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Development of high power density electrical actuators

Final Report Summary - HP-SMART EMA (Development of high power density electrical actuators)

Executive Summary:

The HP-SMART-EMA project is focused on developing and testing an innovative concept of extremely light, reliable and smart electrical actuator for control systems of turbine engines, capable of interfacing and connecting to the engine / turbine control unit in a plug-and-play manner. The electrical actuator will be used to control in position the inlet flaps of a turboshaft engine for helicopter application, replacing the current hydraulic actuators.
The main topics that are being developed in this project are related to the temperature levels and environmental conditions (combustion gas, oxidation) that are the normal aero engine working conditions, and result to be highly demanding for any electromechanical system working under these conditions. One of the major challenges in the aeronautic sector is to have electrical actuators that are light, reliable and easy to interface to a control unit, able to work under severe conditions (high temperatures mainly). In this respect, Electro-Mechanical Actuators (EMA) have several advantages above Electro-Hydraulic Actuators (EHA) like better efficiency or reduced maintainability improving significantly the management of operational interrupts.
So forth, the trend is to design a more electrical aircraft, and in consequence a more electrical engine for actuation and control. The energy from the engine is converted to electrical energy and distributed through a net to cover all the energy aircraft needs. EMA represents the next generation of actuation system for most of the commercial aircrafts and aero engines. This innovative concept of smart electrical actuators is based on a multi-disciplinary approach that considers mechanisms, control electronic, control software and power supply in an integrated way.

Project Context and Objectives:
- System architecture specification (mechanical & electrical): The actuator architecture has been defined based on the EMA working characteristics and operational conditions. The specification details the mechanical and electrical definition of the EMA: General description, Functions to be performed, Operational conditions, Electrical interfaces (bus type, frequency, voltage and current levels), Environmental conditions, Lubrication, Maintenance and Applicable normative
- Functional analysis of the EMA has been performed in order to analyze the functions of each component and all the interactions between them and the electronic control unit. The critical components has been preliminary defined, (objects subjected to jamming, wear or fatigue). All the mechanical and geometrical data for these components (bearings, lubrication systems, ball/roller screws, antirotation mechanism, brakes, motors...) has been defined
- A preliminary safety and reliability analysis has been performed to confirm the specification objectives. It includes identification of the critical aspects and failure possibilities in the different components on the actuator through Failure Mode, Effects and Causes Analysis (FMECA)
- Benchmarking for the mechanical solutions has been doen, satisfying robustness and precision requirements as well as meeting the high demanding working environment the EMA will be faced to. A study of adapted materials has been done, mainly focusing on temperature requirements that will lead to dilatations. The mechanical solution defines materials, tolerances and assembly methods
- Lubricant solutions have been identified and a complete test campaing has been defined to select the best coatings
- Electronics has been designed with special care to face the severe conditions, both in vibrations and temperature aspects. Two technical solutions has been evaluated: the first one with embed the electronics in the actuator itself, having a more compact solution but placing the electronics in high temperature conditions, and the second solution (selected) to place the electronics away from the most heated parts, together with other engine controls
- From the technological solutions selected for the main design elements of the EMA (mechanics and electronics), and in parallel with the conceptual design of the final EMA solution in WP3, the full EMA development plan has been established. This development plan, involving all partners, defines detailed steps for design, manufacturing, set up and validation of the EMA according to the technologies selected

Project Results:
One of the major challenges in the aeronautic sector is to have electrical actuators that are light, reliable and easy to interface to a control unit, able to work under severe conditions (high temperatures mainly). In this respect, Electro-Mechanical Actuators (EMA) have several advantages above Electro-Hydraulic Actuators (EHA) like better efficiency or reduced maintainability improving significantly the management of operational interrupts. EMA represents the next generation of actuation system for most of the commercial aircrafts and aero engines.
The European Aircraft and Engine manufacturers have based their success on some key strategic drivers which can be highlight as follow:
• Innovation with introduction of Fly-by-Wire technology
• Cockpit commonality, which permit a pilot to fly with the aircraft family
• Safety and security for passengers and all users around the aircraft
• Maturity of the aircraft and service to the airliners
• Introduction of new technologies and tools for advanced maintenance
Current approaches in terms of “more electrical aircraft” are based on:
• Three independent power sources
• Large transport category airplanes fitted with three independent hydraulic systems plus two independent electric systems
This leads to the fact that one hydraulic system can be replaced by a set of electrically powered actuators.
So forth the solution has been to design a more electrical aircraft, and in consequence a more electrical engine for actuation and control. The energy from the engine is converted to electrical energy and distributed through a net to cover all the energy aircraft needs.
The main innovations of these Variable Inlet Guide Vanes-VIGVs have been the following:
i) Innovative electrical actuator working in high temperature ambient and in aggressive environment (combustion gases)
ii) Control interface with general engine electronic systems in aero-engines and turbines systems
We have been also able of identifying technological gaps that have not been properly covered yet in the current scientific and technological state of the art:
i) Electronic components high temperatures and harsh environments
ii) Innovative actuation systems
iii) Intelligent control systems
iv) Failure analysis is applied mainly to conceptual phase stage Within this view, the partners of the HP-SMART-EMA project has developed an innovative electrical actuator of high power density that will feature the following breakthroughs and innovations:
1) Development and design of an electronic architecture that will be able to work properly in aero-engines and turbines which means in severe temperature and vibration conditions (Innovation that will tackle gap i). Electronic design shall be done considering the actuator as a flight critical actuation system. Possible impacts of DO178 and DO254 on the electronic design shall be taken into account while choosing the electronic implementation.
2) EMAs in engines for replacing current hydraulic systems (Innovation that will tackle gap ii).
3) Optimised control interface with current aero-engines control systems, and even with the aircraft flight control system (Innovation that will tackle gap iii).
4) A Failure analysis and safety assessment will be applied to all stages of the actuator development: design, manufacturing, assembly and testing (Innovation that will tackle gap iv).

Potential Impact:
The development of these innovative high power density electrical actuators will be in line with the following expected areas:
* Developing "an advanced concept contributing to the all electric aircraft, reducing engine bleed and systems weight, including power generation and distribution"
* Developing an "Advanced concept and technology for increased modularity and integration of avionics components and systems"
This project is thus relevant to ACARE Strategic Research Agenda: This objective of the work programme is coherent with the technological challenges and socio-economic scenarios defined in the Strategic Research Agenda 2 of ACARE (www.acare4europe.org) the European Technology
Platform on aeronautics. In particular, this project contributes to this SRA published in 2007 due to the introduction of alternative solutions to EHA.
Today, aerospace is an area with one of the highest safety requirements. However, fulfilling these requirements by conventional methods often takes place at a high price. The socio-economic strategic impact of the smart actuation technologies that are here investigated has several aspects for aerospace, not only in Europe.
A successful project will ensure a strong strategic impact and will have clear Socio-Economic benefits within the next five to ten years by contributing to:
- Enhance European aeronautic industry competitiveness
- Enhance European employment
- Meet societal needs for more environmental friendly, safer and efficient air transport
- Meet societal needs for more environmental friendly manufacturing
Thus, the benefits to be realised from the implementation of advanced actuators will give the European aerospace industry the opportunity to provide better solutions (operational, environmental and technological) than their competitors, to reduce the direct operating costs and thus to increase their market share.

Societal Benefits
The main outputs are expected to have essential societal impact. Through the decreased aircraft weight and the associated fuel consumption an emission reduction up to 5% is expected in an estimated time scale of 5-10 years. A successful implementation of smart electro-mechanical actuation systems can be linked to an improved design of respective parts.
The research included in the project will provide the opportunity for student research at the participating universities and research institutes. The work programme will be an ideal subject for upstream research and will help in educating the new generation of European aerospace engineers.

List of Websites:

http://www.smart-ema.eu/

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