Camera as Position Sensor for a Ball and Beam Control System

Alejandro-Israel Barranco-Gutiérrez^1,3, Jesús Sandoval-Galarza², Saúl Martínez-Díaz²

¹ Tecnológico Nacional de México, Instituto Tecnológico de Celaya, México. israel.barranco@itcelaya.edu.mx

² Tecnológico Nacional de México, Instituto Tecnológico de La Paz, México. jsandoval@itlp.edu.mx, saulmd@itlp.edu.mx

³ Cátedras CONACyT, México.

Article received on 22/11/2013.
Accepted on 09/03/2015.

Abstract

This paper describes a novel strategy to use a digital camera as a position sensor to control a ball and beam system. A linear control law is used to position the ball at the desired location on the beam. The experiments show how this method controls the positioning of the ball in any location on the beam using a camera with a sampling rate of 30 frames per second (fps), and these results are compared with those obtained by using an analog resistive sensor with a feedback signal sampled at a rate of 1000 samples per second. The mechanical characteristics of this ball and beam system are used to simplify the calculation of the ball position using our vision system, and to ease camera calibration with respect to the ball and beam system. Our proposal uses a circularity feature of blobs in a binary image, instead of the classic correlation or Hough transform techniques for ball tracking. The main control system is implemented in Simulink with Real Time Workshop (RTW) and vision processing with OpenCV libraries.

Keywords: Computer vision, ball and beam system, linear control.

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Acknowledgements

The authors greatly appreciate the support of PROMEP and CONACyT with the project 215435. The work of the second author was partially supported by CONACYT grant 166636 and by TecNM grant 5345.14-P. We would also like to thank Laura Heit for her valuable editorial help.

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