UWE Bristol Engineering showcase 2015

Matt Huxford
BEng Robotics
Project Supervisor
Abdul Farooq
Investigation into Machine Vision Based Object Measurement
Introduction
Machine vison techniques are useful for
automating tasks that would normally require
human involvement. Using a machine vison system
can reduce the time the task takes. Machine vision
can remove human involvement therefore
reducing risk of human error. This also allows the
human to do other tasks. In some cases machine
vison can increase the accuracy and quality of the
task..
I purpose a machine vision system that measures
objects placed on a tabletop. The system will
measure objects quickly and autonomously.
CAD Renderings of Design
Prototype System Photos
Below is a picture of the measurement system The
base is a mat white surface that gives a uniform
background that can be removed using machine
vison.
Camera Calibration
Most cameras (particularly cheaper ones) contain
distortion. In order to remove this distortion the
cameras must be calibrated. This is done by finding
points of a chessboard pattern as the pattern is
displayed in various orientations.
Corner extraction of rectangular box
Undistorted images from the cameras
Project summary
This project involves developing a system that
uses machine vision techniques to measure
the dimensions of boxes. Stereo vision was
chosen as the method to extract depth
information from the scene. Boxes to be
measured are placed on a tabletop
underneath the stereo vision system.
Project Objectives
• Research existing measurement systems
• Produce a technical specification
• Build a prototype solution
• Produce the Machine Vision Software
• Test the effectiveness of the system
Adaptive Thresholding
Project Conclusion
The prototype system is able to detect
corners of boxes placed underneath the
stereo vision system and measure the
distance to each corner.
The images below show the stereo vision system.
The orientation of the cameras can be slightly
altered. This allows the position of the cameras to
be adjusted to be parallel with each other.
Flood Fill
Extracted Box
The system is better at detecting the corners
of boxes which have a darker colour. The
system either fails to detect lighter coloured
boxes, or detects them intermittently.
The system does not require the box edges to
be parallel to the frame. All four corners will
be located when the box is rotated by any
angle.
The boxes corners are most likely to be
located correctly if the box is in the center of
the measurement surface.