This thesis investigates and determines the design considerations to be addressed when designing switched reluctance machines (SRMs) operating at high surface-speeds and high-loads. A new method is introduced to the traditional machine design procedure that captures all of the mechanical, thermal and electro-magnetic considerations for such electric machines. This method is applicable to any motor design; however, is most suitable for machines with rotors that sustain mechanical stresses near the rotor core material limits. The method begins by using common application specifications to identify the maximum diameter and length of a rotor through a series of structural analyses. Maximizing rotor diameter and axial length enables designers to evaluate a machine's theoretical mechanical and electro-magnetic performance limits. The design method is structured such that the designer must use theoretical limits as a constraint for assessing future design decisions which ultimately influence machine cost and performance. The proposed design method is applied to a case study example typical of a large electric vehicle traction machine, a 22,000rpm, 150 kW switched reluctance machine, while attempting to adhere with design practices commensurate with automotive mass manufacturing. To achieve this, a parallel connected 12/8 pole topology was finally developed. The thesis research suggest that a 440 MPa yield strength, 0.27mm thickness lamination with 30 turn stator coils is sufficient to meet the specification requirements within a prescribed power electronic converter voltage and current constraints, while satisfying material mechanical and thermal considerations. Detailed analysis of AC effects, performance characteristics, thermodynamics, noise and vibration is presented to simultaneously demonstrate and validate the proposed machine design and design method. / Thesis / Doctor of Philosophy (PhD)

Digital hydraulics is one of promising technologies having a huge potential to significantly improve energy efficiency in the fluid power industry. In this paper, we present a digital hydraulics solution for mobile market with a large ammount of energy usage by hydraulic components and systems. Specifically, a novel hydraulic architecture, Multiplex Digital Valve (MDV) system that employs digital valves to meet multiple service pressure/flow requirement in off highway vehicles, is introduced. With MDV being integrated in an execavator, signficant hydraulic power saving have been validated compared to the baseline machine with the negative flow control (NFC) architecture. In addition, considering noise is still a critical hurdle for digital hydraulics to be adoped, we develop several noise reduction methods that have been evaluated in simulation environment and implemented in the above MDV. The sound pressure measured from the retrofitted MDV solution with the NVH treatment in the excavator has been improved signficantly over the untreated system such that it is nearly comparable to the baseline machine. The paper also briefly presents the sound quality study for better understanding of human perception and acceptance to nonconventional sound.

Hot spotting of automotive disc brakes is an undesired thermal localisation phenomenon, which is a challenge for numerical modelling in terms of both accuracy and efficiency especially for complex disc geometry. In this research, the aim was to develop a computationally efficient finite element (FE) approach for 2-piece pin-mounted ventilated disc hot spot prediction with acceptable accuracy enabling parametric studies to contribute to the knowledge of the complex mechanisms. A time reduction strategy for the simulations was established by incorporating an axisymmetric brake pad assumption with material scaling factor and the friction characteristics were defined by a user-subroutine. The computing accuracy and efficiency of this method were then verified by comparing with traditional FE models. 2D in-plane, 2D out-of-plane, and 3D models were performed to investigate the effects of ventilated disc hot spotting, radial hot spot/band migration, and hot spotting of realistic complex disc geometry respectively. Both 2D and 3D results were validated using experimental results based on a laboratory dynamometer and showed good correlation. The results suggested that adequate modelling of friction pair contact pressure distribution and the subsequent non-uniform heat generation is essential for hot spot simulation; speed was identified as the determinant for the number of hot spots, whereas hot spot temperature was determined by energy level. Furthermore, recommendations for vent design, pins, disc run-out, cooling, material selection, wear rate, pad length and loading distribution were given. Finally, hot spotting and hot band migration cause-effect chains were established based on the results and discussion.

Hot spotting of automotive disc brakes is an undesired thermal localisation phenomenon, which is a challenge for numerical modelling in terms of both accuracy and efficiency especially for complex disc geometry. In this research, the aim was to develop a computationally efficient finite element (FE) approach for 2-piece pin-mounted ventilated disc hot spot prediction with acceptable accuracy enabling parametric studies to contribute to the knowledge of the complex mechanisms. A time reduction strategy for the simulations was established by incorporating an axisymmetric brake pad assumption with material scaling factor and the friction characteristics were defined by a user-subroutine. The computing accuracy and efficiency of this method were then verified by comparing with traditional FE models. 2D in-plane, 2D out-of-plane, and 3D models were performed to investigate the effects of ventilated disc hot spotting, radial hot spot/band migration, and hot spotting of realistic complex disc geometry respectively. Both 2D and 3D results were validated using experimental results based on a laboratory dynamometer and showed good correlation. The results suggested that adequate modelling of friction pair contact pressure distribution and the subsequent non-uniform heat generation is essential for hot spot simulation; speed was identified as the determinant for the number of hot spots, whereas hot spot temperature was determined by energy level. Furthermore, recommendations for vent design, pins, disc run-out, cooling, material selection, wear rate, pad length and loading distribution were given. Finally, hot spotting and hot band migration cause-effect chains were established based on the results and discussion. / Appendix 1 and Appendix 2 are unavailable online due to copyright restrictions.

The number of electrical machines used in modern road-vehicles is continuously increasing to meet regulatory requirements regarding safety and efficiency, as well as consumer expectations in terms of comfort. For auxiliary applications, such as cooling fan or pumps, permanent-magnet synchronous machines (PMSMs) are extensively used owing to their high power density. This thesis focuses on the modelling aspects of PMSMs, with a particular focus on finite-element and reduced-order models to be used in system-level simulations. 2-D and 3-D parametric finite-element (FE) models are developed, allowing to compute irreversible demagnetization in addition to the standard quantities such as torque, back electromotive force and flux-linkages. The effects of magnet overhang on the performance of an interior PMSM is briefly discussed. Using the FE model, a reduced-order lookup-table (LUT) based electromagnetic model, having similar accuracy as FE analysis, is then developed. Coupled to a mechanical state-space representation obtained from a modal FE analysis, the final model allows to compute electromagnetic induced vibrations under pulse width modulation supply. The validation of the complete workflow is carried out on a 12slot-10pole PMSM used to drive a cooling fan. After fitting the damping coefficient in the structural state-space model, the results are in agreement with the experimental results. Due to the usage of LUTs, the simulation time is low compared to a pure FE analysis. This allows the model to be used to optimize low noise control strategies. To conclude this thesis, the parametric FE model is used in an optimization routine to minimize the cost and vibrations of the motor, whilst satisfying the working points. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Digital hydraulics is one of promising technologies having a huge potential to significantly improve energy efficiency in the fluid power industry. In this paper, we present a digital hydraulics solution for mobile market with a large ammount of energy usage by hydraulic components and systems. Specifically, a novel hydraulic architecture, Multiplex Digital Valve (MDV) system that employs digital valves to meet multiple service pressure/flow requirement in off highway vehicles, is introduced. With MDV being integrated in an execavator, signficant hydraulic power saving have been validated compared to the baseline machine with the negative flow control (NFC) architecture. In addition, considering noise is still a critical hurdle for digital hydraulics to be adoped, we develop several noise reduction methods that have been evaluated in simulation environment and implemented in the above MDV. The sound pressure measured from the retrofitted MDV solution with the NVH treatment in the excavator has been improved signficantly over the untreated system such that it is nearly comparable to the baseline machine. The paper also briefly presents the sound quality study for better understanding of human perception and acceptance to nonconventional sound.

With increasing focus on electromobility many companies are developing vehicles powered by an electric energy source. Previously, engines used to be the most prominent source of noise in a traditional Internal Combustion Engine (ICE) vehicle. Although engines are optimized to produce lower noise levels, the wide frequency range of an engine makes the sound generated by them more acceptable and less annoying when compared to narrow frequency tonal noise exhibited by electric transmission systems. Moreover, structural vibrations and whine noise from electric powertrain is more prominent in absence of the masking effect from engines. Hence, Noise Vibration and Harshness (NVH) study of electric powertrain assembly is of paramount importance even though electric vehicles are quieter than their ICE counterparts. In this thesis, the electric powertrain used for running hydraulic systems in an excavator is analysed in order to study its vibro-acoustic characteristics and optimize the gear design for improved NVH performance. The main objective of this project is to simulate the vibrations generated by motor and gear transmission error excitations, and consequently propose optimization methods to reduce the gear whine noise. The powertrain has been analysed using Romax 2020.1, a drivetrain analysis software. Ansys 2020 R2 has been used as a meshing tool for generating FE mesh of gearbox and motor components. The motor excitation forces are calculated in Ansys Maxwell as a separate student thesis. These forces are then imported into Romax to study the behaviour of the powertrain due to motor excitation forces. Vibration analysis is carried out on the powertrain to understand the effects of various forces on its dynamic response. Further, design of experiments is carried out based on which micro geometry modifications of gear tooth are recommended to optimize the vibration response of the powertrain. / Med ökande fokus på elektromobilitet utvecklar många företag fordon som drivs av batteridrivna elmotorer. Tidigare var förbränningsmotorn den mest framträdande bullerkällan. Buller från förbränningsmotorer är dock mindre irriterade än från elmotorer, eftersom de är optimerade för att generera låga ljudnivåer med breda frekvensområden. Elektriska drivlinor har ett smalfrekvent tonalt brus som upplevs som irriterande. Dessutom är strukturella vibrationer och så kallat kuggvin från belastade kuggväxlar hos en elektrisk drivlina mer framträdande i utan maskeringseffekten från en förbränningsmotor. Detta betyder att vi behöver studera buller och vibrationer, på engelska kallat Noise Vibration and Harshness (NVH), hos elektriska drivlinor även om elfordon är tystare än sina föregångare. I det här arbetet analyserades den elektriska drivlinan som används för att driva hydraulsystemet till en grävmaskin. Drivlinans vibroakustiska egenskaper studerades och målet var att optimera kuggväxeldesignens NVH-prestanda. Huvudsyftet med detta projekt är att simulera vibrationerna som genereras av motor- och växeltransmissionsfelexcitationer och föreslå optimeringsmetoder för att minska växelljudet. Drivlinan har analyserats med hjälp av Romax 2020.1, en programvara för analys av drivlinor. Finita Element (FE)-programmet Ansys 2020 R2 har använts som ett meshverktyg för att generera beräkningsnät av växellåda och motorkomponenter. De motoriska excitationskrafterna beräknades i Ansys Maxwell som en separat studentuppsats. Dessa krafter importerades sedan till Romax för att studera drivlinans beteende på grund av motoriska excitationskrafter. Vibrationsanalys utfördes på drivlinan för att förstå effekterna, den dynamiska responsen, av olika krafter. Vidare genomfördes ett design av experiment baserat på vilka mikrogeometrimodifieringar av kugghjul som rekommenderas för att optimera drivlinans vibrationsrespons.

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