Iterative Self-Tuning Minimum Variance Control of a Nonlinear Autonomous Underwater Vehicle Maneuvering Model
Round 1
Reviewer 1 Report
The paper proposes an iterative self-tuning minimum variance control method to addresses the control problem of an autonomous underwater vehicle. The control algorithm is based on an iteration technique that approximates the original nonlinear model by a sequence of linear time varying equations equivalent to the original nonlinear problem and a self-tuning control method so that the controller is designed at each time on the interval for trajectory tracking and heading angle control. The authors state the benefit of this approach is that the nonlinearities and couplings of the system are preserved, reducing in this manner the uncertainty in the model and increasing the robustness of the controller. Finally, simulations are presented to show good performance of the controller and accurate tracking for certain maneuvering cases. The paper is well organized and logically explained. The quality of the paper can be further improved by addressing the following questions and problems:
- Fig.2 is in poor quality and it is difficult to be clearly seen. Consider re-plot it.
- The formulas writing is not standardized in the paper. Consider improved them.
- The units of the variables in the simulations should be given.
- In equation (5), no dynamic uncertainties and external disturbances are considered in the AUV dynamics, so how to verify the robustness of the proposed controller?
- Some necessary proofs such as the convergence and effectiveness of the proposed controller should be given.
- The literature review is not sufficient, some new works related to the control of AUVs that appear within 5 years should be included. For example, for the sliding mode control of AUVs, the following references: DOI: 10.1109/TII.2019.2949007, DOI: 10.1049/iet-cta.2017.0016 are recommended.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper proposes an iterative self-tuning control method for AUV trajectory tracking. The advantage of the method is claimed to improve the robustness of the controller. However, the description of the contributions is not convincing enough as it lacks comparison results with the existing control methods.
Some other comments:
- The proposed control method lacks proof of the stability.
- The authors should provide the hydrodynamic parameters of AUV in the simulation part. More simulation scenarios are needed to validate the performance of the control method.
- Although the authors claim that the control method considers the nonlinearities and couplings of the system, the reviewer cannot find the necessity description. The advantages (accuracy, robustness or computational efficiency) of the control method is not proved.
- How can we define the number of iteration steps? It is an unchanged number or it should be tuned according to the detailed scenarios? What is the criterion of deciding the iteration steps? It is not mentioned in the manuscript.
- The reviewer suggests to add more recent literatures to the references to strengthen the confidence of the Introduction part.
- The reviewer suggests to add the experimental results to verify the proposed method.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Please to see the attached file, thank you.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I can't agree with the response of last review.
Author Response
We attach a letter with the responses.
Author Response File: 
Author Response.docx
