AIAA Infotech@Aerospace 2010
Exploiting Unmanned Aircraft Systems
Their Role in Future Military Operations
and the Emergent Technologies that
will Shape Their Development
Dr. Werner J.A. Dahm
USAF Chief Scientist
Air Force Pentagon
Headquarters U.S. Air Force
21 April 2010
1
Current Unmanned Aircraft Systems
of the U.S. Air Force and DoD
U.S. Air Force
RQ-4 Global Hawk
MQ-1 Predator
MQ-9 Reaper
RQ-11 Raven
Wasp III BATMAV
RQ-170
Sentinel
U.S. Army
RQ-7 Shadow
MQ-1C Warrior
U.S. Navy / Marines
RQ-11 Raven
Scan Eagle
RQ-8 Fire Scout
RQ-11 Raven
Wasp III BATMAV
RQ-2 Pioneer
2
Rapid Growth in UAS Use by USAF
3
USAF Need for RPA Pilots, Operators,
and Ground Crews is Growing Quickly
RQ-4 Global Hawk
2004
MQ-1 Predator
2009
MQ-9 Reaper
2011
4
Emerging Roles and New Concepts for
Large and Medium Size UAVs

UAS moving beyond traditional
surveillance and kinetic strike roles

Longer-endurance missions require
high-efficiency engine technologies

In-flight automated refueling will be
key for expanding UAS capabilities

May include ISR functions beyond
traditional electro-optic surveillance

LO may allow ops in contested or
denied (non-permissive) areas

Electronic warfare (EW) by stand-in
jamming is a possible future role

Wide-area airborne surveillance
(WAAS) is increasingly important

Directed energy strike capability is
likely to grow (laser and HPM)

Civil uses include border patrol and
interdiction, and humanitarian relief
5
Ultra-Long Endurance Unmanned Aircraft

New unmanned aircraft systems (VULTURE)
and airships (ISIS) can remain aloft for years

Delicate lightweight structures can survive
low-altitude winds if launch can be chosen

Enabled by solar cells powering lightweight
batteries or regenerative fuel cell systems

Large airships containing football field size
radars give extreme resolution/persistence
6
New Multi-Spot EO/IR Sensors for UAVs

Multi-spot EO/IR cameras allow individually
steered low frame rate spots; augment FMV

Gorgon Stare now; ARGUS-IS will allow 65
spots using a 1.8 giga-pixel sensor at 15 Hz

Individually controllable spot coverage goes
directly to ROVER terminals on ground

Autonomous Real-Time Ground Ubiquitous
Surveillance - Imaging System (ARGUS-IS)
7
New LIDAR Systems Allow Large-Area
Three-Dimensional Urban Mapping

Light Detection and Ranging (LIDAR) allows
3D sensing with light-wavelength resolution

Allows detailed mapping of complex urban
areas from unmanned airborne systems

Merge with EO/IR images to give enhanced
spatial cognition and situational awareness

Low-collateral-damage strikes in urban
areas via target-quality 3D pixel coordinates
8
UAS Automated Aerial Refueling (AAR)

Aerial refueling of UAVs from USAF tanker fleet is
essential for increasing range and endurance

Requires location sensing and relative navigation
to approach, hold, and move into fueling position

Precision GPS can be employed to obtain needed
positional information

Once UAV has autonomously flown into contact
position, boom operator engages as normal

Key issues include position-keeping with possible
GPS obscuration by tanker and gust/wake stability
9
Flight Testing of UAS AAR Algorithms

August 2006 initial flight tests of AFRL-developed
control algorithms for automated aerial refueling

KC-135 with Learjet-surrogate UAS platform gave
first “hands-off” approach to contact position

Subsequent positions and pathways flight test
and four-ship CONOPS simulations successful

120 mins continuous “hands-off” station keeping
in contact position; approach from ½-mile away

12 hrs of “hands-off” formation flight with tanker
including autonomous position-holding in turns

Position-holding matched human-piloted flight
10
Increased Autonomy in UAS Missions

Autonomous mission optimization under
dynamic circumstances is a key capability

Must address UAV platform degradation as
well as changes in operating environment

Operator only declares mission intent and
constraints; UAV finds best execution path

Vigilent Spirit is current implementation
11
Distributed/Cooperative Control of UAVs

Optimized scalable solution methods
for multiple heterogeneous UAVs

Allows multiple UAVs to act as single
coordinated unit to meet mission need

Scalability of methods is essential to
allow future application to larger sets

np-hard problem; exponential growth
12
Distributed/Cooperative Control of UAVs

Task coupling of multiple UAVs is key in
complex environments; e.g. urban areas

Must include variable autonomy to allow
flexible operator interaction with UAVs

Allow dynamic task re-assignment while
reducing overall operator workload

Demonstrated in Talisman Saber 2009
13
Growing DoD Need to Improve Process
for Integrating UAS in National Airspace
14
Growing DoD Need to Improve Process
for Integrating UAS in National Airspace
15
Integration of UAS Operations in National,
International, and Military Airspace
National Airspace
Authority:
Federal Aviation Authority (FAA)
Separation:
Cooperative: TCAS / ADS-B
Non-Cooperative: Visual
Airfields:
Friendly and well known
International Airspace
Authority:
Int’l. Civil Aviation Org. (ICAO)
Separation:
Cooperative: TCAS
Non-Cooperative: Visual
Airfields:
Limited access, not well known
Collision
Avoidance
Military Airspace
Authority:
Department of Defense (DoD)
Separation:
Cooperative: IFF
Non-Cooperative: Radar, Visual
Airfields:
Limited, austere, security
Conflict
Avoidance
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UAS Autonomous Collision Avoidance
and Terminal Airspace Operations

Must address all aspects of UAV situational
awareness and control

Airspace deconfliction, air-ground collision
avoidance, terminal area operations

Must be immune to UAS “lost-link” cases;
“remotely-piloted” becomes “unmanned”

Surface avoidance (vehicles, obstructions)
U-2
70K
Global Hawk
Altitude
60K
50K
Heron 2
Predator B
40K
30K
20K
10K
Hermes, Aerostar,
Eagle Eye, Fire
Scout, Hunter
10
Endurance (hours)
20
Heron 1
Predator A
30
17
“Sense-and-Avoid” (SAA) System for
In-Flight Collision Avoidance

Sense-and-Avoid was Global Hawk ATD
for in-flight collision avoidance system

Flight on surrogate aircraft began 2006

Autonomous detection and avoidance of
cooperative & non-cooperative intruders

Jointly Optimal Collision Avoidance
(JOCA) was transition program in 2009
18
Developing Increased Trust in Autonomy:
Verification & Validation of UAS Control


Systems and software V&V is a
major cost and schedule driver
High level of autonomy in UAVs
will require new V&V methods

IVHM for mission survivability

Complex adaptive systems with
autonomous reconfigurability

Approach infinite-state system
even for moderate autonomy

Data/communication drop-outs
and latencies make even harder
System Requirements
System Architecture Design
System Architecture Analysis
Flight Control Requirements
Control Design
Control Analysis
Software Requirements
Software Design



Traditional methods based on
requirements traceability fail
Extremely challenging problem;
must overcome for UAS “trust”
Requires entirely new approach
Software Implementation
Software Test & Integration
System Verification & Validation
19
“Formal Methods” vs “Run-Time Method”
for V&V of UAS Control Systems

Formal methods for finite-state systems
based on abstraction and model-based
checking do not extend to such systems

Probabilistic or statistical tests do not
provide the needed levels of assurance;
set of possible inputs is far too large

Classical problem of “proving that failure
will not occur” is the central challenge

Run-time approach circumvents usual
limitation by inserting monitor/checker
and simpler verifiable back-up controller

Monitor system state during run-time and
check against acceptable limits

Switch to simpler back-up controller if
state exceeds limits

Simple back-up controller is verifiable by
traditional finite-state methods
Run-time
V&V system
20
Batteries & Liquid Hydrocarbon Fuel Cells
Will Be Needed to Power Small UAVs

Small UAVs need suitable power source
for propulsion and on-board systems

Desired endurance times (> 8 hrs) cause
battery weight to exceed lift capacity; IC
engine fuel efficiencies are too low

Fuel cells give lightweight power system
but must operate on logistical LHC fuel

JP kerosene fuels ideal, liquid propane is
usable; need on-board fuel processor

Solid-oxide fuel cells are best to date;
current record held by U. Michigan team
> 9 hrs aloft with propane in small UAV
21
MAVs: New Aerodynamic Regimes and
Microelectromechanical Components

Micro UAVs open up new opportunities
for close-in sensing in urban areas

Low-speed, high-maneuverability, and
hovering not suited even to small UAVs

Size and speed regime creates low-Re
aerodynamic effects; fixed-wing UAVs
become impractical as size decreases

Rotary-wing and biomimetic flappingwing configurations are best at this size

Requires lightweight flexible structures
and unsteady aero-structural coupling
22
Low Reynolds Number Flow Associated
with Flapping-Wing Micro Air Vehicles

Unsteady aerodynamics w/ strong coupling
to flexible structures is poorly understood

AFRL water tunnel with large pitch-plunge
mechanism allows groundbreaking studies

Advanced diagnostics (SPIV) combined with
CFD are giving insights on effective designs

MAV aerodynamics, structures, and control
are accessible to university-scale studies
23
AMASE: Air Force Research Laboratory’s
AVTAS Multi-Agent Simulation Environment

Desktop simulation environment developed
at AFRL for UAV cooperative control studies

Used within AFRL to develop and optimize
multiple-UAV engagement approaches

Public-released by AFRL to universities; no
license restrictions and no acquisition cost

Self-contained simulation environment that
accelerates iterative development/analysis
AMASE User Interface
24
AMASE Can Be Used to Develop/Assess
New Collaborative Control Algorithms

Example shows comparison of control laws for
mission with multiple areas and no-enter zones

Heterogeneous UAVs make intuitive approach
too complex; results show performance differs

Allows effectiveness of control algorithms to
be quantitatively assessed and compared

Enabled maturation of process algebra laws for
UAVs flown in Talisman Saber 2009

AMASE modeling details are documented and
publicly available in AIAA-2009-6139
Comparison of two cooperative
UAS control systems
25
Concluding Remarks

We are still at the very early stages of
UAS evolution, roughly where aircraft
were after WWI; much is changing

Developments over next decade will
span from large UAVs to MAVs as key
technologies and missions evolve:


Advanced platforms and sensors

Operations in non-permissive areas

Automated aerial refueling

Coordinated control of multiple UAVs

UAS integration across airspace

V&V to provide trust in autonomy
Creative approaches and technology
advances will be needed to exploit the
full potential that UAVs can offer
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