Nuttapon Boonpinon Advisor Dr. Attawith Sudsang Department of Computer Engineering,Chulalongkorn University Pattern Formation for Heterogeneous Multi-Robot Systems 1

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Why Multi-Robot ? Some task can’t be done by a single robot 4

Why Multi-Robot ? Require more than one type of robot 5

Why Multi-Robot ? Robustness and False Tolerance is required 6

Multi-Robot vs. Single Robot Go! Get the Ball 7

Multi-Robot vs. Single Robot Go! Get the Ball Do you see the ball? 8

Multi-Robot vs. Single Robot Go! Get the Ball I will get it No, you get it You Get it I will get it 9

Multi-Robot vs. Single Robot 10 Go! Get the Ball 10

Multi-Robot Research Areas Task Allocation / Task Planning Communication Protocol Cooperative Mapping / Localization Motion Coordination / Pattern Formation 11

Multi-Robot Pattern Formations Control Sensors Locomotion Local Planning Global Planning Range Sensor / Motor PID, other control system Obstacle Avoidance Navigation 12

Multi-Robot Pattern Formations Control Sensors Locomoti on Local Planning Global Planning Control Sensors Locomoti on Local Planning Global Planning Control Sensors Locomoti on Local Planning Global Planning Pattern Formation robot1 robot2 robot3 13

Multi-Robot Pattern Formation “ Formation Algorithm 14

Multi-Robot Pattern Formations Control Sensors Locomoti on Local Planning Global Planning Control Sensors Locomoti on Local Planning Global Planning Control Sensors Locomoti on Local Planning Global Planning Pattern Formation robot1 robot2 robot3 Pattern Formation 15

Multi-Robot Pattern Formation Formation 16

Multi-Robot Pattern Formation Formation Global Communication 17

Multi-Robot Pattern Formation Formation Local Communication 18

Multi-Robot Pattern Formation Formation No Communication 19

Multi-Robot Formation Application Robotic Traffic Barrel Land-mine Detection 20

Literature Review :: Multi-Robot Formation Early Researches :: Arai 89, Reynolds 87a,b Decentralized :: Parker 93, Balch98 Mataric 02, Desai 02, Centralized :: Farritor02, Manuela96 21

Early Research :: Reynolds’ Boid A distributer behavior model Used in animation to reduce animators’ work involving many agents Used in “Batman Returns” 22

Centralized Pattern Formation Farritor ’02 “Intelligent Highway Traffic Barrel” Forming a robotic traffic barrel taper Each barrel’s cost must be low enough to allow frequent replacements. A lead robot is used to command each barrel 23

Decentralized Pattern Formation :: Balch 98 Balch’98 “Behavior-based Formation Control for Multi-robot Teams” Propose 4 types of formation Line Formation Column Formation

Decentralized Pattern Formation :: Balch 98 Wedge Formation Diamond Formation

Decentralized Pattern Formation :: Balch 98 Use motor schema control scheme Move to Goal Avoid Static Obstacle Maintain Formation Avoid Robot ∑ ∑ W W W W W W W W Output 26

Decentralized Pattern Formation :: Balch 98 3 type of location determination Unit Center Leader Reference Neighbor Reference 27

Decentralized Pattern Formation::Desai 02 Desai ’02 “A graph theoretic approach for modeling mobile robot team formations” Use graph to represent formation relationship between robot l-l relation l l l  l-  relation 28

Centralized vs. Decentralized 29

30 Formation Decentralized Pattern Formation

Communication Robot Multi- Robot Single Robot Centralized Decentralized No Communication Local Communication Global Communication Global Communication 31

Robot Model Robot Sensing Range Robot θ d Distance d and angle θ can be sensed by the robot Each robots can identify type of robots in range 32

Heterogeneity 33 Oxygen Image CO 2 Oxygen CO 2 Image

Our Problems Decentralized Pattern Formation for Multi-Robot Systems But, What kind of formations ? Line? Diamond? No… Heterogeneity Constrained Coverage Squad Formation 34 Circular Formation

Arrange heterogeneous robot group into single circular shape 35

Circular Formation 36

Circular Formation Challenge Circularity is a global property But we can measure only local No explicit geometric properties in each agent 37

Related works :: Circular Formation Sugihara and Suzuki ‘99, “Distributed Algorithms for Formation of Geometric Patterns with Many Mobile Robots” Each robots follow this rule If distance between itself and the furthest robot is more than diameter of circle then move toward that robot Else, move away from the closet robot 38

Related works :: Circular formation Sometime converged to Reuleaux's Triangle Need information of all robot in workspace Embodied explicit geometric properties of circle in algorithm Reuleaux's Triangle 39

Squad Formation Form a squad composed of k predefined types and distribute squad to cover the workspace Final workspace Initial workspace 40

Squad Formation Challenges No global information, do not know where agent should head Limited communication Scalability 41

Related Works :: Squad Formation Nguyen et. Al. ‘03 “Autonomous Communication Relays for Tactical Robots” Composed of ‘Master’ and ‘Relay slave’ Relay slave keep communication Master  Base alive 42

Constrained Coverage Uniformly cover the workspace only in their corresponding region 43

Constrained Coverage Initial WorkspaceFinal Workspace 44

Constrained Coverage Challenge No prior knowledge about map No absolute localization Uniformly cover the workspace Cover workspace only space that related to agents’ type 45

Related Works :: Constrained Coverage Coverage No n- Constrained Constrained Potential Field Based Voronoi Based Communication Range Communication Type 46

Related Works :: Constrained Coverage Howard et. Al. ‘02 “Mobile Sensor Network Deployment using Potential Fields: A Distributed, Scalable Solution to the Area Coverage Problem” Self-Deployment Implement artificial potential field to disperse mobile sensor network nodes 47

Related Works :: Constrained coverage Tan et. Al. ’04 “Modeling Multiple Robot Systems for Area Coverage and Cooperation “ Robots move to centroid of voronoi region 48

Related Works :: Constrained Coverage Rekleitis et. Al.‘03 “ Limited Communication, Multi-Robot Team Based Coverage” Dynamic Coverage Line of sight communication Cell-Decomposition based 49

Related Works :: Constrained Coverage 50

Related Works :: Constrained Coverage Coverage No n- Constrained Constrained Potential Field Based Voronoi Based Communication Range Communication Type Region 51

3 Problems but common goals Squad FormationCircular Formation Constrained Coverage “Simple” Distributed Algorithm Low computational power needed Need no/local communication only Use Limited-range Sensor “Simple” Distributed Algorithm Low computational power needed Need no/local communication only Use Limited-range Sensor 52

Scope A distributed algorithm for controlling a group of heterogeneous robots in simulation For circular formation, the algorithm must outperform the current method (suzuki’99) For squad formation and constrained coverage, the algorithm must complete the task with acceptable performance Purpose performance matrices for squad formation and constrained coverage 53

Work Plan Preliminary works Study related works Develop algorithm for circular formation Ongoing works Develop algorithm for squad formation and constrained coverage Study performance matrices for squad formation and constrained coverage 54

Thank you, Any question ? 55

Sugihara and Suzuki 56

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