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The introduction of EMA Systems requires the use of redundant inverters to drive the EMA and ensure reliability and safety. Redundant converters allow the implementation of fault tolerant control and high quality operation. Fault control has been implemented by means of redundant converter and fault detection system.

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Actuation is used in all vehicles (aircraft, spacecraft, ground vehicles, etc) to control the position and/or attitude of the vehicle, and also to deploy or retract equipment, particularly for embedded optic instruments (cameras, telescopes). As such, the actuation is a safety critical system, particularly when humans could be catastrophically affected by failures within the system. Applications for actuation are flight controls, landing gear, rotors, suspension, antennae steering, valves, scanning, positioning using hydraulic, electromechanical, magnetic and piezo actuators. In aircraft there is a common goal to reduce the number of hydraulic actuators in vehicles and eventually to replace them completely by electric actuators. The interest for smart suspensions is pushing magnetorheological fluids (MRF) actuators. In UAV, MAV and microsatellites, actuators key drivers are often miniaturisation and low power. Embedded optic & space instruments are leading to improved piezo actuators and motors.
The "All-Electric" aircraft is a concept that emerged in the 1970s and has engendered a large amount of research activity. An all-electric engine, which could replace current aero gas turbines, would drive all accessories electrically, via a distribution network, from motor/generators embedded in the engine spools. Extending the function of the motor/generators to include service as active mag-netic bearings would facilitate deletion of the oil system. The all-electric concept thus offers a huge scope for both engine and airframe reconfiguration and operational improvements, with studies indicating benefits of overall weight reduction, increased reliability, easier maintainability, reduced operating costs (including reduced fuel burn), and enhanced safety. As a stepping stone to the all-electric aircraft, an interim solution has emerged, namely, the More-Electric Aircraft (MEA). Such an aircraft contains some, but not all, of the key features of the all-electric. This incremental approach is attractive because it incurs significantly less risk than a wholesale change to the aircraft electrical system otherwise required. TRW Aeronautical Systems, being a system supplier whose expertise and products include electrical machine design, power management, and engine and flight controls, is particularly well-placed to support progress on the MEA. Furthermore, electric actuation technologies developed by TRW for use in controlling flight surfaces, are currently migrating from the phases of research and development and flight trials, to entering service circa 2006.
Conference Paper
The development of fault tolerant embedded control systems, such as flight control systems, FCS, is currently highly specialized and time consuming. We introduce a conceptual architecture for the next decade control system where all control and logic is distributed to a number of computer nodes locally linked to actuators and connected via a communication network. In this way we substantially decrease the lifecycle cost of such embedded systems and acquire scalable fault tolerance. Fault tolerance is based on redundancy and in our concept permanent faults are covered by hardware replication and transient faults, fault detection and processing by software techniques. With intelligent nodes and the use of inherent redundancy a robust and simple fault tolerant system is introduced with a minimum of both hardware and bandwidth requirements. The study is based on an FCS for JAS 39 Gripen, a multirole combat aircraft that is statically unstable at subsonic speed
Conference Paper
Power-By-Wire (PBW) is a program involving the replacement of hydraulic and pneumatic systems currently used in aircraft with an all-electric secondary power system. One of the largest loads of the all-electric secondary power system will be the motor loads which include pumps, compressors and electrical actuators (EAs). Issues of improved reliability, reduced maintenance and efficiency, among other advantages, are the motivation for replacing the existing aircraft actuators with electrical actuators. An EA system contains four major components. These are the motor, the power electronic converters, the actuator and the control system, including the sensors. This paper is a comparative literature review of motor drive technologies, with a focus on the trends and tradeoffs involved in the selection of a particular motor drive technology. The reported research comprises three motor drive technologies. These are the induction motor (IM), the brushless dc motor (BLDCM) and the switched reluctance motor (SRM). Each of the three drives has the potential for application in the PBW program. Many issues remain to be investigated and compared between the three motor drives, using actual mechanical loads expected in the PBW program
Conference Paper
The C-141 RAMTIP (Reliability and Maintainability Technology Insertion Program) project comprises the development, test, and flight evaluation of fly-by-wire/power-by-wire flight controls for the three primary axes, plus spoilers, on the C-141 aircraft. The C-130 TAPM (Technology Application Program Management) project comprises the development, test, and flight evaluation of an electro-hydrostatic actuation (EHA) subsystem in the HTTB (high technology test bed) aileron system. The author describes the systems being investigated and summarizes the laboratory and flight test demonstrations that have been accomplished. He also addresses current and planned programs for further development, test installations, and flight demonstrations of power-by-wire primary flight control systems
The aerospace industry is currently considering a constant voltage, variable frequency supply for aircraft power systems. This variable frequency system is based on a generator directly driven from the aero-engine, in which the frequency is dependent on engine speed. A number of safety critical loads are placed on this system, and it is essential that failure of any one load does not affect the operation of another. The paper develops the concept of fault tolerant input converters for an electric fuel pump. The converters always act as a unity power-factor load, and can tolerate a range of failures, whilst maintaining both the operation of the pump and minimal impact on the electrical supply. Two converter types are proposed and compared for this application. The operation of these two unity power factor converters from a variable frequency supply is demonstrated. The effect of faults in the selected converters on converter operation and the supply itself is then discussed.
The fundamental issues faced in the aircraft electrical power systems are addressed. A brief description of the conventional and advanced aircraft power system architectures, their disadvantages, opportunities for improvement, future electric loads, role of power electronics, and present trends in aircraft power system research is given, followed by a brief outline of projected future advancements
The author examines a proposal published by D.T. Glass-Hooper (see Flight, Dec. 21, 1916) for controlling an aircraft using solenoids. He than discusses the control systems used almost universally in aircraft through the end of WWII, and the gradual evolution to almost all-electrical flight control (the hydraulic actuator is the last major nonelectrical element). Laboratory testing of electric actuators is considered and the C-141 Aileron electric actuation system is presented. The High Technology Test Bed program, which was implemented to provide a research aircraft for the development and evaluation of aerodynamic, avionic, and flight control system concepts, is described.< >
The paper describes a study and an experimental verification of remedial strategies against failures occurring in the inverter power devices of a permanent-magnet synchronous motor drive. The basic idea of this design consists of incorporating a fourth inverter pole, with the same topology and capabilities of the other conventional three poles. This minimal redundant hardware, appropriately connected and controlled, allows the drive to face a variety of power device fault conditions while maintaining a smooth torque production. The achieved results also show the industrial feasibility of the proposed fault-tolerant control, that could fit many practical applications
Stability, Maneuverability, and Safe Landing in the Presence of Adverse Conditions Aviation Safety Program of the National Aeronautics and Space Administration
  • J Totah