A review of electromechanical actuators for More/All Electric aircraft systems
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paper_title: Electric Control Surface Actuator Design Optimization and Allocation for the More Electric Aircraft

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This work pertains to the optimization of electric actuators for the primary and secondary flight control surfaces of a More Electric Aircraft. Electrohydrostatic and electromechanical actuators are considered and optimized in accordance with the flight loads and actuator requirements identified in a separate work by the same authors. For the purposes of this work, the Boeing 737-800 aircraft is chosen as a test case. However the methodology is general and can be applied to any existing design or proposed design concept. Once the optimized actuator designs are obtained, the possibility of using both actuator types by allocating them to control surfaces on the basis of reliability requirements is considered.
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paper_title: More Electric Aircraft: Review, Challenges, and Opportunities for Commercial Transport Aircraft

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Similar to the efforts to move toward electric vehicles, much research has focused on the idea of a more electric aircraft (MEA). The motivations for this research are similar to that for vehicles and include goals to reduce emissions and decrease fuel consumption. In traditional aircraft, multiple systems may use one type or a combination of types of energy, including electrical, hydraulic, mechanical, and pneumatic energy. However, all energy types have different drawbacks, including the sacrifice of total engine efficiency in the process of harvesting a particular energy, as with hydraulic and pneumatic systems. The goal for future aircraft is to replace most of the major systems currently utilizing nonelectric power, such as environmental controls and engine start, with new electrical systems to improve a variety of aircraft characteristics, such as efficiency, emissions, reliability, and maintenance costs. This paper provides an in-depth look into how the systems have—or will be—changed. Future aircraft capabilities such as electric taxi and gas–electric propulsion for aircraft are also included for discussion. Most recent commercial transport aircrafts are described as the current state-of-the-art electric aircraft system. Future goals, including those of NASA, are presented for future advances in MEA.
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paper_title: Moving towards a more electric aircraft

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The latest advances in electric and electronic aircraft technologies from the point of view of an "all-electric" aircraft are presented herein. Specifically, we describe the concept of a "more electric aircraft" (MEA), which involves removing the need for on-engine hydraulic power generation and bleed air off-takes, and the increasing use of power electronics in the starter/generation system of the main engine. Removal of the engine hydraulic pumps requires fully-operative electrical power actuators and mastery of the flight control architecture. The paper presents a general overview of the electrical power generation system and electric drives for the MEA, with special regard to the flight controls. Some discussion regarding the interconnection of nodes and safety of buses and protocols in distributed systems is also presented
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paper_title: New Actuators for Aircraft and Space Applications

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Actuators are key elements of air- and spacecrafts. In the recent years the concept of the more-electric aircraft pushed the development of electrical actuation systems to substitute hitherto used hydraulic actuators in a broad range of applications such as flight control, landing gear and brake actuation. On top of that the superior dynamics of electrical actuators, especially when utilizing the piezoelectric principle, open new fields of application in noise and vibration control. Novel electrical actuation technologies have to comply with demanding requirements concerning life, reliability, weight, environmental conditions and installation space. The main principles pushed forward in the recent years are electromechanical actuators (EMA) and piezoelectric actuators. These new actuators put strong requirements on electronics systems design and power amplifier stages. It requires highly efficient and reliable electronics to achieve flight worthy products. In Space & Military fields, there is a trend for miniaturisation meet in active optics, fine instruments, robotic missions, micro-satellites, UAVs, MAVs, which directly impact on the actuators. A new generation of small and smart actuators such as piezoelectric actuators and magnetic actuators, are responding to this trend, thanks to their capacity to offer high energy density and to support both extreme and various requirements. The paper presents typical applications to discuss the state-of-the-art performance and deduce further needs.
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paper_title: A Review of More-Electric Aircraft

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The More-Electric Aircraft (MEA) underlines the utilization of the electrical power to power the non-propulsive aircraft systems. Adopting the MEA achieves numerous advantages such as optimizing the aircraft performance and decreasing operating and maintenance costs. Moreover, the MEA reduces the emission of the air pollutant gases from the aircraft, which can contribute in solving the problem of climate change. However, the MEA put some challenge on the aircraft electrical system either in the amount of the required power or the processing and management of this power. This paper introduces a review for the MEA. The review includes the different options of generation and power system architectures.
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paper_title: Automatic test equipment for avionics Electro-Mechanical Actuators (EMAs)

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Abstract This research activity, carried out in cooperation with Umbra Group Aerospace, was focused on the design of an Automatic Test Equipment (ATE) adopted for testing innovative linear electro-mechanical actuators for flight control surfaces. The implemented ATE simulates the aerodynamic force applied to the surface by generating a hydraulic load opposing the actuator movement. During the tests, the system executes the measurement and monitoring of mechanical, hydraulic and electrical parameters as well as the dynamic control of hydraulic load simulator. In the paper the main ATE design choices are analysed, with particular attention to the test program, developed in NI LabWindows CVI environment. An innovative solution based on the multithreading technique has been implemented, to guarantee the correct execution of the required tasks and a precise time alignment of acquired data. The obtained results show a successfully communication and cooperation between the different sections of the system, according to the required performance. Additionally, experimental results related to EMA characterization tests are presented, as confirmation of the effectiveness of the proposed solution.
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paper_title: An integrated approach to vehicle and subsystem sizing and analysis for novel subsystem architectures

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The aerospace industry is currently transitioning to More Electric subsystem architectures due to steadily improving electric technologies and the technology saturation of established conventional architectures. For aircraft with such unconventional architectures, the lack of historical information and the presence of increased inter-subsystem interactions create a significant design challenge. These necessitate a greater focus on subsystems design earlier in the design process than typically seen for aircraft with conventional subsystem architectures. At the same time, however, to be suitable for the early design phases, the subsystem analyses must be computationally inexpensive and not require detailed aircraft definition. This work presents an integrated, modular, and tool-independent approach to the sizing and performance analysis of the aircraft and its subsystems, in which inter-dependencies are established between relevant aircraft and subsystem level parameters. The approach allows the assessment ...
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paper_title: Modelling and simulation of flight control electromechanical actuators with special focus on model architecting, multidisciplinary effects and power flows

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In the aerospace field, electromechanical actuators are increasingly being implemented in place of conventional hydraulic actuators. For safety-critical embedded actuation applications like flight controls, the use of electromechanical actuators introduces specific issues related to thermal balance, reflected inertia, parasitic motion due to compliance and response to failure. Unfortunately, the physical effects governing the actuator behaviour are multidisciplinary, coupled and nonlinear. Although numerous multi-domain and system-level simulation packages are now available on the market, these effects are rarely addressed as a whole because of a lack of scientific approaches for model architecting, multi-purpose incremental modelling and judicious model implementation. In this publication, virtual prototyping of electromechanical actuators is addressed using the Bond-Graph formalism. New approaches are proposed to enable incremental modelling, thermal balance analysis, response to free-run or jamming faults, impact of compliance on parasitic motion, and influence of temperature. A special focus is placed on friction and compliance of the mechanical transmission with fault injection and temperature dependence. Aileron actuation is used to highlight the proposals for control design, energy consumption and thermal analysis, power network pollution analysis and fault response.
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paper_title: Review on signal-by-wire and power-by-wire actuation for more electric aircraft

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The huge and rapid progress in electric drives offers new opportunities to improve the performances of aircraft at all levels: fuel burn, environmental footprint, safety, integration and production, serviceability, and maintainability. Actuation for safety-critical applications like flight-controls, landing gears, and even engines is one of the major consumers of non-propulsive power. Conventional actuation with centralized hydraulic power generation and distribution and control of power by throttling has been well established for decades, but offers a limited potential of evolution. In this context, electric drives become more and more attractive to remove the natural drawbacks of conventional actuation and to offer new opportunities for improving performance. This paper takes the stock, at both the signal and power levels, of the evolution of actuation for safety-critical applications in aerospace. It focuses on the recent advances and the remaining challenges to be taken toward full electrical actuation for commercial and military aircraft, helicopters, and launchers. It logically starts by emphasizing the specificity of safety-critical actuation for aerospace. The following section addresses in details the evolution of aerospace actuation from mechanically-signaled and hydraulically-supplied to all electric, with special emphasis on research and development programs and on solutions entered into service. Finally, the last section reviews the challenges to be taken to generalize the use of all-electric actuators for future aircraft programs.
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paper_title: The roller screw, an efficient and reliable mechanical component of electro-mechanical actuators

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The roller screw exists in three different designs which may be used in very different applications: the three designs are respectively known as planetary, differential planetary and recirculating roller screws. Most EMAs which are using roller screws use the planetary design because of its inherent capacity to withstand very high accelerations and speeds and its ability to handle heavy to very heavy loads for a long time. This capability places the planetary roller screw between large ball screws and hydraulic cylinders. The roller screw compares favorably with both other designs because its resistance to adverse environment is higher than that of ball screws and because it is not prone to leaks and other unpredictable failures of hydraulic cylinders. This paper discusses the efficiency of the planetary roller screw and the means to improve it and maintain it for the life of the component. It also discusses the noise level of roller screws and the way it can be controlled and maintained at a low decibel level (below 72 dB-A). We define a relation between temperature level and necessary oil rate and give a formula based on past experience. Then, we present different modes of failure of the planetary roller screw. We discuss their most common order of precedence; cases of failure and analysis of those failures are presented and analyzed. We establish a tentative reliability formula linking the B10 fatigue life to experimental MTBF. An ongoing application in the aerospace field is used as a basis to calculate this relationship. Reliability levels of 95%, 99%, 99.9% and even 99.95% are achievable with the roller screws.
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paper_title: Challenges for Health Monitoring of Electromechanical Flight Control Actuation Systems

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Flight control systems of civil aircraft have undergone huge developments in the last decades. The current more/all electric aircraft concepts lead to the replacement of the hydraulic actuators in the primary flight control systems by electromechanical systems. Integrating electromechanical systems in safety critical applications implies three main challenges: (a) the detection of all fault cases which could lead to a safety critical state, (b) finding measurement parameters capable to detect faults, and (c) the development of algorithms to detect faults under all flight conditions. Putting the scope on the health monitoring of the mechanical components of a direct drive actuator, a new technology based on piezoresistive thin film sensors (TFS) is presented and its potential shown by using defective ball bearings as an example.
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paper_title: Advanced Electromechanical Actuation System (EMAS), Flight Test

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Abstract : The EMAS flight test project successfully demonstrated, for the first time, the electrical actuation of a primary flight control surface in flight. This test was a major step toward the realization of the All-Electric Airplane (AEA) concept. An electric actuator was installed in a modified C-141A aircraft to power the left aileron. Testing included ground and flight trials to ensure unchanged control system damping. Aircraft roll performance tests included maximum effort rolls, degraded system rolls, and autopilot rolls. Sideslip and trim test points were also performed. It was verified that EMAS performance was similar to the normal hydraulic actuator. Results include lessons on aircraft modification, general system characteristics, maintenance factors, and compatibility with other aircraft systems that may influence future installations. Keywords: Electromechanical actuation system; Ailerons; Flight controls; Damping.
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paper_title: Combining hydraulics and electrics for innovation and performance improvement in aerospace actuation

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The combination of electrics and hydraulics technology is addressed for aerospace actuators. Once compared the inherent advantages and drawbacks of each technology, the evolution of signalling and powering is presented. At the signal level, fly-by-wire, fly-by-light and fly-wireless are rapidly reviewed. At the power level, after presenting the recent designs well established for already flying aircrafts (local hydraulic power generations, direct drive valves, electro-hydrostatic actuators, electro-backup-hydrostatic actuators, electro-backup-hydro-mechanical actuators), hybrid actuation is discussed in detail considering a passive hydraulic backup electromechanical actuator that is presently investigated for landing gear extension and retraction. A simplified analytical model is proposed for assessing rapidly the influence of the passive hydraulic power path on the actuator design and performance.
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paper_title: Electromechanical Actuation Technology for the All-Electric Aircraft

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Electromechanical actuation is a critical element that must be developed and verified to make the all-electric aircraft a viable concept. For several years the Flight Control Division of the Air Force Wright Aeronautical Laboratories has sponsored activities to demonstrate the credibility of electromechanical actuation systems (EMAS) for primary flight control actuation functions. The foundation for these EMAS activities and several electromechanical actuation development programs are described here. One involves the design, fabrication, and laboratory test of a rotary, hingeline electromechanical actuator. Another involves the development and flight test demonstration of a linear electromechanical actuator for controlling an aileron of a C-141 aircraft. A third involves the design and development of a linear electromechanical actuator for missiles having severe performance, temperature, and volumetric requirements. In addition, a brief summary of the results from two aircraft actuation trade studies compare the baseline (conventional) hydraulic flight control system with an all-electric airplane concept including quantitative comparisons of weight, reliability and maintainability, and life cycle costs.
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paper_title: An electromechanical actuator for a transport aircraft spoiler surface

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The More Electric Aircraft Initiative (MEI) embraces the concept of utilizing electrical power for driving aircraft subsystems. Power electronics and motor drives are essential elements of the MEI. Advancements in power semiconductor devices, capacitors, and integrated circuits for control has enabled high density, reliable power electronic and motor drive systems for the MEI. Wright Laboratory and Sundstrand Aerospace have been working on the development of an electromechanical actuator to be compatible with the requirements of a spoiler for a typical transport aircraft. The focus of this development effort is in the motor drive, meaning the controller, inverter and motor utilized to control the actuator. Efforts are underway to increase the power density of the motor drive to achieve 1 kW/lb, with an efficiency of greater than 80%. This paper discusses the design criteria and some of the trade-offs that were accomplished during this development. This work includes the use of a novel soft switched inverter driving a five-phase switched reluctance motor. A digital signal processing (DSP) chip is utilized for responsive controls and field programmable gate arrays (FPGA) to reduce size and increase control electronics reliability. A power electronics module is developed which is comprised of insulated gate bipolar transistor (IGBT) inverter switches, diodes, a current sensor and gate drives. The thermal management system utilizes a reflux heat exchanger with integral phase change material that will enable the motor drive to operate in the environment of the actuator.
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paper_title: Flight test experience with an electromechanical actuator on the F-18 Systems Research Aircraft

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Development of reliable power-by-wire actuation systems for both aeronautical and space applications has been sought to eliminate hydraulic systems from aircraft and spacecraft and thus improve safety, efficiency, reliability, and maintainability. The Electrically Powered Actuation Design (EPAD) program was a joint effort between the Air Force, Navy, and NASA to develop and fly a series of actuators validating power-by-wire actuation technology on a primary flight control surface of a tactical aircraft. To achieve this goal, each of the EPAD actuators was installed in place of the standard hydraulic actuator on the left aileron of the NASA F/A-18B Systems Research Aircraft (SRA) and flown throughout the SRA flight envelope. Numerous parameters were recorded, and overall actuator performance was compared with the performance of the standard hydraulic actuator on the opposite wing. This paper discusses the integration and testing of the EPAD electromechanical actuator (EMA) on the SRA. The architecture of the EMA system is discussed, as well as its integration with the F/A-18 flight control system. The flight test program is described, and actuator performance is shown to be very close to that of the standard hydraulic actuator it replaced. Lessons learned during this program are presented and discussed, as well as suggestions for future research.
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paper_title: Self-monitoring electro-mechanical actuator for medium altitude long endurance unmanned aerial vehicle flight controls

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This article deals with the reliability analysis and architecture definition of a fault-tolerant electro-mechanical actuator system for unmanned aerial vehicle applications. Starting from the basic layout of the flight control system of a medium altitude long endurance unmanned aerial vehicle, the attention is focused on the fault mode analysis of the single electro-mechanical actuator system, with the purpose of pointing out the effects of architectural choices on the system reliability. The electro-mechanical actuator system, developed to be a self-monitoring equipment, has three operating modes: normal, fail-operative and fail-safe. Reliability and safety budgets are quantitatively evaluated via fault tree analysis using typical failure rates of system components, and the most critical paths are identified and discussed.
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paper_title: Review on electro hydrostatic actuator for flight control

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AbstractElectro Hydrostatic Actuator (EHA) is an emerging aerospace technology that aims at replacing centralised hydraulic system by a self-contained and localised direct drive actuator system. EHA has become an important part of modern flight control systems due to the increased efficiency, reduced leakages and lower overall weight compared to conventional hydraulic systems. This paper reviews literature (in English language only) published in the period 1990 to 2015 and available at major technical university libraries or e-journals. It examines the advantages, limitations and possible configurations of the EHA. The paper also includes control strategies, reliability and fault tolerant techniques along with the thermal aspects of the EHA system. EHA is a multi-domain system consisting of electrical, mechanical, hydraulic and control system. It is treated as a mechatronic system and review of publications related to multi-disciplinary modelling/simulation approaches have been presented in the paper. The...
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paper_title: Preliminary design and sizing of actuation systems

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This theme of research has been developed around three areas: ::: ::: •Technologies: mechatronic systems and their actuation systems include power transmission elements from different fields, which are usually treated independently. The goal of my research is to synthesize them in a coupled manner. ::: ::: •Models: the models to set up in order to design a system are of different natures. Simulation models are used to calculate all quantities that influence the choice of the components. Evaluation models enable lifetime or reliability to be calculated. Estimation models give rapid access to component characteristics, generally obtained after detailed design. ::: ::: •Methods: to optimize a design, it is advantageous to develop meta-models to replace time consuming simulations, to analyse the uncertainty of results, and to help the implementation of the design procedures.
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paper_title: Integrated Machine design for Electro Mechanical Actuation

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This paper describes work on an integrated electro mechanical actuator intended as a technology demonstrator to satisfy future aircraft requirements for a typical mid spoiler actuation system for a large civil aircraft. The design and analysis of a directly coupled motor to a roller screw without any intermediate gear box will be detailed in this paper. The main goals of the design are a high level of actuator integration in order to minimize weight and volume, fault tolerance and high reliability.
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paper_title: Robust and perfect tracking control for direct drive EMA system

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The direct drive Electro-mechanical Actuator (EMA) system integrates the ball screw on the motor rotor directly, which eliminates the disadvantages of traditional gear transmission device. However, such construction of system brings challenges to the control strategy for high positioning precision and outstanding load disturbance-rejection ability. To meet the requirement of high static and dynamic performances of EMA system, a control method named Robust and Perfect Tracking (RPT) is applied in this work. Firstly, we address the architecture description of an EMA with a dual three phase permanent magnetic synchronous motor (PMSM). Afterwards, we obtain a decoupled model of motor and cast the overall servo system design into a RPT design framework. Finally, the comparison of simulation results between the conventional and proposed methods demonstrates the feasibility and efficiency of RPT control strategy for EMA system.
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paper_title: Safety-critical design of electromechanical actuation systems in commercial aircraft

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Research is increasingly focusing on the incorporation of electromechanical actuators into future More Electric Aircraft. For an actuator to be feasible in a commercial aircraft, the most critical design factor is attaining the strict safety requirements. The electrical drives used in More Electric technologies must also be suitable for the conventional power supply and control arrangements of aircraft, otherwise feasibility of a new technology may be reduced. This study discusses the generic design requirements for electromechanical actuators from a safety perspective, including the application of fault-tolerant electric drives. Later, two prototype electromechanical actuators, developed by the authors are discussed, comparing the different topologies.
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paper_title: Development of Electromechanical Actuators

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The electromechanical actuator (EMA) represents such a class of position servo systems, which directly or indirectly control the motion of load by servomotors or electrical devices. This paper summarizes the application, the history of structure evolvement and the key technology development of EMA, and introduces the developing trends of EMA. Based on the summaries and analysis, some suggestions are presented on future EMA research and development in the application to aircraft.
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paper_title: Optimal preliminary design of electromechanical actuators

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This paper presents a methodology for the optimal preliminary design of electro-mechanical actuators. The main design drivers, design parameters and degrees of freedom that can be used for preliminary design and optimization of electro mechanical actuator are described. The different types of models used for model-based design (estimation, simulation, evaluation and meta-model), and their associations are presented. The process preferred for its effectiveness in terms of flexibility, and computational time is then described and illustrated with the example of a spoiler electromechanical actuator. The proposed approach, based on meta-models obtained using the surfaces response methods and scaling laws models, is used to explore the influence of anchorage points and transmission ratio on the different design constraints and the overall mass of the actuator.
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paper_title: Analysis of Electro-Mechanical Actuator Systems in MORE ELECTRIC AIRCRAFT APPLICATIONS

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Conventional hydraulic actuators in aircraft are demanding regarding maintenance which implies high operation costs. In recent years the focus therefore has been set on electro-hydrostatic and elec ...
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paper_title: Performance evaluation of two stagematrix converters for EMA in aircraft applications

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This paper presents an analytical and experimental performance assessment on the use of a two stage matrix converter for applications in Electro Mechanical Actuators (EMA) for aircraft. The results presented show the proposed system performance under different operating conditions and using a variable frequency supply (360 to 800 Hz) typical of the new generation aircrafts. Using the two stage matrix converter gives the option of preventing regeneration by means of a brake circuit connected to the virtual dc link, but can also allow energy regeneration back to the electrical network if required.
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paper_title: Failure detection, identification and reconfiguration - applications for a modular iron bird

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The permanently fast growth of airline market must not lead to rising numbers of accidents. To improve aircraft safety, pilot workload has to be reduced especially in critical situations. This paper describes the system architecture of a new test rig to evaluate the effects and advantages of new concepts in the area of flight control. A first application of the iron bird to demonstrate its potential deals with the evaluation of a solution for reconfiguration: elevator failures are compensated by using a new Trimmable Horizontal Stabilizer Actuator concept with higher dynamics, which can be integrated in modern airliners. The test rig enables research on the interactions of different subsystems for failure detection, identification and reconfiguration of the modified controller by using Hardwarein-the-Loop tests of flight control actuators in combination with pilot evaluations in a cockpit simulator.
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paper_title: F-22 Actuator Dynamic Stiffness (Impedance) Testing

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Accurate understanding of flight control hydraulic actuator dynamic stiffness is critically important to the aeroelastic certification of fighter aircraft. A test program was conducted during the F-22 development phase to ensure that analysis models were accurately predicating the dynamic stiffness of the actuators for both hydraulically powered and hydraulically failed conditions. This paper presents the test approach, constraints, test methods, and test data analysis methods. Special emphasis is given to instrumentation design and accuracy requirements as this was considered critical to conducting a successful test.
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paper_title: Dynamic load testing of roller screw EMAs

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In the electromechanical actuators (EMA) laboratory at The University of Alabama, USA, a dynamic load test stand has been designed and built. This test stand uses large load, high bandwidth and hydraulic actuation to generate load profiles under force control. The test stand can accommodate EMAs up to six feet in length. It can generate dynamic loads of up to 100,000 lb at fundamental frequencies of up to 12 Hz against a stiff environment. This test stand has been used to generate severe loading conditions on a large roller screw in an attempt to qualify the effects of large, high frequency loads on roller screw. During the tests performed in the EMA laboratory the screw was fixed at one end and axial loads were applied to the roller nut at the other. Since the end opposite the nut was fixed, only a small amount of relative rotation between the nut and screw was achieved. This rotation was the result of elastic deformation (wind up) of the screw along the length between the fixed end and the nut. This simulates a severe, but likely, application of the roller screw. The results of the tests performed demonstrate that roller screws may be damaged by dynamic loading with load magnitudes that are well within the static load rating of the screw. While the damage that was observed is not catastrophic, it would be expected to substantially decrease the life of the screw.
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paper_title: Experimental and analytical development of health management for Electro-Mechanical Actuators

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Expanded deployment of Electro-Mechanical Actuators (EMAs) in critical applications has created much interest in EMA Prognostic Health Management (PHM), a key enabling technology of Condition Based Maintenance (CBM). As such, Impact Technologies, LLC is collaborating with the NASA Ames Research Center to perform a number of research efforts in support of NASA's Integrated Vehicle Health Management (IVHM) initiatives. These efforts have combined experimental test stand development, laboratory seeded fault testing, and physical model-based health monitoring in a comprehensive PHM system development strategy. This paper discusses two closely related EMA research programs being conducted by Impact and NASA Ames. The first of these efforts resulted in the creation of an electro-mechanical actuator test stand for the Prognostics Center of Excellence at the NASA Ames Research Center. The second effort is ongoing and is utilizing physics-based modeling techniques to develop an algorithm and software package toolset for PHM of aircraft EMA systems using a hybrid (virtual sensor) approach.
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paper_title: Dynamic loading systems for ground testing of high speed aerospace actuators

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Purpose – To develop structured guidelines for the synthesis of dynamic force simulators that are required for the testing of high speed aerospace actuators. To provide realistic and proven solutions at both test bench hardware and control design levels.Design/methodology/approach – The state of the art in control design applied to load simulators in mainly based on complex controllers and does not take into account practical considerations. The objective of the present work is to provide generic preliminary design rules to ensure that the test bench architectures (frame, power transmission and control) and the components specifications are consistent with the targeted performance. Once selected the appropriate power transmission architecture, a linear approach is used as a foundation to generate design rules. Then, preliminary design is achieved thanks to the introduction, as early as possible, of the unavoidable technological defects.Findings – A step‐by‐step methodology allows the designer to select th...
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paper_title: Thermal Vacuum Integrated System Test at B-2

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Abstract The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) Plum Brook Station (PBS) Space Propulsion Research Facility, commonly referred to as B-2, is NASA’s third largest thermal vacuum facility. It is the largest designed to store and transfer large quantities of liquid hydrogen and liquid oxygen, and is perfectly suited to support developmental testing of chemical propulsion systems as well as fully integrated stages. The facility is also capable of providing thermal-vacuum simulation services to support testing of large lightweight structures, Cryogenic Fluid Management (CFM) systems, electric propulsion test programs, and other In-Space propulsion programs. A recently completed integrated system test demonstrated the refurbished thermal vacuum capabilities of the facility. The test used the modernized data acquisition and control system to monitor the facility during pump down of the vacuum chamber, operation of the liquid nitrogen heat sink (or cold wall) and the infrared lamp array. A vacuum level of 1.3 × 10 −4 Pa (1 × 10 −6 torr) was achieved. The heat sink provided a uniform temperature environment of approximately 77 K (139°R) along the entire inner surface of the vacuum chamber. The recently rebuilt and modernized infrared lamp array produced a nominal heat flux of 1.4 kW/m 2 at a chamber diameter of 6.7 m (22 ft) and along 11 m (36 ft) of the chamber’s cylindrical vertical interior. With the lamp array and heat sink operating simultaneously, the thermal systems produced a heat flux pattern simulating radiation to space on one surface and solar exposure on the other surface. The data acquired matched pretest predictions and demonstrated system functionality.
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paper_title: Flight test experience with an electromechanical actuator on the F-18 Systems Research Aircraft

paper_content:

Development of reliable power-by-wire actuation systems for both aeronautical and space applications has been sought to eliminate hydraulic systems from aircraft and spacecraft and thus improve safety, efficiency, reliability, and maintainability. The Electrically Powered Actuation Design (EPAD) program was a joint effort between the Air Force, Navy, and NASA to develop and fly a series of actuators validating power-by-wire actuation technology on a primary flight control surface of a tactical aircraft. To achieve this goal, each of the EPAD actuators was installed in place of the standard hydraulic actuator on the left aileron of the NASA F/A-18B Systems Research Aircraft (SRA) and flown throughout the SRA flight envelope. Numerous parameters were recorded, and overall actuator performance was compared with the performance of the standard hydraulic actuator on the opposite wing. This paper discusses the integration and testing of the EPAD electromechanical actuator (EMA) on the SRA. The architecture of the EMA system is discussed, as well as its integration with the F/A-18 flight control system. The flight test program is described, and actuator performance is shown to be very close to that of the standard hydraulic actuator it replaced. Lessons learned during this program are presented and discussed, as well as suggestions for future research.
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paper_title: Prognostic Health-Management System Development for Electromechanical Actuators

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systemthatdiagnoseselectromechanicalactuatorfaultsandemploysprognosticalgorithmstotrackfaultprogression and predict the actuator’s remaining useful life. The diagnostic algorithm is implemented using a combined modelbased and data-driven reasoner. The prognostic algorithm, implemented using Gaussian process regression, estimates the remaining life of the faulted component. The paperalso covers the selection of fault modes for coverage and methods developed for fault injection. Validation experiments were conducted in both laboratory and flight conditions using a flyable electromechanical actuator test stand. The stand allows test actuators to be subjected to realistic environmental and operating conditions while providing the capability to safely inject and monitor propagation of various fault modes. The paper covers both diagnostic and prognostic run-to-failure experiments, conducted in laboratory and flight conditions for several types of faults. The experiments demonstrated robust fault diagnosis on the selected set of component and sensor faults and high-accuracy predictions of failure time in prognostic scenarios.
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paper_title: Parallel positioning of twin EMAs for Fault-Tolerant flap applications

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This work describes the control technique of a Fault-Tolerant electromechanical system aimed to the actuation of the flap panels of the aircraft. The application provides the adoption of a couple of Fault-Tolerant permanent magnet synchronous motors designed to match minimum load requirements even in case of a fault in one or two phases. The consolidated mechanical synchronization of the mutual actuation is replaced by a fully electronic solution. The usual master-slave configuration of the two actuators with speed control and correction of the tracking error is replaced by the adoption of the parallel position control. This solution allows to avoid a complex management of the tracking error and applies to the couple of actuators the same Fault-Tolerant philosophy adopted inside for the single multiphase motor. The technique is developed and tested on a test-bed designed to emulate the real aerodynamic load condition. The achieved results show the effectiveness of the proposed solution.
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paper_title: Faulty Operations of a PM Fractional-Slot Machine With a Dual Three-Phase Winding

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The permanent-magnet (PM) machine with dual three-phase windings is proposed for applications requiring continuous operating even under a partial fault. The two windings are supplied by two separate inverters. Thus, in the event of a fault of one winding, this is disconnected, and the machine continues to be operated by means of the healthy winding. This paper investigates the PM machine with dual three-phase windings and its capabilities during faulty operating conditions. A fractional-slot interior PM machine with 12 slots and 10 poles is taken into account. Its performance is investigated according to different winding configurations. The torque behavior, overload capability, and thermal limits are evaluated under open-circuit and short-circuit faults. A finite-element analysis as well as experimental tests is carried out on a prototype of such a machine.
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paper_title: Investigation in the dynamic force equalization of dissimilar redundant actuation systems operating in active/active mode

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With the extensive application of power by wire (PBW) actuators in aircraft industry, a lot of challenges have arisen. One important subject is the force equalization of redundant actuation system composed of dissimilar technologies for position control. In the presented work, the research is focused on one hybrid actuation system combining one servo hydraulic actuator (SHA) and one electro-mechanical actuator (EMA). A virtual system is built for reproducing the studied test bench and the key nonlinear effects are modeled with care. Once the model accuracy is evaluated, the virtual system is used for studying the force equalization strategies. The static force equalization has been already presented in a former communication, in view of that, the reported research is focused on dynamic force equalization. According to the studied origin of force fighting, three dynamic force equalization strategies are proposed, analyzed, simulated and compared. The first one uses one trajectory generator and two pre-compensators to balance the actuators position loop dynamics; the second one introduces force fighting feedback to compensate the position loop; the third one sets SHA to force control to track the output force of EMA.
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paper_title: A novel fault tolerant permanent magnet synchronous motor with improved optimal torque control for aerospace application

paper_content:

Abstract Improving fault tolerant performance of permanent magnet synchronous motor has always been the central issue of the electrically supplied actuator for aerospace application. In this paper, a novel fault tolerant permanent magnet synchronous motor is proposed, which is characterized by two stators and two rotors on the same shaft with a circumferential displacement of mechanical angle of 4.5°. It helps to reduce the cogging torque. Each segment of the stator and the rotor can be considered as an 8-pole/10-slot five-phase permanent magnet synchronous motor with concentrated, single-layer and alternate teeth wound winding, which enhance the fault isolation capacity of the motor. Furthermore, the motor has high phase inductance to restrain the short-circuit current. In addition, an improved optimal torque control strategy is proposed to make the motor work well under the open-circuit fault and short-circuit fault conditions. Simulation and experiment results show that the proposed fault tolerant motor system has excellent fault tolerant capacity, which is able to operate continuously under the third open-circuit fault and second short-circuit fault condition without system performance degradation, which was not available earlier.
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paper_title: A force equalization controller for active/active redundant actuation system involving servo-hydraulic and electro-mechanical technologies

paper_content:

The force equalization of a hybrid actuation system combining one servo-hydraulic actuator and one electro-mechanical actuator operated in position control and in active/active mode is addressed for safety critical applications such as primary flight controls. In a first step, an accurate virtual test bench is built to facilitate the analysis of force fighting and the assessment of the performance and robustness of the proposed force equalization strategies. It is validated from real experiments performed for the aileron actuator of a single-aisle commercial aircraft. Static force equalization is achieved first by adding equalization offsets in the position control loops as a function of the integral of the force difference between actuators. In order to keep a high level of segregation, the authority for this action is limited to 4% of the total actuator stroke. The dynamic force equalization is performed by forcing the two actuators to follow the same path. Thus, a trajectory generator is introduced to output the required position, velocity and acceleration from the position set point with realistic reproduction of the actuator power limits. Feedforward actions are used to compensate the major and invariant effects such as servo-hydraulic actuators functional flow and electro-mechanical actuator inertial torque. In this way, the pursuit errors are significantly reduced without decreasing robustness. Then, the accurate virtual test bench is used to assess the robustness of the force equalization strategy by analyzing the sensitivity of performance indicators to parameters and operating conditions. It is shown that the proposed force equalization scheme meets all the requirements, including segregation, robustness and simplicity.
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paper_title: High Reliability Permanent Magnet Brushless Motor Drive for Aircraft Application

paper_content:

Reliability is a fundamental requirement in aircraft safety-critical equipments. Its pursuing involves the adoption of protective design concepts such as fault-tolerant or redundant approaches, aiming to minimize mission failure probabilities. Multi-phase motor drives are gaining a growing interest to this extent, because they permit a boost in torque and power density, allowing the design of very compact high efficiency drives with intrinsic fault-tolerant capabilities. This paper presents a five-phase permanent magnet brushless motor drive developed for an aircraft flap actuator application. The motor is designed to satisfy the load specifications with one or two phases open or with a phase short circuited, while a failure in the rotor position sensors is remedied through a sensorless strategy. Design studies aiming to predict the faulty mode performance in case of different remedial strategies are presented. Experimental tests on the drive prototype are included, which confirm its capability to satisfy the planned degraded modes of operation.
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paper_title: An electromechanical actuator for a transport aircraft spoiler surface

paper_content:

The More Electric Aircraft Initiative (MEI) embraces the concept of utilizing electrical power for driving aircraft subsystems. Power electronics and motor drives are essential elements of the MEI. Advancements in power semiconductor devices, capacitors, and integrated circuits for control has enabled high density, reliable power electronic and motor drive systems for the MEI. Wright Laboratory and Sundstrand Aerospace have been working on the development of an electromechanical actuator to be compatible with the requirements of a spoiler for a typical transport aircraft. The focus of this development effort is in the motor drive, meaning the controller, inverter and motor utilized to control the actuator. Efforts are underway to increase the power density of the motor drive to achieve 1 kW/lb, with an efficiency of greater than 80%. This paper discusses the design criteria and some of the trade-offs that were accomplished during this development. This work includes the use of a novel soft switched inverter driving a five-phase switched reluctance motor. A digital signal processing (DSP) chip is utilized for responsive controls and field programmable gate arrays (FPGA) to reduce size and increase control electronics reliability. A power electronics module is developed which is comprised of insulated gate bipolar transistor (IGBT) inverter switches, diodes, a current sensor and gate drives. The thermal management system utilizes a reflux heat exchanger with integral phase change material that will enable the motor drive to operate in the environment of the actuator.
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paper_title: Fault-tolerant permanent magnet machines: a review

paper_content:

Synchronous permanent magnet (PM) machines have been gaining a lot of interest over the years. This is due to their several advantages including high power density, high efficiency and high reliability. One of the key concerns about PM machines especially in safety-critical applications (such as the more-electric aircraft) has been the issue of fault-tolerance since the machine cannot be de-excited. A lot of work has been done both on the machine side as well as the power converter side (including power converter configuration and remedial control strategies). This study will provide a thorough review and summary of what has been covered in literature up-to-date. The study will highlight the tradeoffs (including weight, cost and reliability) involved in the various proposed methods and strategies with more emphasis on the machine side. The methods discussed in this study include active control methods form converter side, memory motors, doubly-salient and flux-switching machines, use of auxiliary windings, mechanical flux-weakening methods, use of shunts and shields, thermal protection and transverse flux machines. The study will also include some comments about where the research in this area is heading in the future.
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paper_title: Kinematics Analysis of the Roller Screw Based on the Accuracy of Meshing Point Calculation

paper_content:

This paper investigates the meshing behavior of the roller screw, a mechanical transmission device characterized by threaded rollers that transfer a load between the nut and the screw, by analyzing the meshing characteristics between screw and rollers. This study seeks to establish a more accurate mathematical model for the thread surface by creating a modeling process in which the max radiuses of the threads are calculated more precisely. The contact line distribution and the contact location were also calculated in order to confirm the cross section of the meshing points. In the research presented in this paper, the actual transmission ratio is analyzed and the study results in a new method to calculate the actual transmission ratio. In this study, the helical angle and the vertex angle are proven to be of great significance after a careful analysis of their influence is conducted.
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paper_title: Static Load Distribution and Axial Stiffness in a Planetary Roller Screw Mechanism

paper_content:

In this paper, an original approach is proposed to calculate the static load distribution and the axial stiffness of a planetary roller screw (PRS) mechanism. Assuming that the external loading is shared equally over an arbitrary number of rollers, only a sector of the system is represented to save on computing time. The approach consists in using a structure of bars, beams, and nonlinear springs to model the different components of the mechanism and their interactions. This nonlinear model describes the details of the mechanism and captures the shape of the nut as well as the bending deformation of the roller. All materials are assumed to operate in the elastic range. The load distribution and the axial stiffness are determined in three specific configurations of the system for both compressive and tensile loads. Further, the influence of the shape of the nut is studied in the case of the inverted PRS. The results obtained from this approach are also compared to those computed with a three-dimensional finite-element (3D FE) model. Finally, since the calculations appear to be very accurate, a parametric study is conducted to show the impact of the bending of the roller on the load distribution.
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paper_title: Stiffness of the Roller Screw Mechanism by the Direct Method

paper_content:

In this paper, the direct stiffness method is used to construct a stiffness model of the roller screw mechanism. This method models the entire roller screw mechanism as a large spring system composed of individual springs representing the various compliances. In addition to predicting the overall stiffness of the mechanism, the direct stiffness method can calculate the distribution of load across the threads of the individual bodies. With the load on the individual threads known, the contact stresses can be calculated. This allows for a better understanding of the sensitivities of stiffness and contact stresses in the mechanism with various design parameters and can ultimately be used to design roller screws that are stiffer and with lower contact stresses.
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paper_title: Kinematics and Efficiency Analysis of the Planetary Roller Screw Mechanism

paper_content:

This paper analyzes the kinematics and the efficiency of the planetary roller screw mechanism (RSM) to provide a fundamental basis to support its various applications. The mechanical structure and practical advantages are presented in comparison with the conventional ball screw mechanism (BSM). Kinematic analysis involves derivation of the angular and axial motions, as well as the development of the slip pattern between the contacting components. Results show that for any motion of the RSM slip always occurs. Kinematic analysis including elastic deformation is also presented. The load carrying capacity and efficiency of the RSM are derived based on geometric and equilibrium conditions, and the results are compared with the BSM.
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paper_title: Load distribution of planetary roller screw mechanism and its improvement approach

paper_content:

A model of load distribution over threads of planetary roller screw mechanism (PRSM) is developed according to the relationships of deformation compatibility and force equilibrium. In order to make the applied load of PRSM uniformly distributed over threads, an improvement approach is proposed, in which the parameters of thread form of roller and nut are redesigned, and the contact conditions of roller with screw and nut are changed to compensate the axial accumulative deformation of shaft sections of screw and nut. A typical planetary roller screw mechanism is taken as example to analyze the load distribution, and the effects of installation configurations, load conditions and thread form parameters on load distribution are studied. Furthermore, the improvement approach is applied to the PRSM, and it is proved to be beneficial to reach uniform load distribution over threads.
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paper_title: Inner-Loop Control for Electromechanical (EMA) Flight Surface Actuation Systems

paper_content:

This manuscript pertains to the application of an inner-loop control strategy to electromechanical flight surface actuation systems. Modular electromechanical actuators (EMAs) are increasingly used in lieu of centralized hydraulics for the control of flight surfaces in the aerospace sector. The presence of what is termed as a dead zone in these actuators significantly affects the maneuverability, stability, and the flight profiles of aircrafts that use this actuation concept. The hypothesis of our research is that flight surface actuation systems may be desensitized to the effects of dead zone by using a control strategy with multiple inner loops. The proposed strategy involves (a) high-gain inner-loop velocity control of the driving motor and (b) inner-loop compensation for the differential velocity between the motor versus the aileron. The above hypothesis is confirmed by theoretical and simulated analyses using the model of an EMA flight surface actuator. Our results indicate that for small input signals, this strategy is very effective and that it can (a) considerably increase the bandwidth and the crossover frequency of the system and (b) considerably improve the time response of the system. Further to this analysis, this manuscript presents guidelines for the design of EMA systems.
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paper_title: Contact Kinematics in the Roller Screw Mechanism

paper_content:

This paper investigates the nature of the contact between the load transferring surfaces in the roller screw mechanism, i.e., between the screw and roller threads and between the nut and roller threads. The analysis is applied to both planetary roller screws and recirculating roller screws. Prior work has neglected to take a fundamental approach toward understanding the kinematics of the contact between these components and, as a consequence, detailed analyses of aspects such as contact mechanics, friction, lubrication, and wear are not correctly carried out. Accordingly, in this paper, the principle of conjugate surfaces is used to establish contact at the screw/roller and nut/roller interfaces. The in-plane angles to the contact points are derived and it is shown that for the screw/roller interface, the contact point cannot lie on the bodies' line of centers, as has been the assumption in previous papers. Then, based on the curved profile of the roller thread, the radii of contact on the roller, screw, and nut bodies are also derived. Knowledge of the contact point locations is necessary in order to understand the interaction forces between the key components of the roller screw mechanism. The principal radii of curvature at the contact points and the angle between the principal axes are also derived. Lastly, a brief example is developed showing how the developed theory may be used to design a roller screw for improved stiffness and decreased contact stresses.
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paper_title: EMA Health Monitoring: An overview.

paper_content:

This paper presents an overview of the last decade of work on Electromechanical Actuators (EMA) Health Monitoring (HM) of the industrial cooperation between Liebherr- Aerospace in Lindenberg and the DLR Institute of System Dynamics and Control. The efforts on simulation of damage, (component) testing and development of HM algorithms will be presented.
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paper_title: Design of fault-tolerant control functions for a primary flight control system with electromechanical actuators

paper_content:

A concept for the fault-tolerant control of a primary flight control system featuring two parallel electromechanical actuators nominally operating in active-active mode is proposed. A detailed nonlinear model of the system under consideration is created to enable the design of high-level and low-level safety control functions. Three reaction sequences combining five different reactions are proposed for the mitigation of safety-critical faults. Attention is paid to the sequence assigned to those actuator faults that permit the safe continued movement of the control surface while the system operates in active-standby mode. A control concept is developed to reduce the reflected inertial loads in this mode without permanently degrading the system performance. Herewith, the load on the active actuator reaches at the most 95% of the system's limit load when both actuators operate in a highly degraded state, whereas with the original control scheme the limit load is continuously exceeded by 30%.
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paper_title: PRESAGE: Virtual testing platform application to thrust reverser actuation system

paper_content:

The purpose of this article is to demonstrate the interest and the need to rely on modeling and simulation of mechatronic systems in case of testing application and to contribute to the “democratization” of the use of models and “virtual testing”. Indeed, the systems are becoming increasingly complex: more dynamic, more optimized. Add for that the development schedules are more and more restricted with reduced budgets. These constraints which are antagonistic tend to emerge a new generation of designing and testing: the “virtual test platform”. We propose industrial methods and appropriate tools to develop this virtual test platform. It is with this objective that CERTIA (Provider of test benches and studies) and the company AIRCELLE (designer and integrator of nacelles), with significant experience in their respective fields, have developed the platform “PRESAGE” for virtual testing.
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paper_title: Estimation models for the preliminary design of electromechanical actuators

paper_content:

This article presents estimation models for the model-based preliminary design of electromechanical actuators. Models are developed to generate all the parameters required by a multi-objective design, from a limited number of input parameters. This is achieved using scaling laws in order to take advantage of their capability to reflect the physical constraints driving the actuator’s component sizing. The proposed approach is illustrated with the major components that are involved in aerospace electromechanical actuator design. The established scaling laws provide the designer with parameters needed for integration into the airframe, power sizing, thermal balance, dynamics, and reliability. The resulting estimation models are validated with industrial data.
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paper_title: Modelling approach for the Simulation-Based Preliminary Design of Power Transmissions

paper_content:

Abstract The promises of Model-Based Design have led to the development of numerous methodologies and software tools, especially for the specific or detailed design stages, from controller design to finite element analysis. However, the Model-Based Design of actuation systems lacks methodologies and expressive simulation models that are suited to preliminary design, where key technical decisions are taken considering various design alternatives and few available design details. In order to fill this gap, the present paper illustrates how scaling laws and acausal modelling can be used as a design tool, exploiting inverse simulation capabilities to evaluate technological alternatives quantitatively from limited design detail information. The application of the modelling approach is shown for two major components of mechanical transmission systems: roller bearings and ball and roller screws. The scaling laws presented are validated with manufacturers’ data. To conclude, the suitability of the proposed methodology is illustrated with the preliminary sizing of an electromechanical actuator for an aircraft primary flight control surface (aileron).
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paper_title: Inner-Loop Control for Electromechanical (EMA) Flight Surface Actuation Systems

paper_content:

This manuscript pertains to the application of an inner-loop control strategy to electromechanical flight surface actuation systems. Modular electromechanical actuators (EMAs) are increasingly used in lieu of centralized hydraulics for the control of flight surfaces in the aerospace sector. The presence of what is termed as a dead zone in these actuators significantly affects the maneuverability, stability, and the flight profiles of aircrafts that use this actuation concept. The hypothesis of our research is that flight surface actuation systems may be desensitized to the effects of dead zone by using a control strategy with multiple inner loops. The proposed strategy involves (a) high-gain inner-loop velocity control of the driving motor and (b) inner-loop compensation for the differential velocity between the motor versus the aileron. The above hypothesis is confirmed by theoretical and simulated analyses using the model of an EMA flight surface actuator. Our results indicate that for small input signals, this strategy is very effective and that it can (a) considerably increase the bandwidth and the crossover frequency of the system and (b) considerably improve the time response of the system. Further to this analysis, this manuscript presents guidelines for the design of EMA systems.
---
paper_title: Experimental Data Collection and Modeling for Nominal and Fault Conditions on Electro-Mechanical Actuators

paper_content:

Being relatively new to the field, electromechanical actuators in aerospace applications lack the knowledge base compared to ones accumulated for the other actuator types, especially when it comes to fault detection and characterization. Lack of health monitoring data from fielded systems and prohibitive costs of carrying out real flight tests push for the need of building system models and designing affordable but realistic experimental setups. This paper presents our approach to accomplish a comprehensive test environment equipped with fault injection and data collection capabilities. Efforts also include development of multiple models for EMA operations, both in nominal and fault conditions that can be used along with measurement data to generate effective diagnostic and prognostic estimates. A detailed description has been provided about how various failure modes are inserted in the test environment and corresponding data is collected to verify the physics based models under these failure modes that have been developed in parallel. A design of experiment study has been included to outline the details of experimental data collection. Furthermore, some ideas about how experimental results can be extended to real flight environments through actual flight tests and using real flight data have been presented. Finally, the roadmap leading from this effort towards developing successful prognostic algorithms for electromechanical actuators is discussed. *
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paper_title: An integrated approach to vehicle and subsystem sizing and analysis for novel subsystem architectures

paper_content:

The aerospace industry is currently transitioning to More Electric subsystem architectures due to steadily improving electric technologies and the technology saturation of established conventional architectures. For aircraft with such unconventional architectures, the lack of historical information and the presence of increased inter-subsystem interactions create a significant design challenge. These necessitate a greater focus on subsystems design earlier in the design process than typically seen for aircraft with conventional subsystem architectures. At the same time, however, to be suitable for the early design phases, the subsystem analyses must be computationally inexpensive and not require detailed aircraft definition. This work presents an integrated, modular, and tool-independent approach to the sizing and performance analysis of the aircraft and its subsystems, in which inter-dependencies are established between relevant aircraft and subsystem level parameters. The approach allows the assessment ...
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paper_title: Optimal design of electromechanical actuators for active loads

paper_content:

The proliferation of electromechanical actuation promises reduced maintenance requirements and cost, improved efficiency and reliability, and more environmentally friendly operation. Within this paper, the issue of optimal component selection for actuator design is addressed. Optimality is defined as an engineering trade-off concerning power transfer to the load, efficiency, and torque demand. An equivalent circuit for the actuator/active load system is developed and represented in the phasor domain. Sinusoidal steady-state techniques are employed for system analysis and definition of the conditions for optimality in applications where load force and velocity profiles are known. The actuator application of thrust vector control on the Space Shuttle main engine is specifically addressed.
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paper_title: Concepts for position and load control for hybrid actuation in primary flight controls

paper_content:

Abstract Moving towards the More Electric Aircraft, a hybrid actuator configuration, in which an electromechanical actuator (EMA) and an electrohydraulic servoactuator (EHSA) operate on the same control surface, provides an opportunity to introduce electromechanical actuators into primary flight controls. Besides the operation in active/passive or active/active mode, an “active/no-load” mode is promising. In this mode the EMA is controlled such that it actively follows the movement of the control surface without carrying external air loads, thereby reducing power dissipation compared to active/active mode and failure transients compared to active/passive mode. However, force fighting will occur if both actuators are actively controlled. In this paper, control concepts for a hybrid configuration, extending the original actuator control loops, are presented, enabling active/active as well as active/no-load operation. Nonlinear as well as linear models for an EMA, an EHSA, and a control surface structure are derived from technical data for an airworthy EHSA and combined to a model of the hybrid configuration. These models are used for matching of actuator dynamics and simulation of the developed control laws. For active/active mode, maximum force fighting between the actuators is reduced from about 500% to 7% of the stall load. For active/no-load mode, a force control loop is added to the EMA control, causing the EMA to follow movements of the control surface such that the external loads on the EMA are zero in steady-state. Force fighting is reduced to 30% of the stall load.
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paper_title: Modelling and simulation of flight control electromechanical actuators with special focus on model architecting, multidisciplinary effects and power flows

paper_content:

In the aerospace field, electromechanical actuators are increasingly being implemented in place of conventional hydraulic actuators. For safety-critical embedded actuation applications like flight controls, the use of electromechanical actuators introduces specific issues related to thermal balance, reflected inertia, parasitic motion due to compliance and response to failure. Unfortunately, the physical effects governing the actuator behaviour are multidisciplinary, coupled and nonlinear. Although numerous multi-domain and system-level simulation packages are now available on the market, these effects are rarely addressed as a whole because of a lack of scientific approaches for model architecting, multi-purpose incremental modelling and judicious model implementation. In this publication, virtual prototyping of electromechanical actuators is addressed using the Bond-Graph formalism. New approaches are proposed to enable incremental modelling, thermal balance analysis, response to free-run or jamming faults, impact of compliance on parasitic motion, and influence of temperature. A special focus is placed on friction and compliance of the mechanical transmission with fault injection and temperature dependence. Aileron actuation is used to highlight the proposals for control design, energy consumption and thermal analysis, power network pollution analysis and fault response.
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paper_title: Modelling and simulation of mechanical transmission in roller‐screw electromechanical actuators

paper_content:

Purpose – The purpose of this paper is to develop accurate model and simulation of mechanical power transmission within roller‐screw electromechanical actuators with special attention to friction, compliance and inertia effects. Also, to propose non‐intrusive experiments for the identification of model parameters with an integrator or system‐oriented view.Design/methodology/approach – At system design level, the actuation models need to reproduce with confidence the energy losses and the main dynamic effects. The adopted modelling methodology is based on non‐intrusive measurements taken on a standard actuator test‐bench. The actuator model is first structured with respect to the bond‐graph formalism that allows a clear identification of the considered effects and associated causalities for model implementation. Various approaches are then combined, mixing blocked or moving load, position or torque control and time or frequency domains analysis. The friction representation model is suggested using a step‐b...
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paper_title: Development of a Sizing and Analysis Tool for Electrohydrostatic and Electromechanical Actuators for the More Electric Aircraft

paper_content:

This work documents the development of a MATLAB/Simulink based methodology for the sizing, simulation, analysis, and optimization of electric actuators for the primary and secondary control surfaces of a More Electric Aircraft. For a given aircraft and control surface configuration, the control surface flight loads are first evaluated taking into account their aerodynamic characteristics and the critical flight conditions relevant to each. With this information, the performance of a given actuator design can be analyzed via a simulation of the actuator and thermal dynamics. Conversely, for a given objective function and constraint set, the actuator design can be optimized through the solution of a constrained optimization problem. This work focuses on the development of the flight load estimation capability, the modeling and simulation environment, and the weight estimation method, while a separate work describes the actuator optimization problem and a study of actuator-to-surface allocation. While applicable to a wide variety of aircraft, the current work analyzes electrohydrostatic and electromechanical actuators using the Boeing 737-800 aircraft as a test case.
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paper_title: Modelling approaches for the simulation-based preliminary design and optimization of electromechanical and hydraulic actuation systems

paper_content:

This communication proposes to combine non causal modeling, metamodeling and scaling laws in order to take advantage of the inverse simulation capabilities of recent system level simulation software with the main target to assess technological alternatives quantitatively from a limited set of required data. The scaling laws are illustrated here for major hydraulic components (hydraulic cylinders and pumps) and are validated with manufacturers’ data. The proposed methodology is illustrated with the preliminary sizing of an electro-hydrostatic actuator driving an aircraft primary flight control surface (aileron). The design exploration for geometrical integration and mass is realized using to surface response models.
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paper_title: Dynamic Heat Generation Modeling of High Performance Electromechanical Actuator

paper_content:

All-electric aircraft is a high priority goal in the avionics community. Both increased reliability and efficiency are the promised implications of this move. But thermal management has become a significant issue that must be resolved before reaching this goal. Advanced analysis technologies such as finite element method and intelligent control systems such as field oriented control are being used to better understand the source of the heat and to eliminate as much of it as possible. This paper addresses the motivation behind allelectric aircraft and gives an overview of some of the considerations in cooling, simulation and modeling, and control, with an example of one control scheme which is being developed.
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paper_title: High-Performance Electromechanical Actuator Dynamic Heat Generation Modeling

paper_content:

All-electric aircraft is a high-priority goal in the avionics community. Both increased reliability and efficiency are the promised implications of this move. But, thermal management has become a significant problem that must be resolved before reaching this goal. Electromechanical actuators (EMAs) are of special concern. Advanced analysis technologies such as the finite element method (FEM) and intelligent control systems such as field-oriented control (FOC) are being used to better understand the source of the heat and to eliminate as much of it as possible. This paper describes the nonlinear, lumped-element, integrated modeling of a permanent magnet (PM) motor used in an EMA. The parameters, including nonlinear inductance, rotor flux linkage, and thermal resistances and capacitances, are tuned using FEM models of a real, commercial actuator. The FOC scheme and the lumped-element thermal model are also described.
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paper_title: Thermal Management of Electromechanical Actuation System for Aircraft Primary Flight Control Surfaces

paper_content:

Abstract : Electromechanical actuation systems (EMAS) are a key component in the more electric aircraft (MEA). EMAS operate on a power- on-demand basis, reducing energy consumption typically required by hydraulic systems to maintain hydraulic pressure. Additionally, EMAS reduce system weight, lessening system maintenance and operating costs. EMAS convert electrical energy to mechanical energy via an electric rotary machine combined with a rotary to linear or rotary to rotary conversion mechanism. Electrical energy required to complete useful mechanical output depends on the efficiency of the system. Therefore, it is important to characterize electrical and thermal loads associated with an EMAS for primary flight control surfaces, such as an aileron. Electric power draw and thermal management are among the most important parameters of research in electromechanical actuation for a primary flight control (PFC) surface. The aim of this thesis was to build an experimental EMAS system and methodology to analyze EMAS performance against realistic duty cycles and mission environments. Thermal energy, in addition to the rate of change of temperature and temperature difference for temperature sensitive components, was used to determine the most thermally malignant profiles and potential thermal design points. It was found that transient missions of an EMAS presented the greatest electric demand of the aircraft electric power supply system, and holding presented the greatest thermal stress of the EMAS, where the EMAS operated at0 percent efficiency and all electric power was converted to heat.
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paper_title: Estimation models for the preliminary design of electromechanical actuators

paper_content:

This article presents estimation models for the model-based preliminary design of electromechanical actuators. Models are developed to generate all the parameters required by a multi-objective design, from a limited number of input parameters. This is achieved using scaling laws in order to take advantage of their capability to reflect the physical constraints driving the actuator’s component sizing. The proposed approach is illustrated with the major components that are involved in aerospace electromechanical actuator design. The established scaling laws provide the designer with parameters needed for integration into the airframe, power sizing, thermal balance, dynamics, and reliability. The resulting estimation models are validated with industrial data.
---
paper_title: Experimental Data Collection and Modeling for Nominal and Fault Conditions on Electro-Mechanical Actuators

paper_content:

Being relatively new to the field, electromechanical actuators in aerospace applications lack the knowledge base compared to ones accumulated for the other actuator types, especially when it comes to fault detection and characterization. Lack of health monitoring data from fielded systems and prohibitive costs of carrying out real flight tests push for the need of building system models and designing affordable but realistic experimental setups. This paper presents our approach to accomplish a comprehensive test environment equipped with fault injection and data collection capabilities. Efforts also include development of multiple models for EMA operations, both in nominal and fault conditions that can be used along with measurement data to generate effective diagnostic and prognostic estimates. A detailed description has been provided about how various failure modes are inserted in the test environment and corresponding data is collected to verify the physics based models under these failure modes that have been developed in parallel. A design of experiment study has been included to outline the details of experimental data collection. Furthermore, some ideas about how experimental results can be extended to real flight environments through actual flight tests and using real flight data have been presented. Finally, the roadmap leading from this effort towards developing successful prognostic algorithms for electromechanical actuators is discussed. *
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paper_title: Thermo-Mechanical Model and Thermal Analysis of Hollow Cylinder Planetary Roller Screw Mechanism

paper_content:

Planetary roller screw mechanism (PRSM) is widely used for rapid and precise motion translation from rotary into linear motion due to its high stiffness and high position accuracy. However, a high speed PRSM drive system naturally generates significant amount of frictional heat at the contact interfaces, which causes thermal deformation and thermal error and reduces motion accuracy. Preload is usually applied to remove the axial backlash of the PRSM for achieving high accuracy and great stiffness. However, more frictional heat is produced by such preload. On the other hand, larger numbers of angular contact bearings are needed to support the heavy axial load. The friction heat generated in support bearings has also to be investigated. In order to estimate the thermal distribution and thermal error of the hollow cylinder PRSM, a thermo-mechanical model based on finite element method (FEM) is developed, where heat generation from the two main sources of the PRSM, the parameters calculation of heat transfer ...
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paper_title: Weighted bagging gaussion process regression to predict remaining useful life of electro-mechanical actuator

paper_content:

Electro-Mechanical Actuator (EMA) is one of the key components of next generation aircraft. In order to ensure the safety of aircraft, it is critical to predict the remaining useful life (RUL) of EMA. And the RUL prediction can be implemented by utilizing Gaussian Process Regression (GPR). However, the GPR algorithm is extremely complex. Hence, a weighted bagging Gaussian Process Regression (WB-GPR) algorithm is presented in this article. To be specific, the significance of RUL prediction of EMA is analyzed, and the variable which can represent the degradation progress of EMA failure is selected. Then the framework to predict the RUL of EMA is realized, with the proposed WB-GPR. Finally the performance of RUL prediction based on WB-GPR is validated by utilizing the sensor data sets from National Aeronautics and Space Administration (NASA) Ames Research Center. Furthermore, the comparison of RUL prediction with GPR and bagging GPR has been achieved. Experimental results demonstrate that the WB-GPR is effective in the RUL prediction with low error rate and standard deviation.
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Title: A Review of Electromechanical Actuators for More/All Electric Aircraft Systems

Section 1: Introduction  
Description 1: Introduce the trend towards using electrical actuation systems in More/All Electric Aircraft (MEA/AEA), the benefits of power-by-wire (PBW) technology, and outline the main objectives and scope of the review.

Section 2: Background Review  
Description 2: Discuss the basic types of Electromechanical Actuators (EMAs), their components, and how they function in aircraft applications.

Section 3: Development and Application  
Description 3: Detail the development history and the current applications of EMAs in different aircraft systems, including primary and secondary flight controls, landing gears, and engines.

Section 4: Architecture of EMA  
Description 4: Describe the components and structure of EMAs, including motor types, gearboxes, screw mechanisms, and electronic control units (ECUs).

Section 5: EMA Testing System  
Description 5: Explain the different methods and conditions for testing EMAs, such as room temperature, thermal vacuum environment, and iron bird testing setups.

Section 6: Key Technologies and Research Challenges  
Description 6: Discuss the major challenges in EMA development, including fault-tolerant motor design, high-thrust mechanical transmission, multidisciplinary modeling, and thermal management.

Section 7: Conclusions  
Description 7: Summarize the findings of the review, highlight the progress made in EMA technology, note the remaining challenges, and suggest future research directions.

Section 8: Declaration of Conflicting Interests  
Description 8: State the authors' declaration regarding potential conflicts of interest related to the research, authorship, and publication of the article.