Matthew D. Whiting

Performance Evaluation of Mechanical Cherry Harvesters for Fresh Market Grade Fruits

Rising harvest costs and looming labor shortages are threatening profitability in the sweet cherry (Prunus avium L.) industry. The current study obtained baseline data on performance and efficiency for potential mechanical or mechanically-assisted systems for improving harvest efficiency of fresh market grade sweet cherries. We compared a prototype system that detaches fruit using impact force, with a system that detaches fruit using vibration, through a series of excited vibration tests. A group of single axial accelerometers were installed at different locations in sweet cherry trees to record the acceleration in response to applied force. From field experiments with accelerometers and assessment of fruit removal, we found that energy transmission along the woody structure differed with different excitation modes. The vibratory shaker resulted in higher efficiency of fruit removal and less fruit damage compared with impact harvester. Obtained results provide some critical information required for designing a more effective mechanical harvester with better produce quality.

An integrated cloud-based platform for labor monitoring and data analysis in precision agriculture

Harvest labor has became a prevailing cost in cherry and other Specialty Crops industry. We developed an integrated solution that provided real-time labor monitoring, payroll accrual, and labor-data-based analysis. At the core of our solution is a cloud-based information system that collects labor data from purposely designed labor monitoring devices, and visualizes real-time labor productivity data through a mobile-friendly user interface. Our solution used a proprietary process [1] to accurately associate labor data with its related worker and position under a many-to-many employment relation. We also describe our communication API and protocol, which are specifically designed to improve the reliability of data communication within an orchard. Besides its immediate benefits in improving the efficiency and accuracy of labor monitoring, our solution also enables data analysis and visualization based on harvest labor data. As an example, we discuss our approach of yield mapping based on harvest labor data. We implemented the platform and deployed the system on a cloud-based computing platform for better scalability. An early version of the system has been tested during the 2012 harvest season in cherry orchards in the U.S. Pacific Northwest Region.

Efficacy of unmanned helicopter in rainwater removal from cherry canopies

Developed was an in-field sensing system to monitor cherry canopy micro-climate.Unmanned helicopter was evaluated for canopy rainwater removal.Effect of flight altitude and payloads on rainwater removal was quantified. Rain-induced fruit cracking causes significant economic loss for fresh market sweet cherry growers annually. To prevent cherry cracking, timely removal of rainwater from fruit is the key. This study evaluated the efficacy of an unmanned middle-size helicopter to remove rainwater from Y-trellised cherry canopies. Helicopter downwash in hover at four altitudes, with and without a payload, was quantified with six anemometers deployed in tree canopies. Results showed that payload and altitude significantly affected hover downwash, which was greater at higher altitude of 7.6m above ground level (AGL) than lower altitude of 4.9m AGL with payload. In the absence of payload, hover downwash peaked at the altitude of 6.1m AGL. In the efficacy study, 5.0-mm rainwater was applied to cherry canopies by a rainfall simulation system, followed by the helicopter flying over canopies at three altitudes (4.9, 5.5 and 6.1m AGL), two travel speeds (1.3 and 2.7ms-1) and with or without payload. Rainwater removal at bottom (1.1m), middle (1.9m) and top (2.7m) of the canopies was calculated based on the change of leaf wetness of target canopies in 10min after rain. Overall, helicopter with payload flying 2.7ms-1 at 6.1m AGL removed significantly more rainwater (96.3%) from top section of canopies than groups without treatment (71.2%) and compared to other payload and travel speed conditions. Results also confirmed that the unmanned helicopter could provide sufficient downwash to remove rainwater effectively from bottom and middle canopy sections.

Response of UFO (Upright Fruiting Offshoots) on Cherry Trees to Mechanical Harvest by Dynamic Vibratory Excitation

Abstract. A series of mechanical harvest experiments was conducted in a high-density sweet cherry (Prunus avium L.) orchard to advance our knowledge of energy requirements and harvest efficiency. The primary goal of this research was to gain a better understanding of the dynamic response of fruiting wood to the forced vibrations and transmission patterns of vibratory energy on both the target and non-target trees. Experiments were conducted on UFO (upright fruiting offshoots) trees trained to an architecture consisting of unbranched upright offshoots. Field data collected from 31 tested trees revealed constant resonant frequencies within the upright offshoots at 8 to 10 Hz, which was attributed to the simple morphological structure. Single-impact excitation of the same peak force was also applied to the same offshoots. The resulting relative kinetic energy ratio (RKER) showed that resonant oscillation could obtain high amplification of vibratory energy, whereas the impact energy was attenuated. The supporting wire of the trellis system had little effect on the dynamic characteristics of tree limbs but could help in propagating vibratory energy within the tested tree and adjacent trees. In contrast, the foliage and fruits had a significant damping effect on both the dynamic response and vibratory energy transmission along limbs. The experimental assessment of mechanical harvest efficiency revealed a 77% fruit removal by vibratory force applied near the resonant frequency range of tested trees (between 12 and 16 Hz).

Assignation of Sweet Cherry Selections to 3 Taste Groupings Based on Perceived Sweetness and Sourness

UNLABELLED Providing consumers with basic taste properties of sweet cherries at point of purchase would allow consumers to make purchase decisions based on fruits intrinsic sensory attributes. The objective of this study was to develop a model to predict taste-grouping assignation of cherries into the following categories: (1) low sweetness/high sourness, (2) balance between sweetness and sourness, and (3) high sweetness/low sourness. A sensory panel (n = 10) was trained to recognize sweetness and sourness in 5 cultivars of sweet cherries and assign a taste grouping based on the perceived balance of sweetness and sourness. Four of these same cultivars were then evaluated for sweetness and sourness by a consumer panel (n = 117) and instrumentally for titratable acidity (TA) and soluble solids concentration (SSC). Results showed that for 3 of the 4 cherry cultivars, the sweetness/sourness balance of the cherries was not significantly different as evaluated instrumentally or by the trained panel. However, the balance determined by the consumer and the trained panel was different for 3 of the 4 cherry cultivars (P < 0.05). Based on trained panel perceived sweetness and sourness, a multinomial logit model was developed to predict the assignation of cherry taste grouping. The likelihood of group assignment depended on both the perceived sweetness and sourness of the cherry, with taste groupings agreed upon for 3 of 5 sweet cherry cultivars. As previous studies have indicated a positive relationship between cherry sweetness and sourness to consumer acceptance, these groupings show promise for assisting consumers in cherry selection at the point of purchase. PRACTICAL APPLICATIONS The prediction models proposed in this study suggest that both sweetness and sourness are important in the cherry characterization and the ratio between the 2 attributes may be appropriate for making taste-grouping assignments. These groupings may then be used to provide additional sensory information to consumers to assist them in cherry selection at the point of purchase.

Canopy Architecture Affects Light Interception in Sweet Cherry Your

Canopy light interception is fundamental factor contributing to horticultural crop performance and quality. No studies have evaluated light interception of modern fruit tree architectures such as compact fruiting walls. Herein we report on daily trends in Photosynthetically active radiation (PAR) interception in sweet cherry trees trained to vertical (upright fruiting offshoots (UFO)) and angled (Y-trellised) fruiting wall architectures using a new developed mobile sensor system. PAR levels at ca. 35 cm above the soil surface were determined every 2 hours on one day in early July 2011 from 0700 to 1900 hr, and compared with levels under clear sky. Two North-South rows from each architecture were tested. The average of daily light interception (LI%) by the canopies for ‘Y’ trellised trees was 82%, higher than that for UFO, 60%. Difference between architectures increased between sunrise and noon from 4.6% to 51.4%, and then decreased to 3.5% at sunset. Further, UFO architecture had greater variation of light interception throughout the day than Y-trellised architecture did, with standard deviations 0.28 and 0.093, respectively. Our results suggest that, for Y-trellised architecture, light interception values between 900 HR and 1100 HR, or between 1500 HR and 1700 HR are representative of daily interception. For UFO architecture, the representative light interception values are between 900 HR and 1100 HR, or 1300 HR and 1500 HR.

Mechanical harvesting of UFO Cherry: Investigation of tree plant dynamics

A series of harvesting experiments was conducted in a high density sweet cherry (Prunus avium L.) orchard to advance our knowledge of energy requirements and harvest efficiency for mechanical harvest of fresh market quality fruit. Our primary goals were to better understand the dynamic response of fruiting wood to forced vibrations and the transmitting pattern of vibratory energy throughout the target and non-target trees. Experiments were conducted on trees trained to a novel architecture comprised of unbranched upright shoots. Field data collected from 31 trees revealed constant resonant frequencies within upright limbs at 8~10 Hz, which we attribute to the simple morphological structure. Single impact excitation was applied also to the same limbs and with the same peak force. Resulting relative kinetic energy ratio (RKER) showed that resonant oscillation could obtain high amplification of vibratory energy whereas the impact energy was attenuated. The supporting wire of trellis system has little effect on dynamic characteristics of the tree limbs. But it could help in propagating vibratory energy within the tree and the adjacent trees. In contrast, the foliage and fruit have a significant damping effect on both the dynamic response and vibratory energy transmission along limbs. A preliminary assessment on mechanical harvest efficiency revealed 77% fruit removal by vibratory force applied near the resonant frequency range of the trees (between 12 and 16 Hz).To develop an appropriate mechanical harvester suitable for a novel cherry tree architecture system of upright fruiting offshoot (UFO), a series of fruit harvesting dynamics investigation was performed on three-year-old UFO sweet cherry (Prunus avium L.) of ‘Selah’ cultivar in an intensively-managed orchard. Our goal was to obtain a comprehensive understanding of the tree responses to forced vibration as well as the transmittal pattern of vibratory energy which causes fruits to detach. Field data collected from 31 UFO cherry trees indicated that UFO trees featured a low morphological variability and resonant frequencies. Therefore, a representative UFO tree was chosen to test its dynamic behaviors under oscillation of 8~30 Hz and showed its resonant frequency at 10 Hz and 18 Hz. In contrast to oscillation, impact excitation also was applied to the representative tree at the same excited offshoot and the same peak force. Relative kinetic energy ratio (RKER) in the tree showed that resonant oscillation could obtain high amplification of vibratory energy while impact was attenuated. Furthermore, dynamic trials were conducted on UFO cherry tree to assess the effect of cordon and growth stage on the resonant frequency and vibratory energy transmission. The results provided important information on regulating mechanical harvest condition for optimizing yields. The supporting wires have little effect on dynamic behaviors of UFO tree while foliage and fruits have a significant damping effect on the dynamic response and vibratory energy transmission. Accompanying dynamic analysis, mechanical harvest yield of UFO cherry under oscillation was assessed by applying a range of frequency (6~20 Hz). It showed that the resonant frequency region (12~16 Hz) had noticeable efficiency on harvesting the tested UFO cherry trees, which at the highest frequency was above 77%.

Automated Detection of Branch Shaking Locations for Robotic Cherry Harvesting Using Machine Vision

Automation in cherry harvesting is essential to reduce the demand for seasonal labor for cherry picking and reduce the cost of production. The mechanical shaking of tree branches is one of the widely studied and used techniques for harvesting small tree fruit crops like cherries. To automate the branch shaking operation, different methods of detecting branches and cherries in full foliage canopies of the cherry tree have been developed previously. The next step in this process is the localization of shaking positions in the detected tree branches for mechanical shaking. In this study, a method of locating shaking positions for automated cherry harvesting was developed based on branch and cherry pixel locations determined using RGB images and 3D camera images. First, branch and cherry regions were located in 2D RGB images. Depth information provided by a 3D camera was then mapped on to the RGB images using a standard stereo calibration method. The overall root mean square error in estimating the distance to desired shaking points was 0.064 m. Cherry trees trained in two different canopy architectures, Y-trellis and vertical trellis systems, were used in this study. Harvesting testing was carried out by shaking tree branches at the locations selected by the algorithm. For the Y-trellis system, the maximum fruit removal efficiency of 92.9% was achieved using up to five shaking events per branch. However, maximum fruit removal efficiency for the vertical trellis system was 86.6% with up to four shakings per branch. However, it was found that only three shakings per branch would achieve a fruit removal percentage of 92.3% and 86.4% in Y and vertical trellis systems respectively.

Preliminary Testing of a System for Evaluating Picker Efficiency in Tree Fruit

Herein we present a real-time monitoring system that can track and record individual picker efficiency during harvest of tree crops. It integrates a digital weighing scale, RFID reader/writer, RFID tags, computational unit, and a wearable datalogger housed in a protective enclosure attached to the picker’s belt. As harvested fruit is dumped into a standard collection bin situated on the scale, the system reads simultaneously the picker’s ID (RFID tag) and records the incremental weight of fruit. Weight data are transmitted wirelessly to the picker’s datalogger which displays, via LCD, the total weight of harvested fruit. The performance of the prototype system was evaluated during harvest of sweet cherries (Prunus avium L.) and apples (Malus domestica Borkh.). The mean harvest rate for manual harvest of ‘Cowiche’ sweet cherry trees trained to a planar, compact architecture was 0.80 kg/person/min. In addition, preliminary tests showed that harvesting with a mechanical-assist harvest system improved harvest rate in a ‘Skeena’ sweet cherry orchard trained to a Y-trellised system to 1.25 kg/person/min. In comparison, harvest rate of ‘Fuji’ apple trees trained to a moderate density central leader architecture and ‘Braeburn’/’M9’ apple trees trained to a high density tall spindle system was 3.58 kg/person/min and 5.61 kg/person/min, respectively.

In Field Assessment on the Relationship between Photosynthetic Active Radiation (PAR) and Global Solar Radiation Transmittance through Discontinuous Canopies

In many crop models, the process of radiation transmittance through the canopy is normally described as an exponential attenuation process (Beer’s Law equation), which is assumed to be valid for canopies covering the ground with a random spatial distribution of leaves. However, for discontinuous canopies, where a distinctive row pattern of plant exists, there is a more complex situation because of the presence of gaps between individual plants. This must be accounted for when characterizing radiation relationships for these kinds of systems, in particular when short time-scales are of interest. Photosynthetically active radiation (PAR) transmittance (τPAR) is more commonly studied and reported than global solar radiation (Sg) transmittance (τSg). However, both PAR and Sg are important in radiative transfer sub-models used in plant growth simulation. In this work simultaneous measurements of τSg and τPAR under discontinuous canopies were performed, and the hourly changes in radiation transmittance for PAR and global solar radiation were characterized. Two methods were assessed to transform between τSg and τPAR. The two methods yielded similar results for low values of transmittance, but disagreement occurred for higher values of transmittance. The method based on a fixed value for the ratio of extinction coefficients for PAR and S g outperformed the method based on a linear relationship between τPAR and τSg with average relative errors (RE) of 7.97% vs. 13.29% and 2.84% vs. 7.77% for hourly and daily time-scale, respectively.