Double rotor machines, appearing in versatile forms and configurations thanks to the great flexibility of having a pair of rotors, are seen in a number of applications. Double rotor machines show promising prospect in the application of advanced hybrid electric vehicle powertrains due to the requirement of dual electro-mechanical ports in such systems. Integrating these powertrain systems with double rotor machines not only brings design freedom of laying out components, but also reduces number of parts and thus improves compactness. The switched reluctance type double rotor machines, offering unique characteristics of having a simple structure and no permanent magnets, are strong candidates for high performance applications. In this thesis, a family of double rotor switched reluctance machine with segmented rotors is proposed and studied. Compared to double rotor switched reluctance machines with a more conventional structure, the proposed designs exhibit potentials of achieving higher compactness and performance. A prototype double rotor machine of the segmented rotor design is constructed and tested to benchmark an existing double rotor switched reluctance machine. The experiment results show that the proposed design is able to achieve the same output with similar or higher efficiency than the benchmark machine, while occupying only about 60% of overall volume. The double segmented rotor switched reluctance machine demonstrates to be a promising double rotor topology and is worth further research. / Thesis / Master of Applied Science (MASc)

This thesis presents advanced torque control methods for torque ripple reduction and performance improvement in switched reluctance motor (SRM) drives. A new offline torque sharing function (TSF) method is proposed for torque ripple reduction in SRMs. The proposed TSF achieves lower current tracking error by establishing a new current reference generation strategy. The phase current reference is first derived from the torque command using offline calculations and also from the phase current response that is obtained from the dynamic model of the SRM. Then, an optimization problem is formulated to shape the current reference for the objective of minimizing the torque ripple and copper losses, while maintaining the required average output torque at the given operating speed. The dynamic simulation of the SRM model is also utilized in the optimization problem. A new online TSF method is proposed for torque ripple reduction in SRMs. The proposed TSF takes the current dynamics and induced electromotive force into account by establishing a new online current profile generation technique. First, a primary phase current reference derived from the torque reference is applied to the SRM. Then, the decaying phase current after the turn-off angle is sampled, and it is used to update the current reference. A new online optimization strategy is performed to shape the current reference during the operation of the machine. Owing to the proposed current profile generation technique, the optimization process is decoupled to independently minimize the torque ripple by optimizing the turn-on angle and minimizing copper losses by optimizing the turn-off angle. Compared to the conventional TSFs and existing optimization-based TSFs, the proposed two TSFs achieve accurate torque control, improved torque-speed capability, reduced torque ripple, and better current tracking performance. All the proposed TSF methods are validated by both simulations and experiments on a 3-phase, 12/8 SRM. / Dissertation / Doctor of Philosophy (PhD)

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Rotor position estimation of switched reluctance machines (SRMs) is the main focus of this work. Rotor position sensors are a crucial component of optimal motor controls. Fail-safe operation and system cost reduction have been extensively researched and implemented in industry and academia. Position sensorless control on switched reluctance machines introduces a new challenge due to high nonlinearity under different operating conditions. A comprehensive review of SRM analytical modeling is presented, detailing each technique's main advantages and drawbacks. A least square-based analytical model (LSA) is proposed, which provides a simpler implementation and improved performance when compared to the methods commonly used in the literature. A literature review of rotor position sensor technology, position sensor fail modes, and position sensorless control is presented, providing a good roadmap of potential development and current limitations of the current technology. A wide speed range sensorless control is usually required when considering fail-safe techniques, fail detection methods, and low-cost applications. A unified nonlinear optimization-based sensorless control is proposed in this thesis, where a single method is used for startup, low and high speeds, with reduced memory allocation where a look-up table is not required, optimal transient response due to the elimination of a phase-locked-loop (PLL), and robustness against parameter variation. The method is validated at a wide speed range and torque conditions, thus showing the performance against conventional methods. / Thesis / Doctor of Philosophy (PhD)

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)

Switched reluctance machines are becoming more prevalent in various motor drive applications due to their simple construction, robust design, fault tolerant operation, and relatively low-cost construction. There are nonetheless some drawbacks to the switched reluctance machines operational behavior which limit its potential market penetration. The electromagnetic torque ripple is one of those limitations. However, unlike most four-quadrant variable speed electric motors, switched reluctance machines need additional control considerations to operate in generating mode to maximize power returned while minimizing torque ripple. The goal of this thesis is to explore different control schemes which are used in motoring mode and compare their performance in generating mode for different operational points. Using the lessons learned from the comparisons in generating mode, key optimizations objectives are established to improve the switched reluctance machines performance for generating applications. A multi-objective optimizer is used to select conduction angles using established objectives of maximizing torque and minimizing torque ripple. The proposed generating-specific objectives are compared to the motoring-specific objectives to validate the generating performance improvement for a wide torque-speed range. Finally, a setup is constructed to validate the generating performance of a 3-phase 12/8 SRM using the new optimization objectives and it is compared with conventional objectives. / Thesis / Master of Applied Science (MASc)

­^¤å´£­n¡G The objective of this thesis is to simultaneously achieve two- dimensional control of transverse flux linear switched-reluctance machine (LSRM). Based on a theoretical matrix decomposition scheme, the overall structure of the control and drive systems can be constructed, and the associated man/machine interface can be designed. A fuzzy inference scheme has been selected to control the machine motion, while an orthogonal scheme has been developed to control the machine lift force. By realizing the control algorithm through digital signal processor (DSP), results show that the LSRM will be quite applicable for the desired operations of magnetic levitated vehicle.

This dissertation contains the results of research conducted on the design and control characterization of a Switched Reluctance Generator (SRG) for maximum output power. The SRG is an attractive solution to the increasing worldwide demand of electrical energy. It is low cost with a rugged structure, operates with high efficiency over a wide speed range, and is fault tolerant. In many applications, size and weight are the main criteria in selecting the generator. Hence, in design and control of the generator, system designers always strive for increasing power density, or in other words, maximizing the output power for a given size. Despite the extensive research on the motoring operation of the Switched Reluctance Machine, only a few publications have investigated the generating mode of operation of this machine. Results and algorithms from this research can be referenced for better utilizing the SRG in many applications. As the first stage to output power maximization, design parameters and control variables affecting the average output power of the SRG are identified through a systematic approach. The optimal values for maximizing the output power are found through an analytical approach and iterative simulations. The results are then verified experimentally. After finding the optimal values for control variables, a controller is designed. This controller is model dependent. If the model used for design is not accurate or the machine parameters are deviated from the designed values, the machine will not generate the maximum output power. Therefore, a self-tuning algorithm, based on a local search method, is proposed and experimentally tested. It works effectively and does not need extra hardware or rigorous calculations. The attempts to benefit from the SRG may look tantalizing, but it poses a challenge as well. Output power maximization can lead to an oversized SRG converter and its output filter, which will reduce the overall power density of the motor drive. The last piece of this dissertation analyzes the effect of a commutation algorithm on the output filter, reducing its size with active control of phase currents, and proposing a novel control algorithm that was investigated through experiments over all of the speed range.

The objective of this dissertation is to study the switched reluctance machine (SRM) electromagnetic design and optimization. The research of electric machines is mostly driven by the motivation for higher efficiency and lower cost. The demands for high-performance electric machines also come from the development of emerging industries, such as electric vehicles (EV), hybrid electric vehicles (HEV), renewable energy conversion, energy storage and precision manufacturing. The additional requirements for those applications include volume, weight, speed, torque, reliability, fault tolerance capability, etc. The focus of the research effort is on the high speed and high torque applications, where the SRM stands out compared to other types of machines. The conventional design method significantly depends on the designer’s experience, which uses equivalent magnetic circuit models, and therefore the SRM design is not well developed. A novel SRM electromagnetic design and optimization method is developed, which uses the current-fed FEA simulation as the SRM performance estimation tool. This method serves as the main innovation of this research work. First, the proposed method is applicable to any SRM topologies and dimension, and no detailed modeling of a specific SRM configuration is required in advance. Therefore, an automated SRM design and optimization approach is developed. Secondly, great accuracy of the SRM electromagnetic analysis, e.g. flux density, torque, and current calculation, is achieved by using FEA simulation instead of simplified magnetic circuit approximations. This contribution is particularly significant when considering the poor accuracy of conventional SRM analytical analysis methods, where several assumptions and approximations are used. Lastly, the proposed design method takes the typical SRM control strategy into account, where the excitation current profile is characterized as a trapezoid. This method adapts the flux linkage of the first FEA simulation result to specify the excitation current profile for the second FEA simulation, so the calculated SRM performance in FEA simulation agrees with the measurement on a practical machine. The proposed SRM design and optimization method is used for a 12/8 SRM rotor design and for a complete 4/2 SRM design. These design examples validate the applicability of the proposed method to different SRM configurations and dimensions. Detailed design steps are presented for both design cases, and the selection of the parametric design variables are also discussed. The optimization results are demonstrated using multi-dimension diagrams, where the optimal design with the highest torque can be easily identified. The FEA simulation results are compared to the experimental results of a fabricated SRM prototype, and good agreement is found. In addition, a new rotor configuration with a flux bridge is proposed for an ultra high speed SRM design. The primary motivation of this rotor topology is to reduce the windgae losses and the acoustic noise at a high speed of 50,000 rpm. However, care must be taken for the flux bridge design, and the impact of different flux bridge thicknesses to the SRM performance is studied. Meanwhile, the manufacturing difficulties and the mechanical stresses should also be considered when fabricating the flux-bridge rotor. As a result, two SRM prototypes are built, and the two rotors are one without a flux bridge and one with a flux bridge. The prototypes are tested at different speeds (10,000 rpm, 20,000 rpm and 50,000 rpm) respectively, and the experimental results show good agreement with the FEA simulation results.

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