Design and Modeling of an Experimental ROV with Six Degrees of Freedom
Round 1
Reviewer 1 Report
The manuscript addressed the development of an inspection class remotely operated 13 vehicles (ROV) for performing coastal underwater inspection operations. Also, it showed the mathematical model and the 18 results of modeling of the developed ROV.
Here are my comments to improve the quality and readability of the manuscript submitted.
The lesser thrusters require more torque for individual thruster, and this may require the torque that can be offered by the individual thruster. Have you considered this matter? If not, it is recommended to compare the individual thruster's torque consumption and the total torque consumption between the one proposed and the classical one.
The thruster specifications are only addressed in the manuscript. Please include all the hardware properties so that readers can understand the system better.
The test environment explanation is missing. Where did you test it? Are these experimental tests or simulation tests? What sensors did you use to collect the data? I don't see any noise effects.
It is very difficult to see the feasibility of the system without considering combined motions. Also, to highlight the efficacy, the comparison between the classical one and the proposed one must be accompanied.
Author Response
Response to Reviewer 1 Comments
Point 1: The lesser thrusters require more torque for individual thruster, and this may require the torque that can be offered by the individual thruster. Have you considered this matter? If not, it is recommended to compare the individual thruster's torque consumption and the total torque consumption between the one proposed and the classical one.
Response 1: Corrected. For information see section 2.1, added a thruster comparison table 1 for proposed and the classical thrusters arrangement scheme.
Point 2: The thruster specifications are only addressed in the manuscript. Please include all the hardware properties so that readers can understand the system better.
Response 2: Corrected. The article has added information about all available hardware properties.
Point 3: The test environment explanation is missing. Where did you test it? Are these experimental tests or simulation tests? What sensors did you use to collect the data? I don't see any noise effects.
Response 3: Corrected. See section 3.1 for a description.
Point 4: It is very difficult to see the feasibility of the system without considering combined motions. Also, to highlight the efficacy, the comparison between the classical one and the proposed one must be accompanied.
Response 4: Corrected. The article provides information on experiments in which combined movement was also studied.
The first experiment: the robot is located at the origin of the NED frame, it is necessary to first apply a control action to perform a set of movements corresponding to each linear movement degree of freedom sequentially (up-down, forward-backward, left-right consistently), then perform combined motions (backward, up and right).
The second experiment: the robot is located at the origin of the NED frame, it is necessary to first apply a control action to perform a vertical movement to a certain depth, and then sequentially perform a set of movements corresponding to each angular movement degree of freedom sequentially (yaw, pitch, roll).
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Dear authors,
Though not being an expert in the field, I recognise the merit in designing the hardware. However, what follows after you describe the configuration of your thrusters looks more like an exercise than like a real research effort. The article is rather the description of a standard procedure to generate a control model for your vehicle.
There are no real practical results beyond table 2 (still some cyrillic characters left) other than saying that a system was developed. In this case, either realistic simulations or actual missions should be reported. Figures 8 and 9, for instance, bring nothing to paper as they are just simple graphical outputs of the pos, vel, att and angular rates.
The status of the development should be clearly described: what level of maturity you reached is not clear.
All in all, it seems that a prototype was designed and that no real testing or comprehensive simulations have been conducted. You should conduct them or report them in detail.
Author Response
Response to Reviewer 2 Comments
Point 1: Though not being an expert in the field, I recognise the merit in designing the hardware. However, what follows after you describe the configuration of your thrusters looks more like an exercise than like a real research effort. The article is rather the description of a standard procedure to generate a control model for your vehicle.
Response 1: The article describes the new design of the ROV and provides theoretical and experimental results confirming the correctness of the stated results.
In the course of the presentation of the material, the calculation is carried out and the correctness of the stated results is confirmed. Also, an overview of the experimental results (section 3.1), which also confirms the stated results, has been added to the article.
Point 2: There are no real practical results beyond table 2 (still some cyrillic characters left) other than saying that a system was developed. In this case, either realistic simulations or actual missions should be reported. Figures 8 and 9, for instance, bring nothing to paper as they are just simple graphical outputs of the pos, vel, att and angular rates.
Response 2: Corrected. Added information about the real parameters of ROV. Added section 3.1, which describes experiments in an experimental aquarium with ROV. The first experiment: the robot is located at the origin of the NED frame, it is necessary to first apply a control action to perform a set of movements corresponding to each linear movement degree of freedom sequentially (up-down, forward-backward, left-right consistently), then perform combined motions (backward, up and right).
The second experiment: the robot is located at the origin of the NED frame, it is necessary to first apply a control action to perform a vertical movement to a certain depth, and then sequentially perform a set of movements corresponding to each angular movement degree of freedom sequentially (yaw, pitch, roll). The corresponding graphs are given.
Point 3: The status of the development should be clearly described: what level of maturity you reached is not clear.
Response 3: Corrected. The article declares a new design of the ROV as a new result. The novelty of the material proposed in the article lies in the fact that the authors propose a new design of inspection-grade ROV, with a smaller number of thrusters to achieve controllability in six degrees of freedom, as vehicles with a traditional layout. This is discussed in section 2.1. Further, in the course of the presentation of the material, the calculation is carried out and the correctness of the stated results is confirmed. Also, taking into account the remarks, an overview of the experimental results (section 3.1), which also confirms the stated results, has been added to the article. A prototype ROV has been developed. An example of his execution of technological operations is given at the link https://youtu.be/dO5w4mzHYfUYu (see lines 471-472).
Point 4: All in all, it seems that a prototype was designed and that no real testing or comprehensive simulations have been conducted. You should conduct them or report them in detail.
Response 4: Corrected. The description of experimental studies in the experimental aquarium is described in the added section 3.1.
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
This work presents the Design and Modelling of an experimental ROV with 6 Degrees of Freedom.
The work proposed by the authors is interesting and could be useful for future scientific industrial research activities.
However, in the reviewer's opinion, the authors should improve some aspects of their work:
1.- In the introductory part, we can consider the recent contribution of the work doi: 10.3390 / s19245387, which provides significant results on the design and construction of an ROV for underwater exploration.
2.- Since nowadays there are more and more commercial low-cost ROVs of this size with a quite similar architecture, good technical support as well as easily available spare parts (e.g. BlueROV, OpenROV), the main question is why a commercial ROV would not be better for this type of application.
3.- The authors should better highlight the novelty of the paper.
4.- How can they validate the stability of the ROV in a real operation?
5.- It would be very convenient if some experimental results were presented.
Author Response
Response to Reviewer 3 Comments
Point 1: In the introductory part, we can consider the recent contribution of the work doi: 10.3390 / s19245387, which provides significant results on the design and construction of an ROV for underwater exploration.
Response 1: In the introduction, a link to the article is made. Aguirre-Castro, O.A.; Inzunza-González, E.; García-Guerrero, E.E.; Tlelo-Cuautle, E.; López-Bonilla, O.R.; Olguín-Tiznado, J.E.; Cárdenas-Valdez, J. Design and Construction of an ROV for Underwater Exploration. Sensors 2019, 19, 5387. https://doi.org/10.3390/s19245387
Point 2: Since nowadays there are more and more commercial low-cost ROVs of this size with a quite similar architecture, good technical support as well as easily available spare parts (e.g. BlueROV, OpenROV), the main question is why a commercial ROV would not be better for this type of application.
Response 2: Corrected. In the article, the authors propose a new layout of the ROV thrusters according to which three thrusters with a thrust in the horizontal plane and three thrusters with a thrust in the vertical plane are located on the ROV body. The layout is described in section 2.1. on lines 114 - 151.
All thrusters in a complex manner allow achieving full controllability of the ROV in 6 degrees of freedom when using 6 thrusters, which is usually achieved with 8 thrusters in classic layouts, incl. BlueROV, OpenROV, and others. The authors also suggest the commercialization of the results.
Point 3: The authors should better highlight the novelty of the paper.
Response 3: Corrected. The novelty of the material proposed in the article lies in the fact that the authors propose a new design of inspection-grade ROV, with a smaller number of thrusters to achieve controllability in six degrees of freedom, as vehicles with a traditional layout. This is discussed in section 2.1. Further, in the course of the presentation of the material, the calculation is carried out and the correctness of the stated results is confirmed. Also, taking into account the remarks, an overview of the experimental results (section 3.1), which also confirms the stated results, has been added to the article.
Point 4: How can they validate the stability of the ROV in a real operation?
Response 4: To stabilize the robot's movement and realize in the future the possibility of complex trajectory movement in automatic mode, a mathematical model of the robot was developed and its parameters were identified. The description of the model is presented in subsection 2.3. This model was implemented in the Matlab&Simulink system. A computer simulation of the developed model was performed and compared with real experiments, which confirmed the adequacy of the model. The simulation and experimental tests results are presented in section 3.1.
Also in the article in lines 471-472, there is a link https://youtu.be/dO5w4mzHYfUYu, which demonstrates the experimental operation of the considered ROV, where it performs not simple technological operations that require the stability of its movement in all degrees of freedom.
Point 5: It would be very convenient if some experimental results were presented.
Response 5: Corrected. Added section 3.1 with the description of experimental results.
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors reflected all comments raised by the reviewer on the manuscript.
Reviewer 3 Report
Thank you for attending to my suggestions,
whose objective is to make the investigation work more relevant.
Kind regards,
