Mobile Robots for a Synthetic Approach to

Mobile Robots for a Synthetic Approach to Interdisciplinary Research Francesco Mondada LSA - STI - EPFL

Research report February 15, 2005

Contents 1 Introduction

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2 From simulated to real robots 2.1 The Khepera robot . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Evolutionary robotics . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Collective robotics . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 From real robots to real animats 3.1 First animat design attempts . . . . . . . . . . . . . . . . . . . . . . 3.2 Swarm-bots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 From real animats to real animals

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5 Exploitation of the resulting robotics technology

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6 Conclusion

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Introduction

Valentino Braintenberg wrote in 1984 a pioneering book [4] describing how mobile robots can be used to validate some biological scientific hypothesis using an approach combining synthesis and analysis. Indeed, mobile robots, by their ability to process sensor information, move and interact with the environment, are a very special object made of technology but able to mimic the behavior of living organisms such as animals. From the engineering perspective we are used to apply a ”classical” synthetic approach to design robots. From the perspective of a biologist the robot can be a device to be observed, characterized and compared to others creatures. Joining synthesis and analysis we can create an interaction allowing to validate scientific hypothesis on how a natural system work. The results are directly available for engineers, thanks to the robotic implementation of the system. This research work is based on the exploitation of mobile robots to ensure this oscillation between analysis and synthesis of animal-like behavior. This report covers the work made by the author in the last 13 years, showing the progress and the results obtained in this field.

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From simulated to real robots The Khepera robot

In 1991, when the author made his diploma at EPFL, the revolution in artificial intelligence started by Rodney Brooks at MIT was already a full success. A large community was convinced by the control method suggested by Brooks [7] and centered on reactive systems, in opposition to model based systems where internal maps, planning and reasoning were the major elements [6]. Brooks also stressed very much the embodiment of the intelligence [5], pushing the implementation on real robots. In parallel the interest in artificial neural networks, artificial evolution and bioinspired systems was growing. The concept of Braitenberg was considered by biologists and engineers, but the gap between these two communities was still very important. Many biologists started to perform simulations of neural networks and bio-inspired systems, but the access to robot technology required too much specific competencies. For the robotic engineering community, the interest for biology was too small. In this context the author started to work on filling the gap between biologists and robotics. The goal was to make robotics accessible to all scientists interested by a real implementation of their model of creatures. The simulation was accessible to many communities, but the simulation was not the real world and the embodiment stressed by Brooks was an essential factor to validate the experiments done on artificial intelligence, bio-inspired brains and systems. The result of this work has been the Khepera miniature mobile robot, co-developed with Edoardo Franzi and Andr´e Guignard at the LAMI (Laboratoire de Microinformatique), directed by Prof. Nicoud [22]. This robot was very innovative because of its size (55mm in diameter) and the set of development tools associated (C compiler, LabVIEW interface, simple serial protocol for the control), making it accessible to beginners in the field of programming and robotics. The success of this tool in the scientific community has been impressive. The limitation to the simulation was broken and the scientific community moved on the Khepera robot, that became a new standard in the field. Since then, about 1000 universities worldwide have acquired Khepera robots for their research or education.

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A company, K-Team SA, has been created in 1995 to support this diffusion of the robot. The author, in parallel to his research, was director and president of the company between 1995 and 2000, selling the first 1000 Khepera robots especially in Japan and Europe. Both Khepera and the K-Team company received awards for the innovation and quality of the product. The Khepera has appeared on most covers of scientific journals, including Nature [15]. In 1999, the Heinz Nixdorf Institut in Paderborn, Germany, organized the first international Khepera workshop [16] to help Khepera users in exchanging information about their scientific results using this platform. This workshop still exists and has evolved toward a more general conference on miniature mobile robotics.

Figure 1: Khepera robots with several configurations applied to tasks of exploration or collective manipulation. The success of the Khepera robot is due to two main components: (i) the technological innovation and (i) the scientific results achieved on this platform by the author, at the beginning, and by the whole scientific community in the following years. This second element is well shown by the statistics of sales of K-Team1 showing that every important publication, such as the paper in Nature or other announcements of scientific results, has generated a short but very significant increase of sales. As mentioned, the author has been of course the first scientist using the Khepera tools and has played a pioneering role in exploring mechanisms such as neural networks based learning [27], collective systems [17] and artificial evolution [12].

2.2

Evolutionary robotics

In 1993 artificial evolution was applied to the control of abstract simulations of agents or very simplistic robot models. Nobody was able to apply this technique to real robots, for several reasons: • Artificial evolution is a long process, taking days of experimentation if applied on a real robot. Nobody tried or was able to run experiments of this duration. • During artificial evolution, early generations or bad mutations can generate crazy behaviors that make the robot bumping against the walls or perform similar destructive actions. Most existing robots were not capable to resist to this type of treatment. • Most robots were made by engineers for engineers, using very specific programming languages and interfaces. This world was hardly accessible to computer scientists or biologists interested to experiment new approaches. 1 confidential

information

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The Khepera robot was the perfect tool to overcome these problems: • Small, it can be used on a table, connected to the computer and powered by a simple cable equipped with a rotating contact. • The small size, because of physical laws, help in enhancing the mechanical robustness and thus reducing the consequences of collisions. • The very simple control interface available on Khepera, implemented as a simple ASCII protocol on a serial line, was accessible to every computer scientist or simple programmer. All were able, from their favorite programming environment, to send and receive characters on a serial line. Exploiting these characteristics of the Khepera robot, the author, in collaboration with Dario Floreano, made the very first experiment were artificial evolution was applied to a real robot [13]. This experiment started a new era of evolutionary robotic because, running on a real robot, evolution was able to exploit the characteristics of a real environment [21]. This key feature of evolutionary techniques was not exploited at all in simulation. Several experiments followed this first one: evolution of homing [14], grasping [12] or incremental evolution on several robots [20]. These experiments are considered as a reference in the field. A journal paper describing the homing experiment [14] has been classified as representative of an emerging and potentially important research areas by the Science Foresight Project2 , being one of the 481 most co-cited articles in physical and engineering sciences.

2.3

Collective robotics

Another field where the synthetic approach can generate very innovative scientific results is the study of the behavior of social insects. Around 1990 a group of biologists [10, 2] started to develop a theory explaining complex behaviors of social insects by very simple rules. The exploitation of the synthetic approach to validate this theories was interesting for both fields: for biologists to prove the new hypothesis and for engineers to discover a innovative (and simple) way to design robotic systems. The author started to apply his robotic know-how in this research field in 19961997. Beside the experimentation of collective mechanisms exploiting simple rules [20], a scientific goal was to define models that can explain the mechanisms behind this type of distributed system [19]. Khepera was again an excellent tool for this type of research because of its small size, allowing experiments with a large number of robots in a small experimentation area. The author, after some personal experiments made at the end of his PhD thesis, started and coached a research project on this topic, getting several key results related to the probabilistic models of collective systems [18, 17]. Alcherio Martinoli started his PhD during this project and is now one of the major international experts in the field. The author supported also the research effort of Michael Krieger and Jean-Bernard Billeter that explored division of labor and ended in a publication on Nature [15]. 2 The Science Foresight Project is a collaborative project between SPRU, the Science and Technology Policy Research institute located on the University of Sussex campus and Dstl, the UK Defence Science and Technology Laboratory part of the UK Ministry of Defence. The objective of the Science Foresight Project was to identify emerging and potentially important research areas primarily in the physical and engineering sciences using internationally recognized experts selected by co-citation analysis. http://www.sussex.ac.uk/Units/spru/foresight/

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From real robots to real animats

Khepera is a universal robot were the synthetic approach has been applied only at the control level. Using such a robot the embodiment principle is applied but the body is fixed and predefined, limiting very much the application of the methodology. For living organisms the body play an essential role and is evolved together with the brain. It was therefore important to make a new step in the synthetic approach in order to create animats, artificially engineered organisms.

3.1

First animat design attempts

The design of a complete new mobile robot (mechanics, electronics and software) is not a simple task. This type of development takes several man-years, and the goal to create an artificially engineered organism in the framework of a synthetic approach makes this task even more difficult. Some attempts in this direction have been made exploiting the Khepera and the Koala robot (a bigger model) as a basic platform, using their modularity to add specific mechanical and electronic devices. Good results have been achieved by the author for some applications (for instance an autonomous vacuum cleaner based on the Koala robot [28]) but an optimal synthetic approach requires a full re-design of the robot.

3.2

Swarm-bots

Based on the competencies acquired in evolutionary robotics, collective intelligence and robotic design, the author participated to the definition of the swarm-bots european project3 , situated at the intersection of these three fields and exploiting in an optimal way the synthetic approach. The prime goal of this project is the study of a self-organizing robotic systems called swarm-bots and inspired upon the selfassembling behavior of social insects [1, 3] (see figure 2). The swarm-bot exploits the self-assembling property to create a robotic entity composed of many (typically 10 to 30) smaller robots assembled together (see figure 3). These small robots are called s-bots. Each s-bot is a fully autonomous mobile robot equipped with assembling capacities. It can physically connect to other s-bots to form a swarm-bot. The swarm-bot can achieve tasks that are impossible to achieve for a single s-bot, like for instance passing gaps larger than the s-bot size or passing steps higher than the robot itself. The hardware structure is combined with a distributed adaptive control architecture inspired upon ant colony behaviors.

Figure 2: Social insects are able to create structures with their own bodies to solve complex tasks such as pass from one branch to another (on a tree) or pull a big c leaf. Guy Theraulaz [1]

3 http://www.swarm-bots.org

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Figure 3: Typical situations where a swarm-bot robot exploit self-assembling to solve a complex task.

The development of the swarm-bot robot [23] and the related experimentation of self-assembling mechanisms [11] is a very complete example of synthetic approach. It allows both the validation of biological hypothesis and the identification of new approaches to robotic problems such as all-terrain navigation [26] and distributed intelligence [9]. The swarm-bot implemented during this project is the first system demonstrating self-assembling capabilities between many (10-30) real mobile robots. Exploiting biological inputs for the self-assembling capability [25], this system is the first robot able to self-assemble in all terrain conditions (not only a flat well defined surface).

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From real animats to real animals

Swarm-bot is a good example where characteristics of biological systems have been embedded in a artificial creature. The next step would be to create artificial creatures that can interact with animals and be accepted in their societies. This is the general goal of the Leurre4 project, the author joined at the end of 2004 as team leader. Until now, the researchers of the project developed the InsBot robot [8] able to interact with cockroaches (see figure 4). The main goal is to demonstrate that it is possible to mix insects and specifically designed robots that interact and communicate. The project want to show that lure robots (in our case the InsBot) allow the control of the global behavior of a mixed-society. The author is bringing his robotic know-how to finalize the methodology of lure robots design and exploit it for the control of the behavior of group of chickens.

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Exploitation of the resulting robotics technology

The author exploited the robotic know-how accumulated in the research work presented above in several application domains: • Education: The author introduced the use of robots in several teaching activities, improving the motivation of students by a problem based learning approach. He is the organizer of the EPFL annual robotic contest. • Robotic applications: The author contributed to the development of several applications, spanning from airduct robotic inspection to internet robot remote control. 4 http://leurre.ulb.ac.be

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Figure 4: Typical situations of interaction between cockroaches and the InsBot robot.

• Art: The author contributed to more than ten artistic installations based on robotics technology, creating innovative installations such a fully autonomous robot theater [24]. For one of the installations he received a mention at Ars Electronica, the major international event in art and technology.

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Conclusion

The author provided a major scientific contribution in an interdisciplinary research field situated between biology and engineering, exploiting the interaction between engineering synthesis and scientific analysis. The research results achieved have strongly influenced the international scientific community: • The Khepera robot and the related scientific results have pushed the research community to move from simulations to real world experiments. The author has contributed by providing the robotic tools and showing how these tools can be exploited by achieving innovative research results. • The contribution of the author in applying evolutionary techniques to real mobile robots has been decisive for the affirmation of the evolutionary robotics research field. • The author has been a pioneer in collective robotics, performing some experiments that are considered as references in the field and starting several projects that strongly influenced the field. • The swarm-bot robot is probably the most complex system at the international level designed in the perspective of the synthetic approach described in this document. The scientific results achieved using this system open new perspectives in the field of swarm intelligence. • The ongoing work of the author on the integration of robots and animals to create mixed societies is a fully new field and preliminary results show a potential big impact on the understanding of animal societies.

References [1] C. Anderson, G. Theraulau, and J.-L. Deneubourg. Self-assemblages in insect societies. Insectes Sociaux, 49:99–110, 2002. [2] R. Beckers, O. E. Holland, and J.-L. Deneubourg. From local actions to global tasks: Stigmergy and collective robotics. In Brooks R. and Maes P., editors,

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Proceedings of the the Fourth Workshop on Artificial Life, Boston, MA, July, 1994, pages 181–189. MIT Press, 1994. [3] E. Bonabeau, M. Dorigo, and G. Theraulaz. Swarm Intelligence: From Natural to Artificial Systems. Oxford University Press, New York, NY, 1999. [4] Valentino Braitenberg. Vehicles: Experiments in Synthetic Psychology. MIT Press, Cambridge, Massachusetts, USA, 1984. [5] R. A. Brooks. Elephants don’t play chess. Robotics and Autonomous Systems, 6:3–15, 1990. Special issue. [6] R. A. Brooks. Intelligence without representation. 47:139–59, 1991.

Artificial Intelligence,

[7] Rodney Allen Brooks. A Robust Layered Control System for a Mobile Robot. IEEE Journal of Robotics and Automation, 1(2):14–23, April 1986. [8] G. Caprari, A. Colot, R. Siegwart, J. Halloy, and J.-L. Deneubourg. Insbot: Design of an autonomous mini mobile robot able to interact with cockroaches. In Proceedings of the IEEE International Conference on Robotics and Automation, ICRA2004, pages 2418–2423, Piscataway, NJ, 2004. IEEE. Conference, New Orleans. [9] E. S¸ahin, T.H. Labella, V. Trianni, J.-L. Deneubourg, P. Rasse, D. Floreano, L. Gambardella, F. Mondada, S. Nolfi, and M. Dorigo. SWARM-BOTS: Pattern formation in a swarm of self-assembling mobile robots. In A. El Kamel, K. Mellouli, and P. Borne, editors, Proceedings of the IEEE International Conference on Systems, Man and Cybernetics, Hammamet, Tunisia, October 6-9, 2002. Piscataway, NJ: IEEE Press. [10] J.-L. Deneubourg, S. Goss, J. M. Pasteels, D. Fresneau, and J.-P. Lachaud. Selforganisation mechanisms in ant societies (ii): Learning in foraging and division of labor. Behavior in Social Insects, Experientia Supplementum, 54:177–196, 1987. [11] M. Dorigo, V. Trianni, E. S¸ahin, R. Groß, T. H. Labella, G. Baldassarre, S. Nolfi, J.-L. Deneubourg, F. Mondada, D. Floreano, and L. M. Gambardella. Evolving self-organizing behaviors for a swarm-bot. Autonomous Robots, 17(2– 3):223–245, 2004. [12] D. Floreano and F. Mondada. Active perception, navigation, homing, and grasping: An autonomous perspective. In J-D. Nicoud and P. Gaussier, editors, Proceedings of the conference From Perception to Action. IEEE Press, Los Alamitos, CA, 1994. [13] D. Floreano and F. Mondada. Automatic creation of an autonomous agent: Genetic evolution of a neural-network driven robot. In D. Cliff, P. Husbands, J. Meyer, and S. W. Wilson, editors, From Animals to Animats III: Proceedings of the Third International Conference on Simulation of Adaptive Behavior. MIT Press-Bradford Books, Cambridge, MA, 1994. [14] D. Floreano and F. Mondada. Evolution of homing navigation in a real mobile robot. IEEE Transactions on Systems, Man, and Cybernetics-Part B, 26:in press, 1996. [15] M. J. B. Krieger, J.-B. Billeter, and L. Keller. Ant-like task allocation and recruitment in co-operative robots. Nature, 406:992–995, 2000. 9

[16] A. L¨ offler, F. Mondada, and U. R¨ uckert, editors. Experiments with the MiniRobot Khepera. Heinz Nixdorf Institut, Paderborn, Germany, 1999. Proceedings of the 1st International Khepera Workshop. [17] A. Martinoli, A. J. Ijspeert, and F. Mondada. Understanding collective aggregation mechanisms: From probabilistic modelling to experiments with real robots. Robotics and Autonomous Systems, 29:51–63, 1999. Special Issue on Distributed Autonomous Robotic Systems. [18] A. Martinoli and F. Mondada. Probabilistic modelling of a bio-inspired collectiveexperiment with real robots. In P. Dario T. Lueth, R. Dillman and H.Wrn, editors, Proc. of the Fourth Int. Symp. on Distributed Autonomous Robotic Systems DARS-98, pages 289–308, Karlsruhe, Germany, 1998. [19] A. Martinoli, M. Yamamoto, and F. Mondada. On the modelling of bio-inspired collective experiments with real robots. 1997. [20] F. Mondada. Conception de structures neuronales pour le contrle de robots mobiles autonomes. PhD thesis, 1997. [21] F. Mondada and D. Floreano. Evolution and mobile autonomous robotics. In E. Sanchez and M. Tomassini, editors, Towards Evolvable Hardware. SpringerVerlag, Lecture Notes in Computer Science, 1995. [22] F. Mondada, E. Franzi, and P. Ienne. Mobile robot miniaturization: A tool for investigation in control algorithms. In Proceedings of the Third International Symposium on Experimental Robotics, Kyoto, Japan, 1993. [23] F. Mondada, A. Guignard, M. Bonani, D. B¨ar, M. Lauria, and D. Floreano. Swarm-bot: From concept to implementation. In Proceedings of the 2003 IEEE/RSJ International Conference on Intelligent Robot and Systems (IROS 2003), pages 1626–1631, Las Vegas, Nevada, US, October 27 - 31, 2003 2003. [24] F. Mondada and S. Legon. Interactions between art and mobile robotic system engineering. In Proceedings of the 8th International Symposium on Evolutionary Robotics (ER2001), 2001. [25] F. Mondada, G. C. Pettinaro, A. Guignard, I. Kwee, D. Floreano, J.-L. Deneubourg, S. Nolfi, L.M. Gambardella, and M. Dorigo. Swarm-bot: a new distributed robotic concept. Autonomous Robots, 17(2–3):193–221, 2004. [26] F. Mondada, G. C. Pettinaro, I. Kwee, A. Guignard, L. Gambardella, D. Floreano, S. Nolfi, J.-L. Deneubourg, and M. Dorigo. SWARM-BOT: A swarm of autonomous mobile robots with self-assembling capabilities. In C.K. Hemelrijk and E. Bonabeau, editors, Proceedings of the International Workshop on Selforganisation and Evolution of Social Behaviour, pages 307–312, Monte Verit`a, Ascona, Switzerland, September 8-13, 2002. University of Zurich. [27] F. Mondada and P. F. M. J. Verschure. Modeling system-environment interaction: The complementary roles of simulations and real world artifacts. In Proceedings of the Second European Conference on Artificial Life, Brussels, 1993. [28] I. Ulrich, F. Mondada, and J.D. Nicoud. Autonomous vacuum cleaner. Robotics and Autonomous Systems, 19:233–245, 1997.

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