2011 International Conference on Electronic Devices, Systems and Applications (ICEDSA)

Development of a multitasking mobile robot for the construction of educational robotics kits

*Jose Ahirton Batista Lopes Filho, **Will Ribamar Mendes Almeida, **Sergio Gomes Martins *Centro de Ciencias Tecno16gicas, Universidade Estadual do Maranhao - VEMA, Sao Luis, Brasil

**Centro Universitario do Maranhao - UNICEUMA, Sao Luis, Brasil

jose.ahirton@dec.uema.br, willalmeida@hotmail.com, sergio.martins@ceuma.br

Abstract - This article aims to develop the design and implementation of a six wheeled multitasking mobile robot, built with electronic garbage and easy to obtain materials for the viability of educational kits to be used for teaching robotics in schools or colleges. This educational kit is based on the PIC16F628A microcontroller, actuators (dc motors for movement and accomplishing tasks) and sensors (responsible for the interaction with the external environment). An important feature of this prototype lies in the fact that the recording of the program on the microcontroller is made directly on the motherboard itself making it easy to reprogram and test it without the needing to remove any components.

Keywords-: Mobile Robotics, Sensors, PIC Microcontrolers, Educational Robotics.

I. INTRODUCTION

According to [1], there are several ways of using computers and technological tools to support the process of teaching and learning in various educational levels. Among these technologies, educational robotics has been increasing and is largely used mainly for teaching presenting interesting and motivating pedagogical conditions. The robot makes use of some faculties, such as perception, logical thinking and action to solve a large number of problems that can be encountered in daily life.

Personal computers are being used in schools, however, some activities need computational resources with special characteristics such as low energy consumption, mobility, small size, input and output, special sensors and motors. These features are commonly needed when students use computing resources, for example, in their prototypes for a Science Fair [1 ].

Robotics is the area responsible for the development of devices capable of performing tasks with efficiency and accuracy, including those that are impossible for man to be executed without life risk. It seeks the development and integration of techniques and algorithms for creating robots [2]. The robot makes use of faculties, such as perception, thought and action to develop research and proposals aimed at solving the most varied problems encountered in daily life, for example, using robots to explore places that man cannot achieve [3 ].

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The use of robotics as a tool in the teaching-learning process proved to be a strong ally in the knowledge acquisition, since it allows pre-stimulating the design, engineering and computer skills on students featuring robotic activity as being interdisciplinary, so highly relevant to school curriculum [4].

In such an environment consisting of technological resources, such as interfaces, motors, sensors, software and materials, the student and teacher have the opportunity to create all kinds of robotic devices or robots. In the process of creating a robot, a student finds the need to seek information in areas such as mathematics, physics, mechanics, electronics and more. And yet, by defming the project through the use of clear forms of language, will increase the capacity of expression of ideas, research and application of aesthetic concepts [4].

With this, educational robotics joins the other resources used in the teaching-learning process as a tool, which inserted in the classroom activities, allows exploring different themes of the school curriculum.

For teaching robotics some kits are used as the main tools, some of these kits are commercially distributed in a fixed form where only the control logic can be changed, others are sold in blocks containing sensors and actuators that are connected to a main block which is recorded the control logic in order to allow the assembly of the wanted robotic model.

These kits also do not allow changes to hardware so that you can add new features, thus the added disadvantage of being expensive, hindering its purchase by schools and preventing them from carrying out projects of robotics in classrooms.

II. OBJECTIVE

This paper aims at the development of an autonomous mobile robot with materials accessible and affordable to the users. This robot is proposed as the basis for the development of future research in the field of mobile robotics application as the need for interdisciplinary affairs so as to outweigh the importance and enormous potential of robotics in education

Figure I. Arrengement of the wheels and other parts.

III. IMPLEMENTATION METHODOLOGY

The robot presented here was constructed to exert a large number of features, so it was essential to mount it with quality materials at a low cost, such as the acrylic physical structures that supports all the features and a microcontroller with a considerable number of entries and exits and also some additional functions, such as, for example, PWM, capture and compare, analog comparators and USART serial communication channel.

A. Robot Physical Structure

The robot was constructed with two rigid acrylic bases, connected by small metal plates; both bases have holes for fitting the main circuit and sensors using screws and nuts.

The format of the prototype was chosen to enable the docking of two gearboxes with two wheels where each fit two DC motors, which are parts that come from unused remote control cars.

The main circuit also known as the main module has been posted above one of the bases while the other acrylic base was used for the attachment of two single wheels (without engines) and two collision detection sensors.

The arrangement of the wheels, using the four rear wheels for traction, gives greater stability to the robot allowing him to wander into a plan quickly and effectively. Even with fixed rear wheels, the robot is capable of executing turns at any angle when an engine is turned off while the other continues to operate. Figure I shows the arrangement of the robot bases, wheels and other parts.

B. Hardware

The robot hardware was designed in order to implement a system capable of performing a range of functions such as collision detection through contact sensors and electromagnetic sensors, light tracking, monitoring and detection of line track through photo sensors and the existence of USART serial communication that facilitates the programming of the robot via a serial cable without the needing a PIC burner.

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Figure 2. Main module mounted on the robot base

To facilitate the construction of the robot and ensure its dynamism, its hardware consists of a single printed circuit board, where there is both the driving module, wich controls the dc motors and the control module, which contains the PIC

microcontroller and parts required to perform the robot functions.

The main module contains all the control portion of the robot, since the PIC microcontroller to the signal conditioning circuitry necessary to implement the tasks of the robot, and that is where all sensors are connected. This module was developed to make the most of the PIC so that, with minor modifications, could be added other features to the robot. Figure 2 shows the main module mounted on a base of the robot.

The motors used for the robots locomotion are simple dc motors, used in remote control cars wich were easy to adapt because they have continuous rotation. These engines were ideal for the construction of the robot as it was not needed any adjustment in the reduction boxes because they were developed for this type of engine, giving the robot considerable torque and speed.

The motors actuation is accomplished by means of two relays, which turn the motors on or off. There are two relays that perform the inversion of polarity of the motors power, thus allowing the reversal of the same.

The presented prototype has two proposed power supplies consisting of two sets of independent cells. The first consists of 4 AA batteries linked in series for the motors operation and a second source consisting of two cells linked in series to feed the main module.

For greater autonomy of the batteries there is a set of keys that let you enable or disable functions of the robot that are not being used located in the main module.

The functions enable the robot to perform tasks like wandering in a structured environment dodging obstacles, wander over a white surface surrounded by a black line (or on a black surface surrounded by a white line), obeying commands sent by computer, follow light and others.

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Figure 3. Collision detection sensors diagram

For the robot to perform these tasks among others were attached to its structure some devices such as collision detection sensors, track sensors, LDR sensors for light monitoring, a flashlight and a USART interface to connect the robot to the serial port of a computer .

C. Collision Detection Sensors

The collision detection interface is simple, as seen in Figure 3. The sensor output is connected to the PIC and it is in high level, so when the key is pressed, ie, a collision occurs, the signal connected to the PIC becomes low level and the collision is detected.

The robot was tested using three collision detection sensors with good results, distributed as follows: two in the front and one behind, where the two cross-posted in the front are like antennae while the one in the back is secured with a larger contact surface, as a bumper.

D. Track Detection Sensors

The infrared sensor that was used is an LED coupled to a photodiode, installed beneath the robot to allow the track detection, so that the light emitted by the LED and reflected on a surface is captured by the photodiode. The circuit used is shown in Figure 4.

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R2

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Figure 4. Track Detection Sensor Diagram.

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LDR

R1

Figure 5.

E. LDR Sensors

3

LDR Circuit Diagram.

In order for the robot to follow light, we used the LDR (Light Dependent Resistor), a resistance that varies with the incidence of light on its surface.

The LDR circuit is shown in Figure 5. In this circuit, the LDR is part of a voltage divider on the non-inverting input of an operational amplifier, so that the higher the incidence of light on the LDR greater is the strain on this entry. In the inverting input is connected a potentiometer to adjust the sensitivity to light to be detected.

The robot was tested equipped with two light sensors arranged as follows: one in the front of the robot and another in his back as shown in Figure 6, so that the robot can find the direction where there is a higher incidence of light and act according to his programming.

F USART Serial Communication

The USART (Universal Synchronous / Asynchronous Receiver / Transmitter) is a device that translates data between parallel and serial forms, found in the PIC 16F628A microcontroller. This device is used by the computer to communicate with asynchronous and synchronous serial peri herals connected to it .

Figure 6. One of the robots light sensors.

MAX232 C4

C1+ VDD

I C1 3 16 C1- VCC

4 C2+ C2 5 RS232 C2-

T11N T10UT 14

R20UT R21N 8 2

15 GND VEE 6 3

C5

Figure 7. RS232 Communication circuit diagram

USARTs are usually used in conjunction with standard RS232, to connect the robot to the computer was used a MAX232 integrated circuit. The schematic circuit of RS232 communication can be seen in Figure 7. The MAX232 is connected directly to the PIC, since it has the serial communication pins RX, used for receiving data, and TX, used to send data.

There are several programs with high-level routines that simplity serial communication through libraries with complete functions for setting, sending and receiving data from serial instruments that can be used for communication between the robot and the computer. The kit described here can be programmed directly through the Assembly programming language or using a higher level programming language, where the program should be interpreted using an interpreter to be recorded in the microcontroller.

IV. CONCLUSION

Several tests were conducted with the implementation of various tasks and has been proven that this robot can be used as a learning platform for low cost robotics education at various levels, as well as for performing those tasks for which it was designed or additional tasks.

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TABLE I. . AVAREGE COST OF KNOW EDUCATIONAL ROBOTICS KITS

Robotic Kit Manufacturer Price (US$)*

Bioloid Comprehensive Kit Bioloid 899,00

Lego Mindstorms NXT LEGO 489,00

Tomy I-SOBOT Robot Tomy 299,00

Parallax Boe-Bot Robot Kit Parallax 149,00 Inc.

The kit featured in this work 55,00

* november, 20 I 0 quotatIon.

It was noticed that using this kit woke up the curiosity and scientific spirit of apprentices, and the development of logical­mathematical intelligence, through the use of programming language and calculations needed for the construction of the models also promoting the development of linguistic intelligence, and even intrapersonal qualities since it involves working in groups, action planning, modeling and results presentation.

The cost of the robot, as seen in table I, is low compared with the cost of leaming kits for robotics already on the market.

This kit aims to fill a gap in the area of Educational Robotics, since Robotics is not widely used in schools as a full teaching tool, a fact which occurs by the lack of trained professionals as well as the high cost of existing robotics kits on the market. Some studies even begin to address educational theories such as the famous Vygotsky in Robotics [5].

ACKNOWLEDGMENT

The authors wish to thank the received fmancial support of the UNICEUMA, CAPES, CNPQ and F APEMA-MA during the development of this project.

REFERENCES

[I] Dante A. Medeiros Filho, Paulo C. Gonc,;alves. Rob6tica Educacional de Baixo Custo: Uma Realidade para as Escolas Brasileiras. Anais do XXVIII Congresso da SBC, Bell:m, Pani, 2008.

[2] Fernando Pazos, Automal;:iio de Sistemas & Rob6tica, Axel Books, Rio de Janeiro, 2002.

[3] Joao d'Abreu, Introdur;iio ao Robotic Control X - RCX e Robolab, Notas de aula apresentadas na Disciplina Rob6tica: Sistemas Sensoriais e Motor. Universidade de Campinas, Campinas, 200!.

[4] Silvana do Rocio Zilli, A Rob6tica Educacional no Ensino Fundamental: Perspectivas e Pratica, Dissertac,;ao de Mestrado, Universidade Federal de Santa Catarina, Florian6polis - SC, 2004.

[5] A1zira Ferreira da Silva, Ana Maria G. Guerreiro, Akynara Agae, Renata Pitta, Luiz Marcos G. Gonc,;alves, Dennis Barrios Aranibar. Utilizac,;ao da Teoria de Vygotsky em Rob6tica Educativa, Natal, Rio Grande do Norte.