Transcript О системах видеоконференций

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
The optical sensor
D1...Dn
Showing
phase
DB
α1...αn
MathCAD
Teaching
phase
The optical sensor
Testing
phase
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, representing
a displacement of the white stripe center from the image
center.
Stripe recognition (2/2)
The displacement D is calculated with the method of
centre of mass.
n
Nc 
L
i 0
n
i
*i
L
i 0
D  Nc  N0
i
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 .
Sample frame
The 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 movie
This is a sample movie taken during one of experiments.
Experiments’ result


k  0 4
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.
Revealed issues
The control system is very sensitive to a camera position.
Conclusion: we should install a cam angle sensor.
Conclusion
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.
The optical sensor has been successfully used on the
teaching stage of “teaching by showing” methodology.
Contact info
Aleksey Dmitriev
[email protected]
SUAI, Saint-Petersburg, Russia