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Estimation of fruit locations inside orchard tree canopies using radio signal ranging and trilateration
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Paper number 131595170, 2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: http://dx.doi.org/10.13031/aim.20131595170) @2013
Authors: Stavros George Vougioukas
Keywords: Fruit; spatial distribution; mapping; radio waves; trilateration.
Abstract. The design of tree harvesting or harvest-aiding mechanized systems needs to take into account the spatial distribution of fruits in tree canopies. Reported methods for measuring fruit locations on trees have utilized plumb bob on strings and measuring tape, special mechanical linkages, and surveyorâ€™s instruments. These methods require several minutes per fruit and have been used for a very limited number of trees. A novel method is presented, which utilizes high-frequency radio signals and trilateration to measure fruit locations at rates comparable to those of manual harvesting (~ 1 fruit/sec). Each fruit picker wears gloves with an antenna attached on each glove, and a mobile trailer carries four radio beacons that measure their distances from the antennas on the worker gloves. By combining the four distances of each antenna from the beacons, the coordinates of each glove are computed with respect to a coordinate frame attached to the trailer; data from an RTK-GPS and an inclinometer carried on the trailer, make it possible to compute worker glove coordinates with respect to a fixed frame. Finally, every time a worker picks a fruit, the event is registered manually by pushing a button on a wireless controller; the glove position at that time instant gives us the approximate position of the grasped fruit. Data collection was performed in numerous California pear and cling peach orchards for thousands of fruits. Based on the collected data, fruit maps and statistics - like height distribution and horizontal distance distribution from the row centers - were computed.