Short Landing Control Techniques Using Optimization of Flare Time Constant for High-Speed Fixed-Wing UAV
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors1. All variables in formulas must be declared immediately after their first appearance, some variables have insufficient explanations
2.
and 
is component of velocity 
in Equations (18) and (19), but 
is cannot be got by derivation through Equations (17). There is some wrong about 
3. What is the basis for the response time result in Figure 4?
4. Equation (11) only includes three degrees of freedom in the flare phase (two displacements and one pitch angle), and lacks modeling of the other three degrees of freedom. Even though this article only focuses on the pitch channel, altitude and horizontal distance, but in Figure 21, there is a control simulation result of the displacement degree of freedom, which is obviously unreasonable.
5. In Figures 20 to 26, the control simulation results of the glide and flare stages appear at the same time, but the glide stage dynamics model is not given, and the two-stage controller is not derived.
6. For the flare stage, the displacement control target is not seen in Figure 20. Is it the optimized curve? If so, please explain with Figure 27, and explain why the target value is very different from the simulation value?
7. Two sets of control systems are designed for the two stages, resulting in a sudden change in the pitch angle at the transition stage. In actual control, this is unreasonable. Please explain.
8. The control result in Figure 28 is very different from the target. Please explain.
Comments on the Quality of English LanguageThe English writing needs to be improved.
Author Response
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Reviewer 2 Report
Comments and Suggestions for AuthorsAnalytical solution of optimization problems for nonlinear dynamical systems is a well-known problem. Numerical solution of optimization problems for multilink dynamical systems also faces known difficulties. From this point of view, the solution of the considered optimization problem by numerical methods is not difficult.
To solve the optimization problem, the authors apply the Hermite-Simpson collocation. At present, such a method can be referred to the traditional ones. As a rule, the main difficulty in its application is the choice of basis functions. The requirements of smoothness of the solution and convergence are often followed.
The following recommendations and disadvantages should be noted:
1. In the introduction it is advisable to supplement the justification of the relevance of the development of the claimed method. Reference to the fact that the previously known method does not take into account something leads to the question of the need to take into account the pitch angular velocity. If everything works without it, why do something else?
2. Figure 2 formally represents “D”, “T”..... However, the decoding of these designations in the text after the figure and formulas (1) - (3) is not given. All designations are presented on page 23 of the paper. This makes it difficult to study the work. In this case, the formula from Figure 1 is additionally duplicated by expression (16).
3. According to expression (15), the problem considered in the study has two criteria, which are used to construct the corresponding functional. The solution of such an optimization problem will give satisfactory accuracy in the case when the value of xtf is not very large or the constant B characterizing the “value” of the second summand is also not large. In this case, both summands must be non-negative. Therefore, a reference to the literature or a justification for the choice of the functional is required before expression (15).
4. The study lacks a rigorous mathematical formulation of the optimization problem.
Author Response
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Reviewer 3 Report
Comments and Suggestions for Authors- How sensitive is the Sequential Quadratic Programming (SQP) method employed in this work with respect to the initial values?
- kindly provide a description of the degree of nonlinearity considered in the scope of the study.
- It is recommended to include a quantitative assessment of the effectiveness of the proposed methodology, specifically regarding the reduction in flare distance and total time.
- While the proposed method works, no comparison was made with other approaches in solving the nonlinear optimization problem.
- Additionally, only a single condition was evaluated. It is unclear how the proposed method would perform under other conditions.
- Additional clarification is needed on how the weighting factors presented in Table 7 were determined.
Author Response
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Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsIt is acceptable.
Comments on the Quality of English LanguageJust so so.
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Reviewer 2 Report
Comments and Suggestions for AuthorsThe presented study is certainly interesting. The authors have done a lot of work and provided interesting results of mathematical modeling.
Corrections in accordance with comment 2 have improved the presentation of the results of the study. But the changes made are apparently accompanied by typos, e.g. on lines, 115, 137. Also, the information on page 26, for example, duplicates the information on page 4 of the paper. Typos and repetition of information should be eliminated.
It is not clear why the authors introduced new designations (e.g., L in Appendix A) to answer the 4th comment. Why do the authors give 2 problem statements in Appendix A, which can be found in textbooks? In this connection it should be noted that in the title of the article the authors indicate landing control using optimization of the parameter (“...using optimization of flare time constant ...”). At the same time, the article explicitly considers the optimal control problem (paragraph 2.1), which is based on an adequate mathematical model (text fragment introduced in the article as a response to comment 1). As the authors point out, the use of such a mathematical model makes it possible to take into account angular velocity and initial position, which has not been done before and leads to constructive results. From this point of view it is necessary either to set the parameter optimization problem or to correct the title of the paper.
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Reviewer 3 Report
Comments and Suggestions for AuthorsThank you very much on revised version of the manuscript.
- Kindly incorporate the author's responses to comments 2, 4, and 5 in the manuscript
- Kindly improve the literature review by adding more references to justify on the selected optimization method and strategy.
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Round 3
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors' arguments in Response to Comment 4 are clear.
However, in the process of preparing the response to comment 4, information from the textbook was first cited (Response to Reviewer 2 Comments). The relevant information was not adapted to the article's labels. After this was pointed out, the relevant text fragment was deleted. As a result, the current version of the paper still does not explicitly contain a formalized concise formulation of the optimization problem. In this regard, it is not clear what the authors mean by using the equations of motion of the UAV as dynamic constraints (lines 574 - 576). Perhaps an answer to comment 4 would remove this question.
Summary. The paper is a rather interesting and large-scale presentation of the results of mathematical modeling. In the process of answering the review questions, the paper has received refinements that improve it. However, there are inaccuracies in the study concerning the solution of optimization problems. Therefore, in its current form, the presented article cannot be recommended for publication.
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Reviewer 3 Report
Comments and Suggestions for AuthorsPlease systematically review all the literature by describing and analyzing the key aspects of the references that lead to the conclusive findings and also the gaps of the study.
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Round 4
Reviewer 2 Report
Comments and Suggestions for AuthorsOnce again, the authors are pleased with the speed of response to comments. However, inspection of the submitted version of the paper revealed new inaccuracies and errors in expressions (11), (12), (23).
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