This thesis work provides an insight into the design of Force-amplifying Compliant Mechanisms (FaCMs) that are integrated with micromachined resonant accelerometers to increase their sensitivity. An FaCM, by mechanically amplifying the inertial force, enhances the shift in the resonance frequency of the beams used for sensing the acceleration whose effect causes an axial force on the beams. An extensive study on different configurations of resonators namely, single beam resonator, single-ended tuning fork (SETF), and double-ended tuning fork (DETF), is carried out to gain insights about their resonant behavior. The influence of the boundary conditions on the sensor’s sensitivity emerged from the study. We found that not only the force-amplification factor but also the multi-axial stiffness of the FaCM and proof-mass influence the resonance frequency of the resonator as well as the bandwidth of the modified sensor for certain configurations but not all. Thus, four lumped parameters were identified to quantify the effectiveness of an FaCM. These parameters determine the boundary condition of the sensing beams and also the forces and the moment transmitted to them. Also presented in this work is a computationally efficient model, called the Lumped Parameter Model (LPM) for evaluation of the sensitivity. An analytical expression for the frequency-shift of the sensing resonator beams is obtained by considering the FaCM stiffness parameters as well as the lumped stiffness of the suspension of the inertial mass. Various FaCMs are evaluated and compared to understand how the four lumped parameters influence the sensor’s sensitivity. The FaCMs are synthesized using topology optimization to maximize the net amplification factor with the volume constraint. One of the FaCMs outperforms the lever by a factor of six. Microfabrication of resonant accelerometer coupled with FaCM and comb-drive actuator is carried out using a silicon-on-insulator process. Finally, the selection map technique, a compliant mechanism redesign methodology is used for enhancing the amplification of FaCMs. This technique provides scope for further design improvement in FaCMs for given sensor specifications.

Enterprising technologies and policies that focus on energy reduction in buildings are paramount to achieving global carbon emissions targets. Energy retrofits, building stock modelling, heating, ventilation, and air conditioning (HVAC) upgrades and demand side management all present high leverage opportunities in this regard. Advances in computing, data science and machine learning can be leveraged to enhance these methods and thus to expedite energy reduction in buildings but challenges such as lack of data, limited model generalizability and reliability and un-reproducible studies have resulted in restricted industry adoption. In this thesis, rigorous and reproducible studies are designed to evaluate the benefits and limitations of state-of-the-art machine learning and statistical techniques for high-impact applications, with an emphasis on addressing the challenges listed above. The scope of this work includes calibration of physics-based building models and supervised deep learning, both of which are used to estimate building properties from real and synthetic data. • Original grey-box methods are developed to characterize physical thermal properties (RC and RK)from real-world measurement data. • The novel application of supervised deep learning for thermal property estimation and HVAC systems identification is shown to achieve state-of-the-art performance (root mean squared error of 0.089 and 87% validation accuracy, respectively). • A rigorous empirical review is conducted to assess which types of gray and black box models are most suitable for practical application. The scope of the review is wider than previous studies, and the conclusions suggest a re-framing of research priorities for future work. • Modern interpretability techniques are used to provide unique insight into the learning behaviour of the black box methods. Overall, this body of work provides a critical appraisal of new and existing data-driven approaches for thermal property estimation in buildings. It provides valuable and novel insight into barriers to widespread adoption of these techniques and suggests pathways forward. Performance benchmarks, open-source model code and a parametrically generated, synthetic dataset are provided to support further research and to encourage industry adoption of the approaches. This lays the necessary groundwork for the accelerated adoption of data-driven models for thermal property identification in buildings. / Graduate

The Hybrid Norwood (HN) is a relatively new first stage procedure for neonates with Hypoplastic Left Heart Syndrome (HLHS), in which a sustainable univentricular circulation is established in a less invasive manner than with the standard procedure. A computational multiscale model of such HLHS circulation following the HN procedure was used to obtain detailed hemodynamics. Implementation of a reverse-BT shunt (RBTS), a synthetic bypass from the main pulmonary to the innominate artery placed to counteract aortic arch stenosis, and its effects on local and global hemodynamics were studied. A synthetic and a 3D reconstructed, patient derived anatomy after the HN procedure were utilized, with varying degrees of distal arch obstruction, or stenosis, (nominal and 90% reduction in lumen) and varying RBTS diameters (3.0, 3.5, 4.0 mm). A closed lumped parameter model (LPM) for the peripheral or distal circulation coupled to a 3D Computational Fluid Dynamics (CFD) model that allows detailed description of the local hemodynamics was created for each anatomy. The implementation of the RBTS in any of the chosen diameters under severe stenosis resulted in a restoration of arterial perfusion to near-nominal levels. Shunt flow velocity, vorticity, and overall wall shear stress levels are inverse functions of shunt diameter, while shunt perfusion and systemic oxygen delivery correlates positively with diameter. No correlation of shunt diameter with helicity was recorded. In the setting of the hybrid Norwood circulation, our results suggest: (1) the 4.0mm RBTS may be more thrombogenic when implemented in the absence of severe arch stenosis and (2) the 3.0mm and 3.5mm RBTS may be a more suitable alternative, with preference to the latter since it provides similar hemodynamics at lower levels of wall shear stress.

<p dir="ltr">This research developed a lumped volume-based coupled simulation model for gear pumps and motors, which is employed to analyze a reference machine of a compensated crescent- type internal gear pump. The model is composed of simultaneous simulations of the pump fluid domain pressure, lubricating films, and dynamics of the moving components.</p><p dir="ltr">The simulation model developed includes four major novel contributions.</p><p dir="ltr">1. A coupled simulation model was developed for the reference machine which provides (a) a lumped parameter simulation of the fluid pressure within the inter-teeth volumes, (b) CFD simulations of the lubricating interfaces, and (c) a simulation of the micromotion of the pressure compensating components and gear bodies. The simulation tool is developed in C++ and constitutes the simulation core of Multics for internal gear pumps. The model achieved volumetric and mechanical predictions for the reference type of machine, which are validated via experimental investigations.</p><p dir="ltr">2. A flexible pressure solver was established to solve the pressure transience in the fluid domain in gear pumps with general CV geometry exemplified in the reference machine. The approach allows for ample freedom in defining control volumes, including possible volume discontinuities. The new formulation, derived from mass conservation, avoids the numerical evaluation of the volume derivatives so that it allows for simulating a control volume layout with sudden shape changes. The new formulation also considers the sliding motion from volume boundaries when evaluating internal flows, which improves the accuracy of the control volume pressure solutions. The effectiveness of the proposed formulation was examined by applying the method to the simulation of the reference machine. Compared with the state-of-the-art simulations, several improvements in the pressure simulation were observed : (i) the proposed formulation provides free-of-spike fluid pressure simulations, even for discontinuous volumes; (ii) the proposed formulation properly captures the flow component between volumes that is caused by the volume boundary motions, a term previously neglected, which affects the pressure evaluation accuracy, especially in gear meshing zone.</p><p dir="ltr">3. The swift film coupling algorithm proposes a novel artificial inertia damping-based method (AIDM) to simulate this coupling. The proposed method considers modifying the physical body dynamics with artificial inertia and damping values that could achieve significant numerical solver accelerations while maintaining extremely low errors. The artificial inertia and damping are determined based on the instantaneous physical system’s Jacobian so that the first-order dynamics in the solution can be conserved from the original dynamic system. The solver acceleration capability is quantified in time-discretization-based derivations, where additional guidelines for determining the artificial inertia and damping values are found. The proposed approach is used to simulate two model problems for a 1-D slider pad under periodic loading conditions, where one pad is fixed inclined and the other free to move vertically and rotate about its center. Simulation results reported an error lower than 0.01 μm in the gap height geometry prediction by the proposed AIDM approach compared to the state-of-the-art Reynolds film damping-based method (RDM). Meanwhile, the numerical solver speed improved 1000 times for the fixed incline pad problem and one hundred thousand times for the free-to-float pad problem. Derivations showed that additional acceleration potential can be achieved in realistic mechanical systems where a higher degree of freedom is present in the body motions. The error behavior of the proposed AIDM approach is discussed, showing the error is positively related to the absolute magnitude of the modification parameter ϕ used for calculating the artificial inertia and damping, and the error is related to the validity of the linearization assumption on the system dynamics.</p><p dir="ltr">4. Based on a novel experimental set-up to measure the filling characteristics of an internal gear pump under induced gaseous cavitation. An integrated simulation approach was proposed to study the incomplete filling behavior in positive displacement machines. The approach consists of (a) a 1st order predictive model for evaluating the amount of undissolved gas at the pump inlet from the circuit pressure loss, (b) a gas-equilibrium-based cavitation model for predicting the pressure transience in the pump fluid domain, (c) a lumped volume based pump flow evaluation. Experiments performed over a wide range of operating conditions validated the deployment of the first-order gas release prediction (with 8 s time constant for fluid with 6 % total air). The complete simulation approach was validated via a good match with the measured volumetric efficiency for both low-speed and high-speed conditions.</p><p dir="ltr">The reference compensated crescent-type internal gear pump (CCIGP) unit was simulated with the full scope coupled simulation model, with which the methods proposed in this thesis research were validated with experiments. Simulation results matched with volumetric efficiency as well as mechanical efficiency. The model also reports a breakdown of the energy consumption within the reference CCIGP, which promotes the understanding of the operation of the reference machine.</p>

"Thanks to significant worldwide research directed at understanding and predicting structural behavior at elevated temperatures, analytical methods are available to support a rational, performance-based approach to the structural design of buildings for fire conditions. To utilize these analytical methods effectively, structural engineers need guidance on reliable and appropriate approaches to dealing with a variety of factors, including the effects of fire protection measures, temperature-dependent thermal and structural properties, elastic and inelastic behavior of structural components and assemblies, and thermal and structural response of framing connections. To meet the objective of guiding the structural engineer in appropriate analytical methods and parameter values for performance-based structural fire protection, this thesis proposes a comprehensive way of thinking about the design and analysis of structures for fire conditions. This integration of structural engineering and fire protection engineering into a functional framework is defined herein as Fire-Robust Structural Engineering (FRSE). The FRSE process, which is presented as a series of flowcharts, is designed to guide the structural engineer in executing the functions involved in the design of fire-safe structures and to help identify informational needs critical to these tasks. Currently, mechanisms for identifying possible resources to fulfill fire-related informational needs are generally organized for the convenience of the fire research community. Identification of resources that provide appropriate information for fire-robust structural engineering, such as laboratory fire test results, parametric studies of analytical methods, and other sources of guidance, is often difficult because these resources are rarely organized and presented for the benefit of structural engineers. To begin to resolve this problem, this thesis has developed a prototype information management system (IMS) based on the framework of the FRSE process. The IMS addresses the critical challenge of organizing and presenting the available knowledge and data in a format that is consistent with the perspective and informational needs of the structural engineer. The prototype version of the IMS has been implemented using a Microsoft Excel® platform. In addition to guidance in utilizing specific analytical methods and choosing appropriate parameter values, the structural engineer also requires an understanding of the input requirements and accuracy of various analytical methods in order to make informed decisions regarding which methods are appropriate for use with different structural configurations. Therefore, this thesis includes a model study as an example of a resource that could aid the structural engineer in making such decisions. The model study compares various analytical methods (simplified spreadsheet applications and advanced finite element techniques) to published laboratory test data and discusses concerns that the structural engineer must keep in mind when using each method. Conclusions are drawn regarding the appropriateness of each analytical method to the analysis of a fully restrained, spray-protected steel beam. Given this type of information, the structural engineer can make decisions regarding the types of analytical methods and the level of analytical sophistication required to solve a given design problem."

Η θερμική ανάλυση είναι μια σημαντική περιοχή μελέτης και γίνεται περισσότερο σημαντική για την σχεδίαση ηλεκτρικών μηχανών εξαιτίας της ανάγκης για μείωση του όγκου των υλικών και του κόστους κατασκευής τους καθώς και για την αύξηση της απόδοσής τους. Είναι εξίσου σημαντική με την ηλεκτρομαγνητική ανάλυση μιας και η θέρμανση της μηχανής θα οριοθετήσει την ονομαστική της ισχύ καθώς και την διάρκεια ζωής της μόνωσης. Στόχος της παρούσας διπλωματικής εργασίας είναι η εύρεση της κατανομής της θερμοκρασίας στο εσωτερικό ενός ασύγχρονου τριφασικού κινητήρα στη μόνιμη κατάσταση λειτουργίας του με τη μέθοδο των συγκεντρωμένων παραμέτρων. Στο πρώτο κεφάλαιο αναφέρονται βασικές έννοιες της θερμοδυναμικής. Γίνεται αναφορά σε διάφορους συντελεστές, παρουσιάζονται οι θερμοδυναμικοί νόμοι και γίνεται σύντομη αναφορά στους μηχανισμούς μετάδοσης θερμότητας. Στο δεύτερο κεφάλαιο δίνεται η αναλυτική περιγραφή των μηχανισμών μετάδοσης θερμότητας και παρουσιάζεται ένα απλό δίκτυο μοντελοποίησης με ισοδύναμες θερμικές αντιστάσεις. Στο τρίτο κεφάλαιο παρουσιάζεται σύντομα η δομή, η αρχή λειτουργίας και οι τύποι μιας ασύγχρονης μηχανής. Εδώ επίσης αναφέρονται και οι διάφορες μορφές απωλειών ενέργειας κατά την λειτουργία μιας τριφασικής ασύγχρονης μηχανής. Παρουσιάζεται ακόμη ο υπό μελέτη κινητήρας και αναφέρονται τα θερμοστοιχεία που χρησιμοποιούνται στην πειραματική διαδικασία. Στο τέταρτο κεφάλαιο περιγράφεται η μέθοδος θερμικής ανάλυσης με χρήση ισοδυνάμου κυκλώματος θερμικών αντιστάσεων για την μόνιμη κατάσταση. Στη συνέχεια δίνεται το προτεινόμενο κύκλωμα και παρουσιάζονται αναλυτικά οι ισοδύναμες θερμικές αντιστάσεις του μοντέλου. Τέλος στο πέμπτο κεφάλαιο παρατίθενται τα αποτελέσματα της θερμικής ανάλυσης, γίνεται σύγκριση με τα πειραματικά δεδομένα θερμοκρασιακών τιμών που πάρθηκαν από τα θερμοστοιχεία και ακολουθεί η διαδικασία της παραμετροποίησης στους διάφορους συντελεστές που χρησιμοποιήθηκαν είτε υπολογίστηκαν κατά την ανάλυση. / Thermal analysis is an important design area and becoming more important part of the electric motor design process due to the push for reduced weights and costs and increased efficiency. Thermal analysis is of equal importance as the electromagnetic design of the machine, because the temperature rise of the machine eventually determines the maximum output power. The purpose of this study is to record the temperature distribution of the internal parts of an induction motor at steady state using an equivalent thermal circuit with lumped parameters. The first chapter is an introduction of the thermodynamic theory. The laws of thermodynamics are described and there is a brief report of heat transfer mechanisms. The second chapter describes analytically the heat transfer mechanisms. Also, an example of modelling using thermal equivalent resistances is given. The third chapter introduces shortly the operational principles of an induction machine. Here are also referred the various losses that occur during the rotation of an induction motor. The studied induction motor, with the modified stator winding to include thermocouples, is shown. The fourth chapter introduces the method of thermal analysis using thermal equivalent circuit with lumped parameters. The proposed model is given and its components are described in particular. At last, in the fifth chapter the results of temperature distribution are given and compared with experimental data of temperature values that are acquired using the thermocouples. Here also takes apart the parameterising of the various coefficients that were used or calculated during this study.

Suspension systems and wheels play a critical role in vehicle dynamics performance of a car in areas such as ride comfort and handling. Lumped parameter models (LPMs) are commonly used for assessing the performance of vehicle suspension systems. However, there is a lack of clarity with regard to the relative capabilities of different LPM configurations. A comprehensive comparative study of three most commonly used LPMs of increasing complexity has been carried out in the current work. The study reported here has yielded insights into the capabilities of the considered LPMs in predicting response time histories which may be used for assessing ride comfort. A shortcoming of available suspension system models appears to be in representation of harsh situations such as jounce movement which cause full compression of springs leading to ‘jerks’ manifested as high values of rate of change of acceleration of sprung mass riding on a wheel. In the current research work, a modified nonlinear quarter-car model is proposed to account for the contact force that results in jerk-type response. The numerical solution algorithm is validated through the simulation of an impact test on a car McPherson strut in a Drop Weight Impact Testing Tower developed in CAR Laboratory, CPDM. This is followed by a detailed comparison of HCM and QCM to examine their suitability for such analysis. For decades, wheel bearings in vehicles have been designed using simplified analytical approaches based on Hertz contact theory and test data. In the present work, a hybrid approach has been developed for assessing the load bearing capacity of a wheel ball bearing set. According to this approach, the amplitude of dynamic wheel load can be obtained from a lumped parameter analysis of a suspension system, which can then be used for detailed static finite element analysis of a wheel bearing system. The finite element modelling approach has been validated by successfully predicting the load bearing capacity of an SKF ball bearing set for an acceptable fatigue life. For the first time, using a powerful commercial explicit finite element analysis tool, a detailed dynamic analysis has been carried of a deep groove ball bearing with a rotating inner race. The analysis has led to a consistent representation of complex motions consisting of rotations and revolutions of rolling elements, and generated insights into the stresses developed in the various components such as balls and races. In conclusion, a simple yet effective fuzzy logic-based yaw control algorithm has been presented in the current research. According to this algorithm, two inputs i.e. a yaw rate error and a driver steering angle are used for generating an output in the form of an additive steering angle which potentially can aid a driver in avoiding straying from an intended path.

Les machines électriques synchrones à aimants permanents sont susceptibles de rencontrer un disfonctionnement suite à un échauffement non maîtrisé. L’objectif de cette étude est de développer un modèle thermique générique et prédictif pouvant simuler diverses situations d’intérêts: régime permanent, régime transitoire, mode dégradé, entrefer immergé, haute vitesse. Pour cela, la méthode nodale est utilisée pour développer le modèle thermique générique. En parallèle, un banc d’essai et un prototype sont conçus pour valider le modèle. L’étude de sensibilité des résultats du modèle à certains paramètres montrent que certains coefficients de convection, certaines conductances de contact et la conductivité thermique radiale du bobinage ont une influence considérable sur les résultats du modèle. Cependant ces paramètres sont mal connus, car ils sont issus des formules empiriques ou des abaques. Grâce au prototype et au modèle développé, ces paramètres sont identifiés. Trois méthodes d’identification sont testées pour aboutir à une stratégie d’identification: les algorithmes génétiques, la méthode de Gauss-Newton et la méthode de Levenberg-Marquardt. Plusieurs essais sont effectués sur le prototype instrumenté. La mesure des températures à des lieux précis du prototype permet d’identifier les paramètres mal connus et de valider le modèle. / Permanent magnet synchronous machines are likely to break down due to poorly controlled heating. The goal of this study was to develop a generic and predictive thermal model to calculate the temperature of machines during the design phase simulating temperatures at various states. These states include: steady state, transient state, fault mode, axial circulating of a cooling fluid in the air-gap and high speed. The lumped parameter method was used to develop this generic thermal model. Meanwhile, a test bench and a prototype instrumented with thermocouples were manufactured to validate the model at the same time. Sensitivity studies of the results of the model to some parameters demonstrated that some convective coefficients, contact conductances and the thermal conductivity of the winding in the radial direction influenced the model. However, these parameters are poorly known, because empirical formulas or abacus are used to calculate them. Using, the prototype and the developed model, these parameters were identified. Three methods of identification were tested in order to find a strategy for the identification: the genetic algorithms method, the Gauss-Newton method and the Levenberg-Marquardt method. Many tests were done on the prototype. The measure of the temperatures on the specific place allows to identify these parameters and to validate the model.