhdemittaus, jonka tuloksia verrataan laskettuihin tuloksiin. Lämpömallin parannusmahdollisuuksia käsitellään myös hyötysuhdemittauksen tulosten perusteella.

Genetic purity certificate in seeds of hybrid maize using molecular markers

One of the main features that confer high quality to the seed is its genetic purity, in which one of the major causes of contamination is the self-pollination of the female parent. Up to date, there is no accurate and fast methods for detecting such contamination. Thus, this work was carried out to certify the genetic purity in seeds of hybrid maize using different biochemical and DNA-based markers. Two single-cross hybrids and their parental lines derived from the maize breeding program at UFLA were evaluated by isoenzymatic pattern of alcohol dehydrogenase (ADH), esterase (EST), acid phosphatase (ACP), glutamate-oxaloacetate transaminase (GOT), malate dehydrogenase (MDH), isocitrate dehydrogenase (IDH), phosphoglucomutase (PGM), 6-phosphoglucomate dehydrogenase (PGDH), catalase (CAT) and ß-glucosidade (ßGLU) and by microsatellites markers. The enzymatic systems that were able to distinguish the hybrids from their parental line were the catalase, the isocitrate dehydrogenase and the esterase. The esterase showed a Mendelian segregation pattern for UFLA 8/3 hybrid, that enables a safer genetic purity certificate. Microsatellites were able to differentiate the hybrid lines and the respective parental lines. Moreover, this technique was fast, precise and without environment effects. For microsatellites, the amplification pattern was identical when young leaves or seeds were used as DNA source. The possibility of using seeds as DNA source would accelerate and facilitate the role process of the genetic purity analysis.

Real-time simulation of multibody systems with applications for working mobile vehicles

This dissertation describes an approach for developing a real-time simulation for working mobile vehicles based on multibody modeling. The use of multibody modeling allows comprehensive description of the constrained motion of the mechanical systems involved and permits real-time solving of the equations of motion. By carefully selecting the multibody formulation method to be used, it is possible to increase the accuracy of the multibody model while at the same time solving equations of motion in real-time. In this study, a multibody procedure based on semi-recursive and augmented Lagrangian methods for real-time dynamic simulation application is studied in detail. In the semirecursive approach, a velocity transformation matrix is introduced to describe the dependent coordinates into relative (joint) coordinates, which reduces the size of the generalized coordinates. The augmented Lagrangian method is based on usage of global coordinates and, in that method, constraints are accounted using an iterative process. A multibody system can be modelled as either rigid or flexible bodies. When using flexible bodies, the system can be described using a floating frame of reference formulation. In this method, the deformation mode needed can be obtained from the finite element model. As the finite element model typically involves large number of degrees of freedom, reduced number of deformation modes can be obtained by employing model order reduction method such as Guyan reduction, Craig-Bampton method and Krylov subspace as shown in this study The constrained motion of the working mobile vehicles is actuated by the force from the hydraulic actuator. In this study, the hydraulic system is modeled using lumped fluid theory, in which the hydraulic circuit is divided into volumes. In this approach, the pressure wave propagation in the hoses and pipes is neglected. The contact modeling is divided into two stages: contact detection and contact response. Contact detection determines when and where the contact occurs, and contact response provides the force acting at the collision point. The friction between tire and ground is modelled using the LuGre friction model, which describes the frictional force between two surfaces. Typically, the equations of motion are solved in the full matrices format, where the sparsity of the matrices is not considered. Increasing the number of bodies and constraint equations leads to the system matrices becoming large and sparse in structure. To increase the computational efficiency, a technique for solution of sparse matrices is proposed in this dissertation and its implementation demonstrated. To assess the computing efficiency, augmented Lagrangian and semi-recursive methods are implemented employing a sparse matrix technique. From the numerical example, the results show that the proposed approach is applicable and produced appropriate results within the real-time period.

Finding Methods for Recognizing and Classifying Spare Part Criticality – Case Full Deposit Stripping Machines

The aim of this Master’s thesis is to find a method for classifying spare part criticality in the case company. Several approaches exist for criticality classification of spare parts. The practical problem in this thesis is the lack of a generic analysis method for classifying spare parts of proprietary equipment of the case company. In order to find a classification method, a literature review of various analysis methods is required. The requirements of the case company also have to be recognized. This is achieved by consulting professionals in the company. The literature review states that the analytic hierarchy process (AHP) combined with decision tree models is a common method for classifying spare parts in academic literature. Most of the literature discusses spare part criticality in stock holding perspective. This is relevant perspective also for a customer orientated original equipment manufacturer (OEM), as the case company. A decision tree model is developed for classifying spare parts. The decision tree classifies spare parts into five criticality classes according to five criteria. The criteria are: safety risk, availability risk, functional criticality, predictability of failure and probability of failure. The criticality classes describe the level of criticality from non-critical to highly critical. The method is verified for classifying spare parts of a full deposit stripping machine. The classification can be utilized as a generic model for recognizing critical spare parts of other similar equipment, according to which spare part recommendations can be created. Purchase price of an item and equipment criticality were found to have no effect on spare part criticality in this context. Decision tree is recognized as the most suitable method for classifying spare part criticality in the company.

Evaluation of the Efficiency of Line-Start Permanent-Magnet Machines as a Function of the Operating Temperature

The standard squirrel-cage induction machine has nearly reached its maximum efficiency. In order to further increase the energy efficiency of electrical machines, the use of permanent magnets in combination with the robust design and the line start capability of the induction machine is extensively investigated. Many experimental designs have been suggested in literature, but recently, these line-start permanent-magnet machines (LSPMMs) have become off-the-shelf products available in a power range up to 7.5 kW. The permanent magnet flux density is a function of the operating temperature. Consequently, the temperature will affect almost every electrical quantity of the machine, including current, torque, and efficiency. In this paper, the efficiency of an off-the-shelf 4-kW three-phase LSPMM is evaluated as a function of the temperature by both finite-element modeling and by practical measurements. In order to obtain stator, rotor, and permanent magnet temperatures, lumped thermal modeling is used.

Financial working capital - management and measurement

Unexpected changes in cash flow have started to occur more frequently after the financial crisis. The capital structures of companies have also changed, and financial flexibility as well as flexible asset management have therefore become more important. This thesis aims at presenting financial working capital management, a part of flexible asset management, as a possibility to gain financial flexibility and survive the changes. This thesis operates in the interface of corporate finance, strategic management and management accounting, and it has two main objectives: to examine financial working capital management and to develop measures of financial working capital. The research in this thesis has been conducted using archival research and design science. Qualitative comparative analysis and model building are used to formulate tools and strategies for financial working capital management. The tools are tested with simulations, case studies and statistical analysis. The empirical data is collected from companies listed in the Helsinki Stock Exchange. The results of this thesis indicate that there are several possible financial working capital management strategies. FOCAL matrix is created in the thesis to assist in the selection of a strategy. The results also imply that profitability can be improved by reducing financial working capital, which creates a need to change the financial working capital management strategy. Financial flow cycle, and its modification, is developed in this thesis to measure financial working capital. Financial working capital as a concept is presented in this thesis with an orientation towards the management view. New dimensions have also been produced to financial management and working capital management, while providing a holistic approach to financial flexibility. Financial working capital management strategies are presented to managers and practical tools are provided for decision-making.

Design and implementation of machine vision system for the mobile assembly robot

The review of intelligent machines shows that the demand for new ways of helping people in perception of the real world is becoming higher and higher every year. This thesis provides information about design and implementation of machine vision for mobile assembly robot. The work has been done as a part of LUT project in Laboratory of Intelligent Machines. The aim of this work is to create a working vision system. The qualitative and quantitative research were done to complete this task. In the first part, the author presents the theoretical background of such things as digital camera work principles, wireless transmission basics, creation of live stream, methods used for pattern recognition. Formulas, dependencies and previous research related to the topic are shown. In the second part, the equipment used for the project is described. There is information about the brands, models, capabilities and also requirements needed for implementation. Although, the author gives a description of LabVIEW software, its add-ons and OpenCV which are used in the project. Furthermore, one can find results in further section of considered thesis. They mainly represented by screenshots from cameras, working station and photos of the system. The key result of this thesis is vision system created for the needs of mobile assembly robot. Therefore, it is possible to see graphically what was done on examples. Future research in this field includes optimization of the pattern recognition algorithm. This will give less response time for recognizing objects. Presented by author system can be used also for further activities which include artificial intelligence usage.

Factors Affecting Runnability of Press Forming Equipment

The growth of the food packaging industry has raised more interest in bio-based fibre packing. The use of petroleum based packages is unfriendly to the environment while bio-based is a sustainable option for food packing. In this Master Thesis the aim was to discover how the press forming machineries runnability is affected by parameters of the press and how it also affects formability of paperboard trays. Familiarisation of the working operation parameters was done with the KAMA ST 75 flat-bed die cutting machine and the VP3-70 mould press. Some small test runs of moulding trays where done to get acquainted to the adjustment parameters of the machines. Literature study was done on how paperboards physical properties react to the forces applied during press forming. The study of what kind of defects to the paperboard tray might occur during forming process and the causes for these defects. Also how the parameters of the press forming machine affects formability of the tray. Maintenance procedures was done to the press forming machine to enhance the reliably of production process. Tool alignment measurement was done to determine proper alignment. Laboratory test of the physical properties of the test material was done to find any connection to how the test material performs in press forming. An evaluation criterion was made to evaluate the dimensions and defects of the tray. From the test result a conclusion can be drawn on how the parameters of the press forming process affect the paperboard material. Based on the results the adjustment the parameters of moulding machines to the mechanical properties of paperboard it is possible to produce high quality fibre passed trays for the food packaging industry.

Design and Material Selection of High-Speed Rotating Electrical Machines

The increasing emphasis on energy efficiency is starting to yield results in the reduction in greenhouse gas emissions; however, the effort is still far from sufficient. Therefore, new technical solutions that will enhance the efficiency of power generation systems are required to maintain the sustainable growth rate, without spoiling the environment. A reduction in greenhouse gas emissions is only possible with new low-carbon technologies, which enable high efficiencies. The role of the rotating electrical machine development is significant in the reduction of global emissions. A high proportion of the produced and consumed electrical energy is related to electrical machines. One of the technical solutions that enables high system efficiency on both the energy production and consumption sides is high-speed electrical machines. This type of electrical machines has a high system overall efficiency, a small footprint, and a high power density compared with conventional machines. Therefore, high-speed electrical machines are favoured by the manufacturers producing, for example, microturbines, compressors, gas compression applications, and air blowers. High-speed machine technology is challenging from the design point of view, and a lot of research is in progress both in academia and industry regarding the solution development. The solid technical basis is of importance in order to make an impact in the industry considering the climate change. This work describes the multidisciplinary design principles and material development in high-speed electrical machines. First, high-speed permanent magnet synchronous machines with six slots, two poles, and tooth-coil windings are discussed in this doctoral dissertation. These machines have unique features, which help in solving rotordynamic problems and reducing the manufacturing costs. Second, the materials for the high-speed machines are discussed in this work. The materials are among the key limiting factors in electrical machines, and to overcome this limit, an in-depth analysis of the material properties and behavior is required. Moreover, high-speed machines are sometimes operating in a harsh environment because they need to be as close as possible to the rotating tool and fully exploit their advantages. This sets extra requirements for the materials applied.