Electric machines are widely used in for instance the automotive industry in electric vehicles and in wind turbines. The electrical machines have mechanical bearings as an integral part used to transmit power and load. In addition, the main function includes reducing friction between interacting surfaces. However, it is one of the most failing machine elements in these machines. To improve operational sustainability and reduce maintenance costs, understanding bearing failure mechanisms under electrical influence is important. One of the main reasons of bearing failure is linked to high frequency power switches typically used to enhance electric machines’ efficiency. The increase in switching rate induces more frequent common mode voltage fluctuations making the system vulnerable to bearing currents. A small voltage difference of a few ten volts can induce significant electric stress on the bearing depending on the lubricant film thickness and related tribological parameters. The electric charge build-up leads to electric current conduction (arc discharge which happens when the voltage exceeds the breakdown voltage) ultimately damaging the bearing. There are different mitigation strategies which are used to restrict bearing currents through grounding or using completely insulative bearings such as ceramic ones. However, at the moment, there are no satisfactory solutions and there is a need for efficient and economical solutions to the problem. On the other hand, various filters are used to reduce the amplitude and its frequency of bearing currents, but they only partly solve the problem. Similarly, the insulative surface coatings provides high electrical resistance but start acting as capacitors. At a sufficiently high voltage difference, the current passes through the system. Therefore, mitigation strategies are still being explored to improve system performance and service-life. To understand the bearing discharge activity and electrical breakdowns, an electrified ball bearing rig is developed with the ability of testing different electrical properties of lubricants and running conditions. To be able to characterize the electrical properties of a bearing, two electrical circuits are designed. Experimental tests are carried out with PAO-15 and an electrical conductivity-enhanced PAO-15/P-SiSO lubricant with addition of ionic liquids. The influence of different tribological parameters such as rotational speed and viscosity are compared with respect to discharge activity. In addition, two fully formulated experimental oils are compared and evaluated in terms of their electrical performance. The bearing is found to be in different states showing electric-field dependent insulation breakdown ranging from resistive to resistive-capacitive to capacitive states. The electric characterization shows a difference between the boundary, mixed and full film lubrication regimes. Conclusively, the electrical behavior of a mechanical bearing is characterized experimentally to understand discharge problem and roadmap solution opportunities.

Major drivetrain components of the Epiroc machines like axles, gearboxes, transmission, torqueconverter, clutch, and bearings are critical components which are focused upon in this thesis. Failure of these major component results in breakdown of the vehicle and if early fault detection is not existing, then this causes engineers and technicians to spend a substantial amount of time to identify the root cause of the failure. Due to this, the machine stands still until the problem is identified and repaired creating a negative impact on customer satisfaction. Thus, failure of these components results in costly downtime. Ways of improving the uptime of the machine have been an ongoing discussion due to costly downtime subjected to component failure. To improve uptime, reduce MTTR, and create acompetitive edge, a drivetrain sensor system is suggested to implement in this thesis that will monitor real-time operating data from these drivetrain components. In this way, the health of the drivetrain will be continuously monitored and if there is any degrade planned maintenance can be scheduled well in advance and spare parts inventory can be managed more efficiently. In addition, this will generate competitiveness for Epiroc products in the market. Epiroc being in competitive business, continuously aims to improve its products and services to satisfy customer needs, improve total cost of ownership, life cycle cost, and increase sales and profit. Epiroc is a leading productivity partner for the mining, infrastructure, and natural resource industries. It develops and manufactures innovative drilling rigs, quarrying, and construction equipment with state-of-the-art technology and provides world-class service and consumables. / Epiroc bedriver konkurenskraftiv verksamhet. Målet är att kontinuerligt förbättra sina produkter och tjänster för att tillgodose kundernas behov, förbättra den totala ägandekostnaden, livscykelkostnaden samt att öka försäljningen och vinsten. Epiroc är en ledandeproduktivitetspartner för gruv-, infrastruktur- och naturresursindustrin. Det utvecklar och tillverkar innovativa borriggar, stenbrott- och byggutrustning med toppmodern teknik och tillhandahåller service och förbrukningsvaror i världsklass. Att förbättra maskinens drifttid har alltid varit en kontinuerlig diskussion på grund av kostsamma stopp som orsakats av komponentfel. Om det uppstår större komponentfel som leder till att fordonet går sönder ochtidig feldetektering inte existerar, leder detta till att ingenjörer och tekniker måste spendera mycket tid på att identifiera orsaken till felet. På grund av detta står maskinen stilla tills problemet identifieras och repareras vilket skapar en negativ inverkan på kundnöjdheten. Viktiga drivkomponenter som axlar, växellådor, transmission, vridmomentomvandlare, koppling och lager är exempel på sådana kritiska komponenter vars fel resulterar i kostnadstopp. För att förbättra drifttiden, minska MTTR och skapa en konkurrensfördel för Epiroc-produkter, presenteras ett drivsystemsensorsystem i denna rapport som möjliggör övervakning av realtidsdata från dessa drivlinekomponenter. På detta sätt övervakas drivlinanshälsa kontinuerligt och om det uppstår någon försämring kan planerat underhåll planeras i godtid och reservdelslager hanteras effektivare. Dessutom kommer detta att skapa konkurrenskraft för Epiroc-produkter på marknaden.

This study presents the design and optimization of a test rig tailored for upcoming wind turbine design applications. Initial decisions were made regarding component selection, focusing on a gearbox, electric motor, and motor controller. Requirements included continuous power output of 300 kW from the electric motor and the gearbox's ability to handle specified torque and reduce input speed to match the structural limitations. Key challenges revolved around gearbox design and performance, necessitating a right-angle configuration for converting horizontal to vertical torque efficiently. To meet the rotational speed requirements, a 30 to 1 ratio gearbox was selected, ensuring compatibility with the maximum structural rotational speed of 50 revolutions per minute. The electric motor, pivotal in the drivetrain, was chosen based on a balance between economic viability and rotational speed, resulting in a four-pole motor configuration. Coupling mechanisms were employed to connect the motor and gearbox, facilitating energy transfer between shafts. A motor controller was integrated to regulate current flow, voltage application, and frequency modulation, enhancing operational control and adaptability to specific requirements. Radial ball bearings were selected to minimize energy expenditure during rotation, particularly due to downward compressive forces. The test rig setup, situated indoors on a concrete floor, mandated a metal plate foundation to ease component attachment without drilling into the floor. Data simulations were conducted to determine bolt specifications capable of withstanding motor-induced forces. Furthermore, collaboration with industry experts facilitated component selection and quotation analysis, ensuring an optimized drivetrain solution meeting both technical and economic criteria. This research contributes to the advancement of wind turbine design testing methodologies, providing insights into component selection, integration, and optimization for enhanced performance and reliability.

年々増大するエンジントルク変動を低減するために広角トーショナルダンパの適用例が増してきているが，それらに起因する非線形振動のメカニズムや振動低減のための研究例は少ない．本論文の目的は，これらに関する非線形振動の解明および改善，および精度と計算コストを両立するモデルの開発である．そのため，実験検証に基づくモデルを開発し，非線形振動を大幅に削減する手法を検討した．さらに，計算コストを増加させることなく解析精度を改善する不等ピッチ離散化モデル化手法を検討した． / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

<p>The vehicle industry has an endless appetite to get better. Often, this appetite is justified by the need of the hour. In the agricultural space, this translates to improving agricultural productivity in the face of population growth, reduced arable land and shortage of skilled farm labor. As for torsional vibrations, which have been around ever since the wheel was invented, the problem gets redefined with new regulations demanding new powertrains with improved fuel efficiency and reduced emissions.</p><p>A solution to the agriculture problem, involves efficiently automating the harvesting process.The first section of this thesis covers the ‘Auto-Unload’ where the goal of automation is achieved. This was done by building a simulation framework that was used to develop and synthesize the ‘AutoUnload’ controller. This controller was later deployed on a combine and a successful unloading on-the-go was demonstrated with a combine, tractor, and tractor-driven grain cart.</p><p>The solution to the second problem about drivetrain vibrations involved deriving a mathematical model for simulating the powertrain of a medium-duty truck. This was done to confirm resonance seen during testing done on a chassis dynamometer. The consequent control strategy to mitigate undesired vibration was to move the torque excitation away from the natural frequency of the system. This was achieved by a ‘gear-shifting’ algorithm. Comparison between on-road tests with and without the ‘gear-shifting’ algorithm showed that such a control strategy can effectively eliminate resonance. The solution methodology developed in this work is robust and transferable to higher engine torques and harvest speeds.</p>

The VCOST budgeting tool uses a drive cycle simulator to improve fuel economy predictions for vehicle fleets. This drive cycle simulator needs to predict the efficiency of various components of the vehicle's powertrain including any differentials. Existing differential efficiency models either lack accuracy over the operating conditions considered or require too great an investment. A fundamental model for differential efficiency is a cost-effective solution for predicting the odd behaviors unique to a differential. The differential efficiency model itself combines the torque balance equation and the Navier-Stokes equations with models for gear pair, bearing, and seal efficiencies under a set of appropriate assumptions. Comparison of the model with existing data has shown that observable trends in differential efficiency are reproducible in some cases to within 10% of the accepted efficiency value over a range of torques and speeds that represents the operating conditions of the differential. Though the model is generally an improvement over existing curve fits, the potential exists for further improvement to the accuracy of the model. When the model performs correctly, it represents an immense savings over collecting data with comparable accuracy. / text

Predložená doktorandská dizertačná práca (ďalej len práca) sa zaoberá rozsiahlou analýzou valčekového hydrogenerátora s premenlivým geometrickým objemom a predikciou výkonových úspor dosiahnutých aplikáciou navrhnutého valčekového hydrogenerátora s premenlivým geometrickým objemom v hydrostatickom pohone vybraných mobilných pracovných strojov. Teoretický rozbor princípov fungovania valčekového hydrogenerátora a teória jednorozmerného simulačného modelu sú popísané v prvej časti práce. Na základe odvodenej teórie je vytvorený simulačný model, ktorý je vhodný na predikciu priebehu tlaku v komorách valčekového hydrogenerátora, síl pôsobiacich na valček a na predikciu vnútorných únikov vzniknutých skratovaním rozvodovej dosky, ktoré majú priamy vplyv na objemovú účinnosť valčekového hydrogenerátora. Simulačný model bol úspešne použitý pre optimalizáciu rozvodových dosiek valčekového hydrogenerátora a vhodnosť simulačného modelu potvrdili následné merania Práca obsahuje aj analýzu síl pôsobiacich na vodiaci prstenec, ktorej výsledky boli taktiež potvrdené meraním. Analýza týchto síl môže vylepšiť v konečnom dôsledku parametre budúcich tlakových regulácii. Práca ďalej obsahuje základné porovnanie použitých tlakových regulácii. Všetky uskutočnené merania potvrdili, že valčekový hydrogenerátor s premenlivým geometrickým objemom s testovanými tlakovými reguláciami je schopný úspešne pracovať v hydrostatickej prevodovke. Druhá časť práce analyzuje potenciál výkonových úspor valčekového hydrogenerátora s premenlivým geometrickým objemom pre dve mobilné aplikácie - teleskopický nakladač s hmotnosťou 9 ton a kombajn s hmotnosťou 20 ton. Analýza vyžaduje jednorozmerný simulačný model hydrostatického pohonu s teplotnou predikciou hydrostatickej prevodovky. Dva rozdielne koncepty variabilného doplňovacieho systému hydrostatickej prevodovky sú porovnané so štandardným doplňovacím systémom pre pracovný a transportný režim oboch vybraných typov vozidiel. Simulácia pohonu vozidla s valčekovým hydrogenerátorom s premenlivým geometrickým objemom vo funkcii doplňovacieho hydrogenerátora a obtokovou clonou potvrdili vyššie úspory iba v prípadoch, kedy rýchlosť doplňovacieho hydrogenerátora bola výrazne vyššia a prietok cez obtokovú clonu do skrine hlavného hydrogenerátora zabezpečil dostatočné chladenie. Najvyššie výkonové úspory boli dosiahnuté s premenlivým preplachovacím systémom, ktorého prietok sa menil podľa požiadaviek hydrostatickej prevodovky. Záver druhej časti práce sa zaoberá metodikou dimenzovania veľkosti doplňovacieho hydrogenerátora.

When developing three-phase drives for Electric Vehicles (EVs), it is essential to verify the controller design. This will help in understanding how fast and accurately the torque of the motor can be controlled. In order to do this, it is always better to test the controller using the software version of the motor or vehicle drivetrain than using actual hardware as it could lead to component damage when replicating extreme physical behavior. In this thesis, plant modelling of Permanent Magnet Synchronous Machine (PMSM) and vehicle drivetrain in MATLAB/Simulink for Model Based Design (MBD) is presented. MBD is an effective method for controller design that, if adopted can lead to cost savings of 25%-30% and time savings of 35%-40% (according to a global study by Altran Technologies, the chair of software and systems engineering and the chair of Information Management of the University of Technology in Munich) [1]. The PMSM plant models take effects like magnetic saturation, cross- coupling, spatial harmonics and temperature into account. Two PMSM models in d-q frame based on flux and inductance principles were implemented. Flux, torque maps from Finite Element Analysis (FEA) and apparent inductance from datasheets were used as inputs to the flux- and inductance-based models, respectively. The FEA of PMSM was done using COMSOL Multiphysics. The PMSM model results were compared with corresponding FEA simulated results for verification. A comparison of these PMSM models with conventional low fidelity models has also been done to highlight the impact of inclusion of temperature and spatial harmonics. These motor models can be combined with an inverter plant model and a controller can be developed for the complete model. Low frequency oscillations of drivetrain in EVs lead to vibrations which can cause discomfort and torsional stresses. In order to control these oscillations, an active oscillation damping controller can be implemented. For implementation of this control, a three-mass mechanical plant model of drivetrain with an ABS (Anti-lock Braking System) wheel speed sensor has been developed in this thesis. Analysis of the model transfer function to obtain the pole zero maps was performed. This was used to observe and verify presence of low frequency oscillations in the drivetrain. In order to include the effects of ABS wheel speed sensor and CAN communication, a model was developed for the sensor. / Testning av regulatorernas inställningar med hänsyn till snabbhet och noggrannhet i momentreglering är avgörande i trefasiga drivsystem för elektriska fordon. Oftast är det bättre att simulera i stället för att utföra experimentella tester där komponenter kan skadas på grund av fysisk stress. Detta kallas för Model Based Design (MBD). MBD är an effektiv metod för utformningen av styrningen som kan leda till kostnadsbesparingar på 25%-30% och tidsbesparingar på 35%-40% enligt en studie från Altran Technologies i samarbete med Tekniska universitet i München, TUM. Detta examensarbete behandlar en modell för en synkronmaskin med permanentmagneter (PMSM) samt en modell för drivlinan utvecklad i Matlab/Simulink för MBD. PMSMs modellen inkluderar magnetisk mättnad och tvärkoppling, MMF övervågor och temperatur. Två PMSM modeller har utvecklats. Den första baseras på magnetiskt flöde som erhålls från finita element beräkningar i COMSOL Multiphysics medan den andra bygger på induktanser givna från datablad. En jämförelse av dessa PMSM-modeller med konventionella low fidelity-modeller har också gjorts för att illustrera påverkan temperaturberoende och MMF övervågor. Modellerna kan kombineras med en växelriktarmodell för att utveckla en hel styrenhet. Lågfrekventa oscillationer i drivlinan leder till vibrationer som kan orsaka vridspänningar och försämra komforten i elfordonet. En aktiv dämpningsregulator kan implementeras för att kontrollera spänningarna men en mekanisk drivlinemodell med tre massor och en ABS (anti-lock braking system) hastighetssensor behövs. Den mekaniska modellen har implementerats och analyserats även beaktande en modell för en CAN kommunikationskanal. Oscillationer med låg frekvens kunde observeras i modellen.