the optical sensor of the robot phoenix-1 aleksey dmitriev

The optical sensor of the robot Phoenix-1

Aleksey Dmitriev

Introduction

The presented work is devoted to the

description of the optical sensor designed

and experimentally verified as a part of the

students’ project of a mobile robot.

Optical sensor overview

MathCAD

D1...DnThe optical sensor

Showingphase

α1...αn

DB

Teachingphase

Testingphase

The optical sensor

Objectives and criteria The primary objective of the sensor is to measure a

displacement of a contrast stripe from the image center.

Performance of recognition and control algorithms was the main criteria of the optical sensor design.

The principal idea of stripe recognition algorithm is based on the assumption that stripe has homogeneous color and high contrast with the background.

Stripe recognition (1/2)The optical sensor should estimate size D, representinga displacement of the white stripe center from the imagecenter.

Stripe recognition (2/2)The displacement D is calculated with the method ofcentre of mass.

n

ii

n

ii

c

L

iLN

0

0

*

where Nc – pixel number that corresponds to white stripe center, Li – brightness of i pixel in a measuring stripe, n – number of pixels (length) of a measuring stripe .

0NND c

Sample frameThe sensor consists of several measuring stripes which

indications are used by the algorithm of the robot control.

Each stripe has its own parameters: offset from the image center, width and height.

Sample movieThis is a sample movie taken during one of experiments.

Experiments’ result The control algorithm is based on PID-regulator. Indications of the optical sensor and output data of the

control algorithm are used for teaching a neural network.

k 0 4

Revealed issuesThe control system is very sensitive to a camera position.

Conclusion: we should install a cam angle sensor.

Conclusion

The optical sensor has been successfully used on the

teaching stage of “teaching by showing” methodology.

During the tests the algorithm has shown good working

capacity. The speed of the algorithm is at very high

level that allows to write it even to low-performance

microprocessors.

Contact info

Aleksey Dmitriev

megalexx@gmail.com

SUAI, Saint-Petersburg, Russia