Research and Development of a Lettuce Harvester

Shepardson, E. S.; Pollock, J. G.; Rehkugler, G. E.

doi:10.13031/2013.36824

Cited by 5 publications

(4 citation statements)

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“…Shearing characteristics of crop stalks have been used as references for designing cutting devices of harvester [15][16][17][18][19][20][21][22][23][24][25] . Ghahraei et al [26] selected knife edge angle, knife shear angle, knife approach angle, and knife rake angle as the test factors and studied how they affected the cutting force and cutting energy; a rotary impact cutting system was thus developed.…”

Section: Introduction mentioning

confidence: 99%

Effects of cutter parameters on shearing stress for lettuce harvesting using a specially developed fixture

Cui

Wang

et al. 2021

International Journal of Agricultural and Biological Engineering

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To investigate the optimal parameters combination of reciprocating cutter for harvesting hydroponic lettuce automatically, a shear fixture was designed for cutting lettuce stems on a universal materials tester. Effects of blade distance, sliding cutting angle, skew cutting angle, and shearing angle on shearing stress were investigated in this study. The orders of the significance of a single factor and double factors were analyzed using the response surface methodology (RSM). A scanning electron microscope was used to observe the microstructure of the lettuce stem to analyze the shearing characteristics at the microscopic level. The RSM results showed that the order of significance for single factors was (i) sliding cutting angle, (ii) shearing angle, (iii) skew cutting angle, and (iv) blade distance. The sliding cutting angle had a highly significant influence on the shearing stress. The order of significance for double factors was (i) blade distance and shearing angle, (ii) sliding cutting angle and skew cutting angle, and (iii) the sliding cutting angle and shearing angle. A quadratic model of the factors and shearing stress was built according to the response-surface results. The optimized combination of factors that gives the minimum shearing stress was observed that it reduced 69.9% of the maximum shearing stress value. This research can provide a reference for designing lettuce-cutting devices.

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Section: Introduction mentioning

confidence: 99%

Effects of cutter parameters on shearing stress for lettuce harvesting using a specially developed fixture

Cui

Wang

et al. 2021

International Journal of Agricultural and Biological Engineering

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“…Shepardson et al (1974) developed a harvester for lettuce which was seeded two rows per bed. The author investigated the field performance of some cutting devices using stationary knife, band saw, blade saw, overlapping discs, and pinch-off discs.…”

Section: Lettuce Cutting Methodsmentioning

confidence: 99%

“…Shepardson et al (1974) used rod-type chain belting to elevate cut lettuce and eliminate dirt at an inclined angle below 28 . This component could not convey heads in any given orientation and it delivered debris along with lettuce.…”

Section: Methods For Lifting Cut Lettuce Heads From Groundmentioning

confidence: 99%

Development of prototype harvester for head lettuce

Yamane

2015

Engineering in Agriculture, Environment and Food

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a b s t r a c tMethod of manual removal of produce from the field has been a bottle-neck for lettuce production in Japan. In order to reduce the production cost of this fresh commodity, a prototype harvester has been developed for head lettuce production. The harvester consists of a cutting component to slice the lettuce head at the desired location and a lifting component that transports the harvested produce from the cutting site onto elevating conveyor and trimming station. A cutting component with reciprocating blade was proposed.Laboratory tests were performed to verify ability of reciprocating blade to slice lettuce stump at forward cutting speed of 0.1 m/s, reciprocating stroke of 18 mm, and different reciprocating frequencies of 2, 4 and 6 Hz. In addition, power requirement for reciprocating the cutting knife as slicing two lettuce stumps was measure. Tests in lettuce fields were also conducted at different working speed to investigation the cutting and lifting performances of the harvester mounted with the reciprocating-blade cutting component. The results of laboratory tests indicated that the cutting component could smoothly cut lettuce stumps and the maximum cutting torque and cutting power requirement were 0.73 Nm and 27.7 W, respectively at 6 Hz reciprocating frequency. Field test results showed that the harvester could cut and lift the lettuce heads without damaging and blemishing the produce at working speed of 0.04 m/s and the commercial head percentage was 94.5%. At higher working speed of 0.08 m/s, the head damage rate was 12.8% reducing the percent of commercially accepted heads to 87.2%.

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“…There has also been significant work in the development of autonomous weeding or grading systems including a sugar beet classifying system (Lottes, Hörferlin, Sander, & Stachniss, ) and a grape pruning system (Botterill et al, ). There are a number of patents specifically relating to the harvesting of iceberg lettuce (Ottaway, , ; Shepardson & Pollock, ); however, these have not been demonstrated under field conditions and do not clearly demonstrate how selective plant harvesting is possible. These previous approaches include using a belt‐driven band saw‐type mechanisms or water jet cutting.…”

Section: State Of the Artmentioning

confidence: 99%

A field‐tested robotic harvesting system for iceberg lettuce

Birrell

Hughes

Cai

et al. 2019

Journal of Field Robotics

129

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Agriculture provides an unique opportunity for the development of robotic systems; robots must be developed which can operate in harsh conditions and in highly uncertain and unknown environments. One particular challenge is performing manipulation for autonomous robotic harvesting. This paper describes recent and current work to automate the harvesting of iceberg lettuce. Unlike many other produce, iceberg is challenging to harvest as the crop is easily damaged by handling and is very hard to detect visually. A platform called Vegebot has been developed to enable the iterative development and field testing of the solution, which comprises of a vision system, custom end effector and software. To address the harvesting challenges posed by iceberg lettuce a bespoke vision and learning system has been developed which uses two integrated convolutional neural networks to achieve classification and localization. A custom end effector has been developed to allow damage free harvesting. To allow this end effector to achieve repeatable and consistent harvesting, a control method using force feedback allows detection of the ground. The system has been tested in the field, with experimental evidence gained which demonstrates the success of the vision system to localize and classify the lettuce, and the full integrated system to harvest lettuce. This study demonstrates how existing state‐of‐the art vision approaches can be applied to agricultural robotics, and mechanical systems can be developed which leverage the environmental constraints imposed in such environments.

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Research and Development of a Lettuce Harvester

Cited by 5 publications

References 0 publications

Effects of cutter parameters on shearing stress for lettuce harvesting using a specially developed fixture

Effects of cutter parameters on shearing stress for lettuce harvesting using a specially developed fixture

Development of prototype harvester for head lettuce

A field‐tested robotic harvesting system for iceberg lettuce

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