62ª Reunião Anual da SBPC

A. Ciências Exatas e da Terra - 2. Ciência da Computação - 17. Ciência da Computação

TOWARDS FINE ROBOT CONTROL BASED ON SUN SPOT ARCHITECTURE

Cynthia Vasconcellos do Nascimento 1 Luiz Marcos Garcia Gonçalves 1 Anderson Abner de Santana Souza 1 Renato Quarentei Gardiman 1

1. Depto.de Engenharia de Computação e Automação, UFRN

INTRODUÇÃO:

We present current developments towards the development of a robot control architecture based on Sun Spot devices. The main motivation is to get fine control of robots in order to allow more precision in the mapping of areas while working in a higher level programming language. The control is based on the Sun SPOT kit that uses Java language, which is unusual to this kind of application. To this end, we finalized the basis construction, with drivers for fine control of robot motors. We have done a simulation with the control running between two Sun SPOT, one representing the robot basis and the other representing the high level controller itself. This can be used latter by high level controllers to send to the robots signals to drive motion direction and velocity. The mechanical part of the basis is entirely constructed by our team at the Natalnet laboratory (www.natalnet.br) using acrylic plates and recycled pieces. We developed an integrated circuit board, which is implemented to link the SunSPOT with the mechanical basis, using the L293D quadruple half-h driver. It receives the SunSPOT signals, which determinate the direction and velocity and send them to the motors.

METODOLOGIA:

First we explain about the main integrated tools that are fundamental to this work. The mechanical parts, as said above, are handy made using acrylic plates and recycled pieces. Two DC motors complete the electro-mechanical part, which are controlled by the robot electronics. To do this control, we use the L293D quadruple half-h driver, with a printed circuit board designed by using the Eagle package. This is a software that generally used for prototyping circuit boards. The Sun SPOT device is used to link the electronics of the robot to the high level control software. The Sun SPOT is a programmable device by Sun Microsystems that allows a programmer to elaborate commands at the computer, using Java language, and to transfer it to Sun SPOT. This device has input and output pins, its own communication protocol, accelerometer, switches and other tools to facilitate constructing and programming the robot. The outputs can directly communicate to the circuit board to produce motion on the robot actuators. Finally we have designed and built a diagram of operation for integrating the mechanics, electronics and programmable parts. The novelty of this work is that by using Sun SPOT and the half-h L293D it is possible to get a very fine control of the robot movements, using simple PWM signals. Fine control of direction and velocity is important to the final objective of this project that is to map unknown areas.

RESULTADOS:

We have proposed and built a new Sun SPOT based methodology that is working on a robot basis to control fine robot motion. We implemented a high-level controller using Sun SPOT that is also working. This controller uses an accelerometer sensor, switches and LEDs to provide commands to the robot. We tested fine motion control of the robot using different values of PWM signals and programming the Sun SPOT unit with values varying from 0 to 255 (in volts is an average from 0 to +5V) and combined to a constant value signal (+3V) to move the DC motors. Besides testing fine movement of the robot using the PWM signals sent from Sun SPOT, it was also possible to test the communication between two Sun SPOT, that is, a Sun SPOT based controller sends commands of directions to the robot basis Sun SPOT. We have chosen a communication protocol based on the client-server model, where the server is the control module and the client is the robot basis. As the programming language used is Java, we expected that the communication could be slow. However, to this application the communication is good enough, without delays. Immediately when the switch of the controller is pressed the robot car execute the movement sent. The variation of PWM signals allowed us to control velocity and to move the robot car forward, back, right and left.

CONCLUSÃO:

The final purpose of the project related to this work is the development of a robot based on the Sun SPOT architecture to be used in mapping of environments, making it in autonomous way. We have shown promising results in this direction. To this end, we constructed a mechanical basis, at our laboratory, a circuit board, implemented using Eagle software and we successfully linked it to Sun SPOT signals. The Sun SPOT programming that we devised, using functions to output pins, worked in the desired way. We did not report works in the literature that used this architecture to do fine control so this would be a nice contribution to the field. Based on this work, researchers with no depth background of electrical and mechanical engineering can easily construct and program their robots and devote most of their time to their applications instead to robot construction itself. To test the communication and robot motion control, we have implemented a controller and a robot basis. We used a very simple client-server protocol to communicate, which made possible transmission with a low percentage of errors and as fast as necessary for real time applications. The PWM was useful to control the direction and the speed of the robot by software and worked well.

Instituição de Fomento: Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq

Palavras-chave: Robot Control, Sun SPOT, L293D.