Experimental Research on the Coupling Relationship between Fishtail Stiffness and Undulatory Frequency
Round 1
Reviewer 1 Report
In this article, authors imitate the change of stiffness by superimposing rubber sheets, and use experimental methods to test its swimming performance under different swing frequencies. A series of rubber fish tails were made according to analysis of the swimming movement of real fish, giving different stiffness values and changing curves of body. According to experimental results, authors found that with the change of the swing frequency, there are different optimal stiffnesses to make the thrust reach the maximum value, and with the increase of stiffness, the envelope interval of the swing curve gradually widens, the amplitude increases, and the hysteresis of the tail fin relative to the end decreases. However, minor revisions should be made before it can be published, for example, although some literatures are listed. I suggest authors to give a full list about related work of fish-inspired underwater robotics.
Author Response
We would like to thank you for your careful reading, helpful comments, and constructive suggestions, which has significantly improved the presentation of our manuscript.
According your suggestions, we organized a list about related work of fish-inspired underwater robotics in the revised manuscript
Once again, we thank you for the time you put in reviewing our paper and look forward to meeting your expectations.
Reviewer 2 Report
The paper presents an experimental method to simulate the change in fish stiffness through the overlap of rubber sheets. The paper is well presented and with high originality. The conclusions should be deeper to adequately support the findings.Author Response
We would like to thank you for your careful reading, helpful comments, and constructive suggestions, which has significantly improved the presentation of our manuscript.
We supplement the conclusions with your suggestions in the revised manuscript, and conclude with the main value and significance of the paper.
Once again, we thank you for the time you put in reviewing our paper and look forward to meeting your expectations.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The paper provides an empirical discussion about relationship between stiffness and frequency in a fishtail-like mechanism. The topic seems interesting. However, the manuscript is very difficult to read and follow. The reviewer suggests the authors should thoroughly rewrite the manuscript in a readable manner. Some following concerns the authors can consider in their revised version.
- The authors should clearly summarize what the contributions of the paper in Introduction.
- The authors should discuss potential applications of the mechanism.
- Front size of all the figures should be similar and readable. For instance, font size in Figure 1b is different from that in Figures 1a and 1c.
- There is no discussion about Figure 11.
- What is difference between Figures 10 and 11?
- Paper must be sent to a professional proofreader before resubmission.
Other concerns
- Line 28, what is BCF
- Line 33 – 34: “For example, the well-known robot fish tuna at MIT[2], G9 [3] at Essex University and so on.” is not a complete sentence.
- Line 51 - 52 “Simulating the variable stiffness characteristics of fish can further improve the swimming performance and swim more naturally.” is not grammatically right.
- Line 55: “to explore”
- Line 66: “swaming”
- Line 77-78: “In this paper 78 proposes a method that relies on superimposed rubber.” is not a complete sentence.
- Line 148: “And”
- Line 151: “Equation.6”
- It is believed that the color bar in Figure 8 is for Figure 8a. Where is the color bar for Figure 8b? It should be consistent in presentation.
- Figure 9 is not readable. Please make it clear.
Author Response
We would like to thank you for your careful reading, helpful comments, and constructive suggestions, which have greatly improved the way our manuscripts are presented.
We have revised the manuscript according to each of your suggestions. among them, the english of the article does need to be greatly improved, but unfortunately due to the time reasons, the entire article has not been reviewed this time, and the English of the article will be revised in the next issue.
Thank you again for taking the time to review our paper and look forward to meeting your expectations.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The authors have addressed the concerns.
