Design and Optimization of a High-Efficiency Lightweight Permanent Magnet In-Wheel Motor with Torque Performance Improvement
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsPlease follow the recommendations indicated in the attached file
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsThis paper proposes a multi-modulation lightweight permanent magnet in-wheel (LW-PMIW) motor with a dual-rotor structure, featuring an inner and outer double-layer air-gap design. The following suggestions are provided to improve the manuscript:
1: The research motivation should be more clearly articulated in the Introduction section to help readers understand the significance and necessity of the proposed design.
2: In Figure 2, the harmonic ripple components are labeled as having identical frequencies. However, difficult harmonics should typically exhibit distinct characteristic frequencies. Please verify and clarify whether this representation is accurate.
3: The font size across all figures should be standardized to ensure visual consistency throughout the paper.
4: Are there any experimental validations presented? If so, the authors should discuss whether the simulation and analytical results align with the experimental findings. If not, the lack of experimental verification should be acknowledged as a limitation.
5: In the title, the phrase “Torque Enhancement” is somewhat ambiguous. A more precise term such as “Torque Ripple Reduction” or “Torque Performance Improvement” may better reflect the actual contributions of the work.
6: Given the extensive literature on motor design, a comprehensive comparison table summarizing the advantages and disadvantages of the proposed approach versus existing methods should be included in the conclusion or discussion section to highlight the novelty and effectiveness of this work.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript presents a novel design and optimization approach for a lightweight, high-efficiency permanent magnet in-wheel motor (LW-PMIW) based on multi-harmonic modulation, harmonic injection (HI), and dual-rotor architecture. The proposed solution is timely and relevant for agricultural and lightweight electric traction applications, particularly in the context of precision farming and electrification of mobile equipment. While the technical concept is sound and the simulation results are promising, the paper has several issues that must be addressed before it can be considered for publication. These include weaknesses in the writing quality, lack of experimental validation, insufficient discussion of state-of-the-art limitations, and gaps in methodological transparency. The following section-by-section comments are intended to provide constructive feedback to strengthen the scientific rigor, clarity, and overall impact of the manuscript.
Abstract
The abstract introduces the general scope and objective of the paper, yet it lacks precision and technical clarity. It fails to report specific quantitative results, such as torque enhancement or power output gain, which are essential in conveying the true impact of the proposed design. Moreover, the language is grammatically incorrect in several places and needs careful revision to improve clarity and flow. A well-written abstract should succinctly present the problem, methodology, key numerical results, and implications of the findings. Therefore, it is strongly recommended that the authors revise the abstract to include concrete performance improvements and correct the English throughout.
Introduction
The introduction covers a wide range of relevant references, mostly recent and related to agricultural and electric traction systems. However, the literature review lacks a critical perspective and fails to clearly outline the limitations of previous works or articulate how this study overcomes them. As it stands, the novelty of the proposed approach is not fully established. A strong paper must demonstrate the research gap it fills. It is recommended to end the introduction with a comparative analysis, possibly in a table, highlighting the shortcomings of existing designs (e.g., weight, torque ripple, efficiency) and explaining how the proposed multi-modulation method addresses these issues.
Motor Structure and Theoretical Analysis
The motor structure, including the dual-rotor and ironless stator, is well visualized and relevant to lightweight, high-torque applications. The introduction of the trade-off factor YtotalY_{total}, balancing torque, mass, and copper losses, is innovative. However, the selection of weighting coefficients (0.7 for torque, 0.3 for losses) appears arbitrary and is not supported by a sensitivity analysis or application-specific justification. In a design optimization context, these coefficients should be validated through parametric studies or at least explained via realistic load requirements. The authors are encouraged to justify the selection more rigorously or provide a sensitivity analysis to support the weight factors used in YtotalY_{total}.
Permanent Magnet Design
The harmonic injection (HI) concept applied to the PMs is technically sound and represents a novel method to selectively enhance or suppress certain harmonic components. The Fourier-based modeling and the sensitivity analysis are commendable, but the presentation lacks clarity. The equations are introduced without sufficient explanation, and the influence of parameters such as PM width or displacement angle is not intuitively discussed. Additionally, the lack of unit information and normalized data in the figures hinders reproducibility. The authors should present a summary table of optimized PM parameters and provide a more detailed interpretation of how HI improves the airgap field and torque production.
Modulator Design
The use of iron blocks as modulators embedded in the stator frame is a creative solution to enhance harmonic content and torque production. However, the physical interpretation of the modulation effect is underdeveloped. The mathematical formulation is dense and lacks accompanying visualizations that would help readers understand the harmonic generation mechanism. Furthermore, thermal and structural implications of adding iron blocks are not discussed, which could be relevant for lightweight applications. It is recommended to include field simulation plots showing the influence of the modulators and to discuss their mechanical feasibility and thermal impact on the system.
Electromagnetic Performance Evaluation
The comparison among three motor designs (baseline, HI-enhanced, and fully modulated) provides useful insights into performance improvement. Torque, back-EMF, cogging torque, and output power are thoroughly discussed. However, all results are obtained through simulations only, with no experimental validation or prototype discussion. Additionally, essential simulation parameters such as current input, speed, winding configuration, and boundary conditions are not reported, which compromises reproducibility. A table summarizing all simulation settings should be added, and a short section discussing the feasibility of prototyping or future validation would strengthen the study significantly.
Conclusions
The conclusions summarize the technical steps and findings, but do not critically reflect on the study's limitations or propose future research directions. In a high-impact paper, conclusions should not merely restate the content but offer insight into what remains unresolved (e.g., thermal behavior, fabrication challenges, control strategies) and what steps will follow to bring the concept closer to application. The authors are encouraged to revise this section by adding at least two concrete limitations and outlining future work, such as hardware implementation or field testing.
References
The bibliography is recent and relevant to the topic; however, there is a noticeable concentration of citations from the same author group, which may suggest self-citation bias. Furthermore, important comparative or review studies on ironless and in-wheel motors from other institutions and journals are missing. A balanced reference list should include broader contributions from the international research community to contextualize the work within the state of the art. It is recommended that the authors add at least one recent review article and 2–3 comparative studies on similar motor architectures to diversify the cited literature.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
Comments and Suggestions for AuthorsPlease see the attached file for detailed comments and suggestions.
Comments for author File: Comments.pdf
The manuscript, at certain places, suffers from grammatical errors, awkward phrasing, and inconsistent notation. One example is (e.g., “Sensitiviti” in Figure 4). Some figures (e.g., Figures 8 and 9) are quite busy and therefore would benefit from clearer labeling or summarization.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThis paper proposes a multi-modulation lightweight permanent-magnet in-wheel (LW-PMIW) motor with a dual-rotor structure, featuring an inner–outer double-layer air-gap design. The following suggestions are provided to improve the manuscript:
1：Given the wide range of existing motor design approaches, if the work remains purely theoretical, its contribution may be limited. It should also be clarified whether the proposed design method aligns well with experimental validation results.
2：The manuscript presents only a brief qualitative comparison with other design methods; a detailed and quantitative comparison is necessary for journal publication.
3：I If experimental data are unavailable, it is recommended to compare theoretical calculations with simulation results to identify any discrepancies between analysis and simulation. At this stage, quantitative comparisons across different design methods are essential.
4：A quantitative summary table should be included at the end of the manuscript to clearly present the advantages of the proposed method.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsIntroduction
It is recommended to add a paragraph outlining each section of the paper to provide readers with a clear roadmap of the work.
Additionally, the information in this section should be synthesized, as it is currently too lengthy and could be made more concise to improve clarity and focus.
Methodology
Some additional technical details have been included; however, exact configurations, implementation parameters, software versions, and access to code or data are still missing to ensure reproducibility.
Several technical decisions remain insufficiently justified based on previous studies.
The methodological detail is still not adequate for other researchers to reliably replicate the study.
Results and Discussion
While additional figures and tables have been included, significant limitations remain in the analysis and interpretation. There is still a lack of direct and systematic comparison with previous studies, which prevents the findings from being robustly contextualized. No formal statistical tests have been implemented to validate the significance of the results, and numerical discrepancies remain unexplained in the text, without an analysis of the causes of atypical variations.
The discussion, although expanded, remains superficial in its contrast with the literature and does not address threats to validity or alternative hypotheses. It is essential to include a comparative table summarizing the employed methodology and the obtained results, particularly regarding the design and efficiency of the main variables, concerning the existing literature, so that the differential contributions of the proposed approach are highlighted in comparison to prior work.
Conclusions
The conclusions were slightly reformulated but remain generic and do not clearly emphasize the differential contribution or the practical implications.
It is not explicitly stated how the results expand or modify the existing body of knowledge.
No specific future research directions are proposed.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
Comments and Suggestions for AuthorsI am satisfied with the changes made by the authors and would recommend accepting the paper.
Author Response
Dear editor/chief editor,
We are very pleased to receive positive feedback from the reviewers! Thank you very much for informing us that the reviewer is satisfied with the revisions we have made and recommends acceptance of our paper.
We sincerely thank the reviewers for their meticulous and professional review, as well as their recognition of our work.
Thank you again for your and the reviewers' efforts during this process. We eagerly look forward to the formal acceptance of our paper.
Yours sincerely,
Zixuan Xiang, Yu Miao, Yuting Zhou and Feng Li
Round 3
Reviewer 2 Report
Comments and Suggestions for AuthorsMost of the comments are well-addressed. I have no more comments.
