Contents
1. Introduction 1
1.1. Problem Statement . . . . 1
1.2. Preview of Contributions . . . . 2
1.3. Outline . . . . 4
I. Background 7 2. Distributed Robotics 9 2.1. Brief Historical Account . . . . 9
2.2. System Architectures . . . . 10
2.2.1. Multi-Robot Systems . . . . 10
2.2.2. Modular Robot Systems . . . . 14
2.2.3. Swarm-Bot: A Hybrid System . . . . 15
3. Biologically-Inspired Computing 19 3.1. Evolutionary Algorithms . . . . 19
3.1.1. Biological Roots . . . . 19
3.1.2. Overview . . . . 21
3.2. Swarm Intelligence . . . . 23
3.2.1. Biological Roots . . . . 23
3.2.2. Overview . . . . 26
II. Related Work 27 4. Self-Assembly at the Macroscopic Scale 29 4.1. A Brief Excursion into Natural Systems . . . . 29
4.2. Self-Assembly of Externally Propelled Components . . . . 31
4.2.1. Penrose’s Template-Replicating Modules . . . . 31
4.2.2. Hosokawa et al.’s Self-Assembling Hexagons . . . . 32
4.2.3. Breivik’s Template-Replicating Polymers . . . . 33
4.2.4. White et al.’s Self-Assembling Programmable Modules . . . . 33
4.2.5. Griffith et al.’s Electromechanical Assemblers . . . . 33
4.2.6. White et al.’s Systems for Self-Assembly in 3-D . . . . 35
4.2.7. Bishop et al.’s Self-Assembling Hexagons . . . . 35 4.2.8. Bhalla & Bentley’s Self-Assembling Special Purpose Modules 36
xiii
Contents
4.3. Self-Assembly of Self-Propelled Components . . . . 36
4.3.1. Reproductive Sequence Device (RSD) . . . . 36
4.3.2. CEBOT . . . . 38
4.3.3. PolyBot . . . . 38
4.3.4. CONRO . . . . 39
4.3.5. Super-Mechano Colony (SMC) . . . . 39
4.3.6. Bererton & Khosla’s System for Cooperative Repair . . . . . 40
4.3.7. Swarm-Bot . . . . 40
4.3.8. Molecubes . . . . 41
4.3.9. M-TRAN . . . . 42
4.4. Taxonomy and Design Principles . . . . 42
4.4.1. Physical and Electrical Design Characteristics . . . . 42
4.4.2. Outcome and Analysis of Self-Assembly Experimentation . . 51
4.4.3. Process Control . . . . 51
4.4.4. Functionality . . . . 52
5. Group Transport at the Macroscopic Scale 55 5.1. A Brief Excursion into Natural Systems . . . . 55
5.2. Pushing and Caging Strategies . . . . 57
5.3. Grasping and Lifting Strategies . . . . 58
III. Self-Assembling Robots: Control and Analysis in Simulation 59 6. The Adaptive Value of Self-Assembly—Evolution of Solitary and Group Transport 63 6.1. Methods . . . . 63
6.1.1. Task . . . . 63
6.1.2. Simulation Model . . . . 64
6.1.3. Controller . . . . 65
6.1.4. Evolutionary Algorithm . . . . 66
6.2. Results . . . . 68
6.2.1. Quantitative Analysis . . . . 70
6.2.2. Behavioral Analysis . . . . 72
6.2.3. Scalability . . . . 77
7. The Benefit of Biasing Self-Assembly—Evolution of Group Transport 79 7.1. Methods . . . . 79
7.1.1. Simulation Model . . . . 79
7.1.2. Controller . . . . 81
7.1.3. Evolutionary Algorithm . . . . 82
7.2. Results . . . . 83
7.2.1. Quantitative Analysis . . . . 84
7.2.2. Scalability . . . . 86
xiv
Contents
8. An Explicit Task Decomposition—Evolution of Self-Assembly and Group
Transport in Heterogeneous Teams 89
8.1. Methods . . . . 89
8.1.1. Simulation Model . . . . 90
8.1.2. Controller . . . . 90
8.1.3. Evolutionary Algorithm . . . . 95
8.2. Results . . . . 96
8.2.1. Quantitative Analysis (Assembly Module) . . . . 97
8.2.2. Scalability (Assembly Module) . . . . 98
8.2.3. Quantitative Analysis (Transport Module) . . . 103
8.2.4. Scalability (Transport Module) . . . 104
9. Discussion 107 IV. Self-Assembling Robots: Experiments on Self-Assembly Per Se 111 10. Experiments on Flat Terrain 113 10.1. Remarks on Transfer from Simulation to Reality . . . 113
10.2. Autonomous Docking of a Robot to a Prey . . . 116
10.2.1. Experimental Setup . . . 117
10.2.2. Results . . . 117
10.3. Self-Assembly of Two Robots . . . 118
10.3.1. Experimental Setup . . . 118
10.3.2. Results . . . 119
10.4. Self-Assembly of a Group of Six Robots and a Prey . . . 121
10.4.1. Experimental Setup . . . 121
10.4.2. Results . . . 121
10.5. Self-Assembly of a Group of 16 Robots . . . 122
10.5.1. Experimental Setup . . . 122
10.5.2. Results . . . 123
11. Experiments on Rough Terrain 125 11.1. Autonomous Docking of a Robot to a Prey . . . 125
11.1.1. Experimental Setup . . . 126
11.1.2. Results . . . 126
11.2. Self-Assembly of a Group of Six Robots and a Prey . . . 127
11.2.1. Experimental Setup . . . 127
11.2.2. Results . . . 128
12. Experiments with a Different Modular Robotic Platform 131 12.1. Remarks on Transfer from Swarm-Bot to Super-Mechano Colony . . 131
12.2. Self-Assembly of Two Robots . . . 133
12.2.1. Experimental Setup I (Initial Orientation) . . . 133
xv
Contents
12.2.2. Results I . . . 134
12.2.3. Experimental Setup II (Approaching Angle) . . . 134
12.2.4. Results II . . . 135
12.2.5. Experimental Setup III (Difficult Starting Positions) . . . 135
12.2.6. Results III . . . 135
12.3. Self-Assembly and Pattern Formation in a Group of Four Robots . . 137
13. Discussion 139 V. Self-Assembling Robots: Experiments in the Context of Group Transport 143 14. Experiments with Pre-Assembled, Homogeneous Groups of Robots 145 14.1. Remarks on Transfer from Simulation to Reality . . . 145
14.2. Group Transport on Flat Terrain . . . 146
14.2.1. Experimental Setup . . . 146
14.2.2. Results . . . 148
14.3. Group Transport on Rough Terrain . . . 151
14.3.1. Experimental Setup . . . 151
14.3.2. Results . . . 151
15. Experiments with Pre-Assembled, Heterogeneous Teams of Robots 153 15.1. Remarks on Transfer from Simulation to Reality . . . 153
15.2. Group Transport by a Team of One Blind and One Non-Blind Robot 153 15.2.1. Experimental Setup . . . 154
15.2.2. Results . . . 155
15.3. Group Transport by a Team of Six (Blind and Non-Blind) Robots . 157 15.3.1. Experimental Setup . . . 159
15.3.2. Results . . . 159
16. Experiments with Robots that Self-Assemble 163 16.1. Group Transport Towards a Light Beacon . . . 163
16.1.1. Experimental Setup . . . 163
16.1.2. Results . . . 164
16.2. Group Transport Along a Self-Organized Path . . . 167
16.2.1. Experimental Setup . . . 168
16.2.2. Results . . . 168
17. Discussion 171
18. Further Work 175
19. Conclusions 177
xvi
