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United States Department of Agriculture

Agricultural Research Service

Research Project: Quality Based Inspection and Sorting of Specialty Crops Using Imaging and Physical Methods

Location: Healthy Processed Foods Research

Title: X-ray based stem detection in an automated tomato weeding system

Authors
item Haff, Ronald
item Slaughter, David -
item Jackson, Eric

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2011
Publication Date: October 1, 2011
Citation: Haff, R.P., Slaughter, D.C., Jackson, E.S. 2011. X-ray based stem detection in an automated tomato weeding system. Applied Engineering in Agriculture. 27(5):803-810.

Interpretive Summary: A detection system was developed to identify crop plants in an automatic weed control device for use in tomato fields. A portable x-ray source projected an x-ray beam perpendicular to the crop row and parallel to the soil surface. The plant’s main stem absorbs x-ray energy, decreasing the detected signal and allowing stem detection even in the presence of leaves. This signal is used to control the operation of a pair of weed knives. The detector consisted of a linear array of photodiodes aligned perpendicular to the soil. This configuration helps differentiate branches, which are angled and block only some of the photodiodes, and stems which have the same vertical alignment as the array and hence block all photodiodes. A field trial was conducted in a 15 meter section of row containing 39 tomato seedlings. At a speed of 1.6 km/h, the detection system identified all 39 stems of standing plants with no false positives.

Technical Abstract: A stem detection system was developed for automatic weed control in transplanted tomato fields. A portable x-ray source projected an x-ray beam perpendicular to the crop row and parallel to the soil surface. The plant’s main stem absorbs x-ray energy, decreasing the detected signal and allowing stem detection even in the presence of leaves. This signal is used to control the operation of a pair of weed knives. Minimizing the source to detector distance as the system moved along the row allowed for differences in signal strength between stems and background as high as 300 mV (vs. background noise levels around 60 mV) at low x-ray energy and current levels (25 keV, 7 mA), which is a significant advantage for safety reasons. The detector consisted of a linear array of photodiodes aligned perpendicular to the soil. This configuration helps differentiate branches, which are angled and block only some of the photodiodes, and stems which have the same vertical alignment as the array and hence block all photodiodes. A field trial was conducted in a 15 meter section of row containing 39 tomato seedlings. At a speed of 1.6 km/h, the detection system identified all 39 stems of standing plants with no false positives.

Last Modified: 4/23/2014
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