University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Mechanical (and Materials) Engineering -- Mechanical & Materials Engineering, Department Dissertations, Theses, and Student Research of 4-2014 TOWARDS A SUSTAINABLE MODULAR ROBOT SYSTEM FOR PLANETARY EXPLORATION S. G. M. Hossain University of Nebraska-Lincoln, [email protected] Follow this and additional works at: http://digitalcommons.unl.edu/mechengdiss Part of the Applied Mechanics Commons, Electro-Mechanical Systems Commons, Other Astrophysics and Astronomy Commons, and the Robotics Commons Hossain, S. G. M., "TOWARDS A SUSTAINABLE MODULAR ROBOT SYSTEM FOR PLANETARY EXPLORATION" (2014). Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research. 69. http://digitalcommons.unl.edu/mechengdiss/69 This Article is brought to you for free and open access by the Mechanical & Materials Engineering, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. TOWARDS A SUSTAINABLE MODULAR ROBOT SYSTEM FOR PLANETARY EXPLORATION by S. G. M. Hossain A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy Major: Mechanical Engineering and Applied Mechanics Under the Supervision of Professor Carl A. Nelson Lincoln, Nebraska April, 2014 TOWARDS A SUSTAINABLE MODULAR ROBOT SYSTEM FOR PLANETARY EXPLORATION S. G. M. Hossain, Ph. D. University of Nebraska, 2014 Advisor: Carl A. Nelson This thesis investigates multiple perspectives of developing an unmanned robotic system suited for planetary terrains. In this case, the unmanned system consists of unit-modular robots. This type of robot has potential to be developed and maintained as a sustainable multi-robot system while located far from direct human intervention. Some characteristics that make this possible are: the cooperation, communication and connectivity among the robot modules, flexibility of individual robot modules, capability of self-healing in the case of a failed module and the ability to generate multiple gaits by means of reconfiguration. To demonstrate the effects of high flexibility of an individual robot module, multiple modules of a four-degree-of-freedom unit-modular robot were developed. The robot was equipped with a novel connector mechanism that made self-healing possible. Also, design strategies included the use of series elastic actuators for better robot-terrain interaction. In addition, various locomotion gaits were generated and explored using the robot modules, which is essential for a modular robot system to achieve robustness and thus successfully navigate and function in a planetary environment. To investigate multi-robot task completion, a biomimetic cooperative load transportation algorithm was developed and simulated. Also, a liquid motion-inspired theory was developed consisting of a large number of robot modules. This can be used to traverse obstacles that inevitably occur in maneuvering over rough terrains such as in a planetary exploration. Keywords: Modular robot, cooperative robots, biomimetics, planetary exploration, sustainability. DEDICATION To my amazing Mom and Dad. iii ACKNOWLEDGEMENTS Human life has a lot of similarities with a distributed robot system sustaining in a planetary environment, well, except for the reproduction part. We live for a few decades and in this limited time we acquire knowledge from our surroundings – the knowledge developed by the earlier generations, as well as that acquired by our contemporaries based on earlier works. In this way the entire human civilization moves forwards utilizing the knowledge and technology developed by different people living in different decades and even centuries. This was a realization along the long and interesting path of my doctoral study, because achieving the level of my accomplishment would not be possible without the contributions of many. My doctoral research was funded by NASA Nebraska Space Grant and NASA EPSCoR which literally opened up the gateway of the universe in front of me. Throughout my study, my major advisor Dr. Carl Nelson guided me towards academic excellence with his truly transformational advising. His flexible nature left space for me to develop my own ideas which helped eventually to develop myself as an independent researcher. His constructive criticisms guided me to the right path, and his availability made me feel comfortable. My dissertation committee members – especially the readers of this dissertation spent their valuable times to carefully review my work. Thanks Drs. Prithviraj Dasgupta, Carrick Detweiler, Shane Farritor and Wieslaw Szydlowski. Their feedback was considered with care and these have undoubtedly strengthened this dissertation. At this point, I would like to thank all my teachers and mentors throughout my academic life, because of whom I have reached to my terminal degree successfully. My family was a big support for my education and their encouragements always gave me inspirations to reach for higher ground. My friends also provided me with support whenever I needed it throughout this long path. Special thanks to Zhanping Xu for his significant iv contributions with the study of cooperative load transport, also, to Qing Shu and Andrew Mittleider for their cooperation in parts of this dissertation. Thanks to Drs. Leen-Kiat Soh, P.V. Manivannan and Mark Bauer for providing insightful feedback on my projects. I would also like to thank the members of Dr. Nelson’s RANDOM Lab and Dr. Dasgupta’s CMANTIC Lab, they always provided valuable technical suggestions and also working with them was a fun experience. Also, special thanks go to Google for their powerful search engine which undoubtedly saved a huge amount of time to search for scholarly articles and products online. Thank you, Isaac Asimov and Carl Sagan – your writings inspire me to become a roboticist and a space explorer. Finally I would like to thank the two countries that have graciously provided resources for my education. My home country Bangladesh provided me with a quality engineering education almost free of cost. And the United States gave me the opportunities of taking my education to a global level which I mentioned in my applications for studying abroad in the past. The experiences throughout my doctoral study were quite amazing and nourishing and I intend to use this as a springboard to explore further. v Contents Chapter 1: Introduction ................................................................................................................ 1 1.1 Introduction ............................................................................................................................ 1 1.2 Problem description and solution strategies ........................................................................... 2 1.3 Modular self-reconfigurable robots ....................................................................................... 5 1.3.1 Types of modular robots ................................................................................................. 6 1.3.2 Modular robot state of the art ......................................................................................... 8 1.4 Planetary exploration and sustainability .............................................................................. 10 1.5 Self-healing in a modular robot system ............................................................................... 13 1.5.1 Motivation ..................................................................................................................... 13 1.5.2 Docking mechanisms state of the art ............................................................................ 14 1.5.3 Self-healing capable docking mechanisms .................................................................... 15 1.6 Modular robot locomotion gaits ........................................................................................... 16 1.6.1 Motivation ..................................................................................................................... 16 1.6.2 Related Work ................................................................................................................. 17 1.7 Cooperative payload transport ............................................................................................. 19 1.7.1 Motivation ..................................................................................................................... 19 1.7.2 Collective behavior in nature ........................................................................................ 20 1.7.3 Bioinspired multi-robot systems .................................................................................... 22 1.7.4 Multi-robot box-pushing ............................................................................................... 22 1.7.5 Multi-robot payload transport ...................................................................................... 23 1.8 Obstacle traversal ................................................................................................................. 25 1.8.1 Motivation ..................................................................................................................... 25