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

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. 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 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 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 SUAI, Saint-Petersburg, Russia