Fruit Phantoms for Robotic Harvesting Trials—Mango Example
Round 1
Reviewer 1 Report
General comments:
Generally information is well presented and described; however, more pictures and clarity are required in the methods section. This is an empirical design paper, and thus the Methods section must be significantly better illustrated; the benchmark for success should be that another equivalently competent researcher should be able to fully reproduce the performed work with the information provided. Currently, the quality of writing is close (more clarity would be appreciated), but more pictures of the manufacturing process are required. Additionally, I would like to see an analysis of time and cost to manufacture using the selected method, particularly in the context of scaling this manufacturing for large scale testing of robotic manipulators.
Additionally this paper presented some discussion about the stalk design, but this design very weak compared to the work performed on casted fruit body design. Describing both processes in parallel weakens the paper because one is so much weaker than the other; there are many other stalk designs outside of the two that were described in the paper that would solve the challenges described in the paper. Investigation in the stalk design must be improved, or its discussion should only be mentioned in the context of future work.
There are many references in the main text. These should only be reserved for references to non-static content (https://www.mdpi.com/authors/layout#_bookmark93). Consider referencing material datasheets and product specification sheets using conventional citation format (ACS/Chicago).
Specific in-line comments:
71: List density unit (see style guide 6.2 https://www.mdpi.com/authors/layout#_bookmark33)
125-179: images of the various casting processes and their tradeoffs are needed to improve this clarity of this section. Multiple methods are described; images of the selected process are required; however, images of the other investigated process would still improve the paper. It is very difficult for the audience to visualize these process by test description alone.
184: stalk spring in Figure 1 (a) is not a torsion spring, it is a tension spring.
253-257: it seems like mass loss is a irrelevant parameter for all intents and purposes; Table 2 can likely be moved to appendix and the information can be condensed into a single value, i.e., <2% over 320 days.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Your manuscript in the form of a technical note is interesting, but for robotic collection, you need not just model fruits, but fruits that give feedback, which is very important for the design of manipulators.
1. Add a few more keywords, for example (mango fruit model, etc.)
2. Add some justification for the novelty and advantages of your development.
3. References to the fact that you were looking for analogues and did not find similar works are not too correct and require paraphrasing (Lines 44-48). Add "electronic fruits" to the review, with analogues can be arranged in tabular form indicating the advantages and disadvantages. Try to supplement the review. For example, such an article and the like (.file:///C:/Users/user/Downloads/1-s2.0-S0260877417303035-main.pdf).
4. About the color of the fruit, write that in your work you did not pay attention to it in the manuscript, but for recognizing fruits and determining their ripeness, this is a very important indicator, because robotic harvesting is selective, not flow-based.
5. In the materials and methods section, add the devices that measured the indicators in Table 1 and in general the devices that you used in this work.
6. In the description of the manufacture, add the exact time of all operations, which vegetable oil was used to lubricate the molds, (Line 125)?
7. Line 242 – specify the names of the oil and detergent in the blanks?
8. It is unclear why a photo of an orange phantom appeared in Figure 3, although the entire manuscript is written about mango fruits?
9. Part of the research results could be given for clarity in the form of graphs, if this is not necessary for a technical note, then how do you decide.
10. Why did the manuscript stop at only two proportions of mixing starch and silicone? Were there any preliminary studies? If so, then you need to write about them.
11. I recommend adding a section prospects for further research in which to indicate the further development of this topic by equipping fruit phantoms with various sensors (for example, a pressure sensor on the fruit, for evaluating robotic grips). As a further development of your topic. Since with robotic harvesting, not only the size, mass and color are important parameters. But also the traumatizability of fruits. Your work doesn't say anything about it. Since for the study of robotic grips of manipulative types, the efforts of influencing the fruit are important. And control of the compression force. This problem is solved by the use of so-called electronic fruits containing accelerometers and other sensors that evaluate the impact forces on the fruit.
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
General comments:
Manuscript is much improved, as authors revised majority of comments made in original review.
However, I stand by my original comment that the work performed in the fruit stalk design is too weak compared to the work performed on the fruit mold design. I believe the manuscript is sufficient to warrant publication due to the quality of the study on the fruit mold; however, if the study on the fruit stalk is also included in the manuscript, then sufficient context must be provided to the reader that the fruit stalk phantom design is only preliminary.
Novelty in a vacuum is insufficient to warrant publication at the journal level. Quality of work and/or significance of results is also necessary to warrant publication. It is obvious to any outside observer that the effort and scientific validity of the study of the fruit mold is superior to that of the work performed on the fruit stalk. The fruit stalk study lists only two design alternatives, spends very little effort describing the underlying physics, and the tested results do not validate the described physics. The paper mentions that a typical fruit detachment motion includes both a shear/rotation mode and tensile mode, but the results only list the tensile detachment force. The two listed solutions will likely behave very differently when considering both failure modes properly.
A fruit stalk study that I would consider sufficient to warrant a claim publication quality needs to better characterize the physics of fruit detachment by properly characterize the shear and tensile failure modes of typical (real) fruit detachment and provide an understanding of the coupling between those two forces. An understanding of the physics would then inform practical functional/performance requirements for the stalk design, e.g. envelope of ideal shear and tensile force, cost, reproducibility/precision, size, complexity, etc. This information would then lend itself to better exploring the design space of potential solutions; the two tested examples of a tension spring around a wooden dowel and a magnet with a tool steel nut are fine as quick, low cost solutions that were implemented for time expediency, but there are clearly many other potential design solutions. Some examples could include a COTS friction release mechanism, a hydraulic/pneumatic piston, an adhesive, a 3D printed (or similar rapid prototype manufacturing method) a sacrificial member with intentionally weak point of failure, etc. This amount of work could be wholly allocated to to a separate publication.
To be clear, I believe that the work performed on the fruit mold body is sufficient to warrant publication of the manuscript; however, if the work performed on the fruit stalk is not. The manuscript currently lists both studies in parallel, which, if published in its current form, implies a lower standard of scientific rigor by the journal, which will negatively impact the journal and its audience. The author must make it clear to the reader that the fruit mold design is the primary contributor to the scientific body of knowledge, whereas the study on the fruit stalk design is preliminary and requires more investigation before the the fruit phantom design space could be considered sufficiently explored. How the author goes about doing this is to their discretion--if it were me, I would move most of the discussion on the fruit stalk design to the future work section, leaving only the description of the two investigated designs in the methods section, and the results of the tensile test in the results (while being very explicit that the design and its results are only preliminary).
I will not recommend for publication until this distinction is clearly made in the manuscript. But please consider this "good news"--I believe the manuscript is sufficient to warrant publication; however, only if the writing provides sufficient context to which areas are sufficiently explored, and which are not.
Specific comments:
line 42: "silicone" not silicon
line 129: add "e.g.:" to beginning of list of oils if it is a list of examples OR add "i.e.:" to beginning of list of oils of it is a list of particular oils used in the study.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
Most of my wishes have been taken into account, the work looks better and can be published in the journal as a technical note after minor improvements.
Author Response
No action required
Round 3
Reviewer 1 Report
Much improved, thank you for timely revisions. Recommend for publication.
