Network-Level Control of Collaborative UAVs by Joshua Alan Love A dissertation submitted in ...

203 Pages·2011·1.64 MB·English

Network-Level Control of Collaborative UAVs
by
Joshua Alan Love
A dissertation submitted in partial satisfaction of the
requirements for the degree of
Doctor of Philosophy
in
Engineering - Mechanical Engineering
in the
GRADUATE DIVISION
of the
UNIVERSITY OF CALIFORNIA, BERKELEY
Committee in charge:
Professor J. Karl Hedrick, Chair
Professor Francesco Borrelli
Professor Raja Sengupta
Fall 2011
UMI Number: 3498856
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Network-Level Control of Collaborative UAVs
Copyright 2011
by
Joshua Alan Love
1
Abstract
Network-Level Control of Collaborative UAVs
by
Joshua Alan Love
Doctor of Philosophy in Engineering - Mechanical Engineering
University of California, Berkeley
Professor J. Karl Hedrick, Chair
This dissertation addresses how a single human operator can interactively control
a network of collaborative unmanned aerial vehicles (UAVs). It provides a model
of computation for network-level controllers. These network-level controllers enable
a single human operator to monitor, order, and supervise the progress of an en-
tire network of autonomous collaborative UAVs. As the human operator observes
the network’s progress, they may make changes by applying runtime patches to the
network-level controller. The resulting network-level controller can be analyzed to
verify that it meets required conditions.
UAV networks produce significantly more information than any single human can
concentrate on. To ease this cognitive burden, the human operator should interact
with the UAVs at an appropriately high level of abstraction. They should focus on
monitoring what is being done, deciding what should be done, and determining in
what order. Other lower-level decisions can be automated by the network. To this
end, Petri nets are used as a theoretical basis for stating network-level controllers.
Petri nets have a graphical description that is extremely intuitive. They also convey
exactly what is being done, what will be done, and in what order using a network-
focused perspective.
Developing a novel Petri net-based model of computation fornetwork-level control
is the main contribution of this work. This includes forming the syntax and semantics
for network-level controllers. Other relatedcontributions include identifying invariant
and analyzable properties of the network-level controllers, proofs of their correctness,
and interpretations of their meanings. These allow a human operator to understand
and assert that a proposed controller is indeed correct. A runtime patching language
to enable modifications by the human operator is another contribution.
The theoretical concepts behind network-level controllers provide a mathematical
basisforthemoreconcrete CollaborativeSensing Language(CSL). This formalXML-
based language allows a precise specification of network-level controllers for UAVs.
This dissertation also describes an implementation that enabled CSL for the UAV
2
fleet at the Center for Collaborative Control of Unmanned Vehicles (C3UV). CSL
and its implementation are also original contributions.
Previous related research has focused on the detailed off-line specification of indi-
vidual reactive UAV behaviors. This creates a fixed preprogrammed network which
produces a specific but predetermined behavior. The various existing alternatives are
not well suited for interactive control of a network by a single human operator. They
either suffer from no graphical description (process algebras), excessive information
(hybrid systems), an individual component and not network focus (networks of finite
state machines), a fixed dimension network, or a static specification that cannot be
affected on-line. The novelty and usefulness of this dissertation lies in its ability to
address these issues.
Professor J. Karl Hedrick
Dissertation Committee Chair
i
Dedicated to my parents, Randy and Dixie Love, for their continual
and unwavering support and the belief that I can do anything I set
my mind to doing, even when it sounds ridiculous.
ii
Contents
List of Figures v
List of Tables viii
Symbols and Abbreviations ix
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Greater Applicability . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Contents of Dissertation . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Modeling Systems of Systems 6
2.1 Process Algebras . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.1 Communicating Sequential Processes (CSP) . . . . . . . . . . 10
2.1.2 Calculus of Communicating Systems (CCS) . . . . . . . . . . 14
2.1.3 Algebra of Communicating Processes (ACP) . . . . . . . . . . 16
2.1.4 π-Calculus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Finite State Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.1 Individual Finite State Machines . . . . . . . . . . . . . . . . 23
2.2.2 Systems of Finite State Machines . . . . . . . . . . . . . . . . 29
2.2.3 Supervisory Control . . . . . . . . . . . . . . . . . . . . . . . 35
2.2.4 Applications of FSMs to UAVs . . . . . . . . . . . . . . . . . 39
2.3 Hybrid Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.3.1 Individual Hybrid Automata . . . . . . . . . . . . . . . . . . . 44
2.3.2 Networks of Hybrid Automata . . . . . . . . . . . . . . . . . . 50
2.4 Petri Nets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.4.1 Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.4.2 Compositional Modeling . . . . . . . . . . . . . . . . . . . . . 63
2.4.3 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
2.4.4 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
iii
3 Network-Level Controllers 71
3.1 UAVs and Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.1.1 UAVs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.1.2 Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
3.2 The Concept of Network-Level Control . . . . . . . . . . . . . . . . . 77
3.3 Syntax of Network-Level Controllers . . . . . . . . . . . . . . . . . . 80
3.4 Semantics of Network-Level Controllers . . . . . . . . . . . . . . . . . 82
3.5 Example Network-Level Controller . . . . . . . . . . . . . . . . . . . 84
4 Properties of Network-Level Controllers 86
4.1 Invariance Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.1.1 Task-Token Consistency . . . . . . . . . . . . . . . . . . . . . 87
4.2 Analyzable Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 88
4.2.1 Weak Bisimulation . . . . . . . . . . . . . . . . . . . . . . . . 89
4.2.2 Reachability . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.2.3 Boundedness . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.2.4 Liveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
4.2.5 Deadlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
4.2.6 Additional Properties . . . . . . . . . . . . . . . . . . . . . . . 96
5 Runtime Patching Language for Network-Level Controllers 97
5.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.2 Structural Operational Semantics . . . . . . . . . . . . . . . . . . . . 98
5.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
6 Network-Level Controllers Modified By Runtime Patching 103
6.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.2 Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.3 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.4 Invariance Theorems . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.4.1 Well Formed . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.4.2 Fully Representative . . . . . . . . . . . . . . . . . . . . . . . 111
6.4.3 Task-Token Consistent . . . . . . . . . . . . . . . . . . . . . . 112
6.5 Analyzable Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
7 The Collaborative Sensing Language 117
7.1 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
7.2 C UV Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
3
7.3 XML-based Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
7.3.1 CSL’s State Representation . . . . . . . . . . . . . . . . . . . 125
7.3.2 CSL’s Runtime Patches . . . . . . . . . . . . . . . . . . . . . 141
iv
8 Conclusions 148
8.1 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
8.2 Critiques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
8.3 Directions for Future Work . . . . . . . . . . . . . . . . . . . . . . . . 149
Bibliography 151
A Proof of Lemma 6 168
B Proof of Lemma 7 179
C Proof of Lemma 8 183
v
List of Figures
2.1 Notions of Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Behavior of a System of Processes . . . . . . . . . . . . . . . . . . . . 9
2.3 CSP Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4 π-calculus Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.5 State Transition Diagram . . . . . . . . . . . . . . . . . . . . . . . . 24
2.6 System of FSMs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.7 Interleaved System of FSMs . . . . . . . . . . . . . . . . . . . . . . . 30
2.8 Parallel System of FSMs . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.9 Product System of FSMs . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.10 Accessible Product System of FSMs . . . . . . . . . . . . . . . . . . . 33
2.11 Moore Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.12 Mealy Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.13 Feedback Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.14 FSM Controller/Plant Coupling . . . . . . . . . . . . . . . . . . . . . 36
2.15 FSM Feedback Control . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.16 Discretized Environment . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.17 Hybrid Trajectories . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2.18 Liquid Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.19 Liquid Tanks Hybrid Automaton Model . . . . . . . . . . . . . . . . 46
2.20 Liquid Tanks Hybrid Behavior . . . . . . . . . . . . . . . . . . . . . . 48
2.21 Hierarchical Hybrid Automaton . . . . . . . . . . . . . . . . . . . . . 52
2.22 Simplified Automated Highway Example from [56]. . . . . . . . . . . 54
2.23 SHIFT Automata for Simplified Automated Highway from [56]. . . . 54
2.24 Petri Net Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
2.25 Petri Net Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
2.26 State Machine Petri Net . . . . . . . . . . . . . . . . . . . . . . . . . 60
2.27 Marked Graph/State Machine . . . . . . . . . . . . . . . . . . . . . . 61
2.28 Component Petri Sub-nets . . . . . . . . . . . . . . . . . . . . . . . . 63
2.29 FSM Interleaving vs. Petri Net Interleaving . . . . . . . . . . . . . . 64
2.30 Transition Fusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.31 Asynchronous Petri Net Communication . . . . . . . . . . . . . . . . 65