Building cheap autonomous educational robots using obsolete technology
Gonzalo Tejera1, Alexander Sklar2, Santiago Margni3
1.
Introduction
Until not so long ago, robots used to be thought of only as a means towards achieving a goal, and not a goal in themselves. For instance, robots have been extensively used in factories and manufacturing plants to reduce costs and boost productivity and efficiency. Because of the progress of recent decades, the arising of mobile robotics as the next step was imminent. Robotics is a discipline encompassing several other areas; it is of its own right, an interdisciplinary area where both scholars and enthusiasts can converge, attracted either by the academic or recreational aspects. Murphy defines AI Robotics as the discipline that applies AI techniques to robotics. Its study areas are knowledge representation, natural language understanding, learning, problem planning and solving, inference, search, and vision [1]. There is a cornucopia of sporting events worldwide where the players happen to be autonomous robots. On one hand, there are events that include a large number of sports (robotic Olympic Games) and on the other hand events revolving around a specific activity. These competitions harbor many subproblems belonging to cutting-edge research and can be the source for projects at all levels, from first year to postgraduate. Using the recreational element, these endeavors have managed to bring together thousands of students to the world of Robotics and Artificial Intelligence. In this paper we present an account of the experiences at the Computer Science Department (Instituto de Computación) of the Universidad de la República in Montevideo, Uruguay. First, we present the motivation for using robotics in education, viz. mobile robotics in courses and competi-
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InCo-Fing-UdelaR, J. H. y Reissig 565, Uruguay.
[email protected]; University of Miami, Coral Gables, FL., USA.
[email protected]. 3 InCo-Fing-UdelaR, J. H. y Reissig 565, Uruguay.
[email protected]. 2
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Gonzalo Tejera , Alexander Sklar , Santiago Margni
tions. Then, we will expose the robotic developments that took place and their application to competitions and undergraduate courses.
2.
Motivations
The technological revolution that has been taking place for the last decades resulted in computers being now a ubiquitous part of any modern equipment. By using digital computers, one can transfer some of the complexity once hardwired in hardware to software. This allows cutting costs dramatically, and also permits the system to be much more configurable. The implications of technological revolutions on humans are not clear [2, 3]. The abundance of electronic components, along with their very short life cycle, account for an immense accumulation of these components over time. It is logical to try to reuse these components as a means of minimizing costs and being environment-friendly, allowing for the development of such projects in environments with scarce resources. A limited budget provides a fertile ground for ingenuous designs which utilize recycled and obsolete parts and basic construction processes.
3.
Building Low-cost Robots
From the mobile robotics point of view, there are several areas of research; if the problem is approached from a Computer Science standpoint, all of the AI Robotics areas can be tackled with the exception of the mechanical and electrical designs. One of the main limitations of working in mobile robotics is the need to actually have the robot. In general, robots however simple are expensive. This deters many educational institutions to from incorporating robots as a tool in their students’ education. Uruguay, unlike other countries as Japan, has no established culture in the robotics field; in general, the costs needed to research or partake in events are prohibitive. There are some construction kits (e.g. Lego Mindstorm®4) one can purchase at an affordable cost. These kinds of systems are not very scalable from the sensing or actuation points of view. They provide a small number of these devices, which have limited capabilities. These kits can be used with similar goals and overcoming several of their limitations as done in [4]. From an investment point of view, the alternative to these kits are application-specific developments. 4
http://mindstorms.lego.com
Building cheap autonomous educational robots using obsolete technology
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When building a robot on a tight budget, it is natural to use low-cost components and reuse unused hardware components. What is gained by using obsolete technology? The main motivation is determined by the costs associated with working in mobile robotics, but another motivation is the recycling of components that can still be taken advantage of. Some of the generated robotic prototypes are presented below, along with their main characteristics. All of the development process’s products (software, firmware, mechanical design and electrical design) are of free use, and are available in the respective projects’ websites. 3.1 ENZO5 For the ENZO robot [5], the main objective was to build a low-cost robot that was able to move autonomously. The principles followed by the design are: modularity, extensibility and simple electronic implementation. The design has a strong emphasis in the software aspect, which is clear in how modular the architecture is, and how solutions to problems are sought in the realm of software whenever possible. The robot contains a communications module that receives messages originating from a control system and relays them through an I2C bus to the destination module. The distributed architecture is depicted in Fig 1. To reduce costs, Enzo is controlled by a hierarchy of small microcontrollers (μC). The low-level behavior, sensor and actuator control is distributed in this architecture. High-level commands are received from a remote system through a RF link. It was necessary to recycle parts and components of either not-in-use or otherwise unusable equipment. The biggest sources of scrap material were dot-matrix printers, PC power sources, CD-ROM units, network cards and floppy disk drives. Among the obtained parts, we may highlight stepper motors, voltage regulators, crystals, resistors, capacitors, diodes, buttons, sockets, heat sinks, touch sensors, infrared sensors and connectors. The robot was mounted within the chassis of a standard PC power source. The total price for one robot was USD 80, which would have risen to USD 650 had new parts been used.
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http://www.fing.edu.uy/inco/grupos/mina/pGrado/construccion2003
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Gonzalo Tejera , Alexander Sklar , Santiago Margni
μC for Low Level Control
μC for Sensor Data
μC for Reactive Behavior
μC for Radio Frequency Communication
I2C bus Fig. 1. ENZO’s Distributed hardware architecture.
3.2 HDP6 The Human-Droid Prototype [6] was the first project developed in biped robotics in Uruguay. As is more often than not the case, lack of resources motivates creativity and craftiness. The budget for this project was extremely low (U$S 300), most of which was spent in the actuators. The robot has twelve degrees of freedom (joints), whose distribution is shown in Fig. 2. Each DOF is implemented by a servo motor, which was modified to output an additional signal giving the current position of the motor. The behavior logic is distributed between the robot (low-level behavior, in a µC) and a PC program (high-level behavior). By providing feedback on the current position of each motor, one can effectively control the overall behavior of the robot. The main design principles followed were: • A walking procedure that assured stability. This is achieved by limiting the range of movements to those leaving the robot stable at all times and at low individual velocities. The robot is quasistatically stable. Initial verifications of the procedure’s potential success were implemented as simulations using Open Dynamics Engine (ODE)7. • Anthropomorphic walking capabilities, achieved by having the needed number of orthogonal joints, and arranging them in a way that resembled the human body. • Extremely low cost, which implied doing all of the printed circuits, construction, assembly, etc. using only tools and techniques available to the general public at no cost.
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http://www.fing.edu.uy/~pgrobip http://www.ode.org
Building cheap autonomous educational robots using obsolete technology
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• Well-defined, extensible, generic architecture, usable for other robots, not necessarily bipeds.
Fig. 2. The Enzo Robot (left) and HDP’s morphology (right)
3.3 SumBot The construction of this new robot was driven by the need of having robots suitable to host local sumo event8. The driving goal the development of the SumBot mobile robot was to have a robust and reproducible robot fit for local mobile robotics events. Its design was based in the architecture of the ENZO robot and followed the majority of the principles that guided said development; this allowed the verification of the suitability of the proposed architecture. The main difference lies in the use of higher quality motors with higher torque. The SumBot was mounted on top of the metallic base of scrap hard disk drives and the wheels are protected with plate recycled from the chassis of CD-ROM drives. Three such robots were built with the purpose of being
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http://www.fing.edu.uy/inco/eventos/sumo.uy
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Gonzalo Tejera , Alexander Sklar , Santiago Margni
used in the SUMO 2006 local event and in the undergraduate course “AI Robotics”.
4.
Competitions
For several years, sporting tournaments have been taking place in different institutions, where the players are robots, constituting a work environment for multi-agent situated systems. These systems provide a research environment in robotics, AI, image processing, control, coordination, negotiation, communication and planning, among other areas. Other typical problems have also been used to promote research in AI. Chess is the most classical example of a problem that led to the discovery of several powerful search algorithms. However, there are certain criticisms against using such problems because these are considered too abstract, and thus ignore essential difficulties that arise in the real world [7]. 4.1 Robot soccer competitions Robot soccer came about in 1992 as a result of efforts to develop environments where multi-robot experiments could be conducted. In 1993, the first robot soccer tournament was held, motivating the creation of the international project RoboCup9 (Robot Soccer World Cup). In 1997, the FIRA10 (Federation of International Robot-soccer Associations) was created in order to provide newer generations with the challenge of working on mobile autonomous robot systems. Currently, robot soccer provides an adverse, dynamic, continuous and multi-agent environment, which represents an interesting challenge for which to develop and deploy systems. Soccer is a game that offers most of the technical challenges found in the advanced applications of robots in industrial settings. 4.2 Sumo competitions Beside the problem’s topics of academic interest, the reference to the sport itself usually generates great interest in the general public.
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http://www.robocup.org http://www.fira.net
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Building cheap autonomous educational robots using obsolete technology
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The recreational dimension present in sports generates a competitive environment spectators can relate to and enjoy, thus providing the perfect opportunity for hosting meetings between different groups or institutions. 4.3 Our Experience: SUMO.UY As a pioneering event, it was decided to simplify some of the characteristics these kinds of events have at an international level. This decision was taken to persuade potential participants, hesitant because of the construction cost associated to the robot or because of the difficulty of approaching the problem for the first time without any previous experience. Because of these potential turn offs, the tasks associated with the electromechanical design of the robot were resolved by the event’s crew. This allows to greatly lower the investment the participants have to make (they only need to program the robot strategy), thus motivating participation, and is much more attractive than using simulated robots as in programming competitions. This approach, which provides a platform with the mechanical design and the hardware problems already taken care of, has been successfully used in education [4, 9, 10]. The event then becomes a programming challenge targeting many problems of AI and robotics. Sumo.uy main league’s evolution is depicted in Table 1. This year a new freestyle league was added in which the participants are also responsible for the construction of the hardware, so as to include the remaining areas of IA and robotics and to promote the exchange of ideas. Table 1. Evolution of the SUMO.UY event Year 2004 2005 2006 2007
Robot Cube-like robot simulator, using ODE Simple robots using Lego Mindstorm SumBot v1.0 Robot SumBot v2.0 Robot
5. Conclusions and Future Work A humble beginning achieved interesting advances in mobile robotics research and development in Uruguay. Since 2002, 21 undergraduate students’ educational curricula, 12 students in the AI and Robotics course, 70 students in the Firmware Development course, 1 master’s student, 1 research agreement, 11 published papers, internships in the region and a local event are testament to the event’s ongoing success. The sumo event is free and open to all; in its inception it was seen as an early way to integrate
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Gonzalo Tejera , Alexander Sklar , Santiago Margni
high-school students into engineering topics, motivating them in applying mathematics and physics to mobile robotics. Thus, it is necessary to simplify the language and tools used to work with the SumBot, so we expect to research the potential use of the proposal explained in [11]. Currently, Doraemon, a computer vision software package, is used for both the local sumo event and the AI Robotics course despite having some problems with lighting changes and shadows. To improve the system’s robustness, we proposed the migration of the vision system to ERGO which has better patch recognition in more adverse conditions than its predecessor [12]. The short-time objective for the SumBot is to participate this year in events of the F-180 Robocup league. In particular, there is a strong interest to attend the CAFR 2007 in Buenos Aires, Argentina.
References 1. Murphy R. R. (2000) An Introduction to AI Robotics. The MIT Press, 1st edition. 2. Capek J, Capek K. (1961) R.U.R. and The Insect Play. Oxford University Press. 3. Rifkin J. (2004) The End of Work. Tarcher. 4. Papadimitriou V., Papadopoulos E. (2007) Development of an Educational Mechatronics Robotics Platform Using LEGO® Components IEEE Robotics and Automation Magazine,Vol.14, No. 3. 5. López G., Margni S., Martinez C., Tejera G. (2004) Construcción de Robots Móviles a Bajo Costo. Workshop de IA Aplicada a la Robótica Móvil, Facultad de Ciencias Exactas, Tandil, Argentina. 6. Lezama D., Sklar A., Tejera G. (2005) Contribución al desarrollo de robots bípedos de bajo costo. II IEEE LARS, São Luís, Brasil. 7. Brooks, R. A. (1990) Elephants Don't Play Chess- Robotics and Autonomous Systems (6), pp. 3–15. 8. Mirats Tur J.M., Pfeiffer C.F (2006) Mobile robot design in education. IEEE Robotics & Automation Magazine, Vol 13, No 1. 9. Lund, H. H. (1999) Robot Soccer in Education. Advanced Robotics Journal, 13:8, 737-752. 10. Blank, D.S., Kumar, D., Meeden, L., Yanco, H. (2005) Pyro: A Pythonbased Versatile Programming Environment for Teaching Robotics. ACM Journal on Educational Resources in Computing. 11. Baltes J., Sklar E., Anderson J. (2004) Teaching with RoboCup. In Proceedings of the AAAI Spring Symposium on Accessible Hands-on Artificial Intelligence and Robotics Education, pp 146-152 12. Baltes J., Anderson J. (2007) A Global Vision System for Robotics Courses. In Proceedings of the AAAI Spring Symposium on Resources for AI Education
