Exploration of Hybrid and Intelligent Control Architectures in Conjunction with Probabilistic Verification (ONR N00014-97-1-0946) Overview of ONR UCAV Project S.
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Transcript Exploration of Hybrid and Intelligent Control Architectures in Conjunction with Probabilistic Verification (ONR N00014-97-1-0946) Overview of ONR UCAV Project S.
Exploration of Hybrid and Intelligent Control Architectures in
Conjunction with Probabilistic Verification (ONR N00014-97-1-0946)
Overview of ONR UCAV Project
S. Shankar Sastry
ONR Project Review, July 21, 1998
Electronics Research Laboratory
University of California, Berkeley
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Research Objective and Research Thrusts
Research Objective: Design and evaluation of intelligent
control architectures for UCAV’s
Research Thrusts:
Intelligent control architectures for coordinating UCAV’s
Verification and design tools for intelligent control
architectures
Perception and action hierarchies for vision-based control
and navigation
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Project Concept
Central control paradigm (optimization of system-wide mission
objectives) breaks down when dealing with distributed multiagent systems
Real-world environments are complex, spatially extended,
dynamic, stochastic and largely unknown
Autonomous intelligent systems in real-world environments
require
– sensory and control functions
• based on system decomposition based on hierarchical hybrid, and
multi-agent designs using multiple levels of abstraction
– structural and parametric learning methods
• to adapt to initially unknown environments
– generalized estimation methods, uncertainty management and
robust control techniques
• to deal with residual uncertainty in stochastic, partially observable
environments
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Project Concept
Real-time decision making is achieved by
– parallelism
– reflexive control
– compilation
– anytime approximation
Hierarchical perception and control paradigm
– architectural fusion of the central control paradigm with
autonomous intelligent systems
Distributed intelligent systems
– hierarchical or modular to control complexity
– globally organized emergent behavior
– robust, adaptive and fault tolerant and degraded modes of
operation
– architectural organization involving the use of compositionality
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Technology Drivers
Intelligent Multi-Agent Systems
The need for a theoretical framework for an
integrative approach arises from advances in
computation, communication, intelligent materials,
visualization and other technologies which make it
possible to expect more from a multi-agent system,
than a centralized control framework.
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Intelligent Multi-Agent Systems
Unmmaned Autonomous Vehicles
Distributed Command and Control
Simulated Battlefield Environment
Decision Support Aids for Human Centered Systems
Automatic Target Recognition
Robust and Fault tolerant Systems
Distributed Communication Systems
Distributed Power systems
Intelligent Vehicle Highway systems
Air Traffic Management Systems
Intelligent Telemedical Systems
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Berkeley Team
SASTRY: Specializes in decentralized control of distributed systems and hybrid
design and verification techniques, with applications to automated highway
systems, air traffic management systems and robotics.
MALIK: A leader in low-level and intermediate vision, with recent work in crucial
aspects of image segmentation, association, grouping and attribute evaluation.
SENGUPTA: Experience in observation and control for distributed systems.
Extensive background in discrete event and hybrid systems. Application to
transportation and communication problems.
GODBOLE: Hybrid control of multi-agent systems. Extensive background in
applications to automated highway and air traffic management systems. Interagent coordination problems. Design of fault management systems.
LYGEROS. Hybrid control synthesis. Background in automated highway and air
traffic management systems. Formal methods for verification of large-scale
systems. Fault tolerant control systems.
SHAKERNIA. First-year graduate student in EECS. B.S. (1997) EECS, UCB.
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Theoretical Underpinnings
Architectural design for multi-agent systems
–
centralization for optimality
– decentralization for safety, reliability and speed of response
Perception systems sharing many representations
–
hierarchical aggregation
– wide-area surveillance
– low-level perception
Frameworks for representing and reasoning with uncertainty
Incorporation of learning, adaptation and fault toperance: parametric
uncertainty with update and adaptation at the continuous levels,
learning of new “logical entities”, reinforcement learning at the logical
levels and meta-learning for redefining architecture
Soft-computing approaches to intelligence augmentation for humancentered systems: reconciliation of human decision making schemes
with machine performance, intelligent agents, keeping the human in the
loop, sufficing rather than optimizing
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Research Thrust 1: Intelligent Control
Architectures
An architecture design problem is concerned with design
of both the observation and control
An architecture design problem for a distributed system
begins with specified safety and efficiency objectives and
aims to characterize communication, observation and
control
Our investigation of the intelligent control architecture
design problem is concerned with three formalisms
– intrinsic model
– supervisory control of discrete event systems
– hybrid system formalism
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Research Thrust 2: Verification and
Design Tools
Design Mode Verification
Faulted Mode Verification
Probabilistic Verification
– A rapproachment between stochastic control, Bayesian
decision networks and soft computing
– The heart of the approach is to not verify that every run
of the hybrid system satisfies certain safety or liveness
parameters, rather to check that the properties are
satisfied with a certain probabillity, given uncertainties
of actuation and sensing
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Research Thrust 3: Perception and Action
Hierarchies
Hierarchical Vision
Control Around the Vision Sensor
Surveillance
We are designing a perception and action hierarchy
centered around the vision sensor to support the
observation and control functions of air vehicles
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Exploration of Hybrid and Intelligent Control Architectures in
Conjunction with Probabilistic Verification (ONR N00014-97-1-0946)
Architectures for UCAV and Results on
Multi-Agent Coordination
Raja Sengupta and Datta Godbole
ONR Project Review, February 24-25, 1998
Electronics Research Laboratory
University of California, Berkeley
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Outline
Research Thrusts
– Hierarchical UCAV Architecture Design
– Design of Decentralized Observation, Communication and
Control for Discrete Event Systems
• Application to Fault Detection and Identification
– Distributed hybrid control for multi-agent systems
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UCAV Architecture
A group of UCAV’s are a coordinating multi-agent system
with limited centralized control
– mobile communication systems support coordination
– due to limitations on computing and communication
resources the UCAV’s must cooperatively and individually
exhibit a high degree of autonomy
– low bandwidth, asynchronous, event-driven coordination is
preferred to synchronous, time-driven coordination
A single UCAV is a real-time embedded system
The architecture should specify observation and control
semantics at each layer
– the layers should be consistent and programmable
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UCAV Architecture
Mission Control
Ship
Strategic Objective
UCAV
Strategic Layer
Inter-UCAV
Coordination
Trajectory Constraints
Tactical Layer
Sensor Info on
Targets, UCAV’s
Regulation Layer
Environmental
Sensors
Trajectory
Actuator Commands
UCAV Dynamics
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Preliminary UCAV Architecture
Regulation
– control of UCAV actuators
• fully autonomous
Tactical
– safe and efficient trajectory generation and mode control
• fully autonomous
Strategic
– trajectory constraints, UCAV to UCAV/ship coordination,
weapons configuration, fault management
Central Mission Control
– mission planning, resource allocation, mission emergency
response, mission optimization, pilot interface
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PATH AHS Architecture
Network Layer
Link Layer Regulator
(flow control)
SC&P* Info
SC&P* Info
Coordination Layer
(maneuver protocols)
SC&P* Info
Regulation Controller
Throttle Actuator
Brake Actuator
Roadside
Vehicle
Communications
with neighbors
Physical Layer
Steering Actuator
Vehicle Dynamics (Plant)
*Sensory, Capability & Performance
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Example: AHS Architecture
The layers are consistent and programmable
Coordination
– Synchronous, time-driven for platoon stability (regulation)
– Asynchronous, event-driven for maneuvers (coordination)
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Decentralized Observation, Communication,
Control for Multi-agent Systems
Given a strategic objective and local observation what is
the information exchange with the mothership and other
UCAV’s required to command tactical control ?
– Given a distributed control problem and the local
observation at each site, what is the inter-site
communication (minimal) or coordination protocols required
to solve this problem ?
Given a system mission what is the strategic objective
(possibly dynamic) of each UCAV ?
– How to distribute among the available agents a specified
centralized control problem ?
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Literature: Distributed Control with
Decentralized Information
Decentralized control of large-scale systems
– linear systems, time-driven, design for stability
Stochastic scheduling
– queuing networks, time-driven, design for performance
Distributed control of discrete event systems
– event driven, design for correctness, safety
Distributed control of hybrid systems
– time and event-driven, design for correctness, safety
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Communication and Control Synthesis for
DES
Symbolic representation of system actions (events)
Behavior is a causal ordering of symbols (event trace)
Objective:
– Given a DES plant model, specification of the control
objective, local observation and control capability, synthesize
a minimal inter-agent communication and the control law of
each agent.
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Communication and Control Synthesis for
DES
Advantages:
– Will synthesize symbolic, event-driven, inter-agent
communication over a finite message set
– Very simple models permitting logical or combinatorial
analysis and insights
– AHS Example: Worked for most coordinating maneuvers
other than stability properties for vehicle following.
Limitation: No formal way to capture continuous
dynamics
– The semantics of an event is generally some alignment or
safety conditions in velocity, position, and euler angles with
respect to targets or other agents
– Distributed control of hybrid systems
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DES Problem 1: Observation and
Communication
Agent Communication Channels
A1
A2
A3
Plant (Lp)
• The agents have partial observation, but can exchange messages
• The plant has a set of distinguished events (failures)
• OBJECTIVE: Design the inter-agent communication scheme required
to detect and isolate the distinguished events
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DES Problem 1: Observation and
Communication Only
Theorem 1 (Lp, poi, fiiI) is decentrally diagnosable if there exists
n N such that for all sf f, usfv Lp, |v|n, implies
(w Lp) ( i, Ppoi (w) = Ppoi (usfv(sf w.
If any two sufficiently long plant traces look the same to all the diagnosers, then
either they have no failures or have all the same failures.
Synthesis: The communicate all plant observations solution works.
General drawback: Redundant information is communicated. -L(f) may not be
regular even though Lp is regular.
Current focus: Minimal communication, protocol synthesis, trace abstraction
Documentation: Draft paper available and sent to WODES’98
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DES Problem 2: Control, Observation, and
Communication
Each agent has a set of controllable events
The controllable events are a subset of the set of
observable events
The next event is either an uncontrollable event from the
plant, a controllable event enabled by an agent, or a
message event scheduled by an agent
Control objective is specified by a language
Researching the existence and synthesis of coordination
protocols
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Distributed Control and Communication of
Hybrid Systems
Symbolic and flow representation of system actions
Game/Team-theoretic approach to synthesis
– Agents play as a team against a non-cooperative target
• Characterize the saddle disturbance in the team-target game
• Use the saddle disturbance to formulate and solve an optimal
control problem to characterize the saddle team strategy
• Derive the inter-agent communication and individual agent
control from the necessary conditions
Theorem: If for an initial state the worst disturbance is
independent of the team control then the target-team
game has a saddle solution
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Hybrid Approach: Application to AHS Lane
Change
FT generates disturbance in response to downstream
traffic and P,RT play as a team
We guess the saddle disturbance
Use the saddle disturbance to formulate and solve an
optimal control problem for the saddle team control
The inter-agent coordination requires three messages
RT
FT
P
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Summary
Developed a preliminary UCAV architecture
– UCAV to UCAV and UCAV to ship coordination
– Hierarchical control and observation
Focused theoretical research efforts on
– Sensing, Control, and Communication for Distributed
Multi-agent Systems
– Failure Detection and Identification
– Design of Hybrid and Decentralized Control Systems
– Current Results
• Existence and synthesis of inter-agent communications for
partially observed distributed discrete event systems
• Synthesis of safe hybrid control laws for distributed hybrid
systems using game theory and optimal control
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Quick Time Movie of Helicopter Flight
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