UH-60M Upgrade Fly-By-Wire Flight Control
Risk Reduction Using the
RASCAL JUH-60A In-Flight Simulator
Dave Arterburn
U.S. Army
Utility Helicopters Program Office
Redstone Arsenal, AL
Chan Morse
Morse Flight Test
San Diego, CA
Jay Fletcher
Jeff Lusardi
Hossein Mansur
Ernie Moralez
LTC Dwight Robinson
Aeroflightdynamics Directorate (AMRDEC)
U.S. Army RDECOM
Ames Research Center
Moffett Field, CA
Igor Cherepinsky
Joe Driscoll
Sikorsky Aircraft Corporation
Stratford, CT
Kevin Kalinowski
Perot Systems Government Services
Ames Research Center
Moffett 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.
1 Approved for public release; distribution unlimited. Review completed by the AMRDEC Public Affairs Office (14 Feb 2008 and FN 3445).
Outline
• Background and motivation
• UH-60M Upgrade fly-by-wire flight control system
• UH-60M Upgrade risk reduction development
• Handling Qualities evaluation
• Conclusions
2
UH-60M Upgrade Fly-By-Wire
Flight Control System
•
Requirements
– Level I Handling Qualities in GVE and DVE
(per ADS-33)
– Agility and maneuverability (ORD para 4.5.d)
•
After
Key Components
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
3
Before
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
•
Fly-By-Wire
Active Conventional
Controllers
Flight Control
Computer
Main Rotor Servo Actuator
and Tail Rotor Actuator
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
4
UH-60M Upgrade
Control Law Modes
Low Speed / High Speed
Hysteresis Region
Sideslip Envelope
Protection (Passive)
Vy
Full Pedal Command
=
Max Sideslip
5
“ B l e nd e d ”
Sp e e d , k t s
20
40 50
100
Low Speed
Hover
Low
Turn
/ Near
Speed
Coordination
Hover
High
Speed
Response Types & Control Modes
5
Axis
Command
Command
Hold
Pitch
Att // Acc
Acc
Att
Position
Velocity
Velocity
Roll
Attitude
Att / Acc
Attitude
Position
Velocity
Attitude
Attitude
Yaw
Yaw Rate
Rate
Yaw
Sideslip
Heading
Turn
Coord
Vertical
Flight
Climb Path
Rate
Path
Flight
Altitude
FlightPath
Path
Flight
UH-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
6
AFDD Flight Control
Rapid Prototyping Process
Requirements
Control Laws
• AVNS-PRF-10018
• ADS-33E-PRF
• MIL-F-9490
• Architecture
• Gains
• Modes
Math Models
• Gen Hel
• FORECAST
• CIFER SYS ID
•
•
7
Developed to meet S&T goals for reducing FCS development time
Readily applied to UH-60M Upgrade FCS risk reduction development
RASCAL JUH-60A
Research Flight Control System (RFCS) • Fail/Safe architecture • Programmable displays • Active inceptors • Telemetry
8
Flight Mechanics Modeling
Requirements
Control Laws
• AVNS-PRF-10018
• ADS-33E-PRF
• MIL-F-9490
• Architecture
• Gains
• Modes
Math Models
• Gen Hel
• FORECAST
• CIFER SYS ID
9
Model Development & Validation
•
Objectives
– Validation for RASCAL (UH-60A)
Update legacy models for UH60MU
– 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
10
Math Model Fidelity
(Bare Airframe)
–
–
Gen Hel – Non-linear, full flight envelope
simulation model
FORECAST – Linearized extraction from Gen
Hel
Gen Hel (DF)
FORECAST
0
-20
-40
Phase (deg)
-180
-270
-360
-450
-540
1
0.6
0.2
-1
0
1
10
10
Frequency (rad/sec)
Lead-lag mode frequency
Directional response to pedals
Yaw Rate / Pedals
Flight
20
10
Generally Good Fidelity
Deficiencies
–
–
Coherence
Coherence
Phase (deg)
Magnitude (dB)
Pitch Rate / Lon Cyclic
11
•
•
Model Types
Magnitude (dB)
•
10
2
20
0
-20
-40
90
0
-90
-180
-270
1
0.6
0.2
10
-1
10
0
10
1
Frequency (rad/sec)
10
2
UH-60A vs. UH-60M Flight
Dynamics (Bare Airframe)
Coherence
Phase (deg)
Magnitude (dB)
Major Configuration Differences
•
UH-60M
JUH-60A
Rotor Blades
Wide Chord
Narrow Chord
Engines
GE-T700-701D
GE-T700-700
Roll Rate due to Lateral Cyclic
40
All on and off-axis responses to
cyclic and pedals are very similar
Vertical acceleration response to
collective shows largest difference
•
Yaw Rate due to Pedals
40
20
20
0
0
-20
-20
-20
-180
180
0
-360
0
-180
-540
-180
-360
1
1
1
0.6
0.6
0.6
0.2
0.2
0.2
0
UH-60M
JUH-60A
-1
0
1
10
10
Frequency (rad/sec)
10
2
10
Vertical Acceleration due to Collective
40
20
10
12
Dynamic Comparison
-1
0
1
10
10
Frequency (rad/sec)
10
2
10
-1
0
1
10
10
Frequency (rad/sec)
10
2
Control Law Analysis
Requirements
Control Laws
• AVNS-PRF-10018
• ADS-33E-PRF
• MIL-F-9490
• Architecture
• Gains
• Modes
Math Models
• Gen Hel
• FORECAST
• CIFER SYS ID
13
Control Law Analysis and
Optimization with CONDUIT®
Control system defined as
SIMULINK® block diagram
– 139 states for UH-60MU
•
Design Specs
Linked with linear Aircraft model in
SIMULINK®
“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!
14
Airframe Model
Controller Structure
CONDUIT
– 25 state FORECAST model for hover
•
System
Simulation
Optimization
(tuning)
Evaluation
•
Powerful Multi-Objective optimization
engine enables CONDUIT®
Translation
•
Flight Control Engineer
CONDUIT® Predicted Performance
40
20
40
BnwYaH2:BW & T.D.
Other MTEs (Yaw)
RCHH Yaw
S
0.3
0 MIL-F-9490D
0
10
GM [db]
2
H
60
40
0 MIL-F-9490D
0
10
GM [db]
20
DstBwG1:Dist. Rej. Bnw
(linear scale)
ACAH, THETA
2
S
BnwAtH1:Bandwidth (pitch & roll)
Other MTEs;UCE>1; Div Att
0.4
ACAH
S
Level 3
0.1
Pitch
4
Roll
Bandwidth [rad/sec]
DstBwG1:Dist. Rej. Bnw
(linear scale)
ACAH, PHI
Level 2
0.2
0 ADS-33D
0
2
20
2
S
1.8
1.8
1.8
1.6
1.6
1.6
1.4
1.4
1.4
1.2
1.2
1.2
1
4
Bandwidth [rad/sec]
1
Yaw
DstBwG1:Dist. Rej. Bnw
(linear scale)
RCHH, PSI
S
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
200
0 Ames Research Center
0
1
2
Total Cost
Actuator RMS
Specs: 57
Dps: 35
1
0
1
2
0
Bandwidth [rad/sec]
0
-10
-20
-30
-40 ADS-33E
-40
-20
1
2
Bandwidth [rad/sec]
CouPRH2:Pitch-Roll Coupling
Frequency Domain
10
ACAH
C
RmsAcG1:Actuator RMS
1
ACAH
J
0.8
100
0.5
Bandwidth [rad/sec]
ModFoG2:Cost Point
1
ACAH
S
0
1
0
1
r1/hdot(3) [deg/ft]
0.1
0
Average q/p (dB)
States (simplified case): 139
Level 1
0.3
0.2
0 ADS-33D
0
2
15
INNER, POSITION
20
Average p/q (dB)
Phase delay [sec]
60
80
20
0 Ames Research Center
0
10
20
GM (dB)
0.4
INNER, ACVH OUT OF DE
H
PM [deg]
PM [deg]
PM (deg)
60
80
StbMgG1: Gain/Phase Margins
(rigid-body freq. range)
Phase delay [sec]
StbMgG1: Gain/Phase Margins
(rigid-body freq. range)
StbDaG1:Frequency Sweep Spec
ACAH USING FLT DATAH
80
CouYaH1:Coupling
Yaw/Collective
ACVH
C
0.8
0.6
0.4
0.2
0 ADS-33D
-1
0
r3/hdot(3) [deg/ft]
1
System Verification
Requirements
Control Laws
• AVNS-PRF-10018
• ADS-33E-PRF
• MIL-F-9490
• Architecture
• Gains
• Modes
Math Models
• Gen Hel
• FORECAST
• CIFER SYS ID
16
CLAW Integration Verification
Longitudinal Forward Loop
(From Piloted Sweeps)
Longitudinal Broken Loop
(From Injected Sweeps)
CONDUIT®
Flight Test
wc
3.5
3.5
PM
49.7
48.4
-20
GM
13.5
8.5
-40
Lateral
wc
4.2
3.4
PM
50.3
51.8
GM
8.1
7.3
wc
5.7
6.2
0.6
PM
31.1
45.5
0.2
GM
8.2
6.7
wc
1.9
1.6
PM
74.6
64.5
GM
8.9
9.7
Longitudinal
Magnitude (dB)
0
-20
-40
Phase (deg)
0
-90
-180
-270
-360
1
Coherence
Coherence
Phase (deg)
Magnitude (dB)
Flight
20
0.6
0.2
10
-1
10
0
10
1
Frequency (rad/sec)
•
•
17
10
2
40
CONDUIT
20
0
0
-90
-180
-270
-360
Directional
1
10
-1
10
0
10
1
Frequency (rad/sec)
Excellent agreement between analysis and test
Minor discrepancies associated with known model
shortcomings
10
2
Vertical
Lead-Lag Mode Stability
Initial CONDUIT® optimization
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
•
18
Stability improvement verified in flight
Magnitude (dB)
•
20
0
~4dB
16dB
-20
Baseline Gains, Flight
Baseline Gains, FORECAST
Reduced Gains, Flight
-40
0
Phase (deg)
– FORECAST aircraft model
– Adequate stability margins
– Known lead-lag mode errors
Pitch Rate / Longitudinal Cyclic
-180
-360
1
Coherence
•
0.6
0.2
10
-1
0
1
10
10
Frequency (rad/sec)
34r/s
10
2
Flight Test Evaluation
Requirements
Control Laws
• AVNS-PRF-10018
• ADS-33E-PRF
• MIL-F-9490
• Architecture
• Gains
• Modes
Math Models
• Gen Hel
• FORECAST
• CIFER SYS ID
19
Handling 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
20
Quantitative Criteria
!p
"
#
0.2
(sec)
Level
2
0.1
Level 1
1
53
200
Forward
Aft
Collective
150
52
100
51
50
h!est
( col
0
1
2
3
$BW , $BW
"
#
4
0
10
20
30
Minimum attitude change, ) qmin (deg)
(rad/sec)
0.4
2
Yaw Disp
Yaw Disp CONDUIT
Left
Right
Level 1
%
ppk/ )"pk (1/sec)
0.3 Level 3
!p
0.2
(sec)
0.1
Level 2
1
Level 2
Level 1
0
1
2
$BW
3
%
Level 3
4
(rad/sec)
5
0
0
20
40
60
Minimum attitude change, ) qmin (deg)
Level 1 for all criteria evaluated
21
49
he
0
5
50
h
Level 2
Level 1
0
Ke 0.122 s
'
5.0 s & 1
-50
0
1
2
3
4
Time (sec)
5
48
6
Collective (%)
qpk/ )# pk (1/sec)
0.3 Level 3
!p
2
Pitch Disp
Pitch Disp CONDUIT
Pitch Force
Roll Disp
Roll Disp CONDUIT
Roll Force
Climb Rate (ft/min)
0.4
Handling Qualities Ratings (GVE)
10
UH60MU / RASCAL
Avg GVE HQR = 2.8
Handling Qualities Rating
9
8
EH-60L
Avg GVE HQR = 4.3
UH-60A (1999)
Avg GVE HQR = 4.2
7
6
5
4
3
2
Mission Task Element
•
•
22
Mission Task Element
H
o
ov ve
T r
H urn
ov
R
La T u
t R rn
L
La ep o
tR R
e
D po
ep
L
Ab
V e or
rt t
M
an
H
H
o
ov ve
T r
H urn
ov
R
La T u
t R rn
L
La ep o
tR R
e
D po
ep
L
Ab
V e or
rt t
M
an
H
H
H
o
ov ve
T r
H urn
ov
R
La T u
t R rn
L
La ep o
tR R
e
D po
ep
L
Ab
V e or
rt t
M
an
1
Mission Task Element
UH-60MU provides average of 1.5 HQR improvement over EH-60L
EH-60L baseline agrees well with 1999 UH-60A evaluation
Handling Qualities Ratings (DVE)
10
UH60MU / RASCAL
Avg GVE HQR = 2.8
Handling Qualities Rating
9
8
UH60MU / RASCAL
Avg DVE HQR = 3.2
EH-60L
Avg DVE HQR = 5.2
7
6
5
4
3
2
Mission Task Element
•
H
o
ov ve
T r
H urn
ov
R
La T u
t R rn
L
La ep o
tR R
e
D po
ep
L
Ab
V e or
rt t
M
an
H
H
o
ov ve
T r
H urn
ov
R
La T u
t R rn
L
La ep o
tR R
e
D po
ep
L
Ab
V e or
rt t
M
an
H
H
H
o
ov ve
T r
H urn
ov
R
La T u
t R rn
L
L a ep o
tR R
e
D po
ep R
A
V e b or
rt t
M
an
1
Mission Task Element
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)
23
Mission Task Element
Conclusions
24
•
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