Aeroelastic Stability Assessment Of a CS-25 Category Aircraft Equipped With Multi-Modal Wing Morphing Devices

Morphing wing structures have the greatest ambition to dramatically im-prove aircraft aerodynamic performance (less fuel consumption) and reduce aerodynamic noise. Several studies in the literature have shown their potential for increased aerodynamic efficiency across nearly all flight conditions, en-hanced aircraft maneuverability and control effectiveness, decreased take-off/landing length, reduced airframe noise, etc. However, despite a long herit-age of research, morphing wing technology has yet to be approved by the Euro-pean Aviation Safety Authority (EASA) for use in commercial aviation. Models and approaches capable to predict the aeroelastic impact of a morphing wing still need to be matured to safely alter design and operation of future genera-tions of aircraft. Additionally, a number of practical challenges remain to be addressed in the suitable materials, systems reliability, safety and maintenance. Due to the reduced stiffness, increased mass and increased Degree Of Freedom (DOF) with respect to conventional wings, these mechanical systems can cause significant reduction of aircraft flutter margins. This aspect requires dedicated aeroelastic assessments since the early stages of the design process of such an innovative wing. Flutter boundaries predictions need sensitivity anal-yses to evaluate bending/torsional stiffness and inertial distribution variability ranges of the aircraft wing equipped with the morphing wing devices. In such a way, aeroelastic assessments become fundamental to drive a balance between weight and stiffness of the investigated adaptive systems. Furthermore, in pseu-do rigid-body mechanisms-based morphing structures, the inner kinematics is so important that its faults may compromise the general aircraft-level functions. Similarly to the demonstration means of safety compliance, commonly applied to aircraft control surfaces, the novel functions resulting from the integration of adaptive devices into flying aircraft thus impose a detailed examination of the associated risks. In the framework of Clean Sky 2 Airgreen 2 project, the author provides advanced aeroelastic assessments of two adaptive devices enabling the camber morphing of winglets and flaps, conceived for regional aircraft integration (EASA CS-25 category). Segmented ribs architectures ensure the transition from the baseline (or un-morphed) shape to the morphed ones, driven by em-bedded electromechanical actuators. Some of the advantages resulting from the combination of the two aforementioned morphing systems are wing load con-trol, lift-over-drag ratio increase and root bending moment alleviation. The aircraft aeroelastic model was generated by means of the proprietary code SANDY 3.0. Then, the same code was adopted to solve the aeroelastic stability equa-tions through theoretical modes association in frequency domain. To carry out multi-parametric flutter analyses (P-K continuation method), the actuation lines stiffness and winglet/flap tabs inertial parameters were considered in combina-tion each other. Nominal operative conditions as well as systems malfunction-ing or failures were examined as analyses cases of the investigated morphing devices, together with actuators free-play conditions. Proper design solutions were suggested to guarantee flutter clearance in accordance with aircraft stabil-ity robustness with respect to morphing systems integration, evaluated through a combination of “worst cases” simulating the mutual interaction among the adaptive systems. The safety-driven design of the morphing wing devices required also a thorough examination of the potential hazards resulting from operational faults involving either the actuation chain, such as jamming, or the external interfaces, such as loss of power supplies and control lanes, and both. The main goal was to verify whether the morphing flap and winglet systems could comply with the standard civil flight safety regulations and airworthiness requirements (EASA CS25). More in detail, a comprehensive study of systems functions was firstly qualitatively performed at both subsystem and aircraft levels to identify poten-tial design faults, maintenance and crew faults, as well as external environment risks. The severity of the hazard effects was thus determined and then ranked in specific classes, indicative of the maximum tolerable probability of occurrence for a specific event, resulting in safety design objectives. Fault trees were final-ly produced to assess the compliance of the system architectures to the quanti-tative safety requirements resulting from the FHAs

Mathematical Modeling and Control of Nonlinear Oscillators with Shape Memory Alloys

Shape memory alloys (SMAs) belong to an interesting type of materials that have attracted the attention of scientists and engineers over the last few decades. They have some interesting properties that made them the subject of extensive research to find the best ways to utilize them in different engineering, biomedical, and scientific applications. In this thesis, we develop a mathematical model and analyze the behavior of SMAs by considering a one degree of freedom nonlinear oscillator consisting of a mass connected to a fixed frame through a viscous damping and a shape memory alloy device. Due to the nonlinear and dissipative nature of shape memory alloys, optimal control and Lyapunov stability theories are used to design a controller to stabilize the response of the one degree of freedom nonlinear oscillator. Since SMAs exist in two phases, martensite and austenite, and their phase transformations are dependent on stress and temperature, this work is presented in two parts. The first part deals with the nonlinear oscillator system in its two separate phases by considering a temperature where the SMA exists in only one of the phases. A model for each phase is developed based on Landau-Ginzburg-Devonshire theory that defines the free energy in a polynomial form enabling us to describe the SMAs shape memory effect and pseudoelasticity. However, due to the phenomenon of hysteresis in SMAs, the response of the nonlinear oscillator with a SMA element, in either phase, is chaotic and unstable. In order to stabilize the chaotic behavior, an optimal linear quadratic regulator controller is designed around a stable equilibrium for the martensitic and the austenitic phases. The closed-loop response for each phase is then simulated and computational results are presented. The second part of the thesis deals with the entire system in its dynamics by combining the two phases and taking into account the effect of temperature on the response of the system. Governing equations for the system\u27s thermo-mechanical dynamics are constructed using conservation laws of mass, momentum, and energy. Due to the complexity of the derived thermo-mechanical model, and the need to control the nonlinear oscillator, a model reduction based on the Galerkin method is applied to the new system in order to derive a low-dimensional model which is then solved numerically. A linear feedback control strategy for nonlinear systems is then implemented to design a tracking controller that makes the system follow a given reference input signal. The work presented in this thesis demonstrates how SMAs can be modeled by using efficient methodologies in order to capture their behavior, and how SMAs can be made stable and their chaotic behavior can be controlled by using linear and nonlinear control methods

Modeling and Control of Piezoelectric Actuators

Piezoelectric actuators (PEAs) utilize the inverse piezoelectric effect to generate fine displacement with a resolution down to sub-nanometers and as such, they have been widely used in various micro- and nanopositioning applications. However, the modeling and control of PEAs have proven to be challenging tasks. The main difficulties lie in the existence of various nonlinear or difficult-to-model effects in PEAs, such as hysteresis, creep, and distributive vibration dynamics. Such effects can seriously degrade the PEA tracking control performances or even lead to instability. This raises a great need to model and control PEAs for improved performance. This research is aimed at developing novel models for PEAs and on this basis, developing model-based control schemes for the PEA tracking control taking into account the aforementioned nonlinear effects. In the first part of this research, a model of a PEA for the effects of hysteresis, creep, and vibration dynamics was developed. Notably, the widely-used Preisach hysteresis model cannot represent the one-sided hysteresis of PEAs. To overcome this shortcoming, a rate-independent hysteresis model based on a novel hysteresis operator modified from the Preisach hysteresis operator was developed, which was then integrated with the models of creep and vibration dynamics to form a comprehensive model for PEAs. For its validation, experiments were carried out on a commercially-available PEA and the results obtained agreed with those from model simulations. By taking into account the linear dynamics and hysteretic behavior of the PEA as well as the presliding friction between the moveable platform and the end-effector, a model of the piezoelectric-driven stick-slip (PDSS) actuator was also developed in the first part of the research. The effectiveness of the developed model was illustrated by the experiments on the PDSS actuator prototyped in the author's lab. In the second part of the research, control schemes were developed based on the aforementioned PEA models for tracking control of PEAs. Firstly, a novel PID-based sliding mode (PIDSM) controller was developed. The rational behind the use of a sliding mode (SM) control is that the SM control can effectively suppress the effects of matched uncertainties, while the PEA hysteresis, creep, and external load can be represented by a lumped matched uncertainty based on the developed model. To solve the chattering and steady-state problems, associated with the ideal SM control and the SM control with boundary layer (SMCBL), the novel PIDSM control developed in the present study replaces the switching control term in the ideal SM control schemes with a PID regulator. Experiments were carried out on a commercially-available PEA and the results obtained illustrate the effectiveness of the PIDSM controller, and its superiorities over other schemes of PID control, ideal SM control, and the SMCBL in terms of steady state error elimination, chattering suppression, and tracking error suppression. Secondly, a PIDSM observer was also developed based on the model of PEAs to provide the PIDSM controller with state estimates of the PEA. And the PIDSM controller and the PIDSM observer were combined to form an integrated control scheme (PIDSM observer-controller or PIDSMOC) for PEAs. The effectiveness of the PIDSM observer and the PIDSMOC were also validated experimentally. The superiority of the PIDSMOC over the PIDSM controller with σ-β filter control scheme was also analyzed and demonstrated experimentally. The significance of this research lies in the development of novel models for PEAs and PDSS actuators, which can be of great help in the design and control of such actuators. Also, the development of the PIDSM controller, the PIDSM observer, and their integrated form, i.e., PIDSMOC, enables the improved performance of tracking control of PEAs with the presence of various nonlinear or difficult-to-model effects

Dynamic Modeling and Control System Design for Shape Memory Alloy Actuators

Shape memory alloy (SMA) is a type of smart material which remembers its original state. It is light weight and small, and known to provide high contraction force with low noise. Its application has wide range from robotics to medical science. One of its potential applications in space is a supporting system of membrane structure that can be used as synthetic aperture radar (SAR) antenna to achieve high flatness. It exhibits nonlinear phenomena called hysteresis when it's electrically heated. Hysteresis is a nonlinear phenomenon that refers to the dependence of a physical system on the environment. Hysteresis in SMA causes a major difficulty in control system design. Un-modeled or poorly modeled hysteresis introduces inaccuracy in tracking and the performance of the system. Experimental test bench is constructed for one set of SMA actuators that resembles the membrane structure's supporting system. Hysteresis is obtained by running open loop test with the test bench. Dynamic model of the SMA wires is developed using classical Preisach model and modified Maxwell model. Then the inverse model is implemented in feed-forward loop to compensate for nonlinear hysteresis. Simple feedback controllers are added to correct the modeling errors. Experimental results reveal that the error is significantly reduced when comparing feedback controller with hybrid feedback and feed-forward controller

A Methodology Towards Comprehensive Evaluation of Shape Memory Alloy Actuators for Prosthetic Finger Design

Presently, DC motors are the actuator of choice within intelligent upper limb prostheses. However, the weight and dimensions associated with suitable DC motors are not always compatible with the geometric restrictions of a prosthetic hand; reducing available degrees of freedom and ultimately rendering the prosthesis uncomfortable for the end-user. As a result, the search is on-going to find a more appropriate actuation solution that is lightweight, noiseless, strong and cheap. Shape memory alloy (SMA) actuators offer the potential to meet these requirements. To date, no viable upper limb prosthesis using SMA actuators has been developed. The primary reasons lie in low force generation as a result of unsuitable actuator designs, and significant difficulties in control owing to the highly nonlinear response of SMAs when subjected to joule heating. This work presents a novel and comprehensive methodology to facilitate evaluation of SMA bundle actuators for prosthetic finger design. SMA bundle actuators feature multiple SMA wires in parallel. This allows for increased force generation without compromising on dynamic performance. The SMA bundle actuator is tasked with reproducing the typical forces and contractions associated with the human finger in a prosthetic finger design, whilst maintaining a high degree of energy efficiency. A novel approach to SMA control is employed, whereby an adaptive controller is developed and tuned using the underlying thermo-mechanical principles of operation of SMA wires. A mathematical simulation of the kinematics and dynamics of motion provides a platform for designing, optimizing and evaluating suitable SMA bundle actuators offline. This significantly reduces the time and cost involved in implementing an appropriate actuation solution. Experimental results show iii that the performance of SMA bundle actuators is favourable for prosthesis applications. Phalangeal tip forces are shown to improve significantly through bundling of SMA wire actuators, while dynamic performance is maintained owing to the design and implementation of the selected control strategy. The work is intended to serve as a roadmap for fellow researchers seeking to design, implement and control SMA bundle actuators in a prosthesis design. Furthermore, the methodology can also be adopted to serve as a guide in the evaluation of other non-conventional actuation technologies in alternative applications

A review of modelling and analysis of morphing wings

Morphing wings have a large potential to improve the overall aircraft performances, in a way like natural flyers do. By adapting or optimising dynamically the shape to various flight conditions, there are yet many unexplored opportunities beyond current proof-of-concept demonstrations. This review discusses the most prominent examples of morphing concepts with applications to two and three-dimensional wing models. Methods and tools commonly deployed for the design and analysis of these concepts are discussed, ranging from structural to aerodynamic analyses, and from control to optimisation aspects. Throughout the review process, it became apparent that the adoption of morphing concepts for routine use on aerial vehicles is still scarce, and some reasons holding back their integration for industrial use are given. Finally, promising concepts for future use are identified

Earthquake resistance of composite beam-columns.

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Lightweight In-Plane Actuated Deformable Mirrors for Space Telescopes

This research focused on lightweight, in-plane actuated, deformable mirrors, with the ultimate goal of developing a 20- meter light gathering aperture for space telescopes. The 0.127 meter diameter deformable mirror small scale testbed was modelled infinite elements using MSC.Nastran software and then used as a basis for a quasi-static controller. Experimental tracking of Zernike tip, tilt, and defocus modes was accomplished. The analytical solutions to plate-membrane and beam-string ordinary differential equations were developed. A simplified approach to modelling the axisymmetric cases was also presented. A novel static control strategy, the Modal Transformation Method, was developed to form Zernike surfaces within an interior, or clear aperture, region using a number of statically-actuated Bessel-based vibration modes. The scaling problem for membrane optics is addressed. Significantly, it is shown linear modelling may correctly explain the behavior of small-scale models, but only non-linear models will account for the important terms which govern the full-scale large aperture membrane telescopes

Soft-Landing Control of Short-Stroke Reluctance Actuators

Los actuadores de reluctancia se utilizan ampliamente debido a sus altas densidades de fuerza y baja disipación de calor. En particular, los actuadores de reluctancia simples de una sola bobina de carrera corta, como los relés electromecánicos y las electroválvulas, son la mejor opción para operaciones de conmutación de encendido y apagado en muchas aplicaciones debido a su bajo coste, tamaño y masa. Sin embargo, un inconveniente importante es el fuerte impacto al final de cada conmutación, que provoca rebotes, desgaste mecánico y ruido acústico. Son fenómenos muy indeseables que restan valor a las ventajas evidentes de estos actuadores y limitan su rango de aplicaciones potenciales.Esta tesis se centra en el desarrollo y estudio de soluciones de control de aterrizaje suave para actuadores de reluctancia de carrera corta, con el objetivo de minimizar sus velocidades de impacto. Es importante indicar que la eficiencia de dichos dispositivos se produce a costa de serios retos teóricos y prácticos en cuanto a su control, por ejemplo, dinámicas rápidas, híbridas y altamente no lineales, fenómenos electromagnéticos complejos, variabilidad entre unidades y falta de medidas de posición durante el movimiento.El punto de partida es la modelización del sistema, teniendo en cuenta sus subsistemas interconectados eléctricos, magnéticos y mecánicos. El objetivo principal de los modelos es servir para el desarrollo de métodos de control y estimación. Por lo tanto, se trata de modelos de parámetros concentrados expresados como representaciones del espacio de estados. Se especifican diferentes fenómenos electromagnéticos, con especial atención a la histéresis magnética. Se proponen dos tipos de modelos de diferente complejidad según se incorpore o se desprecie el fenómeno de la histéresis magnética.El primer enfoque para el control del aterrizaje suave es el diseño óptimo de las trayectorias de posición y sus correspondientes señales de entrada. La propuesta tiene en cuenta la incertidumbre en la posición del contacto y, por tanto, las soluciones obtenidas son más robustas. Mientras que las señales de entrada generadas son eficaces para las estrategias de control en lazo abierto, las trayectorias de posición generadas pueden utilizarse controles de prealimentación o de retroalimentación.Para mejorar la robustez de los controladores de lazo abierto, también proponemos una estrategia run-to-run que adapta iterativamente las señales de entrada. En concreto, está diseñada para trabajar conjuntamente con un controlador de prealimentación basado en las mencionadas trayectorias de posición construidas de forma óptima. Para el algoritmo de aprendizaje ciclo a ciclo, se elige una técnica de optimización, se ajusta y se compara con dos alternativas.Otro enfoque explorado es el control de retroalimentación para el seguimiento de trayectorias predefinidas de posición. La solución propuesta es un controlador estrictamente conmutativo en modo deslizante. Está enfocado en la simplicidad para facilitar su implementación, al tiempo que se tiene en cuenta la dinámica híbrida. Los análisis teóricos y simulados demuestran que el aterrizaje suave es posible con tasas de muestreo razonables.Los controladores de retroalimentación y otros controladores de seguimiento requieren mediciones o estimaciones precisas de la posición. Como la medición de la posición raramente es práctica, parte de la investigación se dedica al diseño de estimadores de estado. La principal propuesta es un suavizador Rauch-Tung-Striebel ampliado para sistemas no lineales, que incluye varias ideas nuevas relacionadas con el modelo discreto, las entradas y las salidas. Los análisis simulados demuestran que el efecto combinado de las nuevas adiciones da lugar a mucho mejores estimaciones de la posición.Reluctance actuators are widely used due to their high force densities and low heat dissipation. In particular, simple short-stroke single-coil reluctance actuators, such as electromechanical relays and solenoid valves, are the best choice for on-off switching operations in many applications because of their low cost, size and mass. However, a major drawback is the strong impact at the end of each commutation, which provokes bouncing, mechanical wear and acoustic noise. They are very undesirable phenomena that detract from the evident advantages of these actuators and limit their range of potential applications. This thesis focuses on the development and study of soft-landing control solutions for short-stroke reluctance actuators, aiming at minimizing their impact velocities. It is important to indicate that the efficiency of the aforementioned devices comes at the cost of serious theoretical and practical challenges regarding their control, e.g., fast, hybrid and highly nonlinear dynamics, complex electromagnetic phenomena, unit-to-unit variability and lack of position measurements during motion. The starting point is the system modeling, accounting for their interconnected electrical, magnetic and mechanical subsystems. The main purpose of the models is to be used for the development of control and estimation methods. Therefore, they are lumped-parameter models expressed as state-space representations. Different electromagnetic phenomena are specified, with special attention to the magnetic hysteresis. Two model types of different complexities are proposed depending on whether the magnetic hysteresis phenomenon is incorporated or neglected. The first approach for soft-landing control is the optimal design of position trajectories and their corresponding input signals. The proposal considers uncertainty in the contact position, and hence, the obtained solutions are more robust. While the generated input signals are effective for open-loop control strategies, the generated position trajectories can be used in feedforward or feedback control. In order to improve the robustness of open-loop controllers, we also propose a run-to-run strategy that iteratively adapts the input signals. Specifically, it is designed to work in conjunction with a feedforward controller based on the aforementioned optimally constructed position trajectories. For the cycle-to-cycle learning algorithm, an optimization technique is chosen, adjusted and compared to two alternatives. Another explored approach is feedback control for tracking predefined position trajectories. The proposed solution is a purely switching sliding-mode controller. The focus is on simplicity to facilitate its implementation, while also taking into account the hybrid dynamics. Theoretical and simulated analyses show that soft landing is achievable with reasonable sampling rates. Feedback and other tracking controllers require accurate measurements or position estimations. As measuring the position is rarely practical, part of the research is devoted to the design of state estimators. The main proposal is an extended Rauch–Tung–Striebel smoother, which includes several new ideas regarding the discrete model, the inputs and the outputs. Simulated analyses demonstrate that the combined effect of the novel additions results in much better position estimations.<br /