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Research Papers

The Instantaneous Efficiency of Epicyclic Gears in Flight Control Systems

[+] Author and Article Information
Anngwo Wang

MOOG Inc. Aircraft Group, Torrance, CA 90501 e-mail: awang@moog.com

Seth Gitnes

MOOG Inc. Aircraft Group, Everett, WA 98204 e-mail: sgitnes@moog.com

Lotfi El-Bayoumy

MOOG Inc. Aircraft Group, Torrance, CA 90501 e-mail: lelbayoumy@moog.com

J. Mech. Des 133(5), 051008 (Jun 08, 2011) (11 pages) doi:10.1115/1.4004001 History: Received May 03, 2010; Revised April 07, 2011; Published June 08, 2011; Online June 08, 2011

The instantaneous efficiency of an epicyclic gear rotary actuator is an important factor in sizing flight control systems where compound epicyclic gear trains are typically used. The efficiency variation can be smooth or fluctuating depending on the combination and timing of the teeth of ring, planet, and sun gears. In this paper, the instantaneous efficiency characteristics of synchronous and nonsynchronous actuators under forward-driving with opposing load and reverse-driving with aiding load are investigated. The emphasis will be on instantaneous, rather than average efficiency of gears. Several gear arrangements are considered: external and internal gears, simple planetary gears and compound planetary gears. Efficiency will be discussed considering not only the geometry of the mating gears, but also the relative phasing of the planet gears relative to the sun and ring gears. Synchronous compound epicyclic gears are shown to have large fluctuation in their instantaneous efficiency. When reverse-driving efficiency falls below 0%, the unit cannot be back-driven and will chatter. Nonsynchronous compound gears have a smaller variation in instantaneous efficiency. However, extra care must be taken in timing the compound planet gears, as well as clocking position of compound planet gears relative to ring gears and the sun gear.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 4

Instantaneous efficiency of an external gear pair

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Figure 5

Instantaneous efficiency of a synchronous simple planetary gear set

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Figure 6

Instantaneous efficiency of a nonsynchronous simple planetary gear set

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Figure 7

A typical leading edge geared rotary actuator

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Figure 8

A typical trailing edge geared rotary actuator

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Figure 9

Schematic of a typical synchronous compound planetary gear set

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Figure 10

Schematic of a typical nonsynchronous compound planetary gear set

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Figure 11

Instantaneous efficiency of a synchronous compound planetary (six planets)

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Figure 12

Instantaneous efficiency of a nonsynchronous compound planetary (10 planets)

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Figure 16

For the derivation of changes in the roll angle on a (a) planet (odd)—ring mesh and (b) planet (even)—ring mesh

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Figure 18

Schematic of a planetary gear set with the carrier as the output

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Figure 19

Schematic of a planetary gear set with the carrier as the input

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Figure 20

Schematic of a compound planetary gear set

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Figure 1

Forces and friction on an (a) external gear and (b) internal gear of an internal gear pair (forward driving)

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Figure 2

Forces and friction on a (a) driving pinion and (b) driven gear of an external gear pair (forward driving)

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Figure 3

Instantaneous efficiency of an internal gear pair

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Figure 13

Instantaneous efficiency of a compound planetary gear set for example 3

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Figure 14

For the derivation of the radius of curvature Rc (a) when γ > α and (b) when γ < α

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Figure 15

(a) Odd number of teeth and (b) even number of teeth on a planet gear

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Figure 17

For the derivation of changes in the radius of curvature

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