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Research Papers

Inner-Loop Control for Electromechanical (EMA) Flight Surface Actuation Systems

[+] Author and Article Information
Saeid Habibi

Department of Mechanical Engineering, McMaster University, Hamilton, Canada L8S 4L7

Jeff Roach

 Phantom Works, Boeing, St. Louis, MO 63166-2210

Greg Luecke

1620F Howe Hall, Iowa State University, Ames, IA 50011

J. Dyn. Sys., Meas., Control 130(5), 051002 (Aug 01, 2008) (13 pages) doi:10.1115/1.2936382 History: Received May 24, 2005; Revised November 08, 2007; Published August 01, 2008

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.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Controller block diagram

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Figure 3

Block diagram of electrical motor

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Figure 4

Backlash block diagram

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Figure 5

Block diagram of dead zone model used in frequency response analysis

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Figure 6

Backlash/load block diagram

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Figure 7

EMA system using position feedback from the motor

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Figure 8

EMA system with inner-loop control

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Figure 9

Characterization of friction in EMA systems

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Figure 10

Inner-loop control of motor speed

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Figure 11

Simplified EMA block diagram

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Figure 12

Closed-loop gain and phase characteristics—motor position control

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Figure 13

Step response (aileron position) of the conventional system

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Figure 14

Frequency response characteristic relating the input to aileron position under closed-loop control

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Figure 15

Frequency response characteristic relating motor disturbances (including static friction) to aileron position under closed-loop control

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Figure 16

Frequency response characteristic relating load disturbances (including static friction) to aileron position under closed-loop control

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Figure 17

Sensitivity of the closed-loop transfer function to dead zone

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Figure 18

Small signal system time response with the conventional controller

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Figure 19

Small signal ETFE frequency response for system with the conventional controller

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Figure 20

Small signal time response—system with conventional controller and partial inner-loop compensation

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Figure 21

Small signal ETFE frequency response—system with conventional controller and partial inner-loop compensation

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Figure 22

Frequency response characteristic of dynamic coupling term and outer-loop feedback (Dcouple+H)

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Figure 23

Frequency response characteristic associated with inner-loop motor speed control (G2)

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Figure 24

Frequency response characteristic of Gbcomp for Gb=1

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Figure 25

Closed-loop gain and phase characteristics—controller with inner-loop feedback

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Figure 26

Step response (aileron position) of system with inner-loop feedback

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Figure 27

Frequency response characteristic relating motor disturbances (including static friction) to aileron position under closed-loop control with inner-loop feedback

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Figure 28

Frequency response characteristic relating load disturbances (including static friction) to aileron position under closed-loop control with inner-loop feedback

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Figure 29

Sensitivity of the closed-loop transfer function to dead zone with inner-loop feedback

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Figure 30

Small signal system time response with inner-loop compensation

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Figure 31

Small signal ETFE frequency response for system with inner-loop compensation

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