The High Redundancy Actuator (HRA) project investigates a novel approach to fault tolerant actuation, which uses a high number of small actuation elements, assembled in series and parallel in order to form a single intrinsically fault tolerant actuator. Element faults affect the maximum capability of the overall actuator, but through control techniques, the required performance can be maintained. This allows higher levels of reliability to be attained in exchange for less over-dimensioning in comparison to conventional redundancy techniques. In addition, the combination of both serial and parallel elements provides intrinsic accommodation of both lock-up and loose faults. Research to date has concentrated on HRAs based on electromechanical technology, of relatively low order, controlled through passive Fault Tolerant Control (FTC) methods. The objective of this thesis is to expand upon this work. HRA configurations of higher order, formed from electromagnetic actuators are considered. An element model for a moving coil actuator is derived from first principles and verified experimentally. This element model is then used to form high-order, non-linear HRA models for simulation, and reduced-order representations for control design. A simple, passive FTC law is designed for the HRA configurations, the results of which are compared to a decentralised, active FTC approach applied through a framework based upon multi-agent concepts. The results indicate that limited fault tolerance can be achieved through simple passive control, however, performance degradation occurs, and requirements are not met under theoretically tolerable fault levels. Active FTC offers substantial performance improvements, meeting the requirements of the system under the vast majority of theoretically tolerable fault scenarios. However, these improvements are made at the cost of increased system complexity and a reliance on fault detection. Fault Detection (FD) and health monitoring of the HRA is explored. A simple rule-based FD method, for use within the active FTC, is described and simulated. An interacting multiple model FD method is also examined, which is more suitable for health monitoring in a centralised control scheme. Both of these methods provide the required level of fault information for their respective purposes. However, they achieve this through the introduction of complexity. The rule-based method increases system complexity, requiring high levels of instrumentation, and conversely the interacting multiple model approach involves complexity of design and computation. Finally, the development of a software demonstrator is described. Experimental rigs at the current project phase are restricted to relatively low numbers of elements for practical reasons such as cost, space and technological limitations. Hence, a software demonstrator has been developed in Matlab/Simulink which provides a visual representation of HRAs with larger numbers of elements, and varied configuration for further demonstration of this concept.

Un défi à court terme pour les industriels de l’aéronautique est de concevoir des produits sûrs, fiables, compactes, basse consommation et à faible impact environnemental due à la forte concurrence et à l’augmentation des attentes des clients et des autorités de certification. Un défi à plus long terme pour ces organisations est de pérenniser leur savoir-faire et leur expertise qui sont menacés par le départ en retraite de générations d’experts, ingénieurs et techniciens. Relever ces défis n’est pas une tâche facile lorsque les produits concernés sont des systèmes mécatroniques embarqués tel que les systèmes d’actionnement électromécaniques. La conception de ces systèmes complexes nécessite l’intégration de savoirs très hétérogènes dû à l’interaction entre de nombreux métiers de l’ingénierie et entre les différentes lois de la physique qui les caractérisent. De plus, les systèmes mécatroniques embarqués sont constitués de nombreux composants interdépendants. Faire face à l’interdépendance des composants reste une tâche non-triviale et fondamentale du métier d’ingénieur. Ceci provoque des itérations coûteuses durant le cycle de conception et des solutions non-optimisées. Les techniques d’optimisation multidisciplinaire fournissent des fondements théoriques et des outils de calculs permettant l’optimisation de systèmes comportant un grand nombre de variables et des couplages multidisciplinaires. Dans le but d’utiliser ces techniques pour un dimensionnement rapide des produits mécatroniques, des tâches doivent être effectuées : représentation du savoir de conception, décomposition et coordination des modèles pour l’évaluation et l’optimisation des performances du système. Les modèles algébriques ont été choisis pour représenter les différents modèles de conception. Une nouvelle formulation d’optimisation multidisciplinaire est proposée. Elle permet des convergences rapides et s’avère robuste au changement d’échelle. Une approche basée sur la théorie des graphes et le calcul symbolique est proposée pour aider les ingénieurs à la mise en place de problèmes à grand nombre de variables et comportant des couplages multidisciplinaires. Une méthodologie de dimensionnement est présentée ainsi que l’outil logiciel associé. L’objectif principal est de permettre un dimensionnement global des systèmes mécatroniques en se souciant de la réutilisation du savoir et la prise de décision rapide. La méthodologie est illustrée sur un cas académique de système d’actionnement. Ensuite, des systèmes plus complexes sont étudiés. Tout d’abord, la conception d’un système d’actionnement de commandes de vol primaire est effectuée. Enfin, un système d’actionnement d’inverseur de poussée électrique est dimensionné / The critical short term challenge for contemporary aerospace industrial companies is to design safe, reliable, compact, low power consumption and low environmental impact products, forces driven by economic competition and the increasing expectations of customers and certification authorities. A long-term challenge for these organizations is to manage their knowledge and expertise heritage, which is jeopardized due to forthcoming retirement of the current generation of experts, engineers and technicians. Undertaking these challenges is particularly intricate when it comes to embedded mechatronic systems used in electro-mechanical actuation systems. The design of these complex systems involves heterogeneous knowledge due to the interface of multiple engineering specializations and the interacting physical laws that govern their behaviour. Additionally, embedded mechatronic systems are composed of several interdependent components and sub-systems. Dealing with interdependencies remains a non-trivial and fundamental aspect of modern engineering practice. This can result in costly iterations during the design process and final non-optimal solutions. Multidisciplinary System Design Optimization techniques provide theoretical foundations and computational tools for optimizing large and multidisciplinary systems. Tasks must be performed to apply such techniques for rapid initial sizing of mechatronic products: modelling the design knowledge, partitioning and coordinating the models for system performances analysis and optimization. Algebraic analysis functions are chosen to represent the design models. A new Multidisciplinary System Design Optimization formulation for fast and robust analysis is proposed. A theoretic graph approach using symbolic manipulation to assist designers in formulating large and multidisciplinary problems is outlined. A specific design methodology and its associated framework developed are presented. The general objective is to allow holistic sizing of mechatronic engineering systems with emphasis placed on model reusability and rapid decision making. The methodology is illustrated using a simple aerospace actuation system example. More complex actuation systems are then addressed. First, the design of an electro-mechanical primary flight control actuation system is examined, subsequently; the design methodology is applied to an electrical thrust reverser actuation system.

In fin actuation systems, the performance of classical linear control systems is not satisfactory due to uncertainty of the system parameters and disturbances of the working medium. For this reason, sliding mode, H2 or H&infin / robust controllers are widely used in literature for such systems. However, use of such controllers results in very conservative system responses. Based on this fact, in this thesis, development of a more effective robust controller is aimed via integration of the optimum properties of the existent pure H2 and H&infin / type robust controllers. To achieve this, during the controller synthesizing procedure, some of the optimization parameters are weighted according to H2 norm minimization, and parameter uncertainties and other variables are weighted according to H&infin / theorem. First, the system set up to be controlled is physically constructed and performed system identification processes. Then, two different types of robust controllers H2 and H&infin / controllers are designed and tested over both the real system and simulation. Finally an H2/H&infin / mixed type controller synthesized and the results are compared with the outputs of the robust controllers of the previous step.

Lubricated friction issues are central to all hydraulic actuation systems undergoing motion and any in-depth understanding of the nature of lubricated friction will advance future component design. The classic friction models of hydraulic actuation systems under steady state conditions and their dependency on velocity and temperature have been studied extensively over the past years. A model which is commonly employed to represent the characteristics of friction is that of Stribeck in which the dependency of the friction force is based on velocity alone. However, experimentally, it has been found that lubricated friction is dependent on acceleration. Thus, the Stribeck model can be considered as a subset of a dynamic friction model in which acceleration is zero. Thus, it can be concluded that the Stribeck model is best applied to cases when the change rate of the velocities is very small. This thesis considers the dependency of lubricated friction on acceleration when pressure and temperature changes are relatively constant. As such, the basic hypothesis for this study was proposed as follows: “Lubricated friction in hydraulic actuation systems is not only a function of velocity, but is also a function of both velocity and acceleration”. In this thesis several terms are defined which facilitate the description under which friction models are developed. For example, the term non-steady state friction is used to account for the effect of acceleration on lubricated friction force while in motion. Further, the lubricated friction models are divided into two groups: steady state friction models and non-steady state friction models. Nonlinear friction modeling and measuring methods are reviewed in this dissertation. This review also includes nonlinear lubricated friction modeling in hydraulic actuation systems. A conclusion from this review was that limited research has been done in documenting and explicitly demonstrating the role of acceleration on lubricated friction. The research first introduced a methodology to experimentally measure friction as a function of acceleration and to demonstrate this dependency in the form of a three dimensional graph. A novel technique to experimentally obtain data for the lubricated friction model was introduced. This allowed the lubricated friction forces to be measured as a function of velocity in a continuous manner, but with acceleration being held constant as a family parameter. Two different valve controlled hydraulic actuation systems (VCHAS) were studied under a wide variety of accelerations at constant temperature and pressure. To enable repeatable data collection for the different friction conditions and to accommodate for the effect of hysteresis, a periodic parabolic displacement waveform was chosen which enabled the acceleration to be a family parameter. The second phase of the research introduced a method of representing the data (lubricated friction model) in a lookup table form. The relationship of lubricated friction (in this work, pressure differential, ΔP across the actuator) as a function of velocity and acceleration was presented in a unique semi-empirical 2D lookup table (2D LUT). Limitations of this experimental approach were identified, but the dependency on acceleration was clearly established. The last phase of the study implemented this 2D LUT model into a practical software model of an actuator and demonstrated its accuracy when compared to its experimental counterpart. The semi-empirical model (2D LUT) was experimentally verified by implementing the semi-empirical and Stribeck models into a real time simulation of an actuator and by comparing the experimental outputs against simulated outputs for a common sinusoidal input. A sinusoidal actuator displacement input was chosen to test the simulations as it was not used in the collection of the original data. The output of the simulation was compared to the experimental results and it was evident that for the range in which data could be collected in developing the model, the proposed 2D LUT model predicted an output that was superior to a model which used a standard Stribeck model. It was concluded that the semi-empirical model could be integrated into a simulation environment and predict outputs in a superior fashion when compared to the Stribeck friction model. Thus it was concluded that the stated hypothesis is consistent with the experimental evidence shown by all hydraulic actuators considered. Further, it was also observed that the traditional Stribeck form (steady state dynamic friction) does change with increasing acceleration to the point that the standard breakaway friction almost disappears. It is evident that the 2D LUT is a viable tool for modeling the non-steady state friction of hydraulic actuation systems. The semi-empirical 2D LUT model so developed is a more global representation of hydraulic actuator lubricated friction. In this research, only linear hydraulic actuators were considered; however, the novel nonlinear semi-empirical 2D LUT lubricated friction model can be applied to any actuator (linear and rotary) and provides a new way in which the dynamic friction can be viewed and modeled.

[pt] Sistemas pneumáticos são equipamentos leves, baratos, limpos e de baixo risco, sendo apropriados para aplicações que necessitem de força e rapidez de resposta. Por outro lado, esse tipo de sistema apresenta restrições devido à principal característica do ar: sua compressibilidade confere efeitos não lineares ao sistema, desde um escoamento turbulento pelas válvulas de controle até sua atuação dentro do cilindro – a qual inclui alta sensibilidade ao atrito e volumes inativos durante o curso do pistão. Essas características particulares dificultam seu controle e posicionamento preciso e limitam sua aplicação, principalmente considerando seu emprego em um mecanismo tipo Plataforma de Stewart em escala reduzida. No presente trabalho apresenta-se a modelagem, simulação computacional e análise experimental do comportamento dinâmico de um sistema de atuação pneumático que inclui uma válvula de controle de vazão não convencional, composta de quatro válvulas proporcionais, e um atuador com haste simples de dupla ação. O objetivo deste trabalho é, baseado nos resultados experimentais, determinar as características desses componentes para desenvolver estratégias de controle em tempo real capazes de minimizar os efeitos das não linearidades típicas, visando sua utilização no mecanismo anteriormente mencionado. / [en] Pneumatic equipment is lightweight, cheap, clean and low-risk, being suitable for applications that require strength and high responsiveness. Nevertheless, this type of system has some limitations due to the air main feature: its compressibility results in nonlinear effects in the system, from the turbulent flow control valves to its performance inside the cylinder - which includes high sensitivity to friction and dead volumes during the stroke piston. These particular characteristics make its control and precise positioning difficult, limiting its application, especially when considered its use in a mechanism such as a Stewart Platform in a reduced scale. The present paper presents the modeling, computational simulation and experimental analysis of the dynamic behavior of a pneumatic actuation system that includes an unconventional flow control valve, consisting of four proportional valves, and a double acting single rod actuator. The final goal of this work is to, based on experimental results, determine the characteristics of these components in order to develop real-time control strategies which can minimize the effects of those typical nonlinearities for their use in the mechanism mentioned above.

Currently the system development of aircraft engineering concentrates its focus on the reduction of energy consumption more than ever before. As a consequence, the efficiency of subsystems inside the aircraft is highlighted. According to previous investigations the simplification/unification of conventional multifaceted board energy systems by means of electric power management is the most promising way concerning aircraft global efficiency improvement. The main aim of the present work was to optimize a multi-device, heavy duty EHA-System by introducing of a comprehensive perspective. In order to achieve the final, non-plus-ultra improvement level, the attributes of architecture, hardware and operation method were combined in an interactive manner, whereas particular attention has been paid to the mutual enhancing influences. The maximum reduction of losses, the minimizing of consumption and weight optimization can be achieved concurrently when the physical coherences between the involved subsystems are understood and their hidden potentials are exploited. This can only be achieved in one way and the detail follows: The most effective way to reduce both manufacturing effort and weight is to introduce a multiple-allocation philosophy. The highest reliability possible can be achieved by novel cascade-nested system architecture and strict restraining of the control logic. By employing an ultra-low-loss hardware concept, the energy efficiency can be maximized at a necessary minimum own weight. Last but not least, possibly the most important cognition is that an intelligent operation method will improve the actual system and influence the entire system positively and with a lower effort. The final conclusion is that the only and reasonable way to achieve an ultimate optimized solution of an actuation system is an all-encompassing consideration. Eventually it was to recognize that the final result is nothing but ultimate lightweight architecture, i.e. a non-plus-ultra solution. / Gegenwärtig konzentriert sich die Technologieentwicklung für Flugzeuge auf die Reduktion des Energieverbrauchs mehr denn je zuvor. Hierfür ist die Effizienz der an Bord befindlichen, nicht propulsiven Subsysteme neben der Wirkungsgradverbesserung der Triebwerke von zentraler Bedeutung. Laut vorangegangenen Untersuchungen und Studien ist die Vereinfachung bzw. Vereinheitlichung der Vielfalt der konventionellen Bordenergiesysteme durch ein adäquates Energiemanagement unter Verwendung von Elektrizität der aussichtsreichte Weg zur Effizienzverbesserung auf der Gesamtflugzeugebene. Durch die Elektrifizierung wurden die einzelnen Geräte zwar zuverlässiger und energieeffizienter als je zuvor aber gleichzeitig erheblich schwerer, sodaß ein signifikanter Verlust an Nutzlasten auf Gesamtflugzeugebene hervorgerufen wird. Das Hauptziel der vorliegenden Arbeit war es, ein Schwerlast-EHA-System mit mehrfachen Betätigungseinheiten durch Einführung von umfassenden Perspektiven zu optimieren. Durch Einführung der sog. ganzheitlichen Leichtbauweise demonstriert die Arbeit, wie das Subsystem mit mehreren Endgeräten ultimativ optimiert werden kann, ohne Abstriche an Gewichtsbilanz u/o Kompromiß mit der Energieeffizienz zu machen. Um eine wahrhaftige Optimierung, d.h. die Erreichung des ultimativen, Nonplusultra-Verbesserungslevels zu erreichen, wurden die Systemarchitektur, die Hardware und die Operationsmethode interaktiv kombiniert, wobei die besondere Aufmerksamkeit auf die interaktiven, zur Verbesserung führenden Einflüsse gelegt wurde. Die Minimierung des Energieverbrauchs und die ultimative Gewichtsoptimierung gleichzeitig können erreicht werden, wenn die physikalischen Zusammenhänge zwischen den involvierten Subsystemen verstanden und ihre verborgenen Potentiale ausgenutzt werden. Der einzige und vernünftige Weg zur Erreichung der ultimativen Optimierung eines Betätigungssystems ist eine allumfassende Betrachtung, also eine ganzheitliche Betrachtungs- bzw. Vorgehensweise.