Integrated Machine design for Electro Mechanical04374788

Integrated Machine design for Electro Mechanical04374788 -...

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Integrated Machine design for Electro Mechanical Actuation Chris Gerada, Keith Bradley School of Electrical Engineering University of Nottingham Nottingham, UK, NG7 2RD chris.gerada@nottingham.ac.uk Chris Whitley, Graham Towers Smiths Aerospace Actuation Systems Wobaston Road Wolverhampton. WV9 5EW, UK Abstract— 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. I. INTRODUCTION As the modern aircraft heads towards a more electric based generation and distribution system there is an increased drive towards having electrical loads. One of the most researched areas are primary and secondary flight actuation surfaces. Using an electrical supplied actuator gives the distinct advantage of not needing a hydraulic supply whith all its associated disadvantages. In general electrical supplied actuators can be divided into EHAs (Electro Hydraulic Actuators) and EMAs (Electro Mechanical Actuators). EHAs consist of a variable speed pump supplying a local hydraulic actuation system whilst EMAs are often just a variable speed electrical motor drive coupled to a ball or roller screw through a gearbox. Whilst EMAs offer a total leakage free solution, EHAs are often preferred to EMAs in safety critical applications due to the problem of possible mechanical jams in EMAs. The jamming issue with EMAs is currently being researched from both the material surface properties point of view as well as finding safe and effective methods to disengage a jammed EMA from the flight surface. Electrical machines are an enabling technology in reducing the probability of an EMA jamming. This work will look at the compromises and issues with driving a roller screw directly coupled to an electrical machine, rather than driven through a gear box. A foreseeable advantage is the reduced jamming probability and the increased reliability of the actuation system. On the other hand one can argue that a directly coupled motor will lead to a larger motor as motor size is roughly proportional to torque and thus having a heavier and bigger actuator. This work looks at a novel integrated machine and roller screw design directly coupled to each other improving the reliability of the actuator and at the same time reaching the same power densities of the geared system. EMAs for flight surfaces usually consist of a high speed motor coupled through a gearbox to a ball or roller screw. For a given power, the higher the speed of the machine the smaller will be the motor, however the greater the gear ratio and hence the size of the gearbox.
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Integrated Machine design for Electro Mechanical04374788 -...

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