On the Adaptation of an AUV into a Dedicated Platform for Close Range Imaging Survey Missions
Round 1
Reviewer 1 Report
The paper describes in detail several adaptations of a SPARUS II AUV to make it a fully actuated vehicle to be able to perform imaging survey missions. For that effect, two T-200 thrusters were added to generate lateral thrust, the hydrodynamic coefficients of the new platform were determined by fitting data obtained with real experiments and new path-following control and thrust allocation algorithms were applied. The paper is very well written, clear, very informative and the results are significant I just have a couple of minor suggestions:
- Another torpedo-shaped vehicle that is used in imaging missions is the LAUV:
Madureira, Luís, et al. "The light autonomous underwater vehicle: Evolutions and networking." 2013 MTS/IEEE OCEANS-Bergen. IEEE, 2013.
- The paper would be more clear with some more information regarding the inner-loops used to track the references in sway and surge speeds and yaw.
- On lines 97 and 98 where it is written "causing to undesired rolling moment" it should be "causing an undesired rolling moment".
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
It is a huge work presented in this paper, ranging from mechanical design, configuration, dynamic modeling, hydrodynamic coefficient identification, and thruster allocation algorithm to the improved path-following controller. However, this paper looks like a technical report rather than a research paper, because it lacks novelty to some extent.
1. The T-200 is a common commercial propeller, which does not need the introduction in Section 6.2.
2. Section 7 hydrodynamic coefficient identification is very important for the modeling and control of the designed SPARUS II AUV, The author should do more work in this part to show a clear process of hydrodynamic coefficient identification. As stated in line 101, "hydrodynamic coefficients are estimated using experimental data", I think there is a lot of noise in the experimental data, and the maneuvers mentioned in lines 204, 205, and 206 may be subject to external interference.
Please explain the rationality of the proposed method for obtaining hydrodynamic coefficients. Why not use the CFD method?
3. In Section 9 "improved path tracking controller", a PID controller is proposed. The D term in the PID is very sensitive to noise. I wonder how the proposed PID controller can overcome this?
4. In sections 10 and 11, the author should consider the uncertainties of hydrodynamic coefficients and external disturbances. Please add more simulations and experiments to show the performance of the proposed PID controller when considering these uncertainties.
5. Section 1 should review some technical literature related to the topic of "close range imaging survey mission", please update and add some recently published works to illustrate the most advanced methods.
6. It is noted that this paper needs careful editing with language problems, please pay particular attention to grammar, tense, and sentence structure so that the study is clear to the reader.
For example, (1)line 28, … supervision, and … / line 78, is a SPARUS II is)
(2)Between equations 14 and 15, w1,2 … w1,2, should the second one be w4,5?
(3)Several sentences have logic problems. (i.e., line 34-36, collect high-quality image sets … it is mainly performed by hovering type … mainly by)
Please check the whole article and correct the relevant grammar and spelling mistakes
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The author introduced the optimization of existing AUV to adapt to the improvement of the close-range imaging survey missions. The authors focus on the enhancement of the AUV’s maneuverability through the addition of thrusters, adapting a state-of-the-art thrust allocation algorithm, developing a path-following controller, and the development of a dedicated imaging system. I think these tasks are necessary. However, some are lacking in this manuscript.
1. Why the close-range imaging survey mission needs an AUV？ Is there any previous research about imaging survey missions used the same way or did they choose the other path like the new concept of underwater vehicles? the author should explain clearly in this article
2. According to the author's description， “this work focus on the enhancement of the AUV’s maneuverability through the addition of thrusters…development of a path-following controller and the development of a dedicated imaging system”， however, these parts in the article did not describe how to modify according to the close-range imaging survey mission.
3. There is no logicality between each chapter, which can be sequentially or included, but the authors do not do so.
4. The author needs to compare whether the effect will be worse if it is not modified as mentioned in the article to prove the modification is necessary. Also, the thruster which upgraded in “ALICE" needs to describe why not to choose this type rather than another one.
5. The article has some grammatical errors
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Please see the attached file.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Please check the manuscript carefully and cut the long sentences into short sentences for better reading.
Author Response
Dear Reviewer
We thank you for your helpful comments that helped us to improve the article.
Additional English editing was conducted to ensure that no wording or spelling errors are present and that the sentences and paragraphs are well structured.
Reviewer 3 Report
The authors have addressed my concerns
Author Response
Dear Reviewer
We thank you for your helpful comments that helped us to improve the article.
Additional English editing was conducted to ensure that no wording or spelling errors are present and that the sentences and paragraphs are well structured.
Reviewer 4 Report
Only one comment is that the PID controller (i.e., Vreq) in Eq. (19) is proposed, however, the control input in the system model in Eq. (5) is toqure_c. How do they connect each other?
Author Response
Dear Reviewer,
We thank you for your helpful comments that helped us to improve the article.
Additional English editing was conducted to ensure that no wording or spelling errors are present.
Our response is given below following your comment in Italic.
Only one comment is that the PID controller (i.e., Vreq) in Eq. (19) is proposed, however, the control input in the system model in Eq. (5) is toqure_c. How do they connect each other?
Section 7 (line 276) discusses the vehicle's control hierarchy and the relationship between the different control levels.
The path following controller is a top-level controller. In order to follow the required path, it calculates the required velocities (surge, heave, and sway) and orientation (heading).
An inner-loop, consisting of velocity controllers, is used to compute the required force in each DOF (τ in equation 5) based on the velocity inputs.
Finally, to determine the required thrust for each individual thruster, the thruster's allocation algorithm (equation 12) is employed.
