Patrick A. Scharf

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.

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).

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%.

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.

A Hand-Held Mechanical Blossom Thinning Device for Fruit Trees

Abstract. Blossom or green fruit thinning is a common practice for producing larger and higher quality fruit in tree fruit production. Mechanical blossom thinning could decrease production costs when compared to hand thinning of either blossom or green fruit. In stone fruit, a few chemical thinning agents are available or reliable. In apple, chemical thinning agents are under regulatory scrutiny, and efficacy is highly dependent on weather. This study aimed to develop a hand-held mechanical thinning device suitable for thinning blossoms on fruit trees pruned to different architectures. Research prototypes of different configurations have been developed, fabricated, and tested in blossom thinning operations in commercial orchards. Results obtained from field tests verified that a hand-held mechanical blossom thinner could effectively remove blossoms from apple, stone fruits, and sweet cherry. Among all evaluated parameters, spindle speed appeared to have the greatest direct effect on the capacity to remove blooms. Field test results indicated that the test device could remove 61.1%, 30.8%, and 18.0% flowers on a single branch with a swipe around 0.5 m·s -1 under high (2500-3000 rpm), medium (1500-1800 rpm), and low (500-800 rpm) speed settings, respectively. In trees trained to central leader architecture, 85 s was required to remove 50% of blossoms using the hand-held mechanical thinner and at least 180 s when the task was accomplished by hand. Field tests also revealed that a better ergonomic design of the device could further improve operational efficiency.

A Hand-held Mechanical Blossom Thinning Device for Fruit Trees

Blossom thinning is a common practice for producing lager and better quality fruits in tree fruit production. Mechanical thinning has the potential of decreasing production cost comparing with manual thinning and supports more environment friendly production than chemical thinning. This study aimed to develop a hand-held mechanical thinning device suitable for thinning blossoms on fruit trees. Research prototypes of different configurations have been developed, fabricated and tested in actual blossom thinning operations in commercial orchards. Results obtained from field tests verified that a hand-held mechanical blossom thinner could effectively remove blossoms from fruit trees of different pruned structures. Among all evaluated parameters, the spindle speed seems to have the most direct effect on blossom removal capacity. Outcomes obtained from this study proved that a hand-held mechanical blossom thinner could provide tree fruit growers a handy tool to perform effective blossom thinning operation. Field tests using current research prototypes also indicated that the device needed to have a better ergonomic design for further improving operation efficiency through reducing labor intensity.

Dynamic Response of Sweet Cherry Tree to Oscillating Excitations for Mechanical Harvest

Abstract Current mechanical cherry harvest uses either impact or vibration excitations to shake tree branches to create a detachment force on cherry stems to remove cherries from the tree. A comprehensive understanding of fruit detaching energy distribution on cherry trees is essential for designing such mechanical cherry harvesters. This research was conducted to quantify the dynamic response of cherry trees to forced oscillating excitation. In this study, a set of accelerometers were placed at different locations on a sweet cherry tree. Acceleration signals at those locations corresponding to a band of sinusoidal excitations ranging from 2 to 40 Hz, covering the most commonly used excitation frequencies in vibrating harvest, were recorded and then integrated into velocity and displacement responses. A peak excitation force of 28.9 N was used at all excitation frequencies. Results showed that the first two resonant frequencies of the test cherry tree were around 6 and 14 Hz, respectively. The responding displacement at monitoring locations ranged from 1 mm to 11 mm under the first two resonant frequencies. The third resonant frequency was found at around 25 Hz, under which the responding displacement were noticeably lower than the corresponding values at the first two resonant frequencies. Under the same force excitation amplitude, the displacement responses of most branches increased as the location is further away from the excitation point. Experimental results also indicated that the vibratory energy of each branch in the path from the excitation point to the terminal branch was transmitted and observably amplified along the straight transmission path without branch junctions at all resonant frequencies. It implies that cherry trees with simple structure, straight branch orientation and less branch junction will have higher harvest efficiency when in impact or vibration harvesting.