Preliminary design and multi-objective optimization of electro-hydrostatic actuator

Electro-hydrostatic actuator is generally regarded as the preferred solution for more electrical aircraft actuation systems. It is of importance to optimize the weight, efficiency and other key design parameters, during the preliminary design phase. This paper describes a multi-objective optimization preliminary design method of the electro-hydrostatic actuator with the objectives of optimizing the weight and efficiency. Models are developed to predict the weight and efficiency of the electro-hydrostatic actuator from the requirements of the control surface. The models of weight prediction are achieved by using scaling laws with collected data, and the efficiency is calculated by the static energy loss model. The multi-objective optimization approach is used to find the Pareto-front of objectives and relevant design parameters. The proposed approach is able to explore the influence of the level length of linkage, displacement of pump and torque constant of motor on the weight and efficiency of the electro-hydrostatic actuator, find the Pareto-front designs in the defined parameter space and satisfy all relevant constraints. Using an electro-hydrostatic actuator for control surface as a test case, the proposed methodology is demonstrated by comparing three different conditions. It is also envisaged that the proposed prediction models and multi-objective optimization preliminary design method can be applied to other components and systems

A modelling framework to support power architecture trade-off studies for More-Electric Aircraft

Abstract This work presents a modelling framework to enable comparison and trade-off study of different aircraft system architectures. The framework integrates a computational module to select feasible architectures with a modelling platform that simulates the power generation, distribution and fuel consumption of the aircraft as well as system-level models for the system being evaluated. Its capabilities are demonstrated for the case of the electrification of the primary flight control system (PFCS) using different electric technologies (EHA, EMA) and different levels of electrification ranging from the conventional hydraulic to the all-electric. The performances of different architectures are analysed with respect to the change in the mechanical power extracted from the engine, the weight and the fuel burn of the aircraft. The framework demonstrates the capability of evaluating multiple, different, system architectures in a way that is scalable for different systems or different aircraft. It supports a designer evaluating the aircraft-level impact of their design choice at system-level, and it can aid in assessing technology options early in the design process

A Model-Based Systems Engineering Approach for Efficient System Architecture Representation in Conceptual Design: A Case Study for Flight Control Systems

The reduction of the environmental footprint of aviation requires the development of more efficient aircraft. Emergent technologies in aircraft systems, such as more-electrical aircraft, are potential enablers for the next generation of aircraft. To support the adoption of these new technologies and to tackle the underlying integration challenges, aircraft system architectures need to be considered earlier in the aircraft design process, specifically within the conceptual design stage. To deal with the complexity and to make the system architecture development process more efficient and effective, a key enabler is to improve the representation of system architectures early in the design process. Introducing better architecture representations removes ambiguity and allows engineers to develop a shared understanding of the system. Model Based Systems Engineering (MBSE) has emerged as a systematic methodology to address complexity in systems design and overcome the drawbacks of the traditional paper based systems engineering approach used in aircraft development. This thesis investigates the use of the ARCADIA/Capella MBSE environment for the representation and specification of aircraft systems architecture in conceptual design. This thesis includes survey on the needs for system architecture representations in conceptual design. A methodology is developed within Capella to create architecture representations that are suitable for use in conceptual design. The primary flight control systems (PFCS), which by extension also includes the associated power systems, is selected to illustrate the proposed methodology. The proposed methodology consists of capturing architectural features such as interfaces, exchanges and variability. A catalog of modelling artifacts representing the various flight control actuation technologies at system level, logical and physical level has been developed. These elements can be combined to define any primary flight control system architecture. The model-based specification addresses the need to define rapidly many architecture variants for conventional and more-electrical technologies. The developed methodology is applicable to other aircraft systems. Overall, this work is an initial step towards introducing MBSE earlier in the aircraft development process thereby making it more efficient and responsive to the emerging needs of aircraft development

Novel Concept for Electro-Hydrostatic Actuators for Motion Control of Hydraulic Manipulators

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A state-of-the-art assessment of active structures

A state-of-the-art assessment of active structures with emphasis towards the applications in aeronautics and space is presented. It is felt that since this technology area is growing at such a rapid pace in many different disciplines, it is not feasible to cover all of the current research but only the relevant work as relates to aeronautics and space. Research in smart actuation materials, smart sensors, and control of smart/intelligent structures is covered. In smart actuation materials, piezoelectric, magnetostrictive, shape memory, electrorheological, and electrostrictive materials are covered. For sensory materials, fiber optics, dielectric loss, and piezoelectric sensors are examined. Applications of embedded sensors and smart sensors are discussed

Verification and validation of a theoretical model of a direct drive valve-controlled electrohydrostatic actuator for primary flight control

In this work, a theoretical parametric nonlinear model for a hybrid variable pressure actuator was verified through dynamic system modeling techniques and validated using experimental data. The hybrid configuration under investigation combines design features of a valve-controlled hydraulic actuator and an electrohydrostatic actuator resulting in a variable pressure hydraulic actuator. A comparison analysis is conducted to determine the performance and, more specifically, power characteristics of the hybrid configuration relative to the two types of conventional flight control actuation - valve-controlled actuators and electrohydrostatic actuators. The hybrid configuration is unique in the sense that it allows for independent localized hydraulic system pressure control. In this analysis, bang-bang control is implemented by defining low-pressure and high-pressure thresholds resulting in active-passive electrical power consumption. The hybrid configuration was shown to exhibit power input superiority due to duty-cycle behavior of the electrical power element during high-load low-rate scenarios when compared to traditional actuation configurations

Systems study for an Integrated Digital-Electric Aircraft (IDEA)

The results of the Integrated Digital/Electric Aircraft (IDEA) Study are presented. Airplanes with advanced systems were, defined and evaluated, as a means of identifying potential high payoff research tasks. A baseline airplane was defined for comparison, typical of a 1990's airplane with advanced active controls, propulsion, aerodynamics, and structures technology. Trade studies led to definition of an IDEA airplane, with extensive digital systems and electric secondary power distribution. This airplane showed an improvement of 3% in fuel use and 1.8% in DOC relative to the baseline configuration. An alternate configuration, an advanced technology turboprop, was also evaluated, with greater improvement supported by digital electric systems. Recommended research programs were defined for high risk, high payoff areas appropriate for implementation under NASA leadership

Volume 2 – Conference: Wednesday, March 9

10. Internationales Fluidtechnisches Kolloquium:Group 1 | 2: Novel System Structures Group 3 | 5: Pumps Group 4: Thermal Behaviour Group 6: Industrial Hydraulic

Design criterion to select adequate control algorithm for electro-hydraulic actuator applied to rocket engine flexible nozzle thrust vector control under specific load

Rad razmatra problematiku kako na najbolji način izabrati algoritam upravljanja za elektro- hidraulični aktuator sa definisanim opterećenjem. Polazi se od pretpostavke idealnog algoritma upravljanja koji se prilagođava stvarnoj konfiguraciji elektrohidrauličnog aktuatora i definisanom opterećenju. Razmatra se netipično fleksibilno opterećenje, viskozoelastično, sa znatnim histerezisom koji dodatno zavisi od vremena odnosno temperature. Predlažu se dva načina modelovanja opterećenja i prikazuje se koliko opcije modelovanja opterećenja utiču na stvarni odziv aktuatorskog sistema. U razmatranom slučaju glavni poremećaj je spoljna sila prouzrokovana realnim oscilacijama sile potiska.The paper presents the challenge of finding the best criterion in selecting adequate control algorithm for electro-hydraulic actuator with a defined load. The ideal control algorithm that adapts to the actual configuration of electro-hydraulic actuator and defined load is used as an initial assumption. Atypical flexible load that is viscose-elastic, with a significant level of hysteresis that also depends on time and temperature is considered as well. Two types of load modeling approaches are proposed, accompanied by presentation on how load modeling options affect the actual response of an actuator system. The main disturbance, in this case, is considered to be external force generated by thrust force real oscillations

Improving Energy Efficiency and Motion Control in Load-Carrying Applications using Self-Contained Cylinders

Because of an increasing focus on environmental impact, including CO2 emissions and fluid spill pollution, inefficient hydraulic systems are being replaced by more environmentally friendly alternatives in several industries. For instance, in some offshore applications that have multiple diesel generators continuously running to produce electricity, all hydraulic rotating actuators supplied from a central hydraulic power unit have been replaced with AC induction motors containing a variable frequency drive and gearbox. However, hydraulic linear actuators are still needed in most load-carrying applications mainly because of their high reliability associated with external impact shocks. Moreover, their force capacity is higher than that of their linear electromechanical counterparts. Valve-controlled linear actuators (cylinders) supplied from a centralized hydraulic power unit are standard in offshore load-carrying applications. In addition to the advantages mentioned above of hydraulic linear actuators, they have, nevertheless, a number of important drawbacks, which include: 1) a high level of energy consumption due to significant power losses caused by flow throttling in both the pipelines and valves, 2) reduced motion performance due to the influence of load-holding valves, 3) high CO2 emissions and fuel costs related to the diesel generator that supplies electricity to the hydraulic power unit, 4) significant potential for hydraulic fluid leakage because of many leakage points, 5) demanding efforts with respect to installation and maintenance, as well as 6) costly piping due to the centralized hydraulic power supply. The work presented in this dissertation and the appended papers are devoted to replacing inefficient hydraulic linear actuation systems traditionally used in offshore load-carrying applications with more environmentally friendly solutions. Two alternative technologies are identified, namely electro-mechanical and electro-hydraulic self-contained cylinders. The feasibility of replacing conventional valve-controlled cylinders with self-contained cylinder concepts is investigated in two relevant case studies.publishedVersio