With roughly 511 million pounds of blueberry accounting for 60% of world production in 2011, the United States is the largest blueberry-producing country in the world (U.S. Department of Agriculture, 2012). Although the blueberry for the processing market in the United States is mostly machine harvested, 70% of fresh-market blueberries are hand harvested. Hand harvest is labor intensive and costly (Brown, 1983), thus quickly becoming a major bottleneck for U.S. fresh-market blueberry production. There is a great demand to better adapt current machine harvesting technology for fresh-market blueberry, especially in areas where soft-textured southern highbush (SH) blueberry is grown in hot and humid environments where fruit soften quickly upon reaching full maturity. Current mechanical harvesters originally intended for processed blueberries cause unacceptable levels of bruising for the fresh-market SH blueberry. Several studies have shown that bruising damage of blueberry fruit harvested by mechanical harvesters was substantially higher (55% to 78%) than that of fruit harvested by hand (23%) (Brown et al., 1996; Peterson et al., 1997). Clearly, the key to adapting the mechanical harvest to fresh-market blueberry is to reduce bruising to fruit by the machine. To achieve this goal, one critical step is to first understand how blueberry fruit interacts with the harvester; i.e., how many mechanical impacts are created, where they are created, and their magnitude.
To answer these questions, we designed a miniature instrumented sphere (Smart Berry) to mimic a real blueberry fruit by recording all significant impacts as it passes through the harvesting process. The Smart Berry is essentially a data logger with accelerometers, internal power supply, memory, and microprocessor integrated into a 1-inch-diameter sphere cast in silicone rubber. Although various types of instrumented spheres have been developed and used for specific purposes in the past two decades, most have been used in impact evaluation of large fruit and vegetables, such as apples (Malus ×domestica), onions (Allium cepa), and potatoes (Solanum tuberosum), in the packing house, none has been used for small fruit because of their comparatively large size and weight. In contrast, the Smart Berry is only half the size and a fraction of the weight of the current smallest instrumented sphere available on the market, such as Impact Recording Device (Techmark, Lansing, MI).
This paper summarizes the hardware and software of the instrumented sphere sensing system; its application in evaluating a rotary and a slapper harvester design; and how the impact data collected could be translated into fruit bruising rates for two SH blueberries (‘Scintilla’ and FL 05-528). Technical details of sensor design, development, and evaluation have been published in specialized papers (Yu et al., 2011a, 2011b, 2012).
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Yu, P., Li, C., Rains, G. & Hamrita, T. 2011a Development of the Berry Impact Recording Device sensing system: Hardware design and calibration Comput. Electron. Agr. 79 103 111
Yu, P., Li, C., Rains, G. & Hamrita, T. 2011b Development of the Berry Impact Recording Device sensing system: Software Comput. Electron. Agr. 77 195 203
Yu, P., Li, C., Takeda, F., Krewer, G., Rains, G. & Hamrita, T. 2012 Quantitative evaluation of a rotary blueberry mechanical harvester using a miniature instrumented sphere Comput. Electron. Agr. 88 25 31