Quantitative evaluation of a rotary blueberry mechanical harvester using a miniature instrumental sensor

Authors: YU, P - University Of Georgia; LI, C - University Of Georgia; Takeda, Fumiomi; KREWERS, G - University Of Georgia; RAINS, G - University Of Georgia; HAMRITA, T - University Of Georgia

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2012
Publication Date: 1/15/2013
Citation: Yu, P., Li, C., Takeda, F., Krewers, G., Rains, G., Hamrita, T. 2013. Quantitative evaluation of a rotary blueberry mechanical harvester using a miniature instrumental sensor. Computers and Electronics in Agriculture. 88:25-31.

Interpretive Summary: Southern highbush blueberries have been hand harvested if destined for fresh market. Hand harvesting is labor intensive and costly. Mechanical harvesting systems can decrease production cost but current harvesters have low harvest efficiency and cause high fruit damage. A better understanding of how bruising is created during the harvesting process and the dynamic interactions between the blueberry and the mechanical harvester is needed to improve mechanical harvesting technologies. In this study, a miniature, spherical instrumented impact recording device (slightly less than 1-inch diameter) was designed and built to pinpoint critical control points that create most impacts on the blueberry during the mechanical harvesting operation. The results indicated that the fruit impact with the catch pans of the harvester that divert the detached fruit to a conveyor belt for transferring the fruit to a collecting box accounted for over 30% of all mechanical impacts. Another significant impact was caused when the fruit fell into the collection box (20%) and when the fruit was hit by a shaking rod (13%). We concluded that fruit bruising during machine harvesting could be reduced if the hard surface of the catch pan was softened by covering them with padding material. The velocity change and impact force for the fruit falling on cellular silicone padding was only 25% of a falling fruit hitting a hard, plastic catch pan. The miniature impact recording device revealed the duration, magnitude, and number of mechanical impacts during the mechanical harvesting process. The findings have provided valuable information to the mechanical blueberry harvester manufacturers for improving current mechanical harvesting technologies to reduce blueberry bruising.

Technical Abstract: Highbush blueberries are predominantly for the fresh market and, with a few exceptions, are exclusively hand harvested if destined for fresh market. Mechanical harvesting systems for processed blueberries are available but low harvest efficiency and high fruit damage have limited the use of mechanical harvesters for picking blueberries for fresh markets. A key step to enhance the efficiency of the highbush blueberry production is to improve current mechanical harvesting technologies which create excessive bruising and make blueberries unmarketable to the fresh market. The overall goal of this study was to quantitatively measure the dynamic interactions between the blueberry and the mechanical harvester and to understand how bruising is created during the harvesting process. A custom-made miniature instrumented sphere, known as blueberry impact recording device (BIRD), was used to measure the mechanical impacts created by a rotary mechanical harvester (Korvan 37 8000, Oxbo International, Lynden, WA). A close-up, visual recording of the harvesting process was made with a hand-held digital camcorder to pinpoint critical control points that create most impacts on the harvester. Four contacting surfaces (the catch pan, conveyer belt, steel tunnel, and empty lug box) on the harvester, as well as three padding materials, were evaluated by the BIRD sensor with regard to the impact they created. The results showed that the catch pans of the rotary harvester accounted for over 30 percent of all mechanical impacts imposed on a blueberry, followed by the lug (greater than 20 percent), conveyer belt (13 percent), and shaking rod (13 percent). However, the high number of impacts in the lug might be overestimated by measuring only empty lugs. Thus, the most significant reduction in bruising could be achieved through improvements of the catch pans, conveyor belts, and lugs. Harvester surface evaluation confirmed that the catch pan was the hardest surface in the mechanical harvester. Among three padding materials evaluated, the Cellular Silicone provided the best cushioning. This study has shed light on how to reduce blueberry bruising by improving current mechanical harvesters, which will be invaluable to enhance blueberry production efficiency in the long run.