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Air Suspension-based Catching Mechanism for Mechanical Harvesting of Apples
5th IFAC Conference on Sensing, Control and Automation for 5th IFAC 5th IFAC Conference Conference on on Sensing, Sensing, Control Control and and Automation Automation for for Agriculture Agriculture Agriculture Available online at www.sciencedirect.com 5th IFAC Conference on Sensing, Control and Automation for August 14-17, 2016. Seattle, Washington, USA August 14-17, August 14-17, 2016. 2016. Seattle, Seattle, Washington, Washington, USA USA Agriculture August 14-17, 2016. Seattle, Washington, USA
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Air Air Suspension-based Catching Mechanism for Mechanical Harvesting of Air Suspension-based Suspension-based Catching Catching Mechanism Mechanism for for Mechanical Mechanical Harvesting Harvesting of of Apples Apples Air Suspension-based Catching Mechanism for Mechanical Harvesting of Apples Shaochun Ma*. Manoj Karkee**. Apples Han Fu***. Daozong Sun****. Qin Zhang***** Shaochun Shaochun Ma*. Ma*. Manoj Manoj Karkee**. Karkee**. Han Han Fu***. Fu***. Daozong Daozong Sun****. Sun****. Qin Qin Zhang***** Zhang***** Shaochun Ma*. Manoj Karkee**. Han Fu***. University, Daozong Sun****. Qin Zhang***** *College of Engineering, China Agricultural Beijing 100083, China *College *College of of Engineering, Engineering, China China Agricultural Agricultural University, University, Beijing Beijing 100083, 100083, China China (Tel: (86)010-62736638; e-mail: [email protected]). (Tel: (86)010-62736638; e-mail: (Tel: (86)010-62736638; e-mail: [email protected]). [email protected]). *College of Engineering, China Agricultural University, Beijing 100083, China **Center for Precision and Automated Agricultural Systems, Washington State University, **Center and Systems, **Center for for Precision Precision and Automated Automated Agricultural Agricultural Systems, Washington Washington State State University, University, (Tel: (86)010-62736638; e-mail: [email protected]). Prosser, 99350,USA. (e-mail: [email protected]). Prosser, 99350,USA. (e-mail: [email protected]). Prosser, 99350,USA. (e-mail: [email protected]). **Center for Precision and Automated Agricultural Systems, Washington State University, ***College ***College of of Engineering, Engineering, China China Agricultural Agricultural University, University, Beijing Beijing 100083, 100083, China China ***College of Engineering, China Agricultural University, Beijing 100083, China Prosser, 99350,USA. (e-mail: [email protected]). (e-mail: [email protected]). (e-mail: [email protected]). (e-mail: [email protected]). ***College Engineering, China Agricultural University, Beijing 100083,Guangzhou China ****College of of Electronic Engineering, South China Agricultural University, ****College South ****College of of Electronic Electronic Engineering, Engineering, South China China Agricultural Agricultural University, University, Guangzhou Guangzhou (e-mail: [email protected]). 510642, China (e-mail:[email protected]) 510642, China 510642,Engineering, China (e-mail:[email protected]) (e-mail:[email protected]) ****College ofPrecision Electronic South China Systems, Agricultural University, Guangzhou *****Center for and Automated Agricultural Washington State University, *****Center for Precision and Automated Agricultural *****Center for Precision and China Automated Agricultural Systems, Systems, Washington Washington State State University, University, 510642, (e-mail:[email protected]) Prosser, 99350,USA. (e-mail: [email protected]). Prosser, (e-mail: Prosser, 99350,USA. (e-mail: [email protected]). [email protected]). *****Center for Precision and99350,USA. Automated Agricultural Systems, Washington State University,
Prosser, [email protected]). Abstract: Bruise damage is the 99350,USA. most critical(e-mail: barrier for the application of mechanical harvesting Abstract: Bruise damage is most barrier for the application of mechanical Abstract: Bruise damageapples. is the the One mostofcritical critical barrier for of thebruising application offruit-to-catching mechanical harvesting harvesting systems for fresh market the major source is the surface systems fresh apples. One of the source of bruising is surface systems for forBruise fresh market market apples. One ofcritical the major major source of bruising is the theoffruit-to-catching fruit-to-catching surface Abstract: damage is the most barrier for the application mechanical harvesting and fruit-to-fruit contact when fruit detached by harvester is collected by a catching system. In this and fruit-to-fruit contact when fruit detached by harvester is collected by a catching system. In and fruit-to-fruit contact when fruit detached by harvester is bruising collectedisbythea fruit-to-catching catching system. surface In this this systems for fresh market apples. One of the major source of work, a fruit catching mechanism was designed and fabricated using air suspension as a cushion to work, aa fruit mechanism was designed and fabricated using suspension as aa cushion to work, fruit catching catching mechanism was designed and fabricated using air air suspension as cushion to and fruit-to-fruit contact when fruit detached by harvester is collected by a catching system. In this minimize fruit bruising during mechanical harvesting. Various apple cultivars with different bruising minimize fruit bruising during mechanical harvesting. Various apple cultivars with different bruising minimize fruit bruising during mechanical harvesting. Various apple cultivars with different bruising work, a fruit catching mechanism was designed and fabricated using air suspension as a cushion to susceptibility (‘Granny Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’, and ‘Pink lady’) were used susceptibility (‘Granny Smith’, ‘Jazz’, ‘Fuji’, ‘Pacific Rose’, and ‘Pink lady’) used susceptibility (‘Granny Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’, and with ‘Pinkdifferent lady’) were were used minimize fruit bruising during mechanical harvesting. Various apple cultivars bruising to evaluate the performance of an air suspension-based catching mechanism. The results showed that to evaluate performance of air catching mechanism. The results showed that to evaluate the the(‘Granny performance of an an air suspension-based suspension-based catching mechanism. The results showed that susceptibility Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’,ofand ‘Pink lady’) were used fruit catching with air suspension can significantly reduce the percentage damaged apples for all of fruit catching with air suspension can significantly reduce the percentage of damaged apples for all of fruit catching with air suspension can significantly reduce the percentage of damaged apples for allthat of to evaluate the performance of an air suspension-based catching mechanism. The results showed six cultivars evaluated in this work compared to fruit catching without air suspension. It was found that six cultivars evaluated in this work compared to fruit catching without air suspension. It was found that six cultivars evaluated in this workcan compared to fruitreduce catching without air suspension. Itapples was found that fruit catching with air suspension significantly the percentage of damaged for all of the decrease in fruit damage rate with air suspension ranged from 14.5 to 36.9% for different cultivars. the decrease in fruit damage rate with air suspension ranged from 14.5 to 36.9% for different cultivars. the decrease in fruit damage rate with air suspension ranged from 14.5 to 36.9% for different cultivars. six cultivars evaluated in this work compared to fruit catching without air suspension. It was found that The effect of air suspension on the of downgraded apples was significant (compared to The effect air suspension on the percentage percentage of apples was not not (compared to Thedecrease effect of ofin airfruit suspension on percentage of downgraded downgraded apples not significant significant (compared to the damage ratethe with air except suspension ranged from 14.5was toThe 36.9% for different cultivars. catching apples without air suspension) for Pink Lady cultivar. reduction in downgraded catching apples without air suspension) except for Pink Lady cultivar. The reduction in downgraded catching apples without air suspension) except for Pink Lady cultivar. The reduction in downgraded The effect of air suspension on the percentage of downgraded apples was not significant (compared to fruit ranged from 3% to 9.3% among different cultivars (except for Pink Lady(19%)). fruit ranged from 3% among for Lady(19%)). fruit ranged fromwithout 3% to to 9.3% 9.3% among different different cultivars (except for Pink PinkThe Lady(19%)). catching apples air suspension) exceptcultivars for Pink(except Lady cultivar. reduction in downgraded Keywords: market apple; mechanical harvesting; air suspension catching; bruises; © 2016, IFACfresh (International Federation of Automatic Control) Hosting by Elsevier Ltd. Allapple rights reserved. Keywords: fresh market apple; mechanical harvesting; air suspension catching; apple bruises; fruit ranged from 3% to 9.3% among different cultivars (except for Pink Lady(19%)). Keywords: fresh market apple; mechanical harvesting; air suspension catching; apple bruises; downgraded apples. downgraded apples. downgraded apples.market apple; mechanical harvesting; air suspension catching; apple bruises; Keywords: fresh downgraded apples.
1. INTRODUCTION 1. 1. INTRODUCTION INTRODUCTION Apple industry around the world depends currently on 1. INTRODUCTION Apple industry around the Apple industry around the world world depends depends currently currently on on ‘hand picking’ to harvest fruit from random spatial ‘hand picking’ to harvest fruit from random spatial ‘hand picking’ around to harvest fruit from random spatial Apple industry the world depends currently on locations on individual tree canopies. In the past, research locations on tree In past, locations on individual individual tree canopies. canopies. In the the past, research research ‘hand picking’ to harvest fruit from random spatial and development on mechanizing apple harvesting has and development on apple harvesting has and development on mechanizing mechanizing apple harvesting has locations on individual treemethods canopies. In theindividual past, research focused mainly on robotic to pick fruit. focused mainly on robotic methods to pick individual fruit. focused mainly on robotic methods to pick individual fruit. and development on mechanizing apple harvesting has However, due to lack of desired level of accuracy, speed, However, due to lack of desired level of accuracy, speed, However, due to lack of desired level of accuracy, speed, focused mainly on robotic methods to pick individual fruit. robustness and cost, no successful robustness and no commercially commercially successful robotic robotic robustness andtocost, cost, commercially robotic However, due lack no ofavailable desired level ofsuccessful accuracy, speed, harvester have been (Gongal et al., 2015). harvester have been available (Gongal et al., 2015). harvester have been noavailable (Gongal et al., robotic 2015). robustness and cost, commercially successful Alternatively, bulk fruit removal methods have also been Alternatively, bulk fruit removal have also been Alternatively, bulk fruitavailable removal methods methods have also2015). been harvester have been (Gongal et al., investigated (Li et al., 2011; De Kleine, 2015). One of the investigated (Li et al., 2011; De Kleine, 2015). One of the investigated (Libulk et al., 2011; De Kleine, 2015). One ofbeen the Alternatively, fruit removal methods have also commonly used methods for bulk harvesting has been a commonly used methods for bulk harvesting has been commonly used methods forDe bulk harvesting has been investigated (Li et al., 2011; Kleine, 2015). One of theaa linear shaker used to shake the trunk or branches. Bulk linear shaker used to trunk or Bulk linear shaker used to shake shake the trunk or branches. branches. Bulka commonly used methods for the bulk harvesting haslevel been harvesting has the potential to achieve desired of harvesting has the potential to achieve desired level of harvesting has the potential to achieve desired level of linear shaker used to shake the trunk or branches. Bulk speed and cost for mechanized apple harvesting. However, speed and cost for mechanized apple harvesting. However, speed and cost for harvesting. However, harvesting has themechanized potential toapple achieve desired of the method is limited by excessive fruit bruisinglevel during the method is limited by fruit during the method is for limited by excessive excessive fruit bruising bruising during speed and cost mechanized apple harvesting. However, detachment and catching caused primarily by fruit-to-fruit, detachment catching primarily by fruit-to-fruit, detachment and catching caused primarily by fruit-to-fruit, the method and is limited bycaused excessive fruitsurface bruising during fruit-to-branch and fruit-to-catching impacts fruit-to-branch and fruit-to-catching surface impacts fruit-to-branch and fruit-to-catching surface impacts detachment and catching caused primarily by fruit-to-fruit, (Zeebroeck et al., 2007). (Zeebroeck et 2007). (Zeebroeck et al., al.,and 2007). fruit-to-branch fruit-to-catching surface impacts Researchers have conducted a series of studies on fruit (Zeebroeck et al., 2007). Researchers have conducted Researchers have conducted aa series series of of studies studies on on fruit fruit catching devices to reduce the bruise damage of freshcatching devices to reduce the bruise damage of freshcatching devices reduce the bruiseofdamage Researchers have toconducted a series studiesofonfreshfruit catching devices to reduce the bruise damage of fresh-
market fruit during bulk harvesting with mechanical market market fruit fruit during during bulk bulk harvesting harvesting with with mechanical mechanical shakers. Peterson et al. (2003) built upon their previous shakers. Peterson et al. (2003) built upon their previous shakers. Peterson et al.bulk (2003) built upon their previous market fruit during harvesting with mechanical apple harvesting system and created mirrored harvesting apple harvesting system and created mirrored harvesting apple harvesting system and created mirrored harvesting shakers. Peterson et al. (2003) built upon their machines, or a two-sided harvesting system. In thisprevious system, machines, or harvesting system. In system, machines, or aa two-sided two-sided harvesting system. In this this system, apple harvesting system and created mirrored harvesting catching conveyors with padded surface were designed to catching conveyors with padded surface were designed to catching conveyors with harvesting padded surface were designed to machines, or a two-sided system. In this system, intercept falling fruit and elevate the fruit to a collection intercept falling fruit and elevate the fruit to a collection intercept falling fruit and elevate the fruit to a collection catching conveyors with padded surface were designed to conveyor. The results showed that the system achieved an conveyor. The results showed that the system achieved an conveyor. The results showed that the system achieved an intercept falling fruit and elevate the fruit to a collection Extra Fancy fruit quality of 59%. cushion Extra Fancy fruit quality of only only 59%. The The cushion Extra Fancy fruit quality only The cushion conveyor. The results showedofthat the 59%. system achieved an materials used on catching surface can absorb the materials used on catching surface can absorb the materials usedfruit on quality catching surface can The absorb the Extra Fancy of only 59%. cushion mechanical energy during contact, either by slowing down mechanical energy contact, either slowing down mechanical energyonduring during contact, either by by slowing down materials used catching surface can absorb the compression or impact, which significantly affects the fruit compression or impact, which significantly affects the fruit compression or impact, which significantly affects thedown fruit mechanical energy during contact, either by slowing bruise damage (Jarimopas et al., 2007; Opara and Pathare, bruise damage et 2007; and bruise damage (Jarimopas et al., al., 2007; Opara Opara and Pathare, Pathare, compression or(Jarimopas impact, which significantly affects thethree fruit 2014; De Kleine, 2015). In 2011, Ortiz et al. studied 2014; De Kleine, 2015). Ortiz et three 2014; De Kleine, 2015). In Inet2011, 2011, Ortiz Opara et al. al. studied studied three bruise damage (Jarimopas al., 2007; and Pathare, different catching surfaces (a floor, an different catching surfaces (a concrete concrete floor, an elevated elevated different catching surfaces (a concrete floor, an elevated 2014; De Kleine,with 2015). In 2011, Ortiz et al.and studied three canvas provided aa frame and wheels, aa concrete canvas provided with frame and wheels, and concrete canvas provided with a frame and wheels, and a concrete different catching surfaces (a concrete floor, an elevated floor covered with aa shock absorbing canvases) to assess floor covered with absorbing canvases) assess floor covered with a shock shock absorbing canvases) to assess canvas provided with a The frame and wheels, and a to concrete fruit damage on citrus. elevated canvas was the least fruit damage on citrus. The elevated canvas was the least fruit damage on citrus. The absorbing elevated canvas was to theassess least floor covered with a shock canvases) damaging surface to fruit, indicating that shock absorbing damaging surface to fruit, indicating that shock absorbing damaging surface to fruit, indicating that shock absorbing fruit damage on citrus. The elevated canvas was the least canvases could be used to reduce fruit damage. De Kleine canvases could be used to fruit damage. De Kleine canvases could be to used to reduce reduce fruitthat damage. De Kleine damaging surface fruit, indicating shock absorbing and Karkee (2015) also built aa three-tiered catch-frame to and Karkee (2015) also built catch-frame to and Karkee (2015) also to built a three-tiered three-tiered catch-frame to canvases could be used reduce fruit damage. De Kleine collecting fruit removed from trellised apple trees. Plastic collecting fruit removed from trellised apple trees. Plastic collecting fruit removed fromatrellised applecatch-frame trees. Plastic and Karkee (2015) also built three-tiered to mesh fabric was used for apple catching at each tier. The mesh fabric was used apple catching at tier. The mesh fabric wasremoved used for forfrom appletrellised catching at each each tier. The collecting fruit apple trees. Plastic catching devices with different types of cushion materials catching devices with of catching devices with different different types of cushion cushion materials mesh fabric was used for apple types catching at each materials tier. The catching devices with different types of cushion materials
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studied in the past can reduce the fruit damage caused by fruit-to-catching surface contact. However, these devices have limited ability to minimize damage caused by fruit-tofruit contact as the fruit on the catching surface can be hit by fruit detached later. A new type of catching device is desired to address this issue. In this work, we designed and fabricated an innovative concept of catching fruit detached by mechanical shaking devices. The catching mechanism designed in this work included air suspension as a cushion to decelerate (to reduce the contact force between fruit and catching surface) and separate (to reduce fruit-to-fruit contact) fruit before that reach the catching surface. The objective of this paper was to evaluate the performance of air suspension-based catching mechanism in reducing bruise damage levels on fruit harvested in modern apple orchards. 2. MATERIALS AND METHODS 2.1 Air Suspension Catching Before developing the fruit catching prototypes, we designed an air suspension platform (Fig.1a) and set up a series of lab tests to evaluate the air suspension catching concept (Fig.1b). A total of 30 pairs of apples (Golden Delicious) were used to perform the apple-to-apple impact test (Fig.2). Half of the samples (15 pairs) were used for the test with pressurized air (690 Kpa). In this case, an apple was suspending above the platform and another apple dropped from the height of 0.6 m impacting the suspended apple. Another 15 pairs of apples were used for the test without pressurized air. In this case an apple was dropped from a height of 0.6 m to impact another apple placed on the platform without air suspension. All apples were marked and stored for 24 hrs before they were analysed for damages (bruising). The results showed that the damage rate can reach up to 75% without air suspension while the damage rate can be reduced to as low as 16.7% when the pressurized air was used to slowdown and suspend apples. The results showed that air suspension could substantially reduce impact force in the event of apple-to-apple contacts.
Fig. 2. The effect of air suspension on apple damage percentage
Thus, the fruit catching mechanism (Fig. 3) was designed to incorporate the following two critical functionalities: (1) decelerate the fruit falling from branches; and (2) separate fruit before they land on the catching surface. These two functionalities are essential to reduce fruit damage and to achieve desired level of fruit quality during mechanical harvesting. The first prototype of the catching mechanism was fabricated and evaluated during 2015 apple harvesting season in Washington State (Yakima Valley Orchards, Othello, WA). Two air hose couplers (component 2) are used to connect air inlets of catching mechanism to air compressor outlets. Once the hoses are engaged and air compressor is turned on, an air cushion will be generated for decelerating and separating falling fruit. When the air compressor is turned off, the scattered fruit could be landed on the foam surface (component 4) slowly. In addition, the catcher wall (component 1) is used to prevent apples from falling out of the air cushion boundary.
1 4
2 3 Fig. 3. Overview of the conceptual design and prototype of the air suspension-based fruit catching mechanism; 1. Catcher wall; 2. Pressurized air inlet; 3. Air outlet holes on PVC pipe; 4. Foam cushion
2.2 Fruit Catching Process
a)
During apple harvesting process, the pressurized air blown out from small nozzles on the PVC pipes generates an upward force to decelerate the apples accelerating down from the branches. The risk of apple bruises caused by apple-to-apple or apple-to-catcher contact will be decreased because of reduced impact force. As the falling fruit reach the zone with blown air, the fruit clumped together in a random fashion are separated, which minimizes impact with each other leading to reduced level of fruit damage.
b)
Fig.1. a) Air suspension platform; b) Apple-to-apple impact test
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(a) Before Shaking: a cluster of apples are hanging on the trellised limb.
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that the performance of the air suspension mechanism could be evaluated against a standard method. Table 1 showed the repetitions and the total number of apples caught for each experiment. After each test, harvested apples were stored in the lab for 24 hours to let them develop bruising. The diameter of each bruise area was then measured for bruise severity. If there are more than one bruise spot on an apple, the equivalent diameter of multiple bruises were calculated according to equation 1. Based on USDA Grades and Standards (United States Department of Agriculture, 2002; Peterson et al., 2010, De Keline, 2015), apple grade classes for various bruise specifications (diameter of individual bruises or equivalent diameter of multiple bruises) were determined (Table 2).
Where
(1)
equivalent diameter (mm) of multiple bruises on an apple;
diameter (mm) of (i=1, 2, ……, n) bruise on an apple.
(b) During Shaking: the cluster of detached apples were separated and suspended by the pressurized air flow.
Table 1. Field evaluation of catching mechanism with and without air suspension
(c) After Shaking: collected apples are scattered on the foam covered surface of catching mechanism.
Cultivar
Replicates
Grammy Smith Honeycrisp Jazz Fuji Pacific Rose Pink Lady
10 10 10 5 5 5
Number of Apples Tested Pressurized w/o Air (690 Pressurized kpa) Air 90 93 65 94 33 25 32
81 100 25 39 42
Table 2. Classification of apple bruises
Fig. 4. Two major functionalities of the catching mechanism with air suspension: deceleration and separation.
2.3 Field Evaluation of Catching Mechanism The field evaluation was performed in commercial orchards with ‘Granny Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’, and ‘Pink lady’ apple cultivars (Allan Bros., Natches, WA). The performance of the air suspensionbased catching system was evaluated in terms of bruising rate, which was defined as the percentage of apples with a bruise from total number of apples caught by the catching mechanism. Air suspension was achieved with 690 kpa pressurized air blowing out into the fruit falling zone. An experiment was also conducted without pressurized air so
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Class # 1 2 3 4 5 6
USDA Fresh Market Standard “Extra Fancy” “Extra Fancy” “Extra Fancy” “Extra Fancy” “Fancy” Downgraded
Bruise specifications (mm)
, or cuts/punctures of any size
3. RESUSLTS AND DISCUSSION
Figure 5 illustrated the percentage of apples categorized to each of the six classes (1 to 6). The paired histograms show the effect of air suspension-based catching (ASC) mechanism on apples of each class. The percentages of “Extra Fancy” Class 1 apples increased by as much as 26.1%
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for Pacific Rose cultivar. The same for Pink Lady was 14.5%, Jazz was 21.7%, Honeycrisp was 36.9%, Granny Smith was 20.7% and Fuji was 29.3%. The percentages of total damaged apples (sum of percentage of apples in class 2-6) were reduced by as much as 36.9% for Honeycrisp. The same was only 20.7% for Granny Smith and 26.1% for Pacific Rose.
(d) Fuji
(a) Granny smith
(e) Pacific rose
(b) Honeycrisp
(f) Pink lady Fig. 5. Comparison of fruit quality (due to bruising damage) levels w/ and w/o air suspension-based catching (ASC). Fig. a to f present the fruit quality results for six different cultivars of apples detached and caught with a shake-and-catch harvesting system.
(c) Jazz
During shake-and-catch harvesting of six different cultivars of apples without using air suspension method, the percentage of “Extra Fancy” Class 1, on average, was less than 50% (which means the percentage of total apples with certain level of bruising/damage accounted for more than 50%). Particularly, only 10% of Pacific Rose apples were 361
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in Class 1 (90% of apples were damaged to some extent). When the detached apples were caught using the air suspension method, the percentage of Class 1 apples increased at least by 14.5%, especially, for the Pacific Rose cultivar, an increase of 26.1% was found. For Honeycrisp cultivar, the “Extra Fancy” Class 1 increased to as high as 36.9% from 45.2% without air-suspension. In terms of percentage of downgraded apples in Class 6, the Pacific Rose (28.8%) and Pink Lady cultivars (41%) were two of the worst cultivars when caught without pressurized air. Thus, the catching methods/devices had great potential to reduce apple bruise/damage. When the air suspensionbased catching was used, the downgraded percentages of Pink Lady and Pacific Rose were reduced by 19% and 3.3%. In general, the results showed that the air suspension system has a positive impact on fruit quality during shake-andcatch harvesting as shown by a decrease of 14.5 to 36.9% in total damaged apples (sum of Class 2 to 6) and a decrease of 3 to 9.3% (except for Pink Lady (19%)) in downgraded apples. The differences in percentage of total damaged apples with pressurized air (690 kpa) and without pressurized air was significant for all six cultivars of apples at the 95% confidence level based on Student’s t-test (Table 1). For the percentage of downgraded apples, the differences were not significant except for Pink Lady cultivar at the 95% confidence level (Table 2). Table 2. T test of the effect of air suspension-based catching mechanism (ASC) on total damaged apples (sum of Class 2 to 6) Cultivar P (T<=t) Cultivar
Granny Smith 0.024 Fuji
P (T<=t)
0.028
Honey Crisp 0.003 Pacific Rose 0.027
Jazz 0.012 Pink Lady
P (T<=t) Cultivar
Granny Smith 0.68 Fuji
P (T<=t)
0.92
Honey Crisp 0.18 Pacific Rose 0.35
represented by apples in classes 2 to 5 (these classes are attributed only to bruising damage). For the downgrade or Class 6 of apples, the effect of ASC was limited because the apples in this class were not only attributed to bruising damage but also to cut/puncture damages, which would not be minimized by the use of ASC mechanism. Future work in this area could focus on identifying and addressing the sources for fruit cuts and punctures during bulk harvesting, which can then help reduce the percentage of downgraded fruit (Class 6). 4. CONCLUSION This study investigated the effect of air suspension-based catching mechanism (ASC) on apple bruises during shakeand-catch harvesting of six different cultivars of apples. The ASC mechanism was designed and fabricated to using air suspension as a cushion to minimize fruit bruising. To evaluate the significance of the effects of catching mechanism on apple bruises, Sudent’s t-tests were performed. From the study, it can be concluded that the two main functionalities (deceleration and separation) of new catching mechanism can significantly reduce the percentage of damaged apples (as high as 36.9%) for all of six cultivars evaluated in this work compared to fruit catching without air suspension. The effect of ASC mechanism on the percentage of downgraded apples was not significant (compared to catching apples without air suspension) except for Pink Lady. The future work can focus on identifying the sources of fruit cuts and punctures and improving ASC design and functionalities to address those issues. ACKNOWLEDGEMENTS
0.002
Table 2. T test of effect of air suspension-based catching mechanism (ASC) on downgraded Class 6 apples. Cultivar
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Jazz 0.56 Pink Lady 0.01
These findings indicated that ASC mechanism has a greater potential to decrease the percentage of total damaged apples from Class 2 to 6 than the potential to decrease the percentage of downgraded apples (Class 6). One of the reasons behind this result is that ASC can effectively reduce the risk of apple-to-apple and apple-to-catching surface contacts, which are the two main sources of apple bruises 362
This research was supported in part by Washington State University Agricultural Research Center federal formula funds, Project No. WNP0748 and No. WNP0728 received from the U.S. Department of Agriculture National Institutes for Food and Agriculture (NIFA). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture. Any opinions, findings, and conclusions expressed in this paper are those of the authors, and do not necessarily reflect the views of the U.S. Department of Agriculture nor of Washington State University. The authors would also like to express our gratitude to Dr. Long He, Mr. Lin Chen, Dr. Tao Wu, Dr. Weizu Wang, Mr. Patrick Scharf, Mr. Meng Zhang, Dr. Zhiqiang Wang, and Dr. Jintao Yao for their help in field test arrangement and experimental data collection. Also China Scholarship Council (CSC) sponsored Han Fu conducting collaborative PhD Dissertation research at WSU Center for Precision and Automated Agricultural Systems (CPAAS).
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Air Air Suspension-based Catching Mechanism for Mechanical Harvesting of Air Suspension-based Suspension-based Catching Catching Mechanism Mechanism for for Mechanical Mechanical Harvesting Harvesting of of Apples Apples Air Suspension-based Catching Mechanism for Mechanical Harvesting of Apples Shaochun Ma*. Manoj Karkee**. Apples Han Fu***. Daozong Sun****. Qin Zhang***** Shaochun Shaochun Ma*. Ma*. Manoj Manoj Karkee**. Karkee**. Han Han Fu***. Fu***. Daozong Daozong Sun****. Sun****. Qin Qin Zhang***** Zhang***** Shaochun Ma*. Manoj Karkee**. Han Fu***. University, Daozong Sun****. Qin Zhang***** *College of Engineering, China Agricultural Beijing 100083, China *College *College of of Engineering, Engineering, China China Agricultural Agricultural University, University, Beijing Beijing 100083, 100083, China China (Tel: (86)010-62736638; e-mail: [email protected]). (Tel: (86)010-62736638; e-mail: (Tel: (86)010-62736638; e-mail: [email protected]). [email protected]). *College of Engineering, China Agricultural University, Beijing 100083, China **Center for Precision and Automated Agricultural Systems, Washington State University, **Center and Systems, **Center for for Precision Precision and Automated Automated Agricultural Agricultural Systems, Washington Washington State State University, University, (Tel: (86)010-62736638; e-mail: [email protected]). Prosser, 99350,USA. (e-mail: [email protected]). Prosser, 99350,USA. (e-mail: [email protected]). Prosser, 99350,USA. (e-mail: [email protected]). **Center for Precision and Automated Agricultural Systems, Washington State University, ***College ***College of of Engineering, Engineering, China China Agricultural Agricultural University, University, Beijing Beijing 100083, 100083, China China ***College of Engineering, China Agricultural University, Beijing 100083, China Prosser, 99350,USA. (e-mail: [email protected]). (e-mail: [email protected]). (e-mail: [email protected]). (e-mail: [email protected]). ***College Engineering, China Agricultural University, Beijing 100083,Guangzhou China ****College of of Electronic Engineering, South China Agricultural University, ****College South ****College of of Electronic Electronic Engineering, Engineering, South China China Agricultural Agricultural University, University, Guangzhou Guangzhou (e-mail: [email protected]). 510642, China (e-mail:[email protected]) 510642, China 510642,Engineering, China (e-mail:[email protected]) (e-mail:[email protected]) ****College ofPrecision Electronic South China Systems, Agricultural University, Guangzhou *****Center for and Automated Agricultural Washington State University, *****Center for Precision and Automated Agricultural *****Center for Precision and China Automated Agricultural Systems, Systems, Washington Washington State State University, University, 510642, (e-mail:[email protected]) Prosser, 99350,USA. (e-mail: [email protected]). Prosser, (e-mail: Prosser, 99350,USA. (e-mail: [email protected]). [email protected]). *****Center for Precision and99350,USA. Automated Agricultural Systems, Washington State University,
Prosser, [email protected]). Abstract: Bruise damage is the 99350,USA. most critical(e-mail: barrier for the application of mechanical harvesting Abstract: Bruise damage is most barrier for the application of mechanical Abstract: Bruise damageapples. is the the One mostofcritical critical barrier for of thebruising application offruit-to-catching mechanical harvesting harvesting systems for fresh market the major source is the surface systems fresh apples. One of the source of bruising is surface systems for forBruise fresh market market apples. One ofcritical the major major source of bruising is the theoffruit-to-catching fruit-to-catching surface Abstract: damage is the most barrier for the application mechanical harvesting and fruit-to-fruit contact when fruit detached by harvester is collected by a catching system. In this and fruit-to-fruit contact when fruit detached by harvester is collected by a catching system. In and fruit-to-fruit contact when fruit detached by harvester is bruising collectedisbythea fruit-to-catching catching system. surface In this this systems for fresh market apples. One of the major source of work, a fruit catching mechanism was designed and fabricated using air suspension as a cushion to work, aa fruit mechanism was designed and fabricated using suspension as aa cushion to work, fruit catching catching mechanism was designed and fabricated using air air suspension as cushion to and fruit-to-fruit contact when fruit detached by harvester is collected by a catching system. In this minimize fruit bruising during mechanical harvesting. Various apple cultivars with different bruising minimize fruit bruising during mechanical harvesting. Various apple cultivars with different bruising minimize fruit bruising during mechanical harvesting. Various apple cultivars with different bruising work, a fruit catching mechanism was designed and fabricated using air suspension as a cushion to susceptibility (‘Granny Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’, and ‘Pink lady’) were used susceptibility (‘Granny Smith’, ‘Jazz’, ‘Fuji’, ‘Pacific Rose’, and ‘Pink lady’) used susceptibility (‘Granny Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’, and with ‘Pinkdifferent lady’) were were used minimize fruit bruising during mechanical harvesting. Various apple cultivars bruising to evaluate the performance of an air suspension-based catching mechanism. The results showed that to evaluate performance of air catching mechanism. The results showed that to evaluate the the(‘Granny performance of an an air suspension-based suspension-based catching mechanism. The results showed that susceptibility Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’,ofand ‘Pink lady’) were used fruit catching with air suspension can significantly reduce the percentage damaged apples for all of fruit catching with air suspension can significantly reduce the percentage of damaged apples for all of fruit catching with air suspension can significantly reduce the percentage of damaged apples for allthat of to evaluate the performance of an air suspension-based catching mechanism. The results showed six cultivars evaluated in this work compared to fruit catching without air suspension. It was found that six cultivars evaluated in this work compared to fruit catching without air suspension. It was found that six cultivars evaluated in this workcan compared to fruitreduce catching without air suspension. Itapples was found that fruit catching with air suspension significantly the percentage of damaged for all of the decrease in fruit damage rate with air suspension ranged from 14.5 to 36.9% for different cultivars. the decrease in fruit damage rate with air suspension ranged from 14.5 to 36.9% for different cultivars. the decrease in fruit damage rate with air suspension ranged from 14.5 to 36.9% for different cultivars. six cultivars evaluated in this work compared to fruit catching without air suspension. It was found that The effect of air suspension on the of downgraded apples was significant (compared to The effect air suspension on the percentage percentage of apples was not not (compared to Thedecrease effect of ofin airfruit suspension on percentage of downgraded downgraded apples not significant significant (compared to the damage ratethe with air except suspension ranged from 14.5was toThe 36.9% for different cultivars. catching apples without air suspension) for Pink Lady cultivar. reduction in downgraded catching apples without air suspension) except for Pink Lady cultivar. The reduction in downgraded catching apples without air suspension) except for Pink Lady cultivar. The reduction in downgraded The effect of air suspension on the percentage of downgraded apples was not significant (compared to fruit ranged from 3% to 9.3% among different cultivars (except for Pink Lady(19%)). fruit ranged from 3% among for Lady(19%)). fruit ranged fromwithout 3% to to 9.3% 9.3% among different different cultivars (except for Pink PinkThe Lady(19%)). catching apples air suspension) exceptcultivars for Pink(except Lady cultivar. reduction in downgraded Keywords: market apple; mechanical harvesting; air suspension catching; bruises; © 2016, IFACfresh (International Federation of Automatic Control) Hosting by Elsevier Ltd. Allapple rights reserved. Keywords: fresh market apple; mechanical harvesting; air suspension catching; apple bruises; fruit ranged from 3% to 9.3% among different cultivars (except for Pink Lady(19%)). Keywords: fresh market apple; mechanical harvesting; air suspension catching; apple bruises; downgraded apples. downgraded apples. downgraded apples.market apple; mechanical harvesting; air suspension catching; apple bruises; Keywords: fresh downgraded apples.
1. INTRODUCTION 1. 1. INTRODUCTION INTRODUCTION Apple industry around the world depends currently on 1. INTRODUCTION Apple industry around the Apple industry around the world world depends depends currently currently on on ‘hand picking’ to harvest fruit from random spatial ‘hand picking’ to harvest fruit from random spatial ‘hand picking’ around to harvest fruit from random spatial Apple industry the world depends currently on locations on individual tree canopies. In the past, research locations on tree In past, locations on individual individual tree canopies. canopies. In the the past, research research ‘hand picking’ to harvest fruit from random spatial and development on mechanizing apple harvesting has and development on apple harvesting has and development on mechanizing mechanizing apple harvesting has locations on individual treemethods canopies. In theindividual past, research focused mainly on robotic to pick fruit. focused mainly on robotic methods to pick individual fruit. focused mainly on robotic methods to pick individual fruit. and development on mechanizing apple harvesting has However, due to lack of desired level of accuracy, speed, However, due to lack of desired level of accuracy, speed, However, due to lack of desired level of accuracy, speed, focused mainly on robotic methods to pick individual fruit. robustness and cost, no successful robustness and no commercially commercially successful robotic robotic robustness andtocost, cost, commercially robotic However, due lack no ofavailable desired level ofsuccessful accuracy, speed, harvester have been (Gongal et al., 2015). harvester have been available (Gongal et al., 2015). harvester have been noavailable (Gongal et al., robotic 2015). robustness and cost, commercially successful Alternatively, bulk fruit removal methods have also been Alternatively, bulk fruit removal have also been Alternatively, bulk fruitavailable removal methods methods have also2015). been harvester have been (Gongal et al., investigated (Li et al., 2011; De Kleine, 2015). One of the investigated (Li et al., 2011; De Kleine, 2015). One of the investigated (Libulk et al., 2011; De Kleine, 2015). One ofbeen the Alternatively, fruit removal methods have also commonly used methods for bulk harvesting has been a commonly used methods for bulk harvesting has been commonly used methods forDe bulk harvesting has been investigated (Li et al., 2011; Kleine, 2015). One of theaa linear shaker used to shake the trunk or branches. Bulk linear shaker used to trunk or Bulk linear shaker used to shake shake the trunk or branches. branches. Bulka commonly used methods for the bulk harvesting haslevel been harvesting has the potential to achieve desired of harvesting has the potential to achieve desired level of harvesting has the potential to achieve desired level of linear shaker used to shake the trunk or branches. Bulk speed and cost for mechanized apple harvesting. However, speed and cost for mechanized apple harvesting. However, speed and cost for harvesting. However, harvesting has themechanized potential toapple achieve desired of the method is limited by excessive fruit bruisinglevel during the method is limited by fruit during the method is for limited by excessive excessive fruit bruising bruising during speed and cost mechanized apple harvesting. However, detachment and catching caused primarily by fruit-to-fruit, detachment catching primarily by fruit-to-fruit, detachment and catching caused primarily by fruit-to-fruit, the method and is limited bycaused excessive fruitsurface bruising during fruit-to-branch and fruit-to-catching impacts fruit-to-branch and fruit-to-catching surface impacts fruit-to-branch and fruit-to-catching surface impacts detachment and catching caused primarily by fruit-to-fruit, (Zeebroeck et al., 2007). (Zeebroeck et 2007). (Zeebroeck et al., al.,and 2007). fruit-to-branch fruit-to-catching surface impacts Researchers have conducted a series of studies on fruit (Zeebroeck et al., 2007). Researchers have conducted Researchers have conducted aa series series of of studies studies on on fruit fruit catching devices to reduce the bruise damage of freshcatching devices to reduce the bruise damage of freshcatching devices reduce the bruiseofdamage Researchers have toconducted a series studiesofonfreshfruit catching devices to reduce the bruise damage of fresh-
market fruit during bulk harvesting with mechanical market market fruit fruit during during bulk bulk harvesting harvesting with with mechanical mechanical shakers. Peterson et al. (2003) built upon their previous shakers. Peterson et al. (2003) built upon their previous shakers. Peterson et al.bulk (2003) built upon their previous market fruit during harvesting with mechanical apple harvesting system and created mirrored harvesting apple harvesting system and created mirrored harvesting apple harvesting system and created mirrored harvesting shakers. Peterson et al. (2003) built upon their machines, or a two-sided harvesting system. In thisprevious system, machines, or harvesting system. In system, machines, or aa two-sided two-sided harvesting system. In this this system, apple harvesting system and created mirrored harvesting catching conveyors with padded surface were designed to catching conveyors with padded surface were designed to catching conveyors with harvesting padded surface were designed to machines, or a two-sided system. In this system, intercept falling fruit and elevate the fruit to a collection intercept falling fruit and elevate the fruit to a collection intercept falling fruit and elevate the fruit to a collection catching conveyors with padded surface were designed to conveyor. The results showed that the system achieved an conveyor. The results showed that the system achieved an conveyor. The results showed that the system achieved an intercept falling fruit and elevate the fruit to a collection Extra Fancy fruit quality of 59%. cushion Extra Fancy fruit quality of only only 59%. The The cushion Extra Fancy fruit quality only The cushion conveyor. The results showedofthat the 59%. system achieved an materials used on catching surface can absorb the materials used on catching surface can absorb the materials usedfruit on quality catching surface can The absorb the Extra Fancy of only 59%. cushion mechanical energy during contact, either by slowing down mechanical energy contact, either slowing down mechanical energyonduring during contact, either by by slowing down materials used catching surface can absorb the compression or impact, which significantly affects the fruit compression or impact, which significantly affects the fruit compression or impact, which significantly affects thedown fruit mechanical energy during contact, either by slowing bruise damage (Jarimopas et al., 2007; Opara and Pathare, bruise damage et 2007; and bruise damage (Jarimopas et al., al., 2007; Opara Opara and Pathare, Pathare, compression or(Jarimopas impact, which significantly affects thethree fruit 2014; De Kleine, 2015). In 2011, Ortiz et al. studied 2014; De Kleine, 2015). Ortiz et three 2014; De Kleine, 2015). In Inet2011, 2011, Ortiz Opara et al. al. studied studied three bruise damage (Jarimopas al., 2007; and Pathare, different catching surfaces (a floor, an different catching surfaces (a concrete concrete floor, an elevated elevated different catching surfaces (a concrete floor, an elevated 2014; De Kleine,with 2015). In 2011, Ortiz et al.and studied three canvas provided aa frame and wheels, aa concrete canvas provided with frame and wheels, and concrete canvas provided with a frame and wheels, and a concrete different catching surfaces (a concrete floor, an elevated floor covered with aa shock absorbing canvases) to assess floor covered with absorbing canvases) assess floor covered with a shock shock absorbing canvases) to assess canvas provided with a The frame and wheels, and a to concrete fruit damage on citrus. elevated canvas was the least fruit damage on citrus. The elevated canvas was the least fruit damage on citrus. The absorbing elevated canvas was to theassess least floor covered with a shock canvases) damaging surface to fruit, indicating that shock absorbing damaging surface to fruit, indicating that shock absorbing damaging surface to fruit, indicating that shock absorbing fruit damage on citrus. The elevated canvas was the least canvases could be used to reduce fruit damage. De Kleine canvases could be used to fruit damage. De Kleine canvases could be to used to reduce reduce fruitthat damage. De Kleine damaging surface fruit, indicating shock absorbing and Karkee (2015) also built aa three-tiered catch-frame to and Karkee (2015) also built catch-frame to and Karkee (2015) also to built a three-tiered three-tiered catch-frame to canvases could be used reduce fruit damage. De Kleine collecting fruit removed from trellised apple trees. Plastic collecting fruit removed from trellised apple trees. Plastic collecting fruit removed fromatrellised applecatch-frame trees. Plastic and Karkee (2015) also built three-tiered to mesh fabric was used for apple catching at each tier. The mesh fabric was used apple catching at tier. The mesh fabric wasremoved used for forfrom appletrellised catching at each each tier. The collecting fruit apple trees. Plastic catching devices with different types of cushion materials catching devices with of catching devices with different different types of cushion cushion materials mesh fabric was used for apple types catching at each materials tier. The catching devices with different types of cushion materials
Copyright 2016 IFAC IFAC 358 Hosting by Elsevier Ltd. All rights reserved. 2405-8963 © IFAC (International Federation of Automatic Control) Copyright © 2016, 2016 358 Copyright 2016 responsibility IFAC 358Control. Peer review©under of International Federation of Automatic 10.1016/j.ifacol.2016.10.065 Copyright © 2016 IFAC 358
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studied in the past can reduce the fruit damage caused by fruit-to-catching surface contact. However, these devices have limited ability to minimize damage caused by fruit-tofruit contact as the fruit on the catching surface can be hit by fruit detached later. A new type of catching device is desired to address this issue. In this work, we designed and fabricated an innovative concept of catching fruit detached by mechanical shaking devices. The catching mechanism designed in this work included air suspension as a cushion to decelerate (to reduce the contact force between fruit and catching surface) and separate (to reduce fruit-to-fruit contact) fruit before that reach the catching surface. The objective of this paper was to evaluate the performance of air suspension-based catching mechanism in reducing bruise damage levels on fruit harvested in modern apple orchards. 2. MATERIALS AND METHODS 2.1 Air Suspension Catching Before developing the fruit catching prototypes, we designed an air suspension platform (Fig.1a) and set up a series of lab tests to evaluate the air suspension catching concept (Fig.1b). A total of 30 pairs of apples (Golden Delicious) were used to perform the apple-to-apple impact test (Fig.2). Half of the samples (15 pairs) were used for the test with pressurized air (690 Kpa). In this case, an apple was suspending above the platform and another apple dropped from the height of 0.6 m impacting the suspended apple. Another 15 pairs of apples were used for the test without pressurized air. In this case an apple was dropped from a height of 0.6 m to impact another apple placed on the platform without air suspension. All apples were marked and stored for 24 hrs before they were analysed for damages (bruising). The results showed that the damage rate can reach up to 75% without air suspension while the damage rate can be reduced to as low as 16.7% when the pressurized air was used to slowdown and suspend apples. The results showed that air suspension could substantially reduce impact force in the event of apple-to-apple contacts.
Fig. 2. The effect of air suspension on apple damage percentage
Thus, the fruit catching mechanism (Fig. 3) was designed to incorporate the following two critical functionalities: (1) decelerate the fruit falling from branches; and (2) separate fruit before they land on the catching surface. These two functionalities are essential to reduce fruit damage and to achieve desired level of fruit quality during mechanical harvesting. The first prototype of the catching mechanism was fabricated and evaluated during 2015 apple harvesting season in Washington State (Yakima Valley Orchards, Othello, WA). Two air hose couplers (component 2) are used to connect air inlets of catching mechanism to air compressor outlets. Once the hoses are engaged and air compressor is turned on, an air cushion will be generated for decelerating and separating falling fruit. When the air compressor is turned off, the scattered fruit could be landed on the foam surface (component 4) slowly. In addition, the catcher wall (component 1) is used to prevent apples from falling out of the air cushion boundary.
1 4
2 3 Fig. 3. Overview of the conceptual design and prototype of the air suspension-based fruit catching mechanism; 1. Catcher wall; 2. Pressurized air inlet; 3. Air outlet holes on PVC pipe; 4. Foam cushion
2.2 Fruit Catching Process
a)
During apple harvesting process, the pressurized air blown out from small nozzles on the PVC pipes generates an upward force to decelerate the apples accelerating down from the branches. The risk of apple bruises caused by apple-to-apple or apple-to-catcher contact will be decreased because of reduced impact force. As the falling fruit reach the zone with blown air, the fruit clumped together in a random fashion are separated, which minimizes impact with each other leading to reduced level of fruit damage.
b)
Fig.1. a) Air suspension platform; b) Apple-to-apple impact test
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(a) Before Shaking: a cluster of apples are hanging on the trellised limb.
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that the performance of the air suspension mechanism could be evaluated against a standard method. Table 1 showed the repetitions and the total number of apples caught for each experiment. After each test, harvested apples were stored in the lab for 24 hours to let them develop bruising. The diameter of each bruise area was then measured for bruise severity. If there are more than one bruise spot on an apple, the equivalent diameter of multiple bruises were calculated according to equation 1. Based on USDA Grades and Standards (United States Department of Agriculture, 2002; Peterson et al., 2010, De Keline, 2015), apple grade classes for various bruise specifications (diameter of individual bruises or equivalent diameter of multiple bruises) were determined (Table 2).
Where
(1)
equivalent diameter (mm) of multiple bruises on an apple;
diameter (mm) of (i=1, 2, ……, n) bruise on an apple.
(b) During Shaking: the cluster of detached apples were separated and suspended by the pressurized air flow.
Table 1. Field evaluation of catching mechanism with and without air suspension
(c) After Shaking: collected apples are scattered on the foam covered surface of catching mechanism.
Cultivar
Replicates
Grammy Smith Honeycrisp Jazz Fuji Pacific Rose Pink Lady
10 10 10 5 5 5
Number of Apples Tested Pressurized w/o Air (690 Pressurized kpa) Air 90 93 65 94 33 25 32
81 100 25 39 42
Table 2. Classification of apple bruises
Fig. 4. Two major functionalities of the catching mechanism with air suspension: deceleration and separation.
2.3 Field Evaluation of Catching Mechanism The field evaluation was performed in commercial orchards with ‘Granny Smith’, ‘Jazz’, ‘Honeycrisp’, ‘Fuji’, ‘Pacific Rose’, and ‘Pink lady’ apple cultivars (Allan Bros., Natches, WA). The performance of the air suspensionbased catching system was evaluated in terms of bruising rate, which was defined as the percentage of apples with a bruise from total number of apples caught by the catching mechanism. Air suspension was achieved with 690 kpa pressurized air blowing out into the fruit falling zone. An experiment was also conducted without pressurized air so
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Class # 1 2 3 4 5 6
USDA Fresh Market Standard “Extra Fancy” “Extra Fancy” “Extra Fancy” “Extra Fancy” “Fancy” Downgraded
Bruise specifications (mm)
, or cuts/punctures of any size
3. RESUSLTS AND DISCUSSION
Figure 5 illustrated the percentage of apples categorized to each of the six classes (1 to 6). The paired histograms show the effect of air suspension-based catching (ASC) mechanism on apples of each class. The percentages of “Extra Fancy” Class 1 apples increased by as much as 26.1%
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for Pacific Rose cultivar. The same for Pink Lady was 14.5%, Jazz was 21.7%, Honeycrisp was 36.9%, Granny Smith was 20.7% and Fuji was 29.3%. The percentages of total damaged apples (sum of percentage of apples in class 2-6) were reduced by as much as 36.9% for Honeycrisp. The same was only 20.7% for Granny Smith and 26.1% for Pacific Rose.
(d) Fuji
(a) Granny smith
(e) Pacific rose
(b) Honeycrisp
(f) Pink lady Fig. 5. Comparison of fruit quality (due to bruising damage) levels w/ and w/o air suspension-based catching (ASC). Fig. a to f present the fruit quality results for six different cultivars of apples detached and caught with a shake-and-catch harvesting system.
(c) Jazz
During shake-and-catch harvesting of six different cultivars of apples without using air suspension method, the percentage of “Extra Fancy” Class 1, on average, was less than 50% (which means the percentage of total apples with certain level of bruising/damage accounted for more than 50%). Particularly, only 10% of Pacific Rose apples were 361
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in Class 1 (90% of apples were damaged to some extent). When the detached apples were caught using the air suspension method, the percentage of Class 1 apples increased at least by 14.5%, especially, for the Pacific Rose cultivar, an increase of 26.1% was found. For Honeycrisp cultivar, the “Extra Fancy” Class 1 increased to as high as 36.9% from 45.2% without air-suspension. In terms of percentage of downgraded apples in Class 6, the Pacific Rose (28.8%) and Pink Lady cultivars (41%) were two of the worst cultivars when caught without pressurized air. Thus, the catching methods/devices had great potential to reduce apple bruise/damage. When the air suspensionbased catching was used, the downgraded percentages of Pink Lady and Pacific Rose were reduced by 19% and 3.3%. In general, the results showed that the air suspension system has a positive impact on fruit quality during shake-andcatch harvesting as shown by a decrease of 14.5 to 36.9% in total damaged apples (sum of Class 2 to 6) and a decrease of 3 to 9.3% (except for Pink Lady (19%)) in downgraded apples. The differences in percentage of total damaged apples with pressurized air (690 kpa) and without pressurized air was significant for all six cultivars of apples at the 95% confidence level based on Student’s t-test (Table 1). For the percentage of downgraded apples, the differences were not significant except for Pink Lady cultivar at the 95% confidence level (Table 2). Table 2. T test of the effect of air suspension-based catching mechanism (ASC) on total damaged apples (sum of Class 2 to 6) Cultivar P (T<=t) Cultivar
Granny Smith 0.024 Fuji
P (T<=t)
0.028
Honey Crisp 0.003 Pacific Rose 0.027
Jazz 0.012 Pink Lady
P (T<=t) Cultivar
Granny Smith 0.68 Fuji
P (T<=t)
0.92
Honey Crisp 0.18 Pacific Rose 0.35
represented by apples in classes 2 to 5 (these classes are attributed only to bruising damage). For the downgrade or Class 6 of apples, the effect of ASC was limited because the apples in this class were not only attributed to bruising damage but also to cut/puncture damages, which would not be minimized by the use of ASC mechanism. Future work in this area could focus on identifying and addressing the sources for fruit cuts and punctures during bulk harvesting, which can then help reduce the percentage of downgraded fruit (Class 6). 4. CONCLUSION This study investigated the effect of air suspension-based catching mechanism (ASC) on apple bruises during shakeand-catch harvesting of six different cultivars of apples. The ASC mechanism was designed and fabricated to using air suspension as a cushion to minimize fruit bruising. To evaluate the significance of the effects of catching mechanism on apple bruises, Sudent’s t-tests were performed. From the study, it can be concluded that the two main functionalities (deceleration and separation) of new catching mechanism can significantly reduce the percentage of damaged apples (as high as 36.9%) for all of six cultivars evaluated in this work compared to fruit catching without air suspension. The effect of ASC mechanism on the percentage of downgraded apples was not significant (compared to catching apples without air suspension) except for Pink Lady. The future work can focus on identifying the sources of fruit cuts and punctures and improving ASC design and functionalities to address those issues. ACKNOWLEDGEMENTS
0.002
Table 2. T test of effect of air suspension-based catching mechanism (ASC) on downgraded Class 6 apples. Cultivar
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Jazz 0.56 Pink Lady 0.01
These findings indicated that ASC mechanism has a greater potential to decrease the percentage of total damaged apples from Class 2 to 6 than the potential to decrease the percentage of downgraded apples (Class 6). One of the reasons behind this result is that ASC can effectively reduce the risk of apple-to-apple and apple-to-catching surface contacts, which are the two main sources of apple bruises 362
This research was supported in part by Washington State University Agricultural Research Center federal formula funds, Project No. WNP0748 and No. WNP0728 received from the U.S. Department of Agriculture National Institutes for Food and Agriculture (NIFA). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture. Any opinions, findings, and conclusions expressed in this paper are those of the authors, and do not necessarily reflect the views of the U.S. Department of Agriculture nor of Washington State University. The authors would also like to express our gratitude to Dr. Long He, Mr. Lin Chen, Dr. Tao Wu, Dr. Weizu Wang, Mr. Patrick Scharf, Mr. Meng Zhang, Dr. Zhiqiang Wang, and Dr. Jintao Yao for their help in field test arrangement and experimental data collection. Also China Scholarship Council (CSC) sponsored Han Fu conducting collaborative PhD Dissertation research at WSU Center for Precision and Automated Agricultural Systems (CPAAS).
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