A Study Model Predictive Control for Spark Ignition Engine Management and Testing

Pressure to improve spark-ignition (SI) engine fuel economy has driven thedevelopment and integration of many control actuators, creating complex controlsystems. Integration of a high number of control actuators into traditional map basedcontrollers creates tremendous challenges since each actuator exponentially increasescalibration time and investment. Model Predictive Control (MPC) strategies have thepotential to better manage this high complexity since they provide near-optimal controlactions based on system models. This research work focuses on investigating somepractical issues of applying MPC with SI engine control and testing.Starting from one dimensional combustion phasing control using spark timing(SPKT), this dissertation discusses challenges of computing the optimal control actionswith complex engine models. A nonlinear optimization is formulated to compute thedesired spark timing in real time, while considering knock and combustion variationconstraints. Three numerical approaches are proposed to directly utilize complex high-fidelity combustion models to find the optimal SPKT. A model based combustionphasing estimator that considers the influence of cycle-by-cycle combustion variations isalso integrated into the control system, making feedback and adaption functions possible.An MPC based engine management system with a higher number of controldimensions is also investigated. The control objective is manipulating throttle, externalEGR valve and SPKT to provide demanded torque (IMEP) output with minimum fuelconsumption. A cascaded control structure is introduced to simplify the formulation and solution of the MPC problem that solves for desired control actions. Sequential quadratic programming (SQP) MPC is applied to solve the nonlinear optimization problem in real time. A real-time linearization technique is used to formulate the sub-QP problems with the complex high dimensional engine system. Techniques to simplify the formulation of SQP and improve its convergence performance are also discussed in the context of tracking MPC. Strategies to accelerate online quadratic programming (QP) are explored. It is proposed to use pattern recognition techniques to “warm-start” active set QP algorithms for general linear MPC applications. The proposed linear time varying (LTV) MPC is used in Engine-in-Loop (EIL) testing to mimic the pedal actuations of human drivers who foresee the incoming traffic conditions. For SQP applications, the MPC is initialized with optimal control actions predicted by an ANN. Both proposed MPC methods significantly reduce execution time with minimal additional memory requirement

International Conference on Continuous Optimization (ICCOPT) 2019 Conference Book

The Sixth International Conference on Continuous Optimization took place on the campus of the Technical University of Berlin, August 3-8, 2019. The ICCOPT is a flagship conference of the Mathematical Optimization Society (MOS), organized every three years. ICCOPT 2019 was hosted by the Weierstrass Institute for Applied Analysis and Stochastics (WIAS) Berlin. It included a Summer School and a Conference with a series of plenary and semi-plenary talks, organized and contributed sessions, and poster sessions. This book comprises the full conference program. It contains, in particular, the scientific program in survey style as well as with all details, and information on the social program, the venue, special meetings, and more

Study of compliant mechanisms and flexible hinges in topology optimization

This thesis presents a comprehensive study on the application of compliant mechanisms and flexible hinges in topology optimization. Compliant mechanisms are a promising approach for achieving desired functionalities and structural flexibility in engineering designs. By exploiting the inherent elasticity of materials, compliant mechanisms offer advantages such as reduced complexity, improved reliability, and enhanced performance. Topology optimization, conversely, allows obtaining compliant mechanisms with reduced weight through the creation of holes, thus achieving an optimized design. In this work, we explore the integration of compliant mechanisms and flexible hinges within the framework of topology optimization, aiming to propose a method of improvement for the design efficiency and performance of structures in the aerospace field. The thesis begins with a thorough literature review of compliant mechanisms and their role in current aerospace applications. Various design principles and analysis techniques are examined to establish a solid foundation for the subsequent chapters. The study then focuses on the implementation of mathematical models and computational algorithms to incorporate compliant mechanisms and flexible hinges into the topology optimization process. To validate the proposed approach, a series of numerical experiments are conducted. Various case studies are considered, including a gripping and inverter mechanisms. The results demonstrate the effectiveness of compliant mechanisms and flexible hinges in enhancing the performance of optimized structures. The compliant mechanisms exhibit improved flexibility, adaptability, and energy absorption capabilities enabling smooth and controlled motion. Overall, this thesis significantly contributes to the understanding and implementation of compliant mechanisms and their integration with topology optimization techniques. The study not only showcases their potential for creating innovative and efficient designs across various engineering disciplines but also emphasizes their particular relevance in the aerospace field. By exploring the application of compliant mechanisms and topology optimization in aerospace engineering, it has been seen that this cutting-edge technology is opened up for new avenues for further research and development

Advanced interface modelling for 2D shell & 3D continuum problems

This work is motivated by the need for an efficient yet accurate approach for static and dynamic contact analysis of large-scale structures which can a) capture the optimum con- tact position with a moderate number of contact elements, and b) enable across-partition adaptive contact analysis within a parallel processing environment. In addressing these two issues, a novel adaptive node-to-surface contact approach is proposed to discretise the contact boundaries and to trace the evolution of contact locations. Contact search is a demanding process that can become quite complicated for certain types of problem. In this work, an efficient and robust contact search method is proposed, which can a) locally track the master facet of a given slave node despite the appearance of highly non-smooth contact surface, including surfaces with concave/convex regions or with distinct boundaries as well as reversible normals, and b) globally reallocate the master-slave contact pairs based on the penetration state without an expensive global search, providing an effective adaptive contact approach. A dual-interface-based domain decomposition method emphasising across-partition con- tact coupling is proposed. A pair of fully decomposed node-to-surface contact element are proposed to discretise the across-partition contact boundaries. The assumption of small incremental displacements is adopted, which a) avoids the excessive coupling between the decomposed master and slave, b) reduces significantly the communication overhead, and c) facilitates a flexible across-partition adaptive analysis. This strategy is found to provide good results for a sufficiently small time- or load-step, and it also facilitates mix-dimensional contact simulation. Another interest in current thesis is the inaccuracy in non-smooth plates modelled us- ing 2D displacement-based shell elements. In this work the dominant factor causing the inaccuracy is recognised as the incompatible tangential rotations on the two sides of the in- tersection. A 3-noded coupling element is introduced to impose a continuous constraint to couple the incompatible rotations. The significance of the discontinuity in the shell-based folded structure and the effectiveness of the coupling element is demonstrated through numerical studies comparing shell-based models to high fidelity solid-based models.Open Acces

Aerostructural optimization and aeroelasticity of new generation aircraft

Mención Internacional en el título de doctorThe consolidate growth in the European air traffic and passengers’ number is driving commercial aviation to face important changes, like the need to reduce environmental impact and to satisfy an increasing demand for air transportation, It is a common thought that a technological breakthrough is required to achieve such goal. New technological approaches are being pursued for the new aircraft generation, like distributed propulsion systems, structures characterized by new materials and manufacturing processes and nonconventional wing layouts, such as the blended-wing and the box-wing concepts. Nevertheless, to make such new technologies market competitive a new design approach may be needed. Some of these new concepts, in fact, may be remarkably affected by aeroelastic issues, which need to be taken into account in early design, and their enhanced structural flexibility or their peculiar layout may exacerbate coupling between different disciplines (e.g., flight dynamics and aeroelasticity). Moreover, loads and aerodynamic performances prediction may radically differ with respect to what achieved during conceptual design, if considering plain/rigid configurations only. This dissertation contributes tackling some aspects of the above-mentioned issues. In the first part of this work, a unified flight-dynamic and aeroelastic model for stability analysis is used to address for the first time, with physical insights, the dynamic response of an unconventional box-wing configuration. As observed in previous literature efforts on this configuration, flutter onset is significantly different when considering the aircraft being free in the air or fixed in space. Thanks to the adopted formulation, it is shown how the aerodynamic coupling of elastic and rigid modes has a beneficial effect on the dynamic aeroelastic instability (flutter) onset. However, the different modal properties, consequence of the diverse boundary conditions, when switching from fixed-in-space to free-flying aircraft, also play a relevant role in determining the flutter occurrence. Whereas for the longitudinal case both effects are synergistic, contributing to increase flutter speed, for the lateral-directional case the variation in modal properties has a detrimental and dominating effect, leading to a flutter speed well within the flight envelope. Not only effects of rigid and elastic modes interaction is addressed with respect to the aeroelastic side but the consequent effect on the flexible flight dynamics in terms of deterioration of the flying qualities is quantified. Within the adopted formulation, unsteady aerodynamic forces are modeled by means of an enhanced Doublet Lattice Method, able to take into account terms typically neglected by classic formulations. The work also discusses the relevance of such extra contributions on the dynamic response of the aircraft. In the second part of this work a model for high-fidelity gradient-based aerostructural optimization of wings, assisted by algorithmic differentiation and including aerodynamic and structural nonlinearities, is presented. First, the model is illustrated: a key feature is represented by its enhanced modularity. Each discipline solver, employing algorithmic differentiation for the evaluation of adjoint-based sensitivities, is interfaced at high level by means of a wrapper to both solve the aerostructural primal problem and evaluate discrete-consistent gradients of the coupled problem. Second, to demonstrate the feasibility of the method, a framework is ad-hoc set up, within the open-source SU2 multiphysics suite, with the inclusion of a geometrically nonlinear beam FE and an interface module to deal with non-matching 3D surfaces. Finally, the framework is applied to perform aerostructural optimization of aeroelastic test cases based on the ONERA M6 and NASA CRM wings and featuring relevant structural deflections. Single-point optimizations, employing Euler or RANS flow models, are carried out to find wing optimal outer mold line in terms of aerodynamic efficiency. Results remark the importance of taking into account the aerostructural coupling when performing wing shape optimization.El crecimiento consolidado del tráfico aéreo europeo y del número de pasajeros está impulsando a la aviación comercial a afrontar cambios importantes, como la necesidad de reducir el impacto medioambiental y de satisfacer una demanda creciente de transporte aéreo. Es pensamiento común que, para lograr tal objetivo, se requiere un avance tecnológico importante. Se están buscando nuevos enfoques tecnológicos para la nueva generación de aviones, como sistemas de propulsión distribuida, estructuras caracterizadas por nuevos materiales y procesos de fabricación y diseños de alas no convencionales, como los conceptos de blended wings (alas integradas) y box wings (alas en caja). No obstante, para que el mercado de estas nuevas tecnologías sea competitivo, puede ser necesario un nuevo enfoque de diseño. Algunos de estos nuevos conceptos, de hecho, pueden verse notablemente afectados por problemas aeroelásticos, que deben tenerse en cuenta en el diseño inicial, y su aumentada flexibilidad estructural o su diseño peculiar pueden exacerbar el acoplamiento entre diferentes disciplinas (por ejemplo, dinámica de vuelo y aeroelasticidad). Además, la predicción de cargas y rendimiento aerodinámico puede diferir radicalmente con respecto a lo que se consigue durante el diseño conceptual, si se consideran únicamente configuraciones simples/rígidas. Esta tesis contribuye a abordar algunos aspectos de los temas previamente mencionados. En la primera parte de este trabajo, se utiliza un modelo unificado de dinámica de vuelo y aeroelasticidad dedicado al análisis de estabilidad para abordar por primera vez, con conocimientos físicos, la respuesta dinámica de una configuración box wing no convencional. Como se observó en las contribuciones de la literatura anterior sobre esta configuración, el inicio del flameo es significativamente diferente cuando se considera que la aeronave está libre o fija en el espacio. Gracias a la formulación adoptada, se muestra cómo el acoplamiento aerodinámico de los modos elásticos y rígidos tiene un efecto beneficioso sobre el inicio de la inestabilidad aeroelástica dinámica (flameo). Sin embargo, las diferentes propiedades modales, consecuencia de las diversas condiciones de contorno, al cambiar de aeronave fija en el espacio a libre, también juegan un papel relevante en la determinación de la ocurrencia del flameo. Mientras que para el caso longitudinal ambos efectos son sinérgicos en contribuir aumentando la velocidad de flameo, para el caso latero-direccional la variación en las propiedades modales tiene un efecto prejudicial y dominante, conduciendo a una velocidad de flameo muy dentro de la envolvente de vuelo. No solo se han tratado los efectos de la interacción de los modos rígidos y elásticos con respecto a considerar puramente aquellos aeroelásticos, sino que se ha cuantificado el efecto consiguiente sobre la dinámica de vuelo flexible en términos de deterioro de las cualidades de vuelo. Dentro de la formulación adoptada, las fuerzas aerodinámicas no estacionarias se modelan mediante un doublet lattice method mejorado, capaz de tener en cuenta los términos típicamente despreciados por las formulaciones clásicas. El trabajo también analiza la importancia de estas contribuciones adicionales en la respuesta dinámica de la aeronave. En la segunda parte de este trabajo se presenta un modelo de optimización aeroestructural de alas basado en gradientes de alta fidelidad, asistido por diferenciación algorítmica y que incluye no linealidades de tipo aerodinámico y estructural. En primer lugar, se ilustra el modelo: una característica clave está representada por su modularidad. Cada solucionador de disciplinas, que emplea método adjunto y diferenciación algorítmica para la evaluación de los gradientes, está interconectado a alto nivel por medio de un administrador para resolver tanto el problema primario aeroestructural como para evaluar los gradientes de tipo discreto consistente del problema acoplado. En segundo lugar, para demostrar la viabilidad del método, se construye un marco ad hoc, dentro del paquete SU2 multiphysics, con la inclusión de un elemento finito viga geométricamente no lineal y un módulo de interfaz para tratar con superficies 3D no coincidentes. Por último, el marco se aplica para realizar la optimización aeroestructural de casos de prueba aeroelástica basados en las alas ONERA M6 y NASA CRM y que presentan deformaciones estructurales relevantes. Se llevan a cabo optimizaciones de punto único, empleando modelos fluidodinámicos Euler o RANS, para encontrar la línea de molde exterior óptima del ala en términos de eficiencia aerodinámica. Los resultados destacan la importancia de tener en cuenta el acoplamiento aeroestructural al realizar la optimización de la forma del ala.This work has been supported by the Universidad Carlos III de Madrid through a PIF scholarship, awarded on a competitive basis.Programa de Doctorado en Mecánica de Fluidos por la Universidad Carlos III de Madrid; la Universidad de Jaén; la Universidad de Zaragoza; la Universidad Nacional de Educación a Distancia; la Universidad Politécnica de Madrid y la Universidad Rovira i VirgiliPresidente: Domenico Quagliarella.- Secretario: Manuel García-Villalba Navaridas.- Vocal: Rubén Moreno Ramo

Exploiting Smoothness in Statistical Learning, Sequential Prediction, and Stochastic Optimization

In the last several years, the intimate connection between convex optimization and learning problems, in both statistical and sequential frameworks, has shifted the focus of algorithmic machine learning to examine this interplay. In particular, on one hand, this intertwinement brings forward new challenges in reassessment of the performance of learning algorithms including generalization and regret bounds under the assumptions imposed by convexity such as analytical properties of loss functions (e.g., Lipschitzness, strong convexity, and smoothness). On the other hand, emergence of datasets of an unprecedented size, demands the development of novel and more efficient optimization algorithms to tackle large-scale learning problems. The overarching goal of this thesis is to reassess the smoothness of loss functions in statistical learning, sequential prediction/online learning, and stochastic optimization and explicate its consequences. In particular we examine how smoothness of loss function could be beneficial or detrimental in these settings in terms of sample complexity, statistical consistency, regret analysis, and convergence rate, and investigate how smoothness can be leveraged to devise more efficient learning algorithms.Comment: Ph.D. Thesi