<p>Hydraulic systems are commonly used for actuation and manipulation of heavy loads. They are found in a variety of different industries, such as in automotive, manufacturing, robotics, construction, and aerospace. Conventional hydraulic systems use a centralized constant pressure supply system. Pressurized fluid is then channeled to actuators using servo-valves. The advantages of these systems are their high torque to mass ratio, and the ability to control speed and direction with relative precision. However, there are also disadvantages such as the requirement of a bulky centralized supply, leakage, noise, and reduced energy efficiency due to orifice flow and the requirement for maintaining a constant supply pressure.</p> <p>Electro-Hydrostatic Actuation systems (EHA) alleviate many of the above mentioned shortcomings of servo-valve controlled hydraulic systems. In the EHA position control is achieved by regulating the pumping action. Here, a fixed or a variable displacement pump can be used to move oil from one chamber of the actuator to the other. In these actuators, the presence of nonlinearities associated with pump/motor static friction and backlash, pressure drop in the piping system, and nonlinear friction at the load have a significant effect on the performance and positional precision of the system.</p> <p>This research will focus on developing a multiple inner-loop control strategy by implementing multiple inner-loops that utilize the differential pump/load position and velocity. The main goal will be to decrease the effect of the pump backlash as well as the nonlinear friction at the load; both of which negatively impact positional precision. Therefore, the main benefit of this method is an improvement in trajectory tracking precision, which is particularly important for high precision hydrostatic systems. Furthermore, a sliding mode control strategy will be incorporated into the design to suppress load oscillations reported in precision trajectory tracking applications. The research hypothesis states that sliding mode control in conjunction with multiple inner-loops, will improve the trajectory tracking performance of a hydrostatic actuation system by partially compensating the effects of static friction at the load. Theoretical analysis, simulation supported by experimental results are presented to demonstrate the effectiveness of the newly developed methods in suppressing the effects of nonlinearities on the EHA performance, with the downside of an increased complexity due to the increased number of controller parameters.</p> / Doctor of Philosophy (PhD)

In some industrial fields, such as aerospace, electro-hydrostatic actuators (EHAs) are increasingly used to replace conventional standard hydraulic actuators due to their better energy performance. Moreover, implementing different type or technology of actuators in redundant actuation systems working on the same moving part introduced some new challenges. This paper presents a force-tracking controller for an asymmetric electro-hydrostatic actuator that is submitted to an external motion generated by an external source. In this case, the rod displacement is considered as an external disturbance for the hydraulic cylinder, but it is assumed that this disturbance can be easily measured using sensors. The theoretical motivation of this work is discussed along and a variable gain state feedback control based on Linear Parameter Varying control (LPV) theory is proposed to achieve stability, disturbance rejection and tracking performance. The Linear Matrix Inequalities (LMI) framework is used to determine a control law including an augmented state feedback with an integral action that reduces trajectory-tracking errors. Simulation results of the control law are finally given to verify the global performance of this control design.

Electro-hydrostatic compact drives are an emerging technology within a range of industrially available translational drive solutions, combining the specific advantages of hydraulic and electromechanical screw drives. Compared to electromechanical screw drives, hydrostatic drives can vary their transmission ratio with comparably little effort, giving them the key advantage of downsizing the electric drive components for a given load cycle. This paper provides a guideline on how to calculate the downsizing potential of electric motors and inverters arising from variable transmission ratio based on the load regime of a given application. Furthermore, a comprehensive systematisation of the actual switching process is described for systems that are switched by means of switching valves. The presented set of methodology is applied to demonstrators in order to validate the general findings.

<p><h1>Abstract</h1></p> <p>As a compact, robust, and reliable power distribution method, hydraulic systems have been used for flight surface control for decades. Electro-hydrostatic Actuator (EHA) is increasingly replacing the conventional valve-controlled system for better performance, lighter weight and higher energy efficiency. The EHA is increasingly being used for flight control. As such its reliability is thereby critical important for flight safety. This research focuses on fault detection and diagnosis (FDD) for the EHA to enable predictive unscheduled maintenance when fault detected at its inception.</p> <p>An EHA prototype previously built at McMaster University is studied in this research and modified to physically simulate two faults conditions pertaining to leakage and friction. Nine different working conditions including normal running and eight fault conditions are simulated. Physical model has been derived mathematically capable of numerically simulating the fault conditions. Furthermore, for comparison, parametric model was obtained through system identification for each fault condition. This comparison revealed that parametric models are not suitable for fault detection and diagnosis due to the computation complexity.</p> <p>The FDD approach in this research uses model-based state estimation using filters. The filter based combined with the Interacting Multiple Model fault detection and diagnosis algorithm is introduced. Based on this algorithm, three FDD strategies are developed using a combination of the Extended Kalman Filter and IMM (IMM-EKF), the Smooth Variable Structure Filter with Varying Boundary and IMM (IMM-SVSF (VBL)), and the Smooth Variable Structure Filter with Fixed Boundary and IMM (IMM-SVSF (FBL)). All the three FDD strategies were implemented on the EHA prototype. Based on the results, the IMM-SVSF (VBL) provided the best performance. It detected and diagnosed faults correctly at high mode probabilities with excellent robustness to modeling uncertainties. It also was able to detect slow growing leakage fault, and predicted the changing trend of fault conditions.</p> / Master of Applied Science (MASc)

Dans les dernierès années la politique des entreprises s'est concentrée sur la recherche de solutions industrielles plus écologiques pour réduire l'impact sur l'environnement et l'énergie consommée. La tendance s’est élargie aux machines stationnaires dans l'automatisation industrielle. Il inclut la technologie d’entraînement pour contrôler le mouvement séquentiel de plusieurs axes dans les presses à injecter. La conception des systèmes se focalise sur une approche conduisant à l’amélioration du rendement énergétique aussi bien que l’augmentation de la pression de service, la réduction de cycle de la machine et l’amélioration de sa répétabilité. Toutes ces exigences ont poussé la technologie d’entraînement à se développer en augmentant l'intérêt pour les modules électromécaniques et électro-hydrostatiques (EHM). Dans cette thèse, une solution innovatrice d'EHM est proposée qui associe un convertisseur, un servomoteur AC brushless et la pompe à palettes Parker. En détail, l'intérêt de recherche concerne le développement d'un modèle à niveau système de la pompe à palette. L'objectif principal est de permettre l'évaluation des pertes d'énergie de la pompe et la performance de module pendant des phases spécifiques du cycle de la machine : accélération, dépressurisation et phase de maintien de la pression. Premièrement analysée au moyen de l'approche analytique, la dynamique est alors évaluée par des modèles plus avancés basés sur le prototypage virtuel construit dans l'environnement LMS-AMESim. Les avantages concernant la prévision des performances du module EHM et sur l’évaluation des paramètres fondamentaux inconnus (comme la compressibilité du fluide et le contenu d’air dans le fluide) sont montrés par comparaison avec des résultats expérimentaux obtenus dans le laboratoire. Les phénomènes de la cavitation et d’aération sont aussi pris en compte pendant les phases d'accélération et des modèles sont ainsi développés pour prévoir les conditions de fonctionnement qui promeuvent ces phénomènes. La consommation d'énergie de l'EHM est alors analysée au moyen des modèles thermo-hydrauliques capables de déterminer les échanges de chaleur entre les composants de module et l'environnement. / In last years companies’ policy has been focusing on research of more eco-friendly solutions in order to reduce the environmental impact and the consumed energy. The trend has been affecting the stationary machinery in the industrial automation too. It includes the drive technology for motion control in the injection moulding machines. The design studies concern energy efficiency improvement, as well as increased service pressure, shorter cycle time and repeatability over a long period of time. All these requirements have led the drive technology to evolve by increasing the interest for the electro-mechanical and electro-hydrostatic modules (EHM). In this thesis an innovative solution of EHM is proposed that associates industrial inverter, AC brushless servo motor and fixed-displacement low-noise Parker vane pump. In detail, the research interest concerns the development of a system level model of the vane pump. The main objective is to enable assessing the pump energy losses and full module performance in specific phase of machine’s cycle: acceleration, depressurisation and holding pressure phases. Firstly analysed by means of analytical approach, dynamics are then evaluated through more advanced models based on virtual prototyping built in LMS-AMESim environment. The advantages on predicting the EHM performance and on estimating the unknown fundamental parameters (e.g. Bulk Modulus and fluid air content) are showed through comparison with experimental results obtained in laboratory. The cavitation/aeration phenomena are also taken into account during acceleration transients and models are thus developed in order to predict the operating conditions which promote these phenomena. Energy behaviour of the EHM is then analysed by means of thermal hydraulic models able to determine the heat exchanges between module components and environment.

Hydrostatische Zylinderantriebe mit drehzahlvariablem Pumpenantrieb stellen modulare translatorische Antriebssysteme dar, die die Vorteile der elektrome-chanischen und hydraulischen Domänen verbinden. Zusätzlich bieten diese sog. elektrohydrostatischen Kompaktantriebe den Vorteil einer einfach umsetzbaren, diskret variablen Übersetzung. Diese erlaubt es, bei Arbeitsspielen mit dedizierten Eil- und Kraftphasen den elektrischen Antriebsmotor kleiner auszulegen als bei einer Referenz mit fester Übersetzung. Dadurch kann Downsizing-Potential in Bezug auf Größe und Masse des elektrischen Antriebsmotors und der Leistungselektronik erschlossen werden. In der vorliegenden Arbeit werden zunächst die möglichen Ersparnisse durch diese Technologie beleuchtet und die prinzipiellen Möglichkeiten einer schaltbaren Übersetzung dargestellt. Es wird eine Methodik erarbeitet, die es erlaubt, den gesamten Lösungsraum diskret umschaltbarer elektrohydrostatischer Kompaktantriebe systematisch zu erfassen und zu bewerten. Schließlich werden anhand von zwei Demonstratoren die Grenzen und Potentiale der Technologie experimentell untersucht und unterschiedliche, im Rahmen der Arbeit erarbeitete Strategien für den Umschaltvorgang zwischen zwei Übersetzungsstufen validiert. / Hydrostatic cylinder drives with variable speed pumps pose a modern form of modular translational drive systems, which merge the benefits of both electro-mechanic and hydraulic domains. Beyond that, these so called electrohydrostatic compact drives feature a possibility of implementing a discrete variable trans-ission ratio in a cost-effective manner. In the case of work cycles with dedicated rapid and force strokes, this allows the electric drive motor to be designed smaller than in the case of a reference with a fixed transmission ratio. In this way, downsizing potential can be exploited in terms of the size and mass of the electric drive motor and power electronics. In this thesis, the possible gains through this technology are first examined and the fundamental possibilities of a variable transmission are presented. A methodology is developed that allows the entire solution space of discretely switchable electrohydrostatic compact drives to be systematically mapped and evaluated. Finally, the limits and potentials of the technology are investigated experimentally by means of two demonstrators, and different strategies for the switching process between two transmission stages developed in the course of the thesis are validated.

A novel Electro-Hydrostatic Actuator (EHA) prototype – designed to operate on subsea gate valves in deep and ultra-deep water – is analysed and qualified in terms of functionality under design and normative constraints. The prototype is assembled in a test bench for load control in a hyperbaric chamber where the high subsea environmental pressure can be emulated. The process variables under evaluation are monitored through a set of pressure and position sensors, which are part of the prototype design. The experimental results demonstrate a robust behaviour of the actuator concerning the imposed external pressure and load forces even with a forced limitation in its power input. Moreover, the prototype performs consistently throughout the entire endurance trial, asserting high reliability. With the results obtained, the subsea EHA concept is effectually eligible to a technology readiness level 4, according to the API 17N.

Recent Power On Demand approaches, realized by using speed and/or displacement variable pump units, led to a significant increase of energy efficiency on hydraulic forming presses. In this paper we follow up on this development by laying the focus on the energy management and storage design of such machinery. With a derived fluidtronical model, we compare five different topologies that supply and manage the power flow for a forming press with die cushion. Our evaluation criteria are: energy consumption, minimization of the infeed power, and qualitative costs. For a representative forming cycle, the losses occurring on each of the drivetrain components and the power electronics accessory are derived in detail. We expect that this research will lead to deeper investigation of more intelligent energy management systems that use multiple storages in an optimal way and further learn and adapt during operation.

Future more electric aircraft (MEA) architectures require a new generation of power-by-wire actuators, e.g. Electro Hydrostatic Actuators (EHA). These units have to be capable of frontline operation of safety critical flight control surfaces over the entire aircraft life. Prove of robustness becomes a challenging objective. This paper illustrates the Liebherr-Aerospace EHA technology as well as methods for validation of robustness. It gives an insight regarding the design of a robust piston pump.

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.