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UH-60M Upgrade Fly-By-Wire Flight Control Risk Reduction Using the
RASCAL JUH-60A In-Flight Simulator
UH-60M Upgrade Fly-By-Wire Flight Control Risk Reduction Using the
RASCAL JUH-60A In-Flight Simulator
Jay FletcherJeff Lusardi
Hossein MansurErnie Moralez
LTC Dwight RobinsonAeroflightdynamics
Directorate (AMRDEC)U.S. Army RDECOM
Ames Research CenterMoffett Field, CA
Dave ArterburnU.S. Army
Utility Helicopters Program OfficeRedstone Arsenal, AL
Chan MorseMorse Flight Test
San Diego, CA
Igor CherepinskyJoe Driscoll
Sikorsky Aircraft CorporationStratford, CT
Kevin KalinowskiPerot Systems Government Services
Ames Research CenterMoffett Field, CA
DISCLAIMER: Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or favoring by the United States Government. The views and opinions of the authors expressed herein do not necessarily represent or reflect those of the United States Government, and shall not be used for advertising or product endorsement purposes.Approved for public release; distribution unlimited. Review completed by the AMRDEC Public Affairs Office (14 Feb 2008 and FN 3445).
2
OutlineOutline
•
Background and motivation•
UH-60M Upgrade fly-by-wire flight control system
•
UH-60M Upgrade risk reduction development•
Handling Qualities evaluation
•
Conclusions
3
UH-60M Upgrade Fly-By-Wire Flight Control System
UH-60M Upgrade Fly-By-Wire Flight Control System
Fly-By-Wire
Key Components
Main Rotor Servo Actuatorand Tail Rotor Actuator
Active Conventional Controllers
Flight Control Computer
Before After
•
Requirements–
Level I Handling Qualities in GVE and DVE (per ADS-33)
–
Agility and maneuverability (ORD para
4.5.d)
•
Benefits–
Improved safety & survivability •
Reduced pilot workload / improved HQ•
Reduced vulnerable area–
Weight reduction –
improved lift & range–
Reduced O&S cost –
fewer critical parts–
Task Tailored control laws
•
System Description–
Triple redundant full authority system–
Advanced control law implementation–
Conventional control and pedal locations with active feedback
–
Tactile Cueing for Envelope Limiting–
Automatic flight control mode switching–
Selectable coupled Flight Director modes
4
Explicit Model Following Architecture
Explicit Model Following Architecture
•
Aircraft response follows simple, low-order command model–
Command model has known good response characteristics–
Command model can be scheduled to implement task-tailoring•
Forward Path–
Aircraft dynamics approximately cancelled by low-order inverse plant•
Feedback Path–
Compensation for imperfect plant dynamics cancellation–
Provides disturbance rejection, performance robustness, and stability
5
UH-60M Upgrade Control Law Modes UH-60M Upgrade
Control Law Modes
10050
“B l ended ” Spe ed , k t s
Vy
40
520
Low Speed Turn Coordination
Response Types & Control Modes
Axis Command Hold
Pitch Att
/ Acc Velocity
Roll Att
/ Acc Velocity
Yaw Yaw Rate Heading
Vertical Climb Rate Altitude
Axis Command Hold
Pitch Att
/ Acc Position
Roll Att
/ Acc Position
Yaw Yaw Rate Heading
Vertical Climb Rate Altitude
Low Speed
Response Types & Control Modes
Hover / Near Hover
Response Types & Control Modes
High Speed
Response Types & Control Modes
Axis Command Hold
Pitch Att
/ Acc Velocity
Roll Attitude Attitude
Yaw Yaw Rate Heading
Vertical Flight Path Flight Path
Low Speed / High Speed Hysteresis Region
Sideslip Envelope Protection (Passive)
Full Pedal Command=
Max Sideslip
Axis Command Hold
Pitch Att
/ Acc Velocity
Roll Attitude Attitude
Yaw Sideslip Turn Coord
Vertical Flight Path Flight Path
6
UH-60M Upgrade Risk ReductionUH-60M Upgrade Risk Reduction
•
Objective: Accelerate UH-60M Upgrade FCS design maturity by getting to flight as soon as possible
•
Approach–
Fly key FCS elements on the RASCAL JUH-60A before the prototype UH-60M Upgrade
–
Leverage AFDD flight control design, analysis, simulation, and optimization tools
–
Develop and evaluate UH-60MU system performance on RASCAL
7
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
AFDD Flight Control Rapid Prototyping Process
AFDD Flight Control Rapid Prototyping Process
•
Developed to meet S&T goals for reducing FCS development time•
Readily applied to UH-60M Upgrade FCS risk reduction development
8
RASCAL JUH-60ARASCAL JUH-60A
Research Flight Control System (RFCS) •
Fail/Safe architecture •
Programmable displays •
Active inceptors •
Telemetry
9
Flight Mechanics ModelingFlight Mechanics Modeling
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
10
Model Development & ValidationModel Development & Validation
•
Objectives–
Validation for RASCAL (UH-60A) Update legacy models for UH-
60MU
–
Validation for UH-60MU
•
Applications–
FC design and optimization–
Piloted and HWIL simulation–
UH-60A and UH-60M–
Sikorsky and Army•
Types–
Non-linear full-flight-envelope–
Linearized
FFE models–
Identification models
11
-40
-20
0
20
Mag
nitu
de (d
B)
Flight
Gen Hel (DF)
FORECAST
-540
-450
-360
-270
-180
Phas
e (d
eg)
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
Coh
eren
ce
-40
-20
0
20
Mag
nitu
de (d
B)
-270
-180
-90
0
90
Phas
e (d
eg)
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
Coh
eren
ce
Math Model Fidelity (Bare Airframe)
Math Model Fidelity (Bare Airframe)
•
Model Types–
Gen Hel –
Non-linear, full flight envelope simulation model
–
FORECAST –
Linearized
extraction from Gen Hel
•
Generally Good Fidelity•
Deficiencies–
Lead-lag mode frequency–
Directional response to pedals
Pitch Rate / Lon Cyclic Yaw Rate / Pedals
12
UH-60A vs. UH-60M Flight Dynamics (Bare Airframe) UH-60A vs. UH-60M Flight Dynamics (Bare Airframe)
UH-60M JUH-60A
Rotor Blades Wide Chord Narrow Chord
Engines GE-T700-701D GE-T700-700
-20
0
20
40
Mag
nitu
de (d
B)
Roll Rate due to Lateral Cyclic
UH-60MJUH-60A
-540
-360
-180
Phas
e (d
eg)
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
Coh
eren
ce
-20
0
20
40Yaw Rate due to Pedals
-180
0
180
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
Dynamic Comparison•
All on and off-axis responses to cyclic and pedals are very similar
•
Vertical acceleration response to collective shows largest difference
Major Configuration Differences
-20
0
20
40Vertical Acceleration due to Collective
-360
-180
0
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
13
Control Law AnalysisControl Law Analysis
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
14
Control Law Analysis and Optimization with CONDUIT®
Control Law Analysis and Optimization with CONDUIT®
•
Powerful Multi-Objective optimization engine enables CONDUIT®
•
Control system defined as SIMULINK®
block diagram–
139 states for UH-60MU
•
Linked with linear Aircraft model in SIMULINK®
–
25 state FORECAST model for hover
•
“Design Parameters”
selected for manual or automatic tuning
–
35 for UH-60MU hover/low speed
•
Key CONDUIT®
specs –
57 specs evaluated for UH-60MU–
e.g. ADS-33, MIL-F-9490
!
Challenging Optimization Problem!
System
Airframe Model
Flight Control Engineer
Controller Structure
Design SpecsOptimization
(tuning)
Simulation
CONDUIT
Eval
uatio
n
Tran
slat
ion
15
CONDUIT® Predicted PerformanceCONDUIT® Predicted Performance
Specs: 57 Dps: 35 States (simplified case): 139
Level 1
Level 2
Level 3
Pitch
Roll
Yaw
0 10 200
20
40
60
80
GM (dB)
PM (d
eg)
StbDaG1:Frequency Sweep Spec
Ames Research Center
HACAH USING FLT DATA
0 10 200
20
40
60
80
GM [db] PM
[deg
]
(rigid-body freq. range)StbMgG1: Gain/Phase Margins
MIL-F-9490D
HINNER, ACVH OUT OF DE
0 10 200
20
40
60
80
GM [db]
PM [d
eg]
(rigid-body freq. range)StbMgG1: Gain/Phase Margins
MIL-F-9490D
HINNER, POSITION
0 2 40
0.1
0.2
0.3
0.4
Bandwidth [rad/sec]
Phas
e de
lay
[sec
]
Other MTEs;UCE>1; Div AttBnwAtH1:Bandwidth (pitch & roll)
ADS-33D
SACAH
0 2 40
0.1
0.2
0.3
0.4
Bandwidth [rad/sec]
Phas
e de
lay
[sec
]
Other MTEs (Yaw)BnwYaH2:BW & T.D.
ADS-33D
SRCHH Yaw
0 0.5 11
1.2
1.4
1.6
1.8
2
Bandwidth [rad/sec]
(linear scale)DstBwG1:Dist. Rej. Bnw
SACAH, THETA
0 1 21
1.2
1.4
1.6
1.8
2
Bandwidth [rad/sec]
(linear scale)DstBwG1:Dist. Rej. Bnw
SACAH, PHI
0 1 21
1.2
1.4
1.6
1.8
2
Bandwidth [rad/sec]
(linear scale)DstBwG1:Dist. Rej. Bnw
SRCHH, PSI
0 100 2000
0.2
0.4
0.6
0.8
1
Total Cost
ModFoG2:Cost PointSACAH
0 1 20
0.2
0.4
0.6
0.8
1
Actuator RMS
RmsAcG1:Actuator RMS
Ames Research Center
JACAH
-40 -20 0-40
-30
-20
-10
0
10
Average q/p (dB)
Aver
age
p/q
(dB)
Frequency DomainCouPRH2:Pitch-Roll Coupling
ADS-33E
CACAH
-1 0 10
0.2
0.4
0.6
0.8
1
r3/hdot(3) [deg/ft] r1
/hdo
t(3)
[deg
/ft]
Yaw/CollectiveCouYaH1:Coupling
ADS-33D
CACVH
16
System VerificationSystem Verification
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
17
CONDUIT® Flight Test
Longitudinal
wc 3.5 3.5
PM 49.7 48.4
GM 13.5 8.5
Lateral
wc 4.2 3.4
PM 50.3 51.8
GM 8.1 7.3
Directional
wc 5.7 6.2
PM 31.1 45.5
GM 8.2 6.7
Vertical
wc 1.9 1.6
PM 74.6 64.5
GM 8.9 9.7
CLAW Integration VerificationCLAW Integration Verification
Longitudinal Broken Loop(From Injected Sweeps)
Longitudinal Forward Loop(From Piloted Sweeps)
•
Excellent agreement between analysis and test•
Minor discrepancies associated with known model shortcomings
-40
-20
0
20
Mag
nitu
de (d
B)
-360
-270
-180
-90
0
Phas
e (d
eg)
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
Coh
eren
ce
-40
-20
0
20
40
Mag
nitu
de (d
B)
FlightCONDUIT
-360
-270
-180
-90
0Ph
ase
(deg
)
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
Coh
eren
ce
18
-40
-20
0
20
Mag
nitu
de (d
B)
-360
-180
0
Phas
e (d
eg)
Baseline Gains, FlightBaseline Gains, FORECASTReduced Gains, Flight
10-1 100 101 102
0.2
0.6
1
Frequency (rad/sec)
Coh
eren
ce
Lead-Lag Mode StabilityLead-Lag Mode Stability
•
Initial CONDUIT®
optimization–
FORECAST aircraft model–
Adequate stability margins–
Known lead-lag mode errors
•
Pitch/Roll oscillations when velocity/accel
loops closed–
Replace q/lon
with flight test measured frequency response
–
Low gain margin (~4dB) at progressing lead-lag frequency
•
Final CONDUIT®
Optimization–
Substantial stability increase (12dB)–
Other performance unchanged
•
Stability improvement verified in flight
Pitch Rate / Longitudinal Cyclic
~4dB16dB
34r/s
19
Flight Test EvaluationFlight Test Evaluation
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
Control Laws• Architecture• Gains• Modes
Requirements• AVNS-PRF-10018• ADS-33E-PRF• MIL-F-9490
Math Models• Gen Hel• FORECAST• CIFER SYS ID
20
Handling Qualities EvaluationHandling Qualities Evaluation
•
Quantitative Assessment–
Predicted handling qualities criteria from ADS-33–
Frequency sweeps, steps, etc…
•
Qualitative Assessment–
Five ADS-33 Mission Task Elements (MTE):•
Precision Hover•
Hovering Turns•
Lateral Reposition•
Depart / Abort•
Vertical Maneuver–
Five evaluation pilots (2 Sikorsky, 3 Army)–
EH-60L served as baseline for comparison–
GVE and simulated DVE evaluation flights in both aircraft
–
DVE simulated with modified NVGs
(UCE=2+)
•
Data collected–
Performance data and time histories (aircraft, control system, GPS, etc…)
–
Cooper-Harper handling qualities ratings (HQR) and commentary
21
Quantitative CriteriaQuantitative Criteria
1 2 3 4 50
0.1
0.2
0.3
0.4
Level 3
Level 2
Level 1
!p"!p#(sec)
$BW ", $BW
# (rad/sec)
Pitch Disp Pitch Disp CONDUITPitch Force Roll Disp Roll Disp CONDUIT Roll Force
1 2 3 4 50
0.1
0.2
0.3
0.4
Level 3
Level 2
Level 1
!p%
(sec)
$BW % (rad/sec)
Yaw Disp Yaw Disp CONDUIT
0 1 2 3 4 5 6-50
0
50
100
150
200
Time (sec)
Clim
b R
ate
(ft/m
in)
hhe
48
49
50
51
52
53
Col
lect
ive
(%)
Collective
10.5
122.0
&'
sKeh s
col
est
(
!
Level 1 for all criteria evaluated
0 10 20 300
1
2
q pk/ )# p
k (1/s
ec)
Minimum attitude change, )qmin (deg)
Level 1
Level 2
ForwardAft
0 20 40 600
1
2
p pk/ )" p
k (1/s
ec)
Minimum attitude change, )qmin (deg)
Level 1
Level 2
Level 3
Left Right
22
Mission Task Element
Hover
Hov Turn
R
Hov Turn
L
Lat R
epo R
Lat R
epo L
Dep Abo
rt
Vert M
an
Mission Task Element
Hover
Hov Turn
R
Hov Turn
L
Lat R
epo R
Lat R
epo L
Dep Abo
rt
Vert M
an1
2
3
4
5
6
7
8
9
10
Mission Task Element
Hover
Hov Turn
R
Hov Turn
L
Lat R
epo R
Lat R
epo L
Dep Abo
rt
Vert M
an
Han
dlin
g Q
ualit
ies
Rat
ing
Handling Qualities Ratings (GVE)Handling Qualities Ratings (GVE)
UH60MU / RASCALAvg GVE HQR = 2.8
EH-60LAvg GVE HQR = 4.3
UH-60A (1999)Avg GVE HQR = 4.2
•
UH-60MU provides average of 1.5 HQR improvement over EH-60L•
EH-60L baseline agrees well with 1999 UH-60A evaluation
23
Mission Task Element
Hover
Hov Turn
R
Hov Turn
L
Lat R
epo R
Lat R
epo L
Dep Abo
rt
Vert M
an
Mission Task Element
Hover
Hov Turn
R
Hov Turn
L
Lat R
epo R
Lat R
epo L
Dep Abo
rt
Vert M
an
Handling Qualities Ratings (DVE)Handling Qualities Ratings (DVE)
1
2
3
4
5
6
7
8
9
10
Mission Task Element
Hover
Hov Turn
R
Hov Turn
L
Lat R
epo R
Lat R
epo R
Dep Abo
rt
Vert M
an
Han
dlin
g Q
ualit
ies
Rat
ing
UH60MU / RASCALAvg GVE HQR = 2.8
UH60MU / RASCALAvg DVE HQR = 3.2
EH-60LAvg DVE HQR = 5.2
•
UH-60MU provides average of 2 HQR improvement over EH-60L in DVE–
Hold modes provide significant workload reduction–
Smaller degradation in DVE (1/2 HQR) than EH-60L (1 HQR)
24
ConclusionsConclusions
•
UH-60M Upgrade control laws provide significant improvements in hover and low speed handling qualities relative to the UH-60A/L baseline
•
AFDD flight control rapid prototyping tools provide a highly effective means to analyze and optimize sophisticated multi-mode fly-by-wire flight control systems
•
Math models used in flight control analyses and optimization for
fly-by-wire flight control design must accurately represent the lead-lag dynamics to ensure satisfactory stability margin estimates
•
RASCAL JUH-60A flight dynamics are representative of the UH-60M
•
RASCAL development phase for the UH-60M Upgrade FBW FCS has significantly reduced risk for the program