F-35 FLCS CLAW design

Design and construction
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rheonomic

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Unread post28 Nov 2016, 04:08

I would assume in normal flight mode the CLAW controlled variables would be similar to those of WL-TR-96-3099, where
  • Roll (LCV) is a mix of body-axis roll rate p and stability-axis roll rate p_s based on the dynamic pressure (qbar)
  • Pitch (MCV) is body-axis pitch rate q at low dynamic pressure and a mix of q, AOA, and some other stuff based on the approach
  • Yaw (NCV) is a mix of body-axis yaw rate r at low qbar and stability-axis yaw rate r_s, sideslip, and lateral acceleration at high qbar.
As far as I know, CLAWs are based on dynamic inversion with the control objective being meeting 1797 flying qualities.

For STOVL modes, I believe AIAA 1994-3631, "Highly augmented control mode concepts and simulation evaluation for STOVL aircraft" by Bodden and Virnig discusses the CLAW modes for X-35 (paper uses F-16 as a testbed). Also, see "X-35B STOVL Flight Control Law Design and Flying Qualities" by Walker and Allen, AIAA 2002-6018, and "Control Allocation for the X-35B" by Bordingnon and Bessolo, AIAA 2002-6020.
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Unread post28 Nov 2016, 05:23

3 PDFs mentioned by 'rheonomic' above are attached BUT ONLY the free cover pages for an inkling of what they are about.

Highly augmented control mode concepts and simulation evaluation for STOVL aircraft David Bodden & John Virnig
http://arc.aiaa.org/doi/abs/10.2514/6.1994-3631
&
X-35B STOVL Flight Control Law Design and Flying Qualities by Walker and Allen, AIAA 2002-6018
http://arc.aiaa.org/doi/abs/10.2514/6.2002-6018
&
Control Allocation for the X-35B by Bordingnon and Bessolo, AIAA 2002-6020.
http://arc.aiaa.org/doi/abs/10.2514/6.2002-6020
Attachments
X-35B STOVL Flight Control Law Design and Flying Qualities (AIAA) PLUS pp3 FORUM.pdf
(557.08 KiB) Downloaded 808 times
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rheonomic

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Unread post29 Nov 2016, 03:51

I found a free version of the first paper ("Highly augmented control mode concepts and simulation evaluation for STOVL aircraft") here: http://thirdworld.nl/highly-augmented-c ... l-aircraft

There's also an LM powerpoint on the F-35 CLAW design available from the MATLAB people here (PDF)

Finally, I'll note that WL-TR-96-3099, basically the how-to of multivariable flight control, is available through DTIC here (PDF). LM and Honeywell collaborated on this report, which basically surveys modern (ca mid 1990s) flight control. For this, however, you really need to have some background in control theory.
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Unread post29 Nov 2016, 04:06

Thanks for that 'rheonomic'.
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Unread post06 Jan 2017, 17:49

New article from Dolby about landing the F-35A:
https://nettsteder.regjeringen.no/kampf ... en-i-f-35/

It hasn't been translated yet, but Google does a decent job:
https://translate.googleusercontent.com ... en-i-f-35/

It's fairly comprehensive and has some interesting data points:

At MIL power and a 5-10 degree climb gradient, the jet will exceed 300 knots before the end of the runway.

With less than half throttle, the jet will climb at a gradient of 5 degrees, at 300 knots.

At 1500ft (in a circuit), the jet maintains 300-350 knots in a straight line with 20-25% engine power.

When you see an F-35A's nose pitch down at the end of an aerobraking, they're travelling at least 110-120 knots - the jet is more nose-heavy (when the landing gear is involved) than an F-16.

Overall he describes the jet as being like a freight train on rails when dealing with crosswinds, when compared to the F-16.

Dolby also mentions that he's flown Lockheed's most advanced aero simulations of landing the F-35A with a drogue chute on an icy runway; he says to take the results with a pinch of salt, but in the simulation he was able to safely land an F-35A at twice the crosswinds that the F-16 is certified for, without having to cut away the chute (which they sometimes have to do to prevent wind pulling the jet away from centreline).
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Unread post06 Jan 2017, 19:49

Thanks 'Dragon029'.
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Unread post06 Jan 2017, 21:11

Oh, my previous post is unneeded I see. Deleted ;)

For once, gogle translate did an OK job. I'd love to see a "sliding landing" though.
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Unread post11 Mar 2017, 04:32

Was skimming through a new book, Aircraft Control Allocation by Durham, Bordignon, and Beck. A couple of the authors worked flight control for X-35, so was able to find a couple of other references:

Steve Wurth, Tom Mahone, Joe Hart, and Jim Baxter. "X-35B Integrated Flight Propulsion Control Fault Tolerance Development", 2002 Biennial International Powered Lift Conference and Exhibit, Aviation Technology, Integration, and Operations (ATIO) Conferences, http://dx.doi.org/10.2514/6.2002-6019

Glen Tauke and Kenneth Bordignon. "Structural Coupling Challenges for the X-35B", 2002 Biennial International Powered Lift Conference and Exhibit, Aviation Technology, Integration, and Operations (ATIO) Conferences, http://dx.doi.org/10.2514/6.2002-6004

There's a chapter on lessons learned on X-35 CLAW design in the book, although that's probably only of interest to other control engineers. Also, Appendix B (PDF) of the book is freely-available and describes a dynamic inversion implementation in an accompanying simulation that probably gives a rough approximation of what the DI on F-35 looks like.

Also, was skimming through the initial posts of this thread again, and a lot of what was discussed seems like it would fall into the category of task-tailored control laws.

Edit:

Another few papers:

Gregory P. Walker, James W. Fuller, and Steven P. Wurth. "F-35B Integrated Flight-Propulsion Control Development", 2013 International Powered Lift Conference, AIAA AVIATION Forum, (AIAA 2013-4243) http://dx.doi.org/10.2514/6.2013-4243

James Denham. "STOVL Integrated Flight and Propulsion Control: Current Successes and Remaining Challenges", 2002 Biennial International Powered Lift Conference and Exhibit, Aviation Technology, Integration, and Operations (ATIO) Conferences, http://dx.doi.org/10.2514/6.2002-6021

Whatley, D. W.; Virnig, J. C. and Bodden, D. S.: “Implementation of STOVL Task-Tailored Control Modes in a Fighter Cockpit”, AIAA-90-3229, September 1990. I haven't been able to find this one online...
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