||Real-Time and Embedded Systems
Automatic Inspection System for Perspex Sheets with Rule Based Defect Classification
This project involved a laser scanning system
for scanning perspex sheets on a production line. It used a custom
hardware board for defect feature extraction and three Force 68000
boards for data processing. My responsibility was for the defect
classification software on one of the 68000 boards, and for the PC
rule-compiler software, both written in 'C'.
The processing of the data from the laser scanner was done in the
following steps -
The rule compiler allowed the user to write
simple "IF .. THEN .. ELSE .." type rules to classify defects. An
example of a very simple rule to detects scratches (which tend to be
long and thing) might be -
- Feature Extraction. The signal
from the laser scanner was processed by a custom hardware board called
a "feature extractor" that calculated the size and location of defects
on the sheet.
- Master Processor.The defect
parameters were then read by the first 68000 board which logged the raw
data to a PC and passed the data to the other two 68000 boards (display
and defect classification).
- Graphics Display.One of the
68000 boards was responsible for producing a real-time colour display
of the sheet, showing the location and type of the defects.
- Rule-based Classification.The
third 68000 board used the size, shape and location of the defects to
classify them. This information was then passed to the display board,
to allow the type of defect to be displayed in colour, and to the
master 68000 board for logging to the PC. I was responsible for
developing the software for this board, including the defect classifier
software and the PC software for the rule compiler.
IF length > 10 and width < 2 THEN
type = scratch
© 2006 Oram Embedded Technology Ltd.