Computers and Electronics in Agriculture 101 (2014) 8492

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Computers and Electronics in Agriculture

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Measurement of mechanical impacts created by rotary, slapper, andsway blueberry mechanical harvesters

0168-1699/$ - see front matter 2014 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.compag.2013.12.001

Corresponding author. Tel.: +1 706 542 4696; fax: +1 706 542 2475.E-mail address: cyli@uga.edu (C. Li).

Pengcheng Yu a, Changying Li a,, Fumiomi Takeda b, Gerard Krewer c, Glen Rains d, Takoi Hamrita ea College of Engineering, 712F Boyd Building, University of Georgia, Athens, 30602 GA, USAb Appalachian Fruit Research Station, USDA-ARS, Kearneysville, 25430 WV, USAc Department of Horticulture, University of Georgia, Tifton, 31793 GA, USAd Department of Entomology, University of Georgia, Tifton, 31793 GA, USAe College of Engineering, University of Georgia, Athens, 30602 GA, USA

a r t i c l e i n f o

Article history:Received 13 May 2013Received in revised form 4 October 2013Accepted 8 December 2013

Keywords:BruiseAccelerometerInstrumented sphereSensingHighbush blueberry

a b s t r a c t

Blueberry mechanical harvesters cause bruise damage to the fruit. The goal of this study was to test a cus-tom-made sensor (berry impact recording device) to measure the quality and magnitude of mechanicalimpacts created by three major types of commercial blueberry mechanical harvesters (rotary, slapper,and sway). The sensor was mounted on blueberry bushes (cultivated) and harvested at standard operat-ing conditions such that the sensor was detached and experienced the impact forces typically found dur-ing a mechanical harvesting process. The data collected by the sensor revealed that the slapper and swayharvesters generated not only larger number but also higher magnitude impacts than the rotary. Ouranalyses suggest that these disparities were mostly caused by different agitating mechanisms, contactingsurface materials, and designs between the three harvesters. Results indicated that most impacts lasted57 ms in all three harvesters. The distribution of the impacts showed that 90% of impacts from therotary were less than 190 g and 90% of impacts from the slapper and sway were less than 250 g. Corre-sponding measures were identified to reduce potential bruise damage in the harvesters. The informationcould be useful to select harvesters that create the least impacts and to improve current mechanical har-vester designs.

2014 Elsevier B.V. All rights reserved.

1. Introduction

The blueberry industry in the United States (U.S.) has experi-enced explosive growth in the past three decades, making theU.S. the largest blueberry producing country in the world (Brazel-ton and Strik, 2007) with a total yield of 231 million kg in 2011.Half of the U.S. blueberry production went to the fresh market(U.S. Department of Agriculture, 2012), of which the majoritywas hand harvested. High labor cost, low harvest efficiency, andpoor fresh-market quality of machine-harvested blueberries aremajor challenges facing the fresh market blueberry industry(Brown et al., 1983). Using mechanical harvesters to replace tradi-tional hand harvest is the key to improving the overall efficiency ofhighbush blueberry production. Brown et al. (1996) reported that78% of blueberry harvested by commercial mechanical harvestershad severe bruise damage compared to 23% for hand harvestedblueberry. Excessive bruise damage has hampered the wide appli-cation of mechanical harvesters for fresh market blueberry.

Current commercial mechanical harvesters employ three majormechanisms to detach the ripe blueberry from bushes (Mainland,1993; Peterson and Brown, 1996): the slapper uses beater barsthat extend from a vertical axis to hit the bushes from both sidessimultaneously; the sway has a similar mechanism as the slap-per but swings the beater bars to the same direction to move thebushes from side to side; and the rotary consists of horizontalshaking rods extended from a vertical spindle, which agitatesbushes with vertical or horizontal vibrations. A harvester devel-oped by BEI (South Haven, Michigan, USA) in the mid-1990s,known as V45, showed advantages over conventional commercialharvesters in both blueberry bruise and loss of fruit to the ground(Peterson and Brown, 1996; Peterson et al., 1997; Takeda et al.,2008). It was not widely adopted because it operated best at slowground speed (61 km/h), and on plants without upright limbs inthe middle and height less than 2 m. In fact, blueberry harvestersthat are currently used by growers can be operated at groundspeeds greater than 1.6 km/h, and the harvesters are capable ofharvesting plants that are over 2.2 m tall without special plantpruning (Krewer, personal observation).

Several studies have been conducted to compare potential blue-berry mechanical harvesters in their fruit yield and bruise rate of

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P. Yu et al. / Computers and Electronics in Agriculture 101 (2014) 8492 85

the harvested fruit. Van Dalfsen and Gaye (1999) reported reduc-tions in the fruit yield (14 to 30% on average) for three rotary blue-berry mechanical harvesters when compared with human pickersfor three years. Peterson et al. (1997) found that blueberry har-vested by a rotary harvester had 55% moderate and severe bruisedamage; while this number was only 22% for commercial handharvest. In addition to Brown et al.s (1996) study, Takeda et al.(2008) found that blueberry harvested by a sway harvester had sig-nificantly higher bruise rate than those harvested commercially byhand. These studies, however, were not able to describe how theblueberry was bruised during the harvesting process, due to lackof understanding of the interaction between the machine partsand the fruit. During the mechanical harvesting process, a blue-berry is exposed to frequent mechanical impacts when it interactswith different components of a harvester, which may lead to bruisedamage and further fruit quality degradation (Takeda et al., 2013).

In the past, many studies have measured the bruise damage forlarge fruits and vegetables in packing lines by using instrumentedspheres (Lin and Brusewitz, 1994; Mathew and Hyde, 1997; Soberet al., 1990). The instrumented sphere is essentially a sensing de-vice whose size is comparable to a fruit or vegetable of interest.It is usually placed in the packing line and exposed to the samemechanical impacts as the real fruits and vegetables. The mechan-ical impacts recorded by the sensor are a close reflection of what afruit and vegetable experiences. Thus, the sensor is an effective toolto evaluate packing lines in identifying locations that can causebruise damage. Unfortunately, none of the existing instrumentedspheres can be used to evaluate blueberry mechanical harvestersdue to their relatively large size, dissimilar surface properties fromthe blueberry, and relatively small sensing range and sampling fre-quency (Yu et al., 2011b). To measure the mechanical impacts cre-ated by blueberry mechanical harvesters, a research group at theUniversity of Georgia recently developed a miniature instrumentedsphere, known as the Berry Impact Recording Device (BIRD) (Yuet al., 2011a,b). The BIRD sensor is a 25.4 mm (diameter) spherewith three accelerometers to detect mechanical impacts from alldirections. Because southern highbush blueberry with >20 mmdiameter fruit is commercially available, this miniature instru-mented sphere has achieved an unprecedented approximation toa real blueberry. It would be of great value if the quantity and mag-nitude of the mechanical impacts created by various harvesterscould be measured. The information can be used to improve cur-rent mechanical harvesting technologies for fresh market blue-berry. The overall goal of this study was to test and evaluate theBIRD sensor to measure the quantity and magnitude of mechanicalimpacts created by three major types of commercial blueberrymechanical harvesters (rotary, slapper, and sway).

2. Materials and methods

2.1. Berry impact recording device

The BIRD sensor was built in-house and is a microcontroller-based miniature instrumented sphere which can perform dataacquisition, computation, and storage. There are four essentialcomponents within the sphere: a microcontroller (PIC18LF2520,Microchip, Chandler, Arizona, USA), three single-axis accelerome-ters (ADXL001, Analog Devices, Norwood, Massachusetts, USA), a128 kB Ferroelectric Random Access Memory (F-RAM) chip for datastorage (FM25V10, Ramtron, Colorado Springs, Colorado, USA), anda Lithium Ion rechargeable coin battery for power supply (PD2023,Korea PowerCell, Chungnam, Korea). The constructed tri-axisaccelerometer can record mechanical impacts with a maximumsampling frequency of 3 kHz. The sensing range for each sensingaxis is 500 g (g = 9.8 m/s2, gravitational acceleration) and the vec-

tor summation of all three axes is 866 g. Preliminary tests showedthat both the sensing range and sampling frequency were adequateto capture the impacts experienced by blueberry during harvest-ing. With all electronic components being cast in silicone rubber,the diameter of the instrumented sphere is 25.4 mm. Four BIRDsensors were used during the field tests and they were fully cali-brated for their accuracy (0.53%) and precision (0.63%) to ensurethe data collected by the four sensors were comparable. Based onpreliminary test results, a sampling threshold of 18 g was selectedto filter out random noise and to exc