integrated adaptive guidance & control for the x-37 during taem & a/l

1410 Sachem Place ◊ Suite 202 ◊ Charlottesville, VA 22901 www.Barron-Associates.com

Integrated Adaptive Guidance & Control for the X-37 during

TAEM & A/L

J. SchiermanBarron Associates, Inc., Charlottesville, Virginia

Paul Kubiatko The Boeing Company, Huntington Beach

Air Force Research Laboratory ProgramDavid Doman, PM

Presented at the Aerospace Control and Guidance Systems Committee (ACGSC) Meeting

Grand Island, NYOct. 15-17

2

ACGSC, October, 2008

www.Barron-Associates.com

Presentation Outline

Motivation/program background

X-37 IAG&C program

Some details on the developed technologies

Sample experimental results

Conclusions

Boeing presentation…

3



Motivation & Technology Challenges

NASA & Air Force seeking to increase safety & reliability of next generation launch systemsHouse software algorithms onboard to recover the system when physically possible to:

Control effector and other subsystem failuresLarger than expected errors/dispersions

Nominal flying qualities not always recovered w/ inner-loop control reconfiguration aloneGuidance adaptation may be necessary to account for “crippled” vehicleFor unmanned, un-powered vehicles in descent flight phases - energy management problem critical for safe landing

If vehicle characteristics have changed, energy management problem has changed

Energy managed with in-flight trajectory command reshaping

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Feedback ArchitectureFeedback architecture involves three main loops

Inner-loop control / Outer-loop guidance / Trajectory command generation

Maintain attitude stabilityRecover cmd. following performance to extent possible

Inner-loopCmds.

Meas.Resp.Reusable

Launch Vehicle

Reconfigurable Controller

EffectorCmds.

We have borrowed our reconfigurable flight controls

technologiesWe have borrowed our

parameter ID technologies & developed new algorithms

Re-solve energy management problem – critical for autonomous, unpowered vehicles in gliding flight

Traj. Cmds.Trajectory Command Generation

Our main focus!

Maintain flight path stabilityRecover cmd. following performance to extent possible

GuidanceAdaptationAlgorithm

Guidance Laws

New approaches developed

Required InformationVehicle Health

Monitoring,Filters,

Parameter ID,…

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Background - AFRL Program – ’01 to ‘04Air Force’s Integrated Adaptive Guidance & Control (IAG&C) flight test programDemonstration platform: Boeing’s X-40A

Why the X-40A? Boeing accomplished 7 successful drop tests - hoped to eventually repeat drop tests w/new reconfigurable G&C algorithms

Risk reduction flight tests w/TIFSEnsure software can run in real timeVerify simulation-based performance analysis

Nominal approach trajectory

Reconfigured trajectory

Nominaltouchdown aim point

TIFS = Total In-Flight Simulator

TIFS simulated

“X-40A”

dynamics

Flight test results presented at SAE ’04 (Colorado)

6



AFRL Program ExtensionIAG&C program extended – ’04-’05

Next logical step: continue work with Boeing to develop / demonstrate IAG&C technologies for their X-37 RLV

Ruddervators

Speedbrake

Bodyflap

Flaperons

Engineering, Operations & Technology | Phantom Works

Copyright © 2008 The Boeing Company. All rights reserved.Distribution A, Cleared for Public Release, Distribution Unlimited. Case No. 88ABW-2008-0085 WPAFB, OH

Program Summary Chart

Description: • Demonstrate integrated adaptive guidance

and control system with on-line trajectory re-targeting and reconfigurable control to compensate for control effector failures using a real-time hardware in-the -loop simulation.

Value/Benefits: • Safety and Reliability:

System can compensate for unknown model errors.• Weight: Reduce redundancy requirements.Key Technologies: • Adaptive / reconfigurable Guidance and

Control algorithms.Partners/Major Subcontractors• Barron Associates, Inc.

ID Task Name

1

2 1.0 Program Management3 Pogram Management

4 2.0 Guidance and Control5 2.1 Simulation Development and Integration

6 2.2 IAG&C System Design and Consultation

7 Final IAG&C System (Entry I) Delivered from Barrons

8 Final IAG&C (Entry II) System Delivered from Barrons

9 2.3 IAG&C System V&V (Entry I)

10 2.4 IAG&C System V&V (Entry II)

11 3.0 Software12 3.1 FMC S/W Requirements

13 3.2 IAG&C Integration in FMC

14 4.0 Avionics Lab15 4.1 ASIL S/W Requirements

16 4.2 IAG&C (Entry I) Integration in ASIL

17 4.2.1 IAG&C (Entry II) Integration in ASIL

18 4.3 ASIL Test Entry I

19 4.4 ASIL Test Entry II

20 5.0 Documentation and Final Report

5/169/19

Nov Jan Mar May Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar MayQtr 3, 2003 Qtr 1, 2004 Qtr 3, 2004 Qtr 1, 2005 Qtr 3, 2005 Qtr 1, 2006

More technically accurate than flight tests



Program Objectives

• Develop and demonstrate Integrated Adaptive Guidance and Control (IAG&C) algorithms for reusable launch vehicles by simulation analysis.

IAG&C algorithms developed under Phase II SBIRs and AFRL 6.2 X-40A IAG&C program.

• Demonstrate that IAG&C architecture will automatically compensate for control effector failures and plan new feasible trajectories in real time when they exist.

Test on-line ID of ablation effects & failures

• Raise technology and integration readiness levels of IAG&C system by testing algorithms in a real-time relevant simulation environment.

Utilize existing Boeing X-37 Avionics Simulation Integration Lab



X-37 Simulation Environments Utilized

Matlab/Simulink Environment IAG&C System Design Linear Analysis (phase & gain margins) Limited Worst-on-Worst analysis capability

Shuttle Descent-Approach Program (SDAP) Environment Simulation validation Performance Assessment “Worst-on-Worst” Analysis Monte Carlo Analysis

Avionics Systems Integration Lab (ASIL) Environment Real-Time Performance Assessment

}

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Expanded Envelope – TAEM and Approach & Landing

Focus: Boeing’s X-37 drop testsSubsonic portion of TAEMApproach & landing

Trajectory reshaping addresses integrated TAEM/A/L mission

Groundtrack

Heading Alignment Cone

(HAC)

Approach/Landing

Separation & Dive

Touchdown & Rollout

Alt = 40K ftRange = 18.8 NM

Alt = 22.5K ftRange = 9.5 NM

Alt = 10K ftRange = 4.5 NM

Acquisition w/HAC

Groundtrack

Nominal initial

heading = -135 deg.

Heading Alignment Cone

(HAC)

180o heading

-90o heading

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Trajectory Reshaping ApproachNeed fast optimization approach - deliver new trajectory solutions in flight

Redefine complete trajectory in terms of a small number of parameters to be optimizedOnce solution is obtained: map parameters back to full trajectory historyTrajectory parameters:

Initial heading angleAltitude to start HAC turnAltitude to start Final Flare guidance lawDynamic pressure at touchdownCL, CD: models trim CL,CD

under failure condition

Optimization problem posed:Minimize lateral maneuvering

Keeps solution from unrealistic sharp turns

Groundtrack

yrwy

xrwy

o

HHAC

Drop

HAC Turn

HFF TDq

} d

Defines shape of last stage of dynamic pressure profile

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Guidance & Control Laws

L _ ruddervator

R _ ruddervator

L _ flaperon

R _ flaperon

speedbrake

bodyflap

Z cmdNLongitudinal

Guidance

Lateral Guidance

cmd Coordinated Flight

Controller

Receding Horizon Optimal (RHO)

Controller- - - - -

Control Allocator

X-37 Vehicle

cmd

cmd

PR

Modified Sequential Least Squares (MSLS)

Parameter ID

refqf

K

cmdcmd+

-

q

V, D, , q, H, , V , D

CommandedTrajectory States toGuidanceLaw

qK f

3-DOF Plant Model

3-DOF Plant Model

+

-qf

H

f K

cmdcmdf

+-

V, , L, DH

o HAC, H

ff TDH , q

Reshaping AlgorithmReshaping Algorithm

Longitudinal Backstepping Loops

Lateral Backstepping Loops

Ref. Cmds.

CL CD, CL, CD

Trajectory Cmd Generation

Measurement Feedback…

Lift, Drag

Series of backstepping/dynamic inversion feedback loops: maps to commanded trajectory histories(V, , X, H, etc.) that drive guidance loops

d

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X-37 Drop Mission Case StudyWorst case low energy (high drag) failure - SB locked @ 65 deg. & BF locked @ 20 deg.

Ablation effects (add more drag); headwind/crosswind; navigation errors; turbulence

Altitude Profile

Ground Track

• Simulink and RTHIL results very close• Adaptive system commands a “HAC turn”

soon into the mission – “cuts the corner” to reduce downrange distance to runway – conserves energy

• Adaptive system commands much steeper descent – increases kinetic energy at touchdown – allows for greater control authority to execute final flare

Real-Time, HIL results

Real-Time, HIL results

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HAC Angle

Right Rudder

Left Rudder

Body Flap

Speed Brake Direction

Scale Factor

Sink Rate (fps)

Pitch Angle (deg)

Groundspeed (fps)

Downrange (ft)

Crossrange (ft)

28 135 -6 -6 - - 40K EAFB HW 10% - 3.248 8.112 341.929 2151.379 0.168

29 135 -6 -6 - - 40K EAFB TW 10% - 0.456 7.372 304.959 3198.168 5.252

30 135 -6 -6 - - 40K EAFB HWCW 10% - 1.187 7.514 302.618 3293.566 5.557

31 135 -6 -6 - - 40K EAFB TWCW 10% - 0.638 5.433 302.733 3407.623 6.004

32 90 - - 20 65 40K EAFB TWCW 10% - 4.247 12.846 297.295 2222.689 14.536

33 100 - - 20 65 40K EAFB TWCW 10% - 2.941 12.655 296.131 2337.721 -14.367

34 110 - - 20 65 40K EAFB TWCW 10% - 2.746 12.792 295.110 2306.181 -18.777

35 120 - - 20 65 40K EAFB TWCW 10% - 6.915 13.613 308.312 2145.319 -15.605

36 130 - - 20 65 40K EAFB TWCW 10% - 3.050 13.336 303.750 2283.586 -11.120

37 140 - - 20 65 40K EAFB TWCW 10% - 6.749 13.194 309.011 2179.693 -8.396

38 150 - - 20 65 40K EAFB TWCW 10% - 6.151 13.251 308.032 2199.266 -7.053

39 160 - - 20 65 40K EAFB TWCW 10% - 6.963 13.030 311.628 2160.595 -6.790

40 170 - - 20 65 40K EAFB TWCW 10% - 6.882 13.350 308.939 2159.474 -5.692

41 180 - - 20 65 40K EAFB TWCW 10% - 2.429 13.559 301.803 2292.339 -4.995

42 135 - - -20 0 40K EAFB HW 10% - 0.351 5.665 292.011 3612.635 2.030

43 135 - - -20 0 40K EAFB TW 10% - 0.498 8.111 313.568 2884.063 0.658

44 135 - - -20 0 40K EAFB HWCW 10% - 0.525 8.746 257.944 4589.362 3.733

45 135 - - -20 0 40K EAFB TWCW 10% - 1.213 7.903 320.847 2831.176 0.806

46 135 - - 0 0 40K EAFB HW 10% - 2.642 6.965 312.638 2508.943 3.995

47 135 - - 0 0 40K EAFB TW 10% - 3.313 6.561 312.938 2666.653 5.364

48 135 - - 0 0 40K EAFB HWCW 10% - 2.416 6.906 315.066 2516.830 3.881

49 135 - - 0 0 40K EAFB TWCW 10% - 4.497 6.550 317.696 2701.305 4.799

50 135 - - 0 30 40K EAFB HW 10% - 0.765 8.665 303.502 2247.709 1.036

51 135 - - 0 30 40K EAFB TW 10% - 1.247 8.239 309.674 2349.663 1.709

52 135 - - 0 30 40K EAFB HWCW 10% - 0.945 8.609 308.798 2168.552 0.998

53 135 - - 0 30 40K EAFB TWCW 10% - 1.894 8.150 311.511 2365.091 1.613

Touchdown ConditionsAblation Effects

Input File Name

FailureOnset

Alttitude

Wind

Real-Time HIL Experiment Results51 cases run for final set of real-time Hardware-In-the-Loop experiments

Variations included: initial heading (HAC) angle, wind direction, ablation effects, navigation errors, random turbulence, failure condition, and failure onset time

HAC

AngleRight

RudderLeft

RudderBody Flap

Speed Brake Direction

Scale Factor

Sink Rate (fps)

Pitch Angle (deg)

Groundspeed (fps)

Downrange (ft)

Crossrange (ft)

2 135 - - - - - - - - 0.862 4.888 307.616 3146.118 2.089

4 135 - - - - - EAFB HW 10% - 0.151 7.940 332.815 2107.260 -0.357

5 135 - - - - - EAFB TW 10% - 0.886 4.855 305.884 3138.804 2.282

6 135 - - - - - EAFB HWCW 10% - 0.263 7.342 310.121 2888.012 1.903

7 135 - - - - - EAFB TWCW 10% - 1.646 7.433 279.657 4255.383 11.890

8 90 - - - - - EAFB HW 10% - 0.946 4.948 301.318 3090.743 2.893

9 180 - - - - - EAFB TW 10% - 0.785 7.772 339.080 2223.361 -1.217

10 -90 - - - - - EAFB HWCW 10% - 2.741 7.516 362.810 1678.703 0.661

11 -135 - - - - - EAFB HWCW 10% - 1.795 6.308 312.033 2760.766 4.611

12 -180 - - - - - EAFB TWCW 10% - 1.025 4.123 308.488 3317.897 5.073

13 135 - - 20 65 40K EAFB HW 10% - 5.624 13.324 290.315 2223.785 -10.804

14 135 - - 20 65 40K EAFB TW 10% - 3.990 13.133 301.424 2258.649 -7.286

15 135 - - 20 65 40K EAFB HWCW 10% - 6.440 13.252 291.252 2207.018 -10.619

16 135 - - 20 65 40K EAFB TWCW 10% - 2.578 13.413 300.683 2311.176 -8.793

17 135 - - 20 65 35K - - - 4.462 13.203 282.470 2316.449 -9.808

18 135 - - 20 65 34K - - - 5.690 13.745 284.886 2286.887 -9.536

19 135 - - 20 65 33K - - - 3.049 13.081 291.950 2343.315 -10.895

20 135 - - 20 65 40K EAFB HW 10% on 2.719 14.398 272.435 2450.673 -25.214

21 135 - - 20 65 40K EAFB TW 10% on 6.571 14.713 296.541 2255.102 -23.289

22 135 - - 20 65 40K EAFB HWCW 10% on 2.943 14.296 271.692 2467.679 -25.329

23 135 - - 20 65 40K EAFB TWCW 10% on 3.394 14.846 292.592 2315.862 -23.868

24 135 - -6 - - 40K EAFB HW 10% - 1.448 8.150 312.263 2694.925 -15.266

25 135 - -6 - - 40K EAFB TW 10% - 2.730 7.804 316.690 2735.908 -16.530

26 135 - -6 - - 40K EAFB HWCW 10% - 1.846 8.053 313.906 2606.651 -16.504

27 135 - -6 - - 40K EAFB TWCW 10% - 2.871 7.710 319.479 2785.804 -14.749

Touchdown ConditionsAblation Effects

Input File Name

FailureOnset

Alttitude

Wind

Page 2

All 51 cases achieved required touchdown conditions

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ConclusionsBarron Associates focus:

Develop integrated TAEM/Approach & Landing trajectory reshaping and inner-loop reconfigurable controller

Non-real-time Matlab/Simulink experiments performed during development

Substantial number of experiments were run with dispersions in trajectory geometry, winds, failure characteristics, and other errors

Overwhelming majority of these runs resulted in safe landings

Without the advanced algorithms, failures would cause loss of vehicle

Trajectory reshaping coupled with reconfigurable inner-loop control saved vehicle from significant damage under severe effector impairments

Boeing tested algorithms in real-time simulations…

integrated adaptive guidance & control for the x-37 during taem & a/l

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