The role of excitation vector fields and all-polarisation state control of cavity magnonics

Recently the field of cavity magnonics, a field focused on controlling the interaction between magnons and confined microwave photons within microwave resonators, has drawn significant attention as it offers a platform for enabling advancements in quantum- and spin-based technologies. Here, we introduce excitation vector fields, whose polarisation and profile can be easily tuned in a two-port cavity setup, thus acting as an effective experimental knob to explore the coupled dynamics of cavity magnon-polaritons. Moreover, we develop theoretical models that accurately predict and reproduce the experimental results for any polarisation state and field profile within the cavity resonator. This versatile experimental platform offers a new avenue for controlling spin-photon interactions and as such also delivering a mechanism to readily control the exchange of information between hybrid systems

Robotic disassembly of a permanent magnet DC brushless motor

Globally, the transition to electric vehicles (EVs) is accelerating. As these EVs reach the end of their service life, large quantities of valuable components, including electric motors, need to be remanufactured to achieve a more sustainable circular economy. Disassembly, the first step in the remanufacturing process, typically requires human intervention due to difficulties in automating it. This thesis investigates the robotic disassembly of a permanent magnet DC brushless motor. Six typical tasks are defined in motor disassembly, and four of them are studied, including the ‘Press-in’ task, ‘Press-on’ task, Unplugging task and Coil disassembly task. Related to methodology, an analytical model implementing the magnetomotive force method was developed to calculate disassembly forces when removing a rotor with permanent magnets from a stator. This model provides reasonable accuracy in a very short calculation time without requiring high-performance computers compared with the finite element method. The average error rates of the FE method and MMF method are 16.7% and 26.3 %, respectively. By determining the material magnetic hysteresis, the improved analytical model predicts the force optimal positions, adapting to different cases of magnetic fields on the rotor with permanent magnets. Additionally, potential robotic solutions for the press-fit component disassembly tasks and the Coil disassembly task were investigated and experimentally validated. A robotic cell, including two collaborative robots, a set of tools and two devices for disassembling press-fit components, is designed to fully automate the disassembly process. The disassembly quality in the robotic process is superior to that in the manual process, preventing unnecessary damage to the components. The time of the robotic process is 886 s at full capacity, which is 56.93% faster than that of the manual process (1390 s). Robotic disassembly offers significant potential for advancing the circular economy in EV remanufacturing. However, although robotic automation improves disassembly efficiency and sustainability, it faces economic barriers due to high equipment costs. Future research should focus on cost-reduction strategies, expanding task automation, and hybrid approaches that combine robots and humans

High fidelity mechanical and loss modelling of an interior permanent magnet traction machine for electrical vehicles

High-performance permanent magnet electrical machines have become the leading machine technology in the electric vehicle market due to their combination of high efficiency and high-power density. However, their design optimisation involves complex and often strongly coupled mechanical, electromagnetic and thermal behaviour. Of the many possible topologies of permanent magnet machines, interior (IPM) machines have become the favoured machine type as they offer advantages in field weakening, a contribution from reluctance torque and the ability to retain the magnets within the rotor core without the need in many cases for a separate containment sleeve. However, the trade-off between electromagnetic and mechanical performance is especially important in IPMs because of the use of thin bridge-sections within the rotor core. This thesis reports on detailed design study into the mechanical and electromagnetic optimisation of an 8-pole, 100kW IPM machine with a base speed of 4,000rpm and an extended speed range up to 12,000rpm and makes extensive use of structural and electromagnetic finite element analysis to identify a preferred design. The other aspect of IPM performance which is investigated in this thesis is the influence of high frequency converter switching on the iron loss in the machine. An analysis methodology is developed and applied to an IPM machine with combines a SIMULINK model with pre-calculated finite element characteristics of the machine to predict detailed localised element-by-element flux density variations in the cores of an IPM machine which includes realistic representation of switching events. The effect of current ripple and the grounding of the star-point is investigated. These high frequency flux density waveforms are then used as the basis for estimating the effect of high frequency current ripple on iron loss. This aspect includes a detailed investigation of the limitations of different analytical and numerical models for solving the diffusion equation with 3D eddy current finite element simulations providing a baseline against which to test various models. This aspect of the research results in a time-stepped finite difference representation of 1D eddy current flow in laminations and is applied at full machine level as post-processing tool. The thesis concludes with some experimental measurements of core loss with switching ripple which demonstrates the value of including lamination level eddy current effects in loss predictions

Pursuit of optimal synthetic conditions for obtaining colloidal zero-valent iron nanoparticles by scanning pulsed laser ablation in liquids

Liquid-Assisted Pulsed Laser Ablation (LA-PLA) is a promising top-down method to directly synthesize colloidal dispersions of nanoparticles in a eco-friendly manner. However, the role of LA-PLA synthesis parameters is not yet fully agreed. This work seeks to optimize the production of nanoscale zero-valent iron (nZVI) particles suitable for biomedical or environmental applications using nanosecond LA-PLA on iron targets with different ablation media, laser and target scanning parameters. The use of alcohols as solvents produces iron-iron oxide core-shell nanoparticles with amorphous cores, except for a small crystalline fraction corresponding to the biggest core sizes. Decreasing carbon chain length and complexity leads to a thinning of the carbonaceous material coatings and an increase of the colloidal stability and the nanoparticle productivity. Moreover, a decrease of solvent density and surface tension allows obtaining reduced sizes and polydispersity values. Among, laser and scanning parameters, the pulse accumulation per spot displayed a clear effect in boosting size and productivity. As main outcome, aqueous dispersions with suitable colloidal properties are obtained, either by transferring to water of optimized nZVI particles produced in ethanol, or by direct formation of nZVI particles and in situ coating with hydrophilic molecules in aqueous solutions of these moleculesThis research has been funded by the Spanish Ministry of Economy and Competitiveness (MINECO) and FEDER [research projects MAT2015-67354R, MAT2014-53961-R, and MAT2017- 86826-R] and by the Aragón government (DGA) [grant for consolidated group PLATON E31_17R]. OBM thanks the financial support from the “Ramón y Cajal Program” [research project RYC2010-07332] of the Spanish Ministry of Economy and Competitiveness (MINECO) and the H2020 Action H2020-MSCA-IF-2014_ST [grant 656908-NIMBLIS] of the Executive Agency for Research Manages of EU Commissio

Magnetic gears numerical modelling and optimization

The main focus of this thesis is to provide efficient modelling and optimization strategies for a certain electro-magnetic device known as magnetic gear. In particular, magnetic, thermal and mechanical models are discussed and the non-linear material models are examined, including permanent magnets demagnetization algorithms and hysteresis models in laminated sheets. From the magnetic modelling point of view, an analytic approach for the initial simplified gear design is presented. A special focus is given to the computational burden of the method that is especially tailored for stochastic optimization procedures. For the detailed analysis of magnetic gears, an algorithm based on Finite Element / Boundary Element coupling is proposed, including ferromagnetic non-linearities, mechanical ordinary differential equations, eddy currents and circuit equations. Detailed models are introduced and discussed to analyze the effects of soft material hysteresis and permanent magnets magnetization, demagnetization and recoil. Loss mechanisms in magnetic gears are also investigated, and the transmission losses at varying rotational speeds and load angles are analyzed. A simplified mechanical model of the magnetic gear is presented and formulated as a set of inequality constraints, thus giving a direct link to optimization strategies. The mechanical constraints include the iron poles displacements and stresses and the limitations on the rotational speed due to excessive stresses, resonances and vibrations. A simplified analysis based on an equivalent thermal network is also presented, where the axial cooling flux is also considered. Stochastic optimization techniques are discussed for a multi-physic optimized machine design, and the analytic model is embedded in a Differential Evolution scheme. Finally, the optimized results are discussed and compared to commercial mechanical gearboxes. A solution based on the stiffness rods connection is also proposed and analyzed to provide a damping effect when the gear operation becomes asynchronous. During the PhD, there has been a constant effort aimed at building a prototype for the validation of the numerical models but, for different reasons, none of the manufacturers finalized the project. Thus, all the algorithms have been validated by comparing their output with commercial codes or, when possible, with data from experiments retrieved from literature. Because of this reasons and since the major objective of this thesis regards the numerical techniques for magnetic gears simulation, different magnetic transmissions have been adopted as numerical test cases for the validation of the algorithms

Hairpin windings for high reliability and high power density electrical machines

In the last years the increasing demand of higher torque and power densities has led to the adoption of hairpin windings (HWs) in electrical machines, mainly in those intended for automotive applications. However, this winding topology is quite sensitive to AC losses, hence one of their main challenges is represented by their reduction. This work deals with different design aspects related to the enhancements of some performance figures of rotating electrical machines for traction applications, above all power density and reliability, mainly through the adoption of HWs.In the last years the increasing demand of higher torque and power densities has led to the adoption of hairpin windings (HWs) in electrical machines, mainly in those intended for automotive applications. However, this winding topology is quite sensitive to AC losses, hence one of their main challenges is represented by their reduction. This work deals with different design aspects related to the enhancements of some performance figures of rotating electrical machines for traction applications, above all power density and reliability, mainly through the adoption of HWs

Microwave Characteristics of Particulate Magnetic Composites

Spherical magnetic particles have recently become of interest for applications in microwave communications devices as they exhibit magnetic absorption modes at frequencies much larger than conventional materials. These higher order modes allow composites comprising spherical magnetic particles in dielectric matrices to have relative permeabilities above unity at frequencies surpassing conventional magnetic materials. The higher order magnetic modes seen in spherical iron powders are a result of the vortex domain structure of magnetic spheres and exist also in magnetic spherical shells. Composite materials containing these magnetic spheres have use in miniaturisation of communications devices and allow access to frequency bands previously unattainable for communications as the increase in permeability at high frequencies will not only increase the refractive index of the material, but also decrease the impedance of the material, improving impedance matching to air. This thesis presents work for the investigation of higher order modes in spherical iron powders, particularly carbonyl iron powders, with the intent to demonstrate how properties such as particle size distribution affects the higher order resonances exhibited. A stripline technique for broadband characterisation of dielectric and magnetic composites is presented in the thesis, which demonstrates an ability to extract the relative permittivity and permeability of composites across an unprecedented broadband frequency range of 0.2 - 50 GHz. Although the relative permittivity and permeability of composites was able to be extracted for most cases, the refractive index of materials was shown to be significantly more resistant to uncertainty across broad frequencies. This technique employed a simple method for sample manufacture by wet-casting composites for characterisation, giving a fast and reliable method for characterising small amounts of material across a frequency range that surpasses most readily available methods. The technique was used for characterisation of several carbonyl iron powder grades. The carbonyl iron grades were imaged by scanning electron microscopy (SEM) analysis to give particle size distributions that were able to be compared between grades to allow an investigation into how the particle size distribution for carbonyl iron powders affects their microwave characteristics. Particle size distribution was confirmed to be a strong factor when considering the strength and position in frequency of these higher order resonances, so a technique was developed for filtration of powders into subgrades with different particle size distributions and average particle sizes. The results of this investigation displayed that the emergence of higher order magnetic absorption modes in carbonyl iron is heavily dependent on the average size and distribution of sizes for the powder used. The filtration technique developed is able to be used for filtration of spherical particles in the single micron size regime and uses only the flow of air through a set of stainless steel tubing and glass bottles. This experimental method is not only cheap, but is simple to assemble and achieves filtration of powders smaller than most mechanical sieves are capable of filtering. Finally, an investigation into the behaviour of these higher order modes under externally applied magnetic bias fields was performed. Samples were subject to a DC magnetic field during characterisation and the complex refractive index of composites was extracted as a field dependent value across the frequency range 0.2 - 30 GHz. The results showed that the primary absorption mode of these composites, at low GHz frequencies, was strongly affected by the application of a DC bias field, changing in both intensity and position in frequency. The higher order modes showed a less strong dependence on DC bias field strength until saturation fields were reached, and the modes were suppressed. The higher order modes not being supported at high DC bias fields is indicative of the vortex domain structure being necessary for higher order spherical modes to exist in magnetic powders.Engineering and Physical Sciences Research Council (EPSRC

Magnetoelectric Sensor Systems and Applications

In the field of magnetic sensing, a wide variety of different magnetometer and gradiometer sensor types, as well as the corresponding read-out concepts, are available. Well-established sensor concepts such as Hall sensors and magnetoresistive sensors based on giant magnetoresistances (and many more) have been researched for decades. The development of these types of sensors has reached maturity in many aspects (e.g., performance metrics, reliability, and physical understanding), and these types of sensors are established in a large variety of industrial applications. Magnetic sensors based on the magnetoelectric effect are a relatively new type of magnetic sensor. The potential of magnetoelectric sensors has not yet been fully investigated. Especially in biomedical applications, magnetoelectric sensors show several advantages compared to other concepts for their ability, for example, to operate in magnetically unshielded environments and the absence of required cooling or heating systems. In recent years, research has focused on understanding the different aspects influencing the performance of magnetoelectric sensors. At Kiel University, Germany, the Collaborative Research Center 1261 “Magnetoelectric Sensors: From Composite Materials to Biomagnetic Diagnostics”, funded by the German Research Foundation, has dedicated its work to establishing a fundamental understanding of magnetoelectric sensors and their performance parameters, pushing the performance of magnetoelectric sensors to the limits and establishing full magnetoelectric sensor systems in biological and clinical practice

Unified control system for three-phase electric drives operating in magnetic saturation region

The research project aims to study and develop control techniques for a generalized three-phase and multi-phase electric drive able to efficiently manage most of the drive types available for traction application. The generalized approach is expanded to both linear and non- linear machines in magnetic saturation region starting from experimental flux characterization and applying the general inductance definition. The algorithm is able to manage fragmented drives powered from different batteries or energy sources and will be able to ensure operability even in case of faults in parts of the system. The algorithm was tested using model-in-the-loop in software environment and then applied on experimental test benches with collaboration of an external company