Device for Data Preprocessing in an Engineering Vision System

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Device for Data Preprocessing in an Engineering Vision System

Dvorovkin, V. E.; Pankov, V. A.

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CANADA INSTITUTE

FOR SCIENTIFIC AND TECHNICAL

INFORMATION

ISSN 0077-5606

INSTITUT CANADIEN

DE L'INFORMATION SCIENTIFIQUE

ET TECHNIQUE

NRC/CNR TT-2065

TECHNICAL TRANSLATION TRADUCTION TECHNIQUE

V.E. DVOROVKIN AND ·Y.A. PANKOV

A DEVICE FOR DATA PREPROCESSING IN AN ENGINEERING VISION SYSTEM

PRIBORY I SISTEMY UPRAVLENIYA, (9): 39-40, 1982

TRANSLATED BY/TRADUCTION DE

P. HYDE

OTTAWA

1983

1+

National Research

Council Canada

Conseil national

de recherches Canada

NATIONAL RESEARCH COUNCIL CANADA CONSEIL NATIONAL DE RECHERCHES CANADA

TECHNICAL TRANSLATION TRADUCTION TECHNIQUE 2065 Author/Auteur: Title/Titre: Reference/Reference: Translator/Traducteur:

V.E. Dvorovkin and V.A. Pankov.

A device for data preprocessing in an engineering vision system.

Pribory i Sistemy Upravleniya, (9): 39-40, 1982. P. Hyde.

Canadd Institute for Scientific and Technical Information

Institut canadien de l'information scientifique et technique

Ottawa, Canada KIA OS2

A DEVICE FOR DATA PREPROCESSING IN AN ENGINEERING VISION SYSTEM

by V.E. Dvorovkin and V.A. Pankov

U.D.C. 62.506.2

One of the ways of perfecting industrial robots is the development of devices furnishing information on the external environment, namely, sensitisation systems. The use of sensitisation systems makes it possible to broaden the field of application of industrial robots, since in this case the necessity of precise positioning of objects is eliminated and there is a simultaneous enhancement of operating accuracy, as well as a relaxing of the requirements for technological precision.

The most informative of the sensitisation systems are engineering vision systems. These make it possible to identify objects, and to determine their position and orientation in the working scene. At the present time television vision systems and also systems with semi-conducting photomatrices and matrices of devices with charge coupling are being developed. Matrix engineering vision systems are characterised by sensors of smaller dimensions and lower power consumption, possess a high mechanical strength and are conveniently accommodated in the handler. Although inferior to television engineering vision systems in field resolution, matrix engineering vision systems ｡ｾｳｵｲ･ a sufficient measuring precision in numerous applications. When working with simple scenes, where the number of objects is not large, and where there is no overlapping of them and there are no shadows and blinks, matrix engineering vision systems can be used in a binary regime, that is, to obtain silhouettes of the objects and compute the needed data from these silhouettes.

3

-A 16

GY

AI

In this article we present a device for the preprocessing of visual

information from a photomatrix which has a dimensionality of 16 x 16 and is

being used in a binary regime. The purpose of the preprocessing consists in

the extraction of data for computing the coordinates of the geometric centre

(ru) of silhouettes with two axes of symmetry. The device determines the

numbers of the I and J lines and columns of the sensitive surface of the

photomatrix, onto which the image is projected, with the first (If,J

f) and

last (I ,J ) of these transferred for the definitive calculations into a

p

p

control processor UP, where the final operation of the calculations is

performed, i.e., the determination of their arithmetic mean, which is taken as the following estimate of the geometric centre coordinates:

=

(J f+ J

_p)/2;

=

(If + I

_p)/2.

x mean ymean

The functional diagram of the data preprocessing device is presented in the

illustration. Included in the device are: a control unit BY, a buffer unit

BE, units for determining the abscissa of the geometric centre SA and its

ordinate BO, and a photomatrix ｾｍＮ The control unit ensures synchronous

functioning of all the units of the system and controls the processes of

4

-The EA unit determines the numbers of the columns of the photomatrix onto

which are projected the leftmost and rightmost borders of the silhouette, and

the EO unit the numbers of the first and last lines onto which the

silhouette is projected.

The device operates in conjunction with the robot control processor. After

receipt of the "Start" signal from the control processor the control unit EY emits a "CT'" (erasure) pulse, preparing the photomatrix for recording the

silhouette of the object. Then, after a definite time T (storage time),

s

one of the address pulses Ai-A16, controlling the parallel derivation of the

video-signals Ul-U16 from the corresponding column of the photomatrix ¢M, is

generated. Selection of the columns being derived occurs in ascending order

of their numbers: after the selection of one column the control unit EY again generates a "CT" pulse and after the time T has elapsed the address pulse

s

for the derivation of the next column from the photomatrix is transmitted. In

this way, all 16 columns of the photomatrix can be derived, the derivation

time of a complete frame being up to 600 microseconds.

Connected to the outputs of the photomatrix

¢M

is a l6-channel one-digit

analog-to-digital converterAUTI, synchronised by delay pulses V, which succeed

each address pulse with a delay L. The buffer register BP consists of D-type

flip-flops, synchronised by delay pulses W. Each flip-flop of the buffer

register' determines the presence in the Jth column of the photomatrix of

albeit a single cell, the output voltage of which corresponds to the E(J)

voltage - to the logical "1" of the given channel of the analog-to-digital

converter AUTI. Thus, up to the end of the frame some of the BOO-B15 signals

can have the level of the logical "1", and at the end of the frame the binary code corresponding to the projection of the silhouette onto the abscissa of

the coordinate system coupled with the photomatrix, is received in the

ｩｮｦｯｲｾｴｩｯｮ inputs of the data multiplexer ｍｾＮ

5

-A counting sequence HO-H3, corresponding to the number of the running column

of the photomatrix

pM,

is transmitted to the multiplexer controlling inputs

from a 16-digit counter of the control unit EY.

The registers PHA and PKA of the initial and final abscissae consist of

D-flip-flops, to the information inputs of which is transmitted the counting

code of the columns of the photomatrix

pM.

The PHA and PKA registers remember

respectively the codes of the minimal and maximal abscissae of the

silhouette. Here, all the flip-flops of the PHA register are gated once per

frame by the output signal of the minimal abscissa recording gate B3HA, and

the flip-flops of the PKA register - several times (as many as there are units

in the inputs of the data multiplexer M.n;) by the output signals of the

maximal abscissa recording gate B3KA, being constantly gated by the pulses A.

At the end of the frame the codes from the outputs of the PHA and PKA

registers are rewritten by the pulse K into the abscissa register PA and are

transmitted to the robot control system CY (signals A60-A67), where their

arithmetic mean is computed.

The EO unit consists of the minimal and maximal silhouette ordinate recording gates B3HO and B3KO respectively and of the registers for storing the codes of

these ordinates PKO and PHO. The QO-Q3 code of the state of the photomatrix

line counter, being in the control unit BY, is transmitted to the information

inputs of the PHO and PKO registers, consisting of the D-flips-flops. The

BOO-B015 signals arrive at the B3HO gate and, as soon as one of the B(J)

signals assumes the value of a logical "1", the code of the line is recorded

in the PHO register. In turn, the COO-C015 signals corresponding to the

logical states (EOAW)-(E15AW) are transmitted to the B3KO gate, and the codes of the matrix lines having a single cell with a unit state are recorded in the

PKO register. At the close of the frame, the derived OpO-Op7 codes are

rewritten by the pulse K into the ordinate register PO, their arithmetic mean is computed in the robot control system CY and the estimate of the ordinate of the geometric centre is produced.

,

.

-#

6

-For calculating the geometric centres of asymmetrical objects, preprocessing devices can be designed from the following algorithm:

I

f x =

ｾ ｊｾ

. e n '

I

ｾｾ II( r Y = -t e n •

where I and J are the coordinates of the elements of the silhouette; n

K

K

is the number of elements.

The last stage in the processing, namely the division, can be carried out in the robot control system CY.

The speed of engineering vision systems (EVS) when computing the coordinates of the geometric centres of symmetrical objects is mainly determined by the speed of recording of the frame by the photomatrix. This, in turn, depends on the illuminance of the scene, since the higher the illuminance the more rapid is the recording and derivation of the frame from the photomatrix. In experiments with EVSs the recording and derivation of a frame occupied from 0.6 to 10 ms. The EVS achieved by the authors has a lens with a camera angle of 0.2 x 0.2 m2• The field resolution is due mainly to the discreteness of the readout and the magnitude af the 2

S

angle. With these EVS parameters the error in the reading of coordinates on account of discreteness is 6.10-3 m at a scene-to-lens distance of 1 m. For achieving the system, series 155 microcircuits were used; this is the most developed series and correlates well with microprocessor devices. Furthermore, elements of series 198 and 521 were used in the photomatrix control system.