Dynamic Inversion-Enhanced U-Control of Quadrotor Trajectory Tracking

Round 1

Reviewer 1 Report (Previous Reviewer 1)

Comments and Suggestions for Authors

I can see that the authors have made major revisions to the paper and the overall quality has been improved.

Here are some detailed suggestions for the authors to further improve the paper.

1. Some formatting errors: there should be no indent if a sentence is not complete. For example, line No. 247, 267, and so on.

2. The use of colors of the curves in the figures of simulation and experimental results is confusing. For example, in fig10 a and b, the red curves represent two different controllers. The use of color is inconsistent that makes the reader hard to follow the idea. I suggest that through the whole paper, the authors could use one color to describe the results of one certain method to avoid confusion.

3. Another table similar to Table 3 can be provided to summarize the results of the experiments.

4. There should be units for the thrust and torque coefficients C_T and C_Q in Table 1.

Author Response

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Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

The subject matter is engaging, and the paper's structure is satisfactory. However, there are significant Major concerns that require clarification.

Comments:

  1.     The contribution of this study isn’t clear. The Introduction part needs to improve and the final goal of the paper should be clear.

2.     What is the novelty in the controller (6), in comparison with the existing methods?

3.     More explanations about figures 3 and 4 are required.

4.     The simulation part is the main weakness of the paper. Please provide more details and improve the figures and describe the concept in a better way.

 

5.     What are the limitations during the implementation of the method?

Author Response

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Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

This paper presents a Dynamic Inversion Enhanced U-Control of Quadrotor Trajectory Tracking.

In the flight tests, repeat the simulation shown in Fig. 8 and the results in Table 3. If possible, try to place some additional weight on the minidrone to verify the robustness of the proposed controller.

Author Response

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Round 2

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

Accept in the current version.

Author Response

Thank you for accepting the paper for publication in its current version

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper investigates the U-Control approach for the quadrotor control. From the presentation, methodology, and verification results perspectives, this paper has many weaknesses. Here are some detailed comments.

1. The contribution and novelty are unclear. The U-Control, in appearance, is another interpretation of feedback linearization techniques. Most of the control design is in the form of a very classic quadrotor control scheme.

2. Section 2 is more like a tutorial of an existing methodology, which in the reviewer's opinion, is unnecessary. The authors should rather discuss how to implement, or improve the methodology to the considered control plant in some specific scenarios. 

3. Although the authors employ a robust compensator to enhance the U-control's performance, the simulation results are not even compared to the PID control in many cases. This makes the proposed controller insignificant with respect to both methodology and application. Moreover, the experimental verification and comparison are not provided, and therefore it is hard to justify the value of this work in practice.

4. The stability and control performance analysis are not provided mathematically.

5. Some minor text formatting errors exist.

 

Author Response

 

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Reviewer 2 Report

Comments and Suggestions for Authors

Dear

In fact, an approach presented in a paper is an extension of some approaches based on invert dynamics control.

The problem I can see is that invert dynamics could require plant with numerator’s orders higher than denominator’s. This will probably produce calculation numerical issues in real experiment.

But concluding I appreciate some tricky way however I Wonder if real flight are scheduled?

The structure and layout of the paper are correct. The paper contains all necessary components.

Author Response

 

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Reviewer 3 Report

Comments and Suggestions for Authors

The major issue with the paper lies in the lack of validation for XY-directional flight control. While simulations yield promising results, there remains a significant gap in theoretical validation. Achieving consistent experimental results would prove the feasibility of the theory. Currently, this crucial step has not been implemented.

Additionally, the description of the experimental platform lacks important details. It is essential to include parameters such as the type of positioning system used, sampling frequency, and accuracy. Without these details, readers may question whether the experiments were truly conducted using the Parrot platform.

Formula 14 should have an error—the numerator should not be 1 but rather G(s).

Comments on the Quality of English Language

The expression is clear and straightforward, making it easy to understand the intended correction.

Author Response

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Reviewer 4 Report

Comments and Suggestions for Authors

Could you in paragraph 2.2 make a comparison between the proposed U-control approach and robust Flat control techniques? Can you explain the differences between them as well as compare performances.

Comments on the Quality of English Language

A new control formalism is proposed to use already known control techniques,  bibliography with the same application (rotor-craft flight control).

Author Response

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Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have made revisions to the paper, however, some concerns are not resolved.

1. The contribution of this work is questionable in both theoretical and practical aspects. There is, in the reviewer's opinion, no novel design nor methodological improvement. Moreover, the application of the method to a real quadrotor shows unstable behavior in the flight tests.

2. The Lyapunov stability analysis is wrong, starting from eq. (44). 

3. The chattering is the inherent drawback of employing sign function in the controller, and this issue is not resolved in both design and implementation, which makes the value of the method very limited.

Reviewer 4 Report

Comments and Suggestions for Authors

Objectively the answer to my question about Flat Differential control has not been developped sufficiently.

Comment relation (27).

No information is provided about the dynamic performances and limitations of actuators and sensors .