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Document Type

Thesis - University Access Only

Award Date

1996

Degree Name

Master of Science (MS)

Department / School

Agricultural Engineering

First Advisor

Daniel S. Humburg

Abstract

A machine vision system was developed and tested to locate and describe geometric characteristics of harvestable size mushrooms in a growing environment. An imaging system was built to scan half of a commercial mushroom tray. A camera perpendicular to the tray surface collected images, which were used to calculate diameter and estimate X and Y axes coordinates for each mushroom. A camera placed at an angle of approximately 45 degrees to the tray surface collected images of structured laser light on each mushroom. The actual 3-D coordinates of the mushroom center were calculated along with orientation in X and Y direction with this information. A second measurement system, referred to as the electromechanical measurement system, was developed as a standard to asses [sic] the capability of the machine vision system. The electromechanical measurement system was designed to measure 3-0 coordinates, diameter and tilt of mushrooms in a growing tray. This system was made up of two linear transducers, an ultrasonic sensor, inclinometer and digital caliper. These components were interfaced with an IBM compatible PC through RS-232 serial ports, a mouse communication port and a Keithley DAS 800 data acquisition board. A program developed using Microsoft C++ and assembly programming languages performed the data collection and manipulation. The 3-D center coordinates, diameter and tilt of mushrooms located correctly by both measurement systems were compared. Confidence intervals were calculated for all the parameters measured. The following conclusions were drawn for the machine vision system. The X coordinate measured by the machine vision system was determined to a region of ± 1.3 cm about the value measured by the electromechanical system at a 95% confidence level. The Y coordinate, at a 95% confidence level, was determined to a region of ± 1.5 cm. Errors in height measured on side two were more variable than side one of the tray because of compost height variation. A 95% confidence interval was used to determine mushroom heights to within ± 1.2 cm of the height measured by the electromechanical system on side one. The diameter estimates showed more variability on side two of the tray. Mushroom diameters measured from side one of the tray [sic] were estimated by the machine vision system within ± 8.85 mm about the diameter measured by the electromechanical measurement system at a 95% confidence level. Angle estimations were better in the X direction than in the Y direction, but both were poor. The machine vision system had more problems identifying severely tilted mushrooms.

Library of Congress Subject Headings

Mushrooms -- Selection -- Automation
Mushrooms -- Harvesting -- Automation
Computer vision
Image processing -- Digital techniques

Format

application/pdf

Publisher

South Dakota State University

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