Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
L₁adaptive control of a generic fighter aircraft
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This master's thesis was performed at the section of Flight Control Systems at SAAB Aeronautics in Linköping as a part of my Master of Science in Aerospace Engineering at KTH, Stockholm. This report examines the use of L₁ adaptive control to stabilize the inner longitudinal and lateral loops of a generic fighter aircraft, in the event of failure of the system that measures current speed and altitude.

The philosophy of the L₁ adaptive controller is to decouple the adaptation from the control loop by using a state-predictor based adaptation scheme, still only compensating for the uncertainties within the bandwidth of the control channel by the use of low-pass filters.

The main goal of the project was to investigate in the tuning of the L₁ adaptive controller with respect to the nonlinear uncertainties related to the failure, and with a limited sampling rate of 60 Hz. The desired closed-loop dynamics for the statepredictor was designed by linearising the aircraft dynamics in a point in the middle of the flight envelope and placing the poles of the system with respect to flying qualities. The modified piecewise constant adaptation law was chosen as adaptation law, which achieves faster adaptation by increasing the sampling rate, yielding better performance at a given sample rate compared to the piecewise constant adaptation law [1]. All the states were transformed to discrete time in order to be implementable digitally.

Results have shown that augmenting a state-feedback controller with a L₁ adaptive controller increases robustness in the whole flying envelope, with good flying qualities. Problems were discovered in the low speed regions of the envelope, where the L₁ adaptive controller did not provide the desired performance. A switching scheme between two L1 adaptive controllers was examined. The switch between the controllers was done by knowing when the landing gear was up or down. The second state-predictor was designed with linearised dynamics in landing speed and altitude. The switching scheme was own in a simulator with a nonlinear generic fighter aircraft model with good results

Abstract [sv]

Detta examensarbete utfördes vid sektionen för styrsystem på SAAB Aeronautics i Linköoping som en del av min Master of Science i Aerospace Engineering vid KTH, Stockholm. Rapporten undersöker användningen av L₁adaptiv reglering för att stabilisera de inre longitudinella och laterala looparna i ett generisk stridsflygplan, i händelse av ett fel på det system som mäter aktuell hastighet och höjd.

Filosofin med L₁ adaptiv reglering ar att frånkoppla anpassning från reglerkretsen med en prediktorbaserad anpassningslag, men kompenserar bara för osäkerheterna inom bandbredden för styrkanalen med hjälp av lågpassfilter.

Det huvudsakliga målet med projektet var att undersöka finjusteringen av en L₁ adaptiv regulator med avseende på de olinjära osäkerheterna i händelse av ett fel, och med en begränsad samplingsfrekvens på 60 Hz. Den önskade dynamiken för det slutna systemet i prediktorn designades genom att linjärisera flygplanets dynamik i en punkt i mitten av flygenveloppen och placera polerna för systemet med avseende på flygegenskaper. Den modifierade styckvis konstanta anpassninglagen valdes som anpassninglag. Den uppnår snabbare anpassning genom att öka samplingshastigheten och ger bättre prestanda vid en given samplingsfrekvens jämfört med den styckvis konstant anpassninglagen [1]. Alla tillstånd transformerades till diskret tid för att kunna implementeras digitalt.

Resultaten har visat att genom att utöka en vanlig tillståndsåterkoppling med en L₁ adaptiv regulator ökar robustheten i hela flygenveloppen med goda flygegenskaper. Problem upptäcktes i de låga hastighetsregionerna, där den L₁ adaptiva regulatorn inte ger önskad prestanda. En växlingsmetodik mellan två L₁ adaptiva regulatorer undersöktes. Växlingen mellan regulatorerna gjordes genom att veta när landningsstället är uppe eller nere. Den andra tillståndsprediktorn utformades med linjäriserad dynamik i landningshastighet och höjd. Växlingsmetodiken flögs i en simulator med en olinjär generisk flygplansmodell med goda resultat

Place, publisher, year, edition, pages
2013. , 62 p.
Series
TRITA-MAT-E, 2013:12
National Category
Mathematics
Identifiers
URN: urn:nbn:se:kth:diva-120569OAI: oai:DiVA.org:kth-120569DiVA: diva2:617156
External cooperation
SAAB Aeronautics, Linköping
Subject / course
Systems Engineering
Educational program
Master of Science - Aerospace Engineering
Uppsok
Physics, Chemistry, Mathematics
Supervisors
Examiners
Available from: 2013-04-22 Created: 2013-04-11 Last updated: 2013-04-22Bibliographically approved

Open Access in DiVA

fulltext(1296 kB)854 downloads
File information
File name FULLTEXT01.pdfFile size 1296 kBChecksum SHA-512
67541ce7b94cb3c8af877ea085951ccd0b274aa31e4b1aefe91b4c714311a2853f3e92f6b32b0aa89b4fe6d27e55abb05c711e705059c1ae194ef66bf644ef34
Type fulltextMimetype application/pdf

By organisation
Optimization and Systems Theory
Mathematics

Search outside of DiVA

GoogleGoogle Scholar
Total: 854 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 885 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf