Quantitative evaluation of a rotary blueberry mechanical harvester using a miniature instrumented sphere

Southern highbush blueberries (Vaccinium corymbosum interspecific hybrids) are predominantly for the fresh market and, with a few exceptions, are hand harvested. Though mechanical harvesting systems are available for processed blueberries, low harvest efficiency and high fruit damage have limited their use for picking blueberries for fresh market. To improve the current machine harvester design, it is apparent that the interaction between the machine harvester and fruit should be well understood. The goal of this study was, therefore, to provide such an understanding by using a custom-made miniature instrumented sphere. The miniature Berry Impact Recording Device (BIRD) was used to measure the mechanical impacts created by a rotary mechanical harvester during fruit harvesting. A closeup video recorded the harvesting to pinpoint critical control points where most impacts were created. The results showed that the catch plates on the rotary harvester accounted for over 30% of all mechanical impacts imposed on the BIRD, followed by the empty fruit collection box (lug) (>20%). Impacts created by the conveyer belt and shaking rods combined accounted for only 25% of mechanical impacts. Thus, the most significant reduction in bruising could be achieved through modifications in the catch plates and lugs. The impact of three contacting surfaces (the catch plates, conveyer belt, and steel tunnel) on the harvester and three commercial padding materials (Cellular Silicone, Slow Rebound, and No Bruze) were evaluated. Harvester surface evaluations revealed that the catch plate was the hardest surface. Among the three padding materials evaluated, the Cellular Silicone provided the best cushioning. This study proved the efficacy of using a customized miniature instrumented sphere in measuring mechanical impacts created by various machine parts during harvesting. It provided a better understanding of how the berries interact with different machine parts of a rotary harvester.