Design and Experimental Validation of a Tailless Flapping-Wing Micro Aerial Vehicle with Long Endurance and High Payload Capability

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents the design, prototyping, and experimental validation of a tailless flapping-wing micro aerial vehicle intended to achieve long endurance and high payload capacity. The topic is timely and relevant. However, some areas require clarification to strengthen the contribution.

I consider that the manuscript requires a clearer articulation of the problem addressed, a deeper situating of the work within recent literature, and a more systematic evaluation of the MAV’s performance.

The manuscript repeatedly presents qualitative claims (long endurance, stable hovering, high payload capability). However, no provider provides quantitative metrics or statistical evidence.

The aerodynamic and structural design choices are insufficiently justified. However, aspects such as wing stiffness, flapping kinematics, and actuator selection require explicit references.

Lines 35.54: The literature review is brief and does not sufficiently compare tailless vs tailed flapping-wing MAVs.

The structural model is insufficiently described. It is unclear if the wing stiffness was analytically modeled or derived empirically.

Line 185: The thrust measurement setup is mentioned briefly. I suggest including details such as sensor model, accuracy, and sampling frequency.

Lines 250-270: The authors mention “stable hovering,” but there is no data showing control signals, trajectory deviation, or attitude stability metrics.

Line 280: Payload demonstration lacks experimental detail. Report the payload mass relative to body mass and show how the MAV behaves under this load.

The control scheme appears to rely on a standard PID-based structure, but the tuning methodology is not described.

The manuscript relies heavily on older sources. I suggest incorporating recent references on flapping-wing MAV design, aerodynamics, and control to properly situate the work within current literature.

Author Response

Please refer to the attached file "Response to reviewers"

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents the design, optimization, and experimental validation of a tailless flapping-wing micro aerial vehicle (FW-MAV) achieving record endurance (33.2 min) and high payload capacity, representing a meaningful advancement in the field of insect-scale aerial robotics.

The work is technically solid, well grounded in the literature, and supported by extensive experiments including torque characterization, attitude recovery tests, endurance, load capability, fast flight, and a demonstration scenario.

However, the manuscript requires moderate revisions to improve clarity, structure, and completeness. The main observations are:

1. Several sections contain long and dense paragraphs that should be reorganized for readability.

1. Minor grammatical and syntactic inconsistencies appear throughout the text.
2. Some transitions between subsections are abrupt and would benefit from improved cohesion.
3. Improving the English expression (especially in Sections 2 and 3) will significantly strengthen the presentation.
4. While the methods are generally well described, some elements require clarification to ensure full reproducibility:

• The control system architecture (Figure 8) is described but lacks specific controller gains or tuning procedures.
• The throw test lacks specifics on initial conditions (released height, attitude perturbation magnitude).
• The experimental lift measurement setup (Fig. 4) should specify sampling rate, filtering, and calibration procedures.
• The material and manufacturing tolerances of the wings and mechanism could be described in more detail since they strongly affect performance.

6. Although generally clear, some figure captions are brief and could better support interpretation:

• Figures 3, 7, 10, 13, 15, 17, and 18 contain composite images with no scale bars or descriptive annotation of key events.
• Figures 4 and 5 would benefit from including standard deviations or error bars to reflect measurement variability.
• Labeling in flight test figures should be larger for readability.

7. The introduction is well referenced; however:

• Additional comparisons in Table or paragraph form would strengthen the contrast between X-fly and state-of-the-art insect-like MAVs.
• References [3–5] and [12–21] used for performance comparison should be integrated into a more explicit "state-of-the-art performance table".

8. The claim of “tripling the longest previously reported endurance” is supported by data, but it would be beneficial to:

• Include a small summary table of endurance values from previous works to make the comparison explicit.
• Clarify whether indoor hovering represents a fair comparison to outdoor free flight endurance of other MAVs.

 

9. The manuscript presents results clearly, but the interpretation of those results is somewhat brief. Suggested additions:

• Discuss how the crank-rocker mechanism compares dynamically to string-based or motor-driven systems.
• Explain the implications of high lift-to-power ratio on long-term system reliability.
• Include a short subsection on limitations (battery efficiency drop, actuator wear, sensitivity to environmental disturbances).

Author Response

Please refer to the attached file "Response to reviewers"

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Title: Design and Experimental Validation of a Tailless Flapping-Wing Micro Aerial Vehicle with Long Endurance and high Payload Capability

This paper investigates the design of tailless FW-MAV named X-fly, incorporating a lightweight crank-rocker mechanism with high thrust-to-weight ratio. The paper is very interesting and well written. The authors should deeply review the writing of the paper, there are some typos and English mistakes, which could be avoided. The reviewer has some concerns regarding this paper as follows.

1) There are some typos in the Introduction. See line 57 and 311, for instance. In addition, avoid using long sentences. Long sentences must compromise the clear understanding of some sections.

2) All coefficients and parameters used to define any equation must be defined right next to the corresponding equation. Please, revise the whole paper.

3) How are the parameters chosen to investigate the optimization of flapping wings? Do they present the major contribution in the dynamics and control?  Have the authors investigated the relation between additional weight and lift?

4) The authors mentioned that “The experimental results highlight that wings with larger wing lengths generate 256 higher lift at the same input voltage …. “, however Figure 5 does not show that. Could the authors better explain this comment?

5) There is a wrong expression in Figure 8 “Desire Angle”, which might be “Desired angle”. Please, revise this figure and the text.

6) Regarding the results, why not include any additional Figure from the experimental trials? A Figure about the trajectory tracking could be an interesting result.

Author Response

Please refer to the attached file "Response to reviewers"

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I would like to thank the authors for the careful work invested in addressing the previous comments. The revisions are clear and satisfactory, and at this point, I have no additional comments.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for your thorough revisions. I am satisfied with the improvements and wish you every success in your future research endeavors!