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UID:0-473@aerospace.technion.ac.il

DTSTART;TZID=Asia/Jerusalem:20160907T163000

DTEND;TZID=Asia/Jerusalem:20160907T173000

DTSTAMP:20230603T191337Z

URL:https://aerospace.technion.ac.il/events/elastic-deformations-control-o
 f-highly-flexible-aircraft-in-trimmed-flight-and-gust-encounter/

SUMMARY:Elastic Deformations Control of Highly Flexible Aircraft in Trimmed
  Flight and Gust Encounter
DESCRIPTION:Lecturer:Leeran Yagil\n Faculty:Department of Aerospace Enginee
 ring\n Institute:Technion – Israel Institute of Technology\n Location:Cl
 assroom 165\, ground floor\, Library\, Aerospace Eng.\n Zoom: \n Abstract:
  \n Details: \n High-altitude\, long-endurance (HALE) UAVs are characteriz
 ed by very large aspect ratio wings and low structural weight\, and theref
 ore are inherently highly flexible. As a result\, these platforms are more
  susceptible to very large structural deformation in flight and in atmosph
 eric turbulence. These deformations may severely affect the performance of
  the aircraft or its function\, as in the case of a wing-embedded antenna.
  In addition\, analysis of large elastic deformations requires the use of 
 computationally expensive nonlinear models. This work aims to control the 
 large wing deformations that highly flexible aircraft undergo in flight\, 
 by performing trim optimization to constrain wing deformation in steady tr
 immed flight\, and by minimizing the dynamic response to gust encounter.\n
 The flexible wing is trimmed and controlled via multiple control surfaces\
 , typically located along the leading and trailing edges. Due to the use o
 f multiple controls\, trimming the aircraft is cast as a trim optimization
  problem with constraints to find the control surface deflections that tri
 m the vehicle to a required maneuver while minimizing a specified objectiv
 e function. In the current study\, the optimization problem is to trim the
  aircraft to a symmetric maneuver while minimizing the control effort as a
 n objective\, and constraining wing elastic deformations to a user defined
  value. Trim optimization is performed using linear programming.\nWhile at
  trimmed flight\, gust disturbances may result in a large dynamic response
 . A robust control scheme is designed and applied using H-infinity loop sh
 aping\, to demonstrate that although the control surfaces are used for tri
 mming the aircraft\, they have enough authority left to effectively minimi
 ze elastic wing deformations during gust penetration.\nThe above methodolo
 gy is demonstrated on a highly flexible flying wing\, similar to the NASA 
 Helios aircraft. It is controlled via two leading- and two trailing-edge c
 ontrol surfaces. Trim optimization effectively allows trimmed flight at va
 rious load factors and dynamic pressure values in the flight envelope\, wh
 ile maintaining small structural deformations\, of about 1/40 of the wing 
 span. The H-infinity controller significantly reduces the maximum wing def
 lection experienced by a gust disturbance. Thus\, large structural deforma
 tions can be prevented\, avoiding related performance issues and the need 
 for complex structural geometrically nonlinear analyses for such highly fl
 exible airframes.
CATEGORIES:Seminars
LOCATION:Classroom 165\, ground floor\, Library\, Aerospace Eng.

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