Pablo De Crist´foris, Sol Pedre, Javier Caccavelli, Andr´s Stoliar o e Departamento de Computaci´n, Facultad de Ciencias Exactas y Naturales, UBA o November 24, 2009
Mobile mini-robots are commonly used for research, education and popularization of science. There are many commercialmini-robots available. However, these minirobots often don’t quite ﬁt the characteristics needed for the tasks we want to pursue, and are very diﬃcult to adapt because thy have proprietary software and hardware. For Example, Khepera  mini-robots are wellknow, widely used for research and education, but they are very limmited when modiﬁcations to their sensing or programming capabilities areneeded. Another example of commercial mini robots are LEGO Mindstorm , which are a good tool for some activities of popularization of robotics in High School and University. However, if the students have to learn electronics or programming concepts for robotics, Mindstorm are not the right tools. They are also not suitable for research. Taking as a premise that “There’s no robotics withoutrobots”, and knowing that often the commercialy available robots do not have the characteristics we need when facing some tasks, developing new robots prototypes for research, education and popularization of science becomes a relevant task. Another important drawback in commercial minirobots is their cost, often too much for many latin american universities or study centers to aﬀord. This limits theopportunities to upgrade or by the robots, or work with many robots (multi-robots systems). The motivation of this work is to design and build a robot prototype of reduced cost with a reconﬁgurable sensing system and the characteristics that an embedded PC oﬀers to allow the on-board execution of computational intelligendce algorithms and to process the sensors information. In the rest of these articlewe present the ExaBot: a mini-robot developed in the Laboratorio de Rob´tica o y Procesamiento Embebido del Departamento de Computaci´n de la Facultad de Ciencias Exactas y Naturales, o Universidad de Buenos Aires. Section 2 describes some relevant details of robot architecture: processing units, communications, sensors, motors, etc. Section 3 discusses the results of this work. Finally,conclusions and future work are presented in section 4. 1
The main focus of this work is in the design, development and implementation of the electronics and software needed for the construction of the robot. For this reason, we choose to use a pre-built kit, in order to leave mechanical problems aside. We reviewed several models, and decided to use the Traxster Kit  because it has small dimmensions(229 mm length × 203 mm wide × 76 mm height), it is quite light because it is aluminium made, it comes with two direct current motors of 7,2 V and 2 Amp/hour, it has built-in quadrature encoders and two caterpillars as traction means, that allows the robot to move in diﬀerent environments and go over small obstacles.
The Exabot requires diﬀerent sensors to allow theimplementation of a wide variety of applications. For these reason, we included contact, line-following, distance and encoder sensors, and a video camera to capture images. To measure distances, infrarred telemeters and a sonar are used. The infrarred telemeters are short range punctual sensors (the range varies depending of the model, but is less than a meter). They are relatively fast and low cost. Sonarsare non-punctual, long range (several meters) sensors, but slower and more expensive. We choose to install a sonar in the front of the robot in order to achieve a long range sensing in the front, and a telemeter ring to sense the environment surrounding the robot within a rather short range. In this manner, the robot has both types of sensors and the cost is not rissen. The chosen sonar is...