Intelligent Patrolling Intelligent Patrolling

Sarit KrausDepartment of Computer Science

Bar-Ilan University

Collaborators: Noa Agmon, Gal Kaminka, Efrat Sless

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Physical Security with Physical Security with

Bounded ResourcesBounded Resources• Limited security resources prevent full security

coverage at all times; allows adversaries to observe and exploit patterns in selective patrolling or monitoring.

• Randomized patrolling or monitoring is necessary.

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Randomized CheckpointsRandomized Checkpoints

Multi-Robot Adversarial Multi-Robot Adversarial PatrolPatrol

• Motivation:

• High security facilities

• Large military bases

• Neighborhood watch

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Protecting a Parade: Protecting a Parade: route is announcedroute is announced

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Protecting a Moving Protecting a Moving Target: randomizing the Target: randomizing the

routeroute

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Why Do We Need Why Do We Need Automated Methods Automated Methods

for Randomizationfor Randomization??• People are not good at randomization

• The randomized strategy should depend on:o the adversary and the defenders’ utilitieso the environment parameters

o the defender’s resources.

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Multi-Robot Multi-Robot Adversarial Patrol: Adversarial Patrol: The EnvironmentThe Environment

• PerimeteroDivided into segmentsoUniform time-distanceoRobot travels through one segment per time

unit

• Adversaryo Tries to penetrate through the perimetero Takes t>0 time units to penetrate

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Robotic ModelRobotic Model• k homogenous robots

• Robotic movement model:o Robots’ movement is directedo Turning around “costs” τ time units

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Algorithm FrameworkAlgorithm Framework• Patrol algorithm:

o Continue straight with probability po Turn around with probability 1-p

• PPD: Probability of Penetration Detection

• p depends on the distance between robots and on the penetration time.

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Robot MovementRobot Movement

• Optimal: Robots are uniformly placed around the perimeter

• Coordinatedo If decide to turn around they do it simultaneouslyo Preserve uniform distance

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• Optimal: Robots are uniformly placed around the perimeter

• Coordinated

– If decide to turn around they do it simultaneously

– Preserve uniform distance

Robot MovementRobot Movement

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• Optimal: Robots are uniformly placed around the perimeter

• Coordinated

– If decide to turn around they do it simultaneously

– Preserve uniform distance

Robot MovementRobot Movement

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• Optimal: Robots are uniformly placed around the perimeter

• Coordinated

– If decide to turn around they do it simultaneously

– Preserve uniform distance

Robot MovementRobot Movement

Handling EventsHandling EventsWhat if a robot needs to inspect the penetration?

•Once a penetration is detected, one robot is extracted from the team to inspect it

•Coordinated attacks are beneficial to the adversary

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What Happens If What Happens If Penetration DetectedPenetration Detected??

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What Happens If Penetration What Happens If Penetration

DetectedDetected??• Robot that detected the penetration will inspect it

• Other k-1 robots will spread uniformly o To achieve optimal behavior for k-1 robots

Phase 1: k robots (before event), steady statePhase 2: ReorganizationPhase 3: k-1 robots (after event), steady state

Optimal patrol known

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Naïve ApproachNaïve Approach• Deterministic:

Each robot goes straight to its final position

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Randomized Randomized ReorganizationReorganization

• Challenges: o each robot needs to move differentlyo How much time to spend on the reorganization?

• We randomized over possible paths

• Finding the strategy is complex, in theory, but we used heuristics to find it in reasonable time

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Physical Security with Physical Security with

Bounded Resources: SummaryBounded Resources: Summary• Randomized patrolling or monitoring is necessary.

• Automated randomization is important

• Interesting problems? sarit@cs.biu.ac.il