Modeling and Estimation of the Pitch Angle for a Levitating Cart in a UAV Magnetic Catapult Under Stationary Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors developed a method to model and estimate the orientation of a launch cart in a UAV catapult's magnetic suspension system. They used Hall sensors and Time-of-Flight sensors to measure the magnetic field and determine the cart's pitch angle. The CRISP-DM methodology was applied to analyze data and create models, with the best models evaluated based on mean squared error. But the manuscript has some drawbacks that needs to be revised before the publication:

1. The quality of the figures in this paper could be improved to meet professional standards. Specifically:

l  Figure 1 is quite blurry, making it difficult to clearly discern the information presented. Images included in a paper should have a minimum resolution of 300 pixels per inch to ensure clarity. Additionally, the two sub-figures within Figure 1 should be labeled separately as (a) and (b). For instance: Figure 1. Vector representation of the magnetic field at a height of (a) 5 mm and (b) 10 mm above the tracks.

l  The sharpness of Figures 2, 5, 6, 7, 8 and 9 also needs improvement, and Figure 2 should include sub-labels for each image.

l  Figure 5(a) appears unprofessional, as an unexplained horizontal line is visible in the image.

l  The font used in Figures 6, 7, 8, and 9 should not be italicized to align with standard formatting practices.

l  Part of the picture is missing in Figure 6 (a).

 

2. Hall sensors have previously been applied in magnetic levitation systems. I noticed a 2009 paper from your team titled "A Concept for Application of Hall Sensors in Measurement of Magnetic Field over Magnetic Catapult Tracks," which appears to have already explored this concept. Given this context, the claim that "The novelty of this research lies in the application of Hall sensors for the precise determination of changes in the position and orientation of a cart levitating over magnetic tracks" may not fully stand as a novel contribution. Could you clarify how this work advances beyond the earlier study?

 

3. Why were Hall sensors and Time-of-Flight (ToF) distance sensors chosen for this application, especially considering that other sensors like accelerometers, displacement sensors or visual tracking systems might also provide orientation and position data? Could you provide a comparison of the performance of these sensor types in your system?

 

4. The content of the "Understanding Data" section in 3.2 could be integrated into section 2.2, immediately following the discussion of the acquired data. This restructuring would enhance the reader's comprehension of the data presented in Figure 5 by providing relevant context earlier in the text.

 

5. The format of Table 3 and Table 7 is not standard. And there is no conclusion in this paper, the last part section 4 is discussion.

 

6. You mention using the CRISP-DM methodology for modeling. Why was the CRISP-DM methodology specifically chosen for this study? Could other methodologies such as SEMMA have been more suitable for modeling magnetic tracks and estimating cart orientation? A comparison with alternative methodologies could provide more clarity on the rationale behind the choice.

 

7. You mention that the observed systematic errors in pitch angle estimation are within acceptable limits for practical applications. Could you elaborate on how these errors might impact the performance of the UAV system in real-world scenarios, particularly during launch operations? Would they affect safety or efficiency?

Author Response

Dear Reviewer,
comments on article attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In general, it is an interesting article. The results could be used in the  designing launchers for unmanned aircraft, which can be used for taking off. However, the  the idea of using such devices in landing procedures is debatable (line 43 of the introduction). This would require a highly advanced measurement and control system system, and it is also questionable what the practical purpose of landing on a magnetic launcher would be. Despite the overall positive impression of the article, this sentence requires clarification or discussion.

Author Response

Dear Reviewer,

Thank you for the valuable conclusion. We agree that utilizing a magnetic launcher in landing procedures requires an especially advanced measurement and control system. This possibility was highlighted in the manuscript as a potential direction for future research. The authors are aware of the limitations of such a solution. These limitations have been discussed, among other aspects, in the article [7] cited in this manuscript. Simulations of landing conducted in study [7] confirmed these challenges, particularly in synchronizing the UAV's position and velocity with the launch cart under dynamic conditions. Practical implementation of such a solution would require precise synchronization, which, while currently challenging, is not impossible. The benefits of this approach were explored in the GABRIEL project (https://cordis.europa.eu/article/id/92581-magnetic-takeoff-and-landing-for-fuelefficient-aircraft) and have been described in the following works:

• Rohacs D., Rohacs J., Magnetic levitation assisted aircraft take-off and landing (feasibility study – GABRIEL concept), Progress in Aerospace Sciences, 2016, 85: 33–50. DOI: 10.1016/j.paerosci.2016.06.001
• Ładyżyńska-Kozdraś E., Sibilska-Mroziewicz A., Czubaj S., Falkowski K., Sibilski K., Wróblewski W., Take-off and landing magnetic system for UAV carriers, Journal of Marine Engineering and Technology, 2017, 16: 298–304. DOI: 10.1080/20464177.2017.1369720

Reviewer 3 Report

Comments and Suggestions for Authors

fig.1 - too small

At lines 166 and 168 an accelerometer is mentioned, but it is mentioned nowhere else in the text or in the figures (probably a part of MPU-9250). The role of the accelerometer for the experiment must be explained.

Why the cart was asymmetrically placed over the tracks ( x and z data in table 2 differs for left and right tracks)? Was it intentional? Could the difference of the modeling results for the left and right tracks (section 3) be explained by this?

Obviously the measurements were conducted without superconductors in the levitating supports. Could the superconductors cause  deformation of the magnetic field lines and thus different readings from the Hall sensors?

The measurements and the modelling were performed on a stationary placed cart. Are the results adequate for a moving, levitating catapult cart?

There is no mention about the force that will accelerate the cart. If it is an electromagnetic force would it affect the Hall sensors?

Many more questions like the mentioned above require more systematic analysis of the operating conditions and requirements to the position measurement system of the catapult cart.

 

Author Response

Dear Reviewer,
comments on article attached.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript discusses modelling and estimating the pitch angle of a levitating cart in a UAV magnetic catapult system. The work appears novel and aligns with advancements in transportation and UAV launch technologies. However, several critical issues in structure, methodology, and presentation detract from overall impact and readability. Therefore, I recommend major revision to this submission to consider the following comments before it can be accepted for publication. 

Major Comments:

Lines 16–29 (Abstract) The abstract lacks quantitative details about results (e.g., MSE values or error reduction percentages). The phrases "accurate orientation modeling" and "facilitating analysis" are too vague. Terms like "CRISP-DM methodology" and "Meissner effect" are introduced without brief explanations. Include key numerical results (e.g., "The model achieved a mean squared error of 0.084° for pitch angle estimation"). Briefly explain technical terms (e.g., "Meissner effect: the expulsion of magnetic fields from superconductors").

Lines 33–39: "Passive magnetic suspension systems...to modernize their aircraft carriers."The section is overly broad, with examples (EMALS, AAG) that detract from the core focus on UAV catapults. Focus on UAV applications and briefly contrast passive vs. active suspension systems to set the stage for your unique contribution.

Lines 48–56: "In the analyzed catapult...absence of friction between the moving cart and the stationary tracks."The explanation of the Meissner effect is too basic for a technical audience. It also lacks a reference to physical limitations, such as sensitivity to temperature fluctuations or magnetic irregularities. Briefly mention challenges with superconductors (e.g., maintaining liquid nitrogen cooling) to provide a balanced perspective.

Lines 70–76: "The magnetic levitation system reaches...when the launcher is located on a ship."This section is unnecessarily repetitive. It reiterates stability concerns without advancing the argument. Condense this discussion and emphasize the importance of pitch angle control in maintaining stability.

Lines 87–98 (Literature Review):The comparison with prior studies is superficial. It lists references (e.g., [11], [12]) without explaining their methodologies or limitations. Highlight how your method improves upon prior work. For instance: "Unlike [11], which used Hall sensors for rotor orientation, our study combines Hall sensors with ToF sensors for enhanced spatial resolution."

Lines 104–114: "The novelty of this research lies...advanced estimation and data processing techniques."The novelty claim is too general and lacks a clear differentiation from prior studies. Specify the unique contributions, e.g., "This study integrates Hall sensors with ToF sensors and employs neural networks for real-time pitch angle estimation, a novel approach for UAV catapult systems."

Line 123 (Figure 2): The figure lacks descriptive labeling. The caption does not clarify how the components (e.g., supports, tracks) interact. Add arrows or annotations in the figure to highlight key components (e.g., "Levitating supports contain superconductors cooled by liquid nitrogen").

Lines 124–138: "The measurement stand is equipped...to ensure the parallel alignment of the tracks and crossbars."The detailed description of the setup (e.g., polyurethane foam walls) lacks justification for design choices. Explain why each design choice was made, e.g., "Polyurethane foam walls were added to minimize sensor noise from environmental disturbances."

Lines 163–172 (Figure 5): The graphs show sensor measurements but lack clarity in axis labeling (e.g., voltage, position). The choice of presenting separate plots for left and right tracks is not explained. Merge the plots for comparison or explain why separate plots are necessary. Ensure all axes are labeled with units.

Lines 199–20 The explanation of magnetic field intensity is oversimplified, assuming prior knowledge of field polarity effects. Include a brief explanation of how magnetic poles affect Hall sensor readings.

Lines 213–225 The normalization formula is correct but not justified in terms of its impact on the neural network’s performance. Add a sentence explaining the benefits of normalization, e.g., "Normalization ensures consistent input scaling, improving neural network convergence."

Lines 227–248 The choice of architecture (32:16:8) is not justified. Why were these layers and neurons selected? Was hyperparameter tuning performed? Include a brief discussion of how the architecture was optimized (e.g., through cross-validation or grid search).

Line 249 (Figure 6): The error density plots are insightful but not discussed in detail. Explain what the plots indicate about model performance (e.g., "The sharp peak near zero indicates low error variance, suggesting high model reliability").

Lines 252–260 (Table 6): The evaluation highlights systematic errors but does not suggest potential solutions. Discuss strategies for addressing systematic errors, such as sensor recalibration or alternative modeling approaches.

Lines 265–275: "The obtained height will then be used to estimate the pitch angle..."The process for selecting sensor pairs is not explained in detail. Why were these specific pairs chosen? Justify the choice based on factors like sensor placement or error minimization.

Lines 288–295: "The research on estimating the pitch angle...effective data analysis and model optimization. "This section is overly self-congratulatory and lacks a critical evaluation of limitations. Include a balanced discussion of strengths and weaknesses, e.g., "While the method demonstrates high accuracy, it is sensitive to sensor misalignment, which could affect real-world performance."

 

 

Comments on the Quality of English Language

Overuse of passive voice (e.g., "The measurement stand was designed...") makes the text less engaging. Use active voice where possible (e.g., "We designed the measurement stand to...").

Many sentences are unnecessarily long and could be split for clarity.

 

Example: "The levitation effect of the superconductors, resulting from the Meissner effect, allows the cart to stably hover above the launch tracks" → "The Meissner effect enables superconductors to levitate the cart, ensuring stable hovering above the tracks."

Author Response

Dear Reviewer,
comments on article attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The comments fo the previous round of the review are addressed by the authors satisfactory.

The title should be changed to reflect more precisely the essence of the research at its current stage. Suggestion:

"Test bench for Modeling and Estimation of the Pitch Angle for a Levitating Cart in a UAV Magnetic Catapult in stationarry conditions"

Author Response

Dear Reviewer,

Thank you for the suggestion regarding the title. We have changed it to "Modeling and Estimation of the Pitch Angle for a Levitating Cart in a UAV Magnetic Catapult Under Stationary Conditions." This updated title better reflects the focus and scope of the study, emphasizing its practical aspects and stationary conditions. We appreciate your insightful comments and support throughout the review process.

 

Reviewer 4 Report

Comments and Suggestions for Authors

I have reviewed the revised manuscript and the authors' responses to my previous comments, and I am pleased with the thorough and thoughtful revisions made. The authors have effectively addressed all the concerns raised, incorporating quantitative results and clear explanations in the abstract, refining the focus on UAV applications, and adding necessary technical details and discussions on challenges, such as superconductors and sensor performance. The improved literature review and articulation of the study's novelty significantly enhance the manuscript's impact, while the updates to figures, justification of design choices, and discussion of systematic errors and limitations contribute to its technical rigor. The revisions have greatly improved the clarity, depth, and quality of the work, and I am satisfied that the manuscript is now suitable for acceptance.

Author Response

Dear Reviewer,

Thank you for your thorough review and positive feedback on our revisions. We are delighted that the changes we implemented addressed your concerns and enhanced the clarity, depth, and quality of the manuscript. We sincerely appreciate the time and effort you dedicated to this process.