Citrus Fruit Movement Assessment Related to Fruit Damage during Harvesting with an Experimental Low-Frequency–High-Amplitude Device

Round 1

Reviewer 1 Report

This paper aims to analyzes the fruit movement during the vibration with the experimental shaker, compared to the movement when vibrating with an orchard tractor mounted trunk shaker, related to the increase of slightly damaged fruit when using the experimental shaker. However, no experimental results about the fruit damage was provided in the manuscript. Therefore, the conclusions cannot be directly verified. I strongly recommend providing detailed experimental data on fruit damage before the paper is suitable for publication. Some comments are listed as follows

1. Please explain the work of image processing in detail, such as the acquisition of the trajectory of the center of mass.
2. How many trees will be tested for all experiments, and are the conclusions applicable to all fruit trees?
3. Please unify the variable in Equation 1 and Equation 2, d or de?
4. It is recommended to explain the principle and performance parameters of the light-weight shaker, etc.
5. The legend of the Fig.4 may be wrong, please check

Author Response

This paper aims to analyzes the fruit movement during the vibration with the experimental shaker, compared to the movement when vibrating with an orchard tractor mounted trunk shaker, related to the increase of slightly damaged fruit when using the experimental shaker. However, no experimental results about the fruit damage were provided in the manuscript. Therefore, the conclusions cannot be directly verified. I strongly recommend providing detailed experimental data on fruit damage before the paper is suitable for publication. Some comments are listed as follows

1. Please explain the work of image processing in detail, such as the acquisition of the trajectory of the center of mass.

Thank you for the requirement, some information about the acquisition of the trajectory has been added.

- The image analysis software ImageJ (https://imagej.nih.gov/ij/) was used to track the position of the fruit during the vibration using a semi-manual process, through the menu “Tracing tool/ analyze/Measure”. The image analysis software was used to identify the citrus fruit from the rest of the image. Every four photograms, the center of the analyzed fruit was manually marked and the coordinates (xi, yi) registered. The trajectory of the fruit was traced with the coordinate change according to time. Then, fruit distance (d), fruit       displacement (de), speed (v), and acceleration (a) were calculated.” (New lines 130-137).

 

2. How many trees will be tested for all experiments, and are the conclusions applicable to all fruit trees?

- Six trees from every harvesting system were vibrated and the operation recorded. From these trees one tree from each harvesting system was selected to assess fruit movement, considering the tree structure, the quality of the high-speed video recordings and the position of the fruits (mostly in the xy plane (perpendicular to the video recording direction)). From these selected trees five fruits were chosen to be studied according to the position of the fruit and the lack of leaves around the movement covering the image.

All the trees had similar size and structure, therefore the tested trees were representative and the conclusions can be generalized. (New lines 116-124).

 

3. Please unify the variable in Equation 1 and Equation 2, d or de?

- Thank you for your comment.

The differences between ‘d’ and ‘de’ have been clarified.

Equation 1 explains the distance of the fruit related to the initial position (d, fruit distance (m)), being (xi, yi) the position of the fruit at time i and (xo, yo) the position of the fruit at the initial time, before vibrating.

Equation 2 explains the relative displacement of the fruit (de, fruit displacement (m)), being (xi+1, yi+1) and (xi, yi) the positions of the fruit at two consecutive times. (New lines 136-143)

 

4. It is recommended to explain the principle and performance parameters of the light-weight shaker, etc

- Information about the working mechanism of the light-weight-shaker has been added:

“The ELWS consists of a disc that is driven by a hydraulic motor, therefore, by modifying the hydraulic flow, the vibration frequency can be modified. A rod is connected to the disk. The disc and connecting rod assembly transforms the rotating movement of the hydraulic motor into a reciprocating linear movement. The connecting rod can be attached to the disc through holes located at different distances from the center, with which the stroke can be modified. The opposite end of the rod is connected to a slider for pure reciprocating linear motion. The slider is connected to an arm, at the end of which is the clamp with cushioned fingers, that holds the branch (Figure 1).” (New lines 93-105)

 

5. The legend of the Fig.4 may be wrong, please check

- It has been checked. Figure 4 shows the discriminant analysis classification of the fruits according to maximum distance (m) and RMS acceleration in the two harvesting systems. Fruits vibrated with the experimental light weight shaker had lower maximum distance and higher RMS acceleration.

Reviewer 2 Report

The manuscript presents the results on the fruit movement during the vibration. The commercial trunk shaker and an experimental light-weight shaker were compared.

There are a lot of points that should be corrected or explained:

Please add numerical results to the Abstract. Also, a more detailed description of the methods should be included in the Abstract.

The article includes very few references. There are mostly self-citations.

The novelty of the current research should be more clearly emphasized against the background of research findings on a global scale.

line 66: How was the nutritional condition of trees assessed?

lines 88-91: Please describe briefly the methods of measurements and the number of repetitions.

Video recording is insufficiently described. More detailed information about the devices should be added.

lines 92-94: The analysis of variance is not sufficiently described. Have the assumptions been met? What differences were compared?

For the caption of Table 1, it has been written: "Same superscript letter in the same row is not significantly different". The table does not include superscript letters. Should the word 'column' be used instead of 'row'? Should the letter a be for both values in the case of RMS for Fruit acceleration?

Discriminant analysis is not included in section 2. Materials and Methods.

The discussion should contain more references besides self-citations.

Suggestions for future studies should be indicated in the conclusion.

 

Author Response

The manuscript presents the results on the fruit movement during the vibration. The commercial trunk shaker and an experimental light-weight shaker were compared.

There are a lot of points that should be corrected or explained:

-Thank you very much for your interesting comments.

Please add numerical results to the Abstract. Also, a more detailed description of the methods should be included in the Abstract.

- Numerical results have been added to the Abstract “Results showed that the higher vibration amplitude produced a maximum distance experienced by the fruits (maximum displacement of 0.135 m with the experimental shaker compared to 0.078 m with the trunk shaker) that could cause a higher damage level (74 percent of slightly damaged fruits using the experimental shaker compared to 14 percent using the trunk shaker).” The numerical information about fruit damage has also been added to the introduction. (New lines 13-17).

- A more detailed description of the methods has been included in the Abstract, “Fruit movement parameters (fruit distance, fruit displacement, speed and acceleration) when using the two harvesting systems (experimental shaker and trunk shaker) were compared analyzing the high video recordings”. (New lines 11-13).

The article includes very few references. There are mostly self-citations.

New references have been added in the introduction and in the discussion. (New lines 21-28 and 198-267).

“… and are harvested by hand. The mechanical harvesting technology is being developed in fruit and nut crops with the aim of reducing the cost of harvesting and the limitations of available labour (Gupta et al 2016). Canopy shaker and trunk shaker systems are presented as technologies able to increase labour productivity by up to 15-fold and reduce costs by up to 50 % (Whitney 2000). Previous studies showed the effectiveness of vibration systems for mechanical citrus harvesting ([ Whitney et al, 1988]; [Savary et al 2010]). Canopy shaking systems have been developed in citrus for industrial transformation, where damage to the fruit is less important. These systems are under development and have a promising future (Savary et al. 2011; Liu et al, 2017). However, the fruit damages produced are crucial for fresh market.”

New references added to the introduction:

Savary, S.K.J.U.; Ehsani, R.; Schueller, J.K.; Rajaraman, B.P. 2010. Simulation study of citrus tree canopy motion during harvesting using a canopy shaker. Trans of the ASABE, 2010; 53(5): 1373–1381

Savary, S.K.J.U.; Ehsani, R.; Salyani, M.; Hebel, M.A.; Bora, G.C. Study of force distribution in the citrus tree canopy during harvest using a continuous canopy shaker. Comput. Electron., 2011 Agric., 76(1), 51-58.

Whitney. J. Performance of mechanical citrus harvesters in Florida. Proceedings of the International Society of Citriculture, 2000; 277–279.

Whitney, J.D.; Churchill, D.B.; Hedden, S.L.; Smerage, G.H. Trunk shakers for Citrus harvesting—Part I: Measured trunk shaker and tree trunk motion. Appl. Eng. Agric. 1988, 4 (2), 93–101. https://doi.org/10.13031/2013.26588.

New references added to the discussion:

Gupta, S. K., Ehsani, R., & Kim, N. H. (2016). Optimization of a Citrus Canopy Shaker Harvesting System: Mechanistic Tree Damage and Fruit Detachment Models. Transactions of the ASABE, 59(4), 761–776. https://doi.org/10.13031/TRANS.59.10819

He, L., Liu, X., Du, X., & Wu, C. (2020). In-situ identification of shaking frequency for adaptive vibratory fruit harvesting. Computers and Electronics in Agriculture, 170, 105245. https://doi.org/10.1016/J.COMPAG.2020.105245

Liu, T. H., Ehsani, R., Toudeshki, A., Zou, X. J., & Wang, H. J. (2017). Experimental Study of Vibrational Acceleration Spread and Comparison Using Three Citrus Canopy Shaker Shaking Tines. Shock and Vibration, 2017. https://doi.org/10.1155/2017/9827926

Pu, Y., Toudeshki, A., Ehsani, R., & Yang, F. (2018). Design and evaluation of a two-section canopy shaker with variable frequency for mechanical harvesting of citrus. International Journal of Agricultural and Biological Engineering, 11(5), 77–87. https://doi.org/10.25165/IJABE.V11I5.4445

The novelty of the current research should be more clearly emphasized against the background of research findings on a global scale.

- The novelty of the current research has been emphasized in the modified discussion section.

Lline 66: How was the nutritional condition of trees assessed?

- The trees were selected from the field by the agriculture cooperative technician and the nutritional condition was assessed by the agriculture cooperative technician, “The trees ('Caracara' variety) were in good health and nutritional condition (assessed by the agriculture cooperative technician)”. New lines 80-82.

lines 88-91: Please describe briefly the methods of measurements and the number of repetitions”

- Fifty fruits were manually collected in order to measure fruit quality parameters. (New line 111).

Video recording is insufficiently described. More detailed information about the devices should be added.

- More detailed information has been added.

“The image analysis software was used to identify the citrus fruit from the rest of the image. Every four photograms, the center of the analyzed fruit was manually mark and the coordinates (xi, yi) registered. The trajectory of the fruit was registered with the coordinate change according to time”. (New lines 133-136)

“Six trees from every harvesting system were vibrated and the operation recorded. From these trees one tree from each harvesting system was selected to assess fruit movement, considering the tree structure, the quality of the high-speed video recordings and the position of the fruits (mostly in the xy plane (perpendicular to the video recording direction)). From these selected trees five fruits were chosen to be studied according to the position of the fruit and the lack of leaves around the movement covering the image”. (New lines 116-124)

Llines 92-94: The analysis of variance is not sufficiently described. Have the assumptions been met? What differences were compared?

- The effect of the factor harvesting system (CTS and ELWS) on the variables velocity and acceleration values measured on fruit during the harvesting process, and fruit displacement related to the initial fruit position was addressed. (New lines 148-150).

For the caption of Table 1, it has been written: "Same superscript letter in the same row is not significantly different". The table does not include superscript letters. Should the word 'column' be used instead of 'row'? Should the letter a be for both values in the case of RMS for Fruit acceleration?

- Thank you for the correction, the mistake has been corrected. The word row is correct, “Same letter in the same row is not significantly different"

Discriminant analysis is not included in section 2. Materials and Methods.

- The information has been included in section 2, “A step-by-step discriminant analysis was also developed to classify the fruit between the two groups (vibrated by the experimental shaker and vibrated by the trunk shaker) according to the registered and calculated variables”. (New lines 150-153).

The discussion should contain more references besides self-citations.

-  More references have been added to the discussion. (New lines 198-267).

New references added to the discussion:

Gupta, S. K., Ehsani, R., & Kim, N. H. (2016). Optimization of a Citrus Canopy Shaker Harvesting System: Mechanistic Tree Damage and Fruit Detachment Models. Transactions of the ASABE, 59(4), 761–776. https://doi.org/10.13031/TRANS.59.10819

He, L., Liu, X., Du, X., & Wu, C. (2020). In-situ identification of shaking frequency for adaptive vibratory fruit harvesting. Computers and Electronics in Agriculture, 170, 105245. https://doi.org/10.1016/J.COMPAG.2020.105245

Liu, T. H., Ehsani, R., Toudeshki, A., Zou, X. J., & Wang, H. J. (2017). Experimental Study of Vibrational Acceleration Spread and Comparison Using Three Citrus Canopy Shaker Shaking Tines. Shock and Vibration, 2017. https://doi.org/10.1155/2017/9827926

Pu, Y., Toudeshki, A., Ehsani, R., & Yang, F. (2018). Design and evaluation of a two-section canopy shaker with variable frequency for mechanical harvesting of citrus. International Journal of Agricultural and Biological Engineering, 11(5), 77–87. https://doi.org/10.25165/IJABE.V11I5.4445

Suggestions for future studies should be indicated in the conclusion.

- Suggestions for future studied have been indicated, “Further studies should be addressed to verify the results with other citrus varieties and identify the field combination of vibration amplitude and frequency that reduces fruit damages using the experimental device”. (New lines 289-292).

Round 2

Reviewer 1 Report

Although most of the questions have been replied, the most important one has not been completed:

No experimental results about the fruit damage were provided in the manuscript. Therefore, the conclusions cannot be directly verified. I strongly recommend providing detailed experimental data on fruit damage before the paper is suitable for publication.

Author Response

Although most of the questions have been replied, the most important one has not been completed:

No experimental results about the fruit damage were provided in the manuscript. Therefore, the conclusions cannot be directly verified. I strongly recommend providing detailed experimental data on fruit damage before the paper is suitable for publication.

- Thank you for your comment. The experimental results (and description) about fruit damage were presented in two previous publications ([21] and [22]). More information has been added in the introduction about these previous works to clarify the state of the art (“Low frequency commercially available canopy shakers, that work with lower frequency, can not be used in Valencia (Spain) citrus orchards due to the big size of the machines and the excessive damage to the fresh market fruit. Then, the light-weight experimental shaker suscesfully used in ornamental trees was improved to harvest fresh citrus orchards, gripping the main branches [21]. Elevated canvases were employed to collect the fruit without damage. Severe damages were very low (2 percent of the detached fruits). However, fruit light damages on the tree during the high amplitude vibration seemed to be relevant, 78 percent of slightly damaged fruits when using the experimental shaker compared to 14 percent when using a trunk shaker, [22]. The higher damage percentage could be due to the fact that some of the fruits are being rubbed against the branches and other fruits during the vibration”) (New lines 68-78).

The objective off the study has been improved to clarify the main idea of the research, (“The objective of this study was to analyze the fruit movement during the vibration with the experimental shaker, compared to the movement when vibrating with an orchard tractor mounted trunk shaker, related to the previously proven increase of slightly damaged fruit when using the experimental shaker”) (New lines 78-82).

The two references have been included in the Discussion section (“However, previous studies showed that these high displacements may cause slight damage when the fruit impacts nearby branches and fruit ([21], [22]). This fact could explain that more fruit are rubbed against the branches and other fruits during the vibration, and it would be responsible for the higher percentage of slightly damaged fruit registered in the case of the trees vibrated by ELWS compared to the trees vibrated by CTS”) (New lines 261-266).

More information has been also added in the conclusions (“This fact could explain the previous results showing that more fruit are rubbed against the branches and other fruits during the vibration, and it would be responsible for the higher percentage of slightly damaged fruit”) (New lines 306-309).

Reviewer 2 Report

The authors did not answer some of the questions satisfactorily, such as:

Table 1: Should the word 'column' be used instead of 'row'? Should the letter 'a' be for both values in the case of RMS for Fruit acceleration?

The analysis of variance is not sufficiently described. Have the assumptions (normality, homogeneity of variance) been met? What tests were used? 

Discriminant analysis in section 2. Materials and Methods should be described in more detail.

It has been written: "The trees (’Caracara’ variety) were in good health and nutritional condition (assessed by the agriculture cooperative technician)." - On what basis did good health and nutritional condition be found? What features were considered?

lines 112-115: Please describe briefly the methods of measurements.

Video recording is insufficiently described. More detailed information about the devices should be added. - This still needs to be completed.

Author Response

The authors did not answer some of the questions satisfactorily, such as:

Table 1: Should the word 'column' be used instead of 'row'? Should the letter 'a' be for both values in the case of RMS for Fruit acceleration?

- Thank you very much for the correction. The word 'column' has been used instead of 'row'.

- For fruit velocity RMS value, significant differences were found between CTS and ELSW (not for maximum value). However, for fruit acceleration RMS value, no significant differences were found between the two system, but significant differences in fruit acceleration maximum value were found.

The analysis of variance is not sufficiently described. Have the assumptions (normality, homogeneity of variance) been met? What tests were used? 

- The assumptions and the ANOVA test have been explained in the manuscript:

- “The LSD Fisher (less significant difference) was used for mean separation at P<0.05. Although the data did not follow homocedastiticity and normal distribution of residuals, the results of ANOVA were considered valid due to the robustness of the ANOVA” (New lines 168-171).

Discriminant analysis in section 2. Materials and Methods should be described in more detail.

- Information about the variables used in the discriminant analysis has been added.

- “A step-by-step discriminant analysis was also developed to classify the fruit between the two groups (vibrated by the experimental shaker and vibrated by the trunk shaker) according to the registered and calculated variables (fruit maximum displacement (m) and fruit RMS acceleration (m s-2))” (New lines 171-174).

It has been written: "The trees (’Caracara’ variety) were in good health and nutritional condition (assessed by the agriculture cooperative technician)." - On what basis did good health and nutritional condition be found? What features were considered?

- The features considered were:

• Appropriate growth according to the variety and the age of the tree.
• No nutritional deficiencies.
• No broken or dead branches.
• No bark damage.
• Proper leaf color, shape, and size.

- The following paragraph has been included in the manuscript:

- “The trees ('Caracara' variety) were in good health and nutritional condition, assessed by the agriculture cooperative technician, with no particular nutritional deficiencies and appropriate growth and characteristics according to the variety and age” (New lines 85-88).

lines 112-115: Please describe briefly the methods of measurements.

- The measurement methods have been explained.

- “Retention force was measured using a digital dynamometer (Advanced Force Gauge 500 N, Mecmesin, England) with a cylindrical structure that allowed to pull the fruit in the horizontal direction. The fruit collected using the dynamometer were transported to the laboratory the same day where they were tested. Mass was measured using an electronic balance (Mettler Toledo AL104 electronic balance, Rondo Tower, Switzerland). Diameters were registered using a digital caliper electronic vernier scale (Holite Electrical Co.). Soluble solid content was determined with a digital refractometer (Atago model PAL-3; Atago Co., Tokyo, Japan). Tritatable acidity was measuring with an automatic titrator (Mettler Toledo T50, Rondo Tower, Switzerland)” (New lines 119-128).

Video recording is insufficiently described. More detailed information about the devices should be added. - This still needs to be completed.

- Information about the recording device has been included:

- “…(with a camera Casio EX-F1, at a rate of 300 images per second, was used to acquire the images with a size of 584 x 312 pixels and a resolution of 3.65 mm/pixel).” (New lines 146-148).