a multi-agent system for tracking the intent of surface contacts in ports and waterways

A Multi-Agent System for

Tracking the Intent of Surface Contacts

in Ports and Waterways

Tan, Kok Soon Oliver Project Manager

C4IT-IKC2DSTA

[email protected]

Agenda

• Introduction

• Concepts

• Multi-agent System Design

• System Validation Scenarios

• Recommendations and Conclusion

Introduction

• A thesis on modeling the intent of surface contacts with a multi-agent system (MAS) for asymmetric threat identification in busy ports and waterways

• Inspired by similar work done in the area of air threat assessment in Air Defense Laboratory (ADL) [Ozkan 2004, NPS]

Thesis Questions

• How can surface contact intent be modeled with a MAS for the identification of potentially hostile behaviors and threats in ports and waterways?

• Will the models be sufficiently realistic to be used as a decision aid in maritime security?

Why a MAS?

A multi-agent model is a distributed intelligence model that is a “natural” solution of a large-scale real-world problem1

• The real world problem is physically distributed– Every surface contact is an autonomous entity that we are interested in knowing its

probable intentions;• The knowledge to solving the real world problem is widely distributed and

heterogeneous– No one agent or system is "knowledgeable" enough to trawl and mine databases,

process real-time sensor data, monitor for rule violations or suspicious behaviours etc;

• The sources of data are distributed over networks– Naturally this encourages us to take a distributed view of a solution for the real world

problem; and• The real world problem is too complex to be analysed as a whole

– There are too many parameters and constraints to be considered altogether. Local approaches, partitioning the large problem into smaller and more tractable sub-problems, can produce results quickly.

1. Ferber, J., Multi-Agent Systems An Introduction to Distributed Artificial Intelligence, Addison-Wesley, 1999.

MAS Objectives

A multi-agent system (MAS)• To help the human operator sieve through

hundreds of surface contacts• To integrate intelligence and information from as

many sources as possible• To highlight any suspicious or potentially hostile

surface contacts

Requirements of the MAS

• Support rules and regulations of a Vessel Traffic Service (VTS) such as:– Traffic Separation Scheme (TSS), part of the

International Navigation Rules defined by the International Maritime Organization

– the 1972 Collision Regulations (72 COLREGS)– International Ships and Port Facilities Security (ISPS)

Code (To be implemented)– all other practices of safe navigation and prudent

seamanshipPredefined safe speed limits in TSSSafe speed limits for different surface track types

Requirements of the MAS cont…

• Use Surface Warfare Threat Assessment cues and corresponding perception of threat [Liebhaber 2002, SPAWAR Systems Center, San Diego]

• Obtained through empirical and observational studies of the threat assessment process by experienced surface warfare officers

• Each cue has a Threat Level Change Rating (TCR) that changes the threat level posed by a surface contact

1. Platform/Weapon Envelope/ESM

2. Origin-Flag

3. Range/Distance from Own-Ship (subsumed under CPA)

4. Heading (subsumed under CPA)

5. Closest Point of Approach (CPA)/Speed

6. Number of vessels (To be implemented)

7. Own support in area (To be implemented)

8. Destination

9. History/Voice communication

10 Sea Lane/Other intelligence

11. Superstructure Type (To be implemented)

12. Coordinated Activity (To be implemented)

Requirements of the MAS cont…

• Use information from ship-borne • Automatic Identification system (AIS)

• Transponder for large vessels (>300gt)• International Maritime Organization (IMO) recommendation

• Harbor Craft Transponder system (HARTS)• For smaller vessels• Applies to the Port of Singapore only

1. Track Type

2. Callsign (To be implemented)

3. IMO Number (Lloyd’s Register Number) (To be implemented)

4. Maritime Mobile Service Number (To be implemented)

5. ETA (To be implemented)

6. Destination (To be implemented)

Thesis Scope

• Identify and track the intent of surface contacts• Borrowing the ideas and techniques suggested

for identifying air threats in the Air Defense Laboratory (ADL) and use them to identify asymmetric maritime threats

• The thesis does not cover the issue of track detection i.e. assumes perfect instantaneous detection with 100% reliability

• The issue of interdiction when a potentially hostile track has been identified is also beyond the scope of this thesis

Some Concepts

• Traffic Separation Scheme (TSS)

• Security Zones for HVUs

• Security Zones for Restricted Areas

• Areas-To-Be-Avoided (ATBA)

• Safe Speed Limits

Skip Concepts

Traffic Separation Scheme (TSS)

• A TSS is a sea lane with a predefined traffic direction

• A TSS may also has a predefined safe speed (for prudent seamanship)

• A violation occurs when a track is traveling against traffic direction or is traveling at an excessive speed

Security Zones for HVUs

• Every High Value Unit (e.g. cruise liner, tanker) have their own predefined multiple security zones

• Only some type of tracks (e.g. Police Coast Guards) are allowed within these security zones

• Each security zone is defined with an alert time threshold (represents a measure of urgency when these zones have been infringed)

Radius = 0.2nm, Alert Time = 15min



Security Zone Violation Example

A A security zone violationsecurity zone violation occurs i.e. a track is occurs i.e. a track is coming in coming in too near,too near, too too soonsoon,, if an if an unauthorized unauthorized tracktrack has has

1.1. a a CPACPA (Closest Point of (Closest Point of Approach) within a zone, Approach) within a zone, andand

2.2. a a TCPATCPA (Time to CPA) Time to CPA) below alert time below alert time thresholdthreshold

TCPA = 3min

CPA

Radius = 0.2nm, Alert Time = 15minRadius = 0.5nm, Alert Time = 10minRadius = 0.8nm, Alert Time =

5min

““Too near! Too soon!”Too near! Too soon!”

Security Zones for Restricted Areas (Static HVUs)

• Restricted areas (e.g. harbor, oil refineries, military installations) can have their own predefined multiple security zones

• Only some type of tracks (e.g. Police Coast Guards) are allowed within security zones

• Each security zone is defined with an alert time threshold




Areas-To-Be-Avoided (ATBA)

• Restricted areas (e.g. harbor, oil refineries, military installations)

• Only allow certain types of tracks (e.g. Police Coast Guards) or certain types of track activity within these areas

• An ATBA violation occurs when an unauthorized track intrudes into a restricted area

Safe Speed Limits

• Some locations or restricted areas (e.g. harbor) may only allow tracks to travel at predefined speed limits

• Speed limits can be defined for different track types

• A violation occurs when a track exceeds any of these speed limits

The Compound Multi-agent System

• A compound multi-agent system (MAS) designed for surface contact intent tracking

• Each surface contact is represented by a track agent

• Every track agent has a nested MAS (“Russian Doll”)

Anatomy of a Track Agent

Speed Threshold Violation Agent

Friendly Intent Agent

Neutral Intent Agent

Potentially Hostile Intent Agent

Unknown Intent Agent

Track Flag Data Ticket

Track Origin Data Ticket

Track Destination Data Ticket

Track Position Data Ticket

Track Activity Data Ticket

Track Comm Data Ticket

Track ESM Data Ticket

Track Heading Data Ticket

Track Speed Data Ticket

TSS Heading Violation

Agent

Speed Violation

Agent

Location Agent

ATBA Zone Track Activity Violation Blend

ATBA Zone Track Type

Violation Blend

Security Zone Violation

Blends

Speed Threshold Violation Blend

Speed Violation

Blend

TSS Heading Violation

Blend

Composite Agents

Reactive Agents

Track Type Data Ticket

Cognitive Agents

Area-To-Be-Avoided (ATBA) Violation Agent


Agent


Blends

The Compound Multi-agent System cont…

• Agents in the nested MASs continuously process incoming information about their respective surface contacts

• Agents communicate and co-ordinate in order to discover the likely intent of surface contacts

Conceptual Blending

• Conceptual Blending1 is a theory about how humans process the information coming from the environment and how humans rationalize the events happening around them

• Blending is a set of mental operations for combining cognitive models in a network of mental spaces

• Mental spaces are small conceptual packets

1. Gilles, F., Turner, M., The Way We Think, Basic Books, New York, 2002

Conceptual Blending cont…

• Mental spaces are connected to long-term schematic knowledge called “frames” e.g. – The frame of sailing along a ferry route, or – The frame of traveling inside a maritime traffic

separation scheme (TSS), – Long-term specific knowledge such as a memory of

an event such as past track incursions into Area-To-Be-Avoided (ATBA) zones.

• Mental spaces are interconnected in working memory which can be modified dynamically


• Building a conceptual integration network involves setting up several mental spaces.

• Two input mental spaces with cross-space mapping to connect counterparts in these input mental spaces

• However not all elements and relations from the input spaces are projected into the blend.

• Generic spaces are used for the generic structures they contain to guide the selective projection of elements from the input spaces into blended spaces

• The blended space is the mental space where, during blending, the structure from the input mental spaces is projected onto, represented by the dotted lines

Blend

Generic Space

Input Space 1

Input Space 2

A Basic Conceptual Integration Network


• Any mental space can participate in multiple networks.• Complex integration networks can be built with arrays of

mental spaces that are connected through blending operations.

Conceptual Blending Examples

• Example of how a Security Zone violation is detected

Blend

Generic Space

Track High Value Unit

Track CPA(Closest Point of Approach)

Security Zone Radius

CPA < Security Zone Radius


Track TCPA(Time to CPA)

Security Zone Alert TimeTime Vital Relation

TCPA < Security Zone Alert Time

Identity Vital Relation Allowed Track TypesTrack TypeTrack Type ≠ Allowed Track Types

Distance Vital Relation


• Example of how a ATBA Zone Track Activity violation is detected

Blend

Generic Space

Track ATBA Zone

Track Activity Allowed

Activity Type

Activity Vital Relation

Track Activity ≠ Allowed Activity Type

ATBA Zone Track Activity Violation

Activity Vital Relation

Location Vital RelationTrack Location Zone

Name

Track Location = Zone Name

The CMAS Library

• The communication and coordination among many different agents in the nested MAS is achieved using the Connector-based Multi-agent Simulation Library (CMAS) [John Hiles, NPS]

• The basic elements for agent communication and control within the CMAS framework are connectors.

• The agents use these connectors to externalize portions of their internal states into the multi-agent environment.

• Connectors are like plugs and receptacles that can be extended or retracted

• Signaling and coordination between the two agents occur when there are matching pairs of plug-receptacle connectors and the connectors get connected

• Stimergy (communication through change of local environment) among agents

Agent 1

Agent 2

Retracted connector

Extended response connector (Receptacle)Plug-

Receptacle match Extended stimulus

connector (Plug)

A MAS of MASs (“Russian Doll”)

• A track agent appears as a single agent that exists in another external MAS environment

• In this external MAS environment, there is a layer of regional agents that monitor behaviors of all track agents

• Two types of regional agents detect coordinated behavior that resembles an impending swarm or a “wolf-pack attack

Detection of Coordinated (Swarm/ “Wolf-pack”) Attack on a moving HVU

If two or more track have If two or more track have 1.1. CPAsCPAs to a HVU to a HVU (High Value Unit)

that are that are very closevery close e.g. 0.1 nm, e.g. 0.1 nm, andand

2.2. TCPAsTCPAs violations against the same HVU that are about to occur within a very short period of time e.g. 5 mins

““Too near!Too near! Too soon! Too many!”Too soon! Too many!”

The MAS will consider multiple near-simultaneous security zone violations a possible sign of an impending coordinated attack i.e. too near, too soon, too many

Note: A “wolf-pack” attack is a common maritime terrorist attack tactic comprising of a cluster of small terrorist craft approaching and surrounding a larger target craft from multiple directions simultaneously

Detection of Coordinated (Swarm/Wolf-pack) Attack on a static HVU

If two or more track have If two or more track have 1.1. CPAsCPAs to a restricted location to a restricted location

(static HVU) that are very close (static HVU) that are very close e.g. 0.1 nm, ande.g. 0.1 nm, and

2.2. TCPAsTCPAs violations against the same location that are about to occur within a very short period of time e.g. 5 mins

““Too near!Too near! Too soon! Too many!”Too soon! Too many!”

The MAS will consider this a possible sign of an impending coordinated attack i.e. Too near, Too soon, Too many

Anatomy of a Regional Agent

Swarm Detection (Location)

Agent

Swarm Detection (Track)Agent

Swarm Detection (Location) Blend

Swarm Detection (Track) Blend

Track Agent 1

Security Zone (Track)

Violation Blend

Swarm Detection (Track)

Weighting Agent


Weighting Agent

Track Agent 2


Weighting Agent


Weighting Agent

Regional Agent 1

Regional Agent 2

Security Zone (Location)

Violation Blend

Security Zone (Location)

Violation Blend

Cognitive Agents

Security Zone (Track)

Violation Blend


• Example of how a Coordinated Attack (Swarm/Wolf-pack) by 2 or more different tracks on the same HVU is detected by a Regional Agent

Blend

Generic Space

Security Zone

Violation Blend A

CPA(A) CPA(B)

HVU(A) == HVU(B)

Swarm Detection Blend

TCPA(A)TCPA(B)

Time Vital Relation

(CPA(A) – CPA(B)) < CPA_DIFFERENCE_THRESHOLD

Identity Vital Relation HVU (B)HVU (A)

(TCPA(A) – TCPA(B)) < TCPA_DIFFERENCE_THRESHOLD

Security Zone

Violation Blend B

Track BTrack A

Distance Vital Relation

Too much of a coincidence?

The Intent Agent

• The top layer of agents of the nested MAS environment inside a track agent

• Each intent agent has a corresponding intent model• Four intent agents:

1. Friendly,

2. Neutral,

3. Potentially Hostile, and

4. Unknown• Intent agents use information provided by internal

agents from the lower layers as well as from external regional agents

Anatomy of an Intent Agent

Track Type Track Flag Track Origin Track Destination Track CommTrack ESM

ATBA Zone Track Activity

Violation

ATBA Zone Track Type

Violation


Speed Threshold Violation

Speed Violation TSS Heading Violation

WeightingStrategy

Weighting Agents



MARSEC Level(bias)

Competitive Intent Models

• An Intent agent is a composite agent– Family of weighting agents is responsible for obtaining

information • User-defined weights (similar to Threat Level Change

Ratings) assigned to each piece of track information (attributes and violations)

• The intent model in an intent agent is represented by a weighting strategy

• Weighting agents receive track information on track attributes and track violations and informs the weighting strategy

• Weighting strategy computes a weighted score using a set of user-defined weights

• The intent models will compete and the one with the highest score represents the current intent of the track

Weighting Biases based on Regional Intelligence

• Maritime Security (MARSEC) Levels

• Warning against unidentified potential threats

• Equivalent to HSAS• Heightens/Lowers the

“alertness” of the weighting strategies by applying biases to the computed weighted scores.

The VTS-C2 MAS System

Features of the VTS-C2 system• A Java-based mock C2

(Command & Control) system• Supports geo-rectified maps,

tactical overlays and symbol drawing, graphical and tabular displays of C2 information

• Shows graphics representing tracks, TSSes, and restricted areas

• Integrated CMAS-based (Connector-based Multi-agent Simulation Library) compound MAS

• Integrated Simkit-based DES (Discrete Event Simulation) simulator [Arnold Buss, NPS]

– Tracks are linear uniform movers with delays at waypoints

– Proximity sensors are used to report location of tracks

Capabilities of the VTS-C2 MAS

1. Ability to detect future incursions into the security zones of HVU (high value units)

2. Ability to detect future incursions into restricted areas e.g. cruise center, oil refineries, military installations

3. Ability to detect illegal activities in restricted areas e.g. fishing in non-fishing zone

4. Ability to detect TSS (traffic separation schemes) violations e.g. against traffic direction, stopping in TSS termination zones

5. Ability to detect speed violations in restricted areas e.g. harbor

6. Ability to detect atypical track behaviors e.g. excessive speed

7. Ability to perform surface threat assessment based on tracks’ attributes e.g. platform, flag, origin, ESM, destination

8. Ability to detect VTS (Vessel Traffic Service ) violations e.g. collision detection, wrong/unknown destination, no verbal communication

9. Ability to detect coordinated maneuvers/attacks e.g. swarm/”wolf-pack”

10.Ability to incorporate regional intelligence e.g. MARSEC levels

Capabilities of the VTS-C2 MAS cont…

System Architecture

Compound MAS

Java-basedVTS-C2 system

TSS Definitions(traffic direction, speed limits)

ATBA (Area-To-Be-Avoided) Definitions(allowed track types, allowed track activity)

Safe Speed Limits for each track type

Security Zone Definitions(CPA radius and alert time)

Pre-defined Information

Maritime Sensors(Simkit-based Discrete Event

Simulator)Safe Speed Limits for certain locations and zones

Hourly/Ad-hoc Reports(Police Coast Guards/ Military Patrols)

24-hour Offshore Advance Reports(International Maritime Organisation Standard Ship Reporting System)

Databases (Lloyds, ICA)

Track Position, Speed, Heading, Destination

Automatic Identification System

Track Type, Callsign, IMO Number (Lloyd’s Register Number), Maritime Mobile Service Number, ETA, Destination

To be implemented

Information Sources (MPA)

Ship Manifests(Cargo/ Crew/ Passenger information) (ICA)

MAS of MASs

MARSEC Level

Harbor Craft Transponder System

Anecdotal Anomalies Detection

Operational Anomalies Detection

Pre-defined Information Settings

Weight and Bias Settings

Agent Threshold Parameters

Intent Scores Information

Validation Process

• Four validation sessions held with four groups of surface warfare assessment experts or naval officers from the Republic of Singapore Navy (RSN) and the US Navy

• Participants have more than 100 years of harbor security, patrol or at-sea experience between them

• Participants are first briefed on the features of the MAS and the mock VTS-C2 system

• Participants are next presented with several discrete-event simulations on scenarios involving the Port of Singapore and the surrounding waterways

Validation Process cont…

• Each scenario features multiple surface contacts of different types, moving in an area that is populated with traffic separation schemes and restricted areas

• The scenarios will feature different kinds of hostilities that may exist but the participants are not told of the details in advance

VTS-C2 System Demo

Validation Scenarios

Skip Scenarios

Sample Scenario 1(TSS violations, Impending collision)

TSS violation (speed and heading) and an impending collision between a leisure craft and a cruise liner

Sample Scenario 2 (Coordinated attacks by multiple tracks)

Possible coordinated attack by two fishing vessels on SZone3

Sample Scenario 3 (Incursion into security zone around HVU)

Detected incursion by fishing vessel in the security zone around tanker

Validation Results

• Very encouraging responses from the participants – good “proof of concept” that demonstrates

how a decision support tool can help the decision maker identify potentially hostile contacts

• Officers from the RSN commented that the MAS can be an important decision support tool in their existing C2 systems

Validation Results cont…

• Some concerns:– Although the system is able to process large amount

of information, there may still be an overwhelming information glut

– Intent labels not semantically suitable according to operational doctrine if the MAS was to be integrated into an existing C2 system

– False alarms that may arise due to the heavy traffic conditions in the Port of Singapore compounded by clutter caused by non-moving surface contacts; Need to select weights carefully to reduce the number of false alarms; “False alarms is better than no alarms”

– System is highly dependent on accuracy and reliability of information sources e.g. sensors, humans etc.

Future Work To Be Done

• Need to fine-tune the MAS and verify that system works well against real world vessel traffic situations in the waters of Singapore.

– The system may be tested during maritime security experiments

• Further validation with objective measures of performance:

1. Type I (false negatives) and Type II (false positives) errors,2. Number of factors that the system can process as

compared to a human operator,3. Time taken by the system to identify hostilities as

compared to a human operator i.e. amount of lead time the system is able to provide in situations of hostilities

Future Work To Be Done cont…

• Detect more unusual track maneuvers1. Many maneuvers / zig-zags2. Suspicious course changes that seem to match the movement

of a HVU3. Monitor course/heading of tracks in more detail (e.g. in terms of

Steady and closing/opening or Turn to closing/opening)4. Hiding or evading from PCG/Military Patrols5. More co-ordinated activities among tracks e.g. Simultaneous

attacks on multiple HVUs or restricted areas• Additional VTS violations

1. Failure to submit Offshore Advance reports, and2. Wrong/unknown destinations

• Incorporate specific intelligence based on 1. track attributes e.g. track type, origin, activity; and2. historical data e.g. piracy reports

Future Work To Be Done cont…

• Beyond more than just rules, it is also possible to have complex cognitive agents that can learn and adapt:– automatically learn appropriate weight settings to reduce false

alarms, or – automatically “retire” agents that are producing too many false

alarms, or– Automatically re-adjust security zone radii according to traffic

conditions, or– have the ability to “forgive”, over time, tracks for their past

violations• Act as proxies to external entity/relationship engines,

information fusion/search engines or web services i.e. distributed intelligence– Pro-active search by agents for anecdotal anomalies i.e. form a

paper trail from information sources such as ship registries, sail plans, Offshore Advance reports, cargo/passenger manifests etc

Conclusion

• Thesis question 1 – “How can surface contact intent be modeled with a MAS for the identification of potentially hostile behaviors and potential threats in ports and waterways?”– A multi-agent system has been developed to track the intent of

multiple surface contacts moving in ports and waterways.– Four intent models have been developed based on VTS rules,

surface warfare threat assessment cues and track behaviors

• Thesis question 2 – “Will the models be sufficiently realistic to be used as a decision aid in maritime security?”– Face validation showed that the system can be a useful decision

support tool in the maritime security of Singapore

a multi-agent system for tracking the intent of surface contacts in ports and waterways

Documents

surface contact1

intent of surface contacts

multiagent systems

multiagent model

threat assessment process

hundreds of surface

area of air threat assessment

distributed intelligence