Testing the Influence of Null-Flux Coil Geometry Parameters on Levitation and Stability of Electrodynamic Suspension Systems Using a New Stationary Simulation Platform
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper presents relevant work in the study of the optimal Null-Flux coil geometry parameters to maximize levitation and stability of electrodynamic suspension systems. The following minor improvements are recommended:
1) The title is very extensive and could bore readers. I would advice a more attractive smaller title like the following: "Testing the influence of Null-Flux Coil geometry parameters on levitation and stability of electrodynamic suspension systems using a stationary simulation testbench platform".
2) The acronym "JR", in the first paragraph of the introduction on line 38, needs a description.
3) The description "Magnetic Field Source" for the acronym "MFS" should be done the first time it appears in the body text.
4) More detail should be given on the magnetic polarization arrangement of the four magnet flux sources on the side of the Bogie frame.
5) Please provide description for all four terms in the right side of equation (4). It seems that the indexes U and L refer to the upper and lower null-flux coils, and the indexes Un and Ln refer to the upper adjacent and lower adjacent null-flux coils.
6) The description of the term M_U,L in the right side of equation (5) is missing.
7) Please inclease the font sizes of the 3D axes numbers and colour legends of figures 5, 8 and 9, to become legible.
Author Response
Comments 1: The title is very extensive and could bore readers. I would advice a more attractive smaller title like the following: "Testing the influence of Null-Flux Coil geometry parameters on levitation and stability of electrodynamic suspension systems using a stationary simulation testbench platform".
Response 1: Thank you for your suggestion. We have revised the title to “Testing the Influence of Null-Flux Coil Geometry Parameters on Levitation and Stability of Electrodynamic Suspension Systems Using a New Stationary Simulation Platform” as recommended.
Comments 2: The acronym "JR", in the first paragraph of the introduction on line 38, needs a description.
Response 2: We apologize for the omission. We have replaced “JR Central” with “Central Japan Railway Company” to provide a clearer description.
Comments 3: The description "Magnetic Field Source" for the acronym "MFS" should be done the first time it appears in the body text.
Response 3: We have added the full description of “Magnetic Field Source” when “MFS” first appears in the manuscript.
Comments 4: More detail should be given on the magnetic polarization arrangement of the four magnet flux sources on the side of the Bogie frame.
Response 4: Thank you for pointing this out. We have added a detailed explanation of the magnetic polarization arrangement of the four magnet flux sources on the side of the bogie frame in figure2(a).
Comments 5: Please provide description for all four terms in the right side of equation (4). It seems that the indexes U and L refer to the upper and lower null-flux coils, and the indexes Un and Ln refer to the upper adjacent and lower adjacent null-flux coils.
Comments 6: The description of the term M_U,L in the right side of equation (5) is missing.
Response 5&6: Thank you for your comments. We have added the missing descriptions for the terms in equation (4) and terms in equation (5) to ensure clarity. The revised explanation of the variables in the equations is as follows, with the added text appearing in lines 112 to 113 of the article.
“ represents the mutual inductance between the upper (or lower) coil of a given NFC and the upper (or lower) coil of the th adjacent NFC.”
Comments 7: Please inclease the font sizes of the 3D axes numbers and color legends of figures 5, 8 and 9, to become legible.
Response 7: Thank you for your advice.We have increased the font sizes of the 3D axis numbers and color legends in Figures 5, 8, and 9 to improve readability.
We appreciate your constructive feedback and believe these revisions have significantly improved our manuscript. Thank you again for your valuable time and comments.
Best regards,
Jun Zheng, Prof.
E-mail: jzheng@swjtu.edu.cn
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript is based on a fixed experimental setup to investigate the effect of different NFC gaps on the EDS system. The research provides a certain reference for the design of EDS systems. The research is generally well-conducted and the conclusions are reasonable. There are several issues that need to be addressed before it can be considered for publication.
1.The manuscript fails to provide sufficient details when introducing the EDS stationary simulation method, particularly with regard to Figure 3(a), which has not been explained. Please make the necessary corrections.
2.The scanning parameters used in the analysis of coil geometric parameters are not uniform, which leads to unnatural results in the corresponding figures, such as Figure 4 and Figure 5. Please explain the reasoning behind this approach.
3.The experimental results presented in the manuscript show unusual curve trends in the lift-to-drag ratio when the NFC length is relatively long. As the coil length increases, the ratio of magnetic flux to resistance inside the coil should also increase, thereby improving the lift-to-drag ratio. Please provide further explanation for this phenomenon.
4.Figure 7 mentions the effect of different NFC lengths when the NFC gap is 400mm. However, such a large NFC gap value has never been mentioned earlier in the text. Please provide a reasonable explanation for this discrepancy.
5.The keyword “geometric optimization” appears in the manuscript, but there is no mention of any optimization processes throughout the text. This keyword is therefore inaccurate.
6.The NFC structure presented in Figure 2(b) is overly simplistic and lacks a detailed description of the specific structure of the NFC. Please provide more explanation in the figure.
7.Equation (4) mentions the coil U and coil L, but no explanation of these terms is provided in the surrounding text. Please provide their specific definitions.
8.Equation (6) refers to a matrix that contains many zero elements. Please explain the reason for this.
Comments on the Quality of English LanguageNo.
Author Response
Comments 1: The manuscript fails to provide sufficient details when introducing the EDS stationary simulation method, particularly with regard to Figure 3(a), which has not been explained. Please make the necessary corrections.
Response 1: Thank you for pointing this out. We have revised the manuscript to provide a more detailed explanation of the EDS stationary simulation method, including a description of Figure 3(a).
Comments 2: The scanning parameters used in the analysis of coil geometric parameters are not uniform, which leads to unnatural results in the corresponding figures, such as Figure 4 and Figure 5. Please explain the reasoning behind this approach.
Response 2: We acknowledge the concern regarding the inconsistency in scanning parameters. We have added an explanation to clarify the rationale behind this approach and how it impacts the results. The revised explanation of the scanning variables is as follows, with the added text appearing in lines 170 to 175 of the article.
“The NFC length was scanned in the range of 90 mm to 250 mm with a step size of 20 mm. Considering that smaller NFC lengths may result in larger parameter variations; an additional NFC length of 100 mm was included. The NFC gap was scanned in the range of 0 mm to 60 mm with a step size of 10 mm. However, since an NFC gap of 0 mm could introduce significant errors in mutual inductance calculations, 5 mm was used instead as the minimum parameter.”
Comments 3: The experimental results presented in the manuscript show unusual curve trends in the lift-to-drag ratio when the NFC length is relatively long. As the coil length increases, the ratio of magnetic flux to resistance inside the coil should also increase, thereby improving the lift-to-drag ratio. Please provide further explanation for this phenomenon.
Response 3: Thank you for your insightful comment regarding the unusual trends in the lift-to-drag ratio when the NFC length is relatively long. We believe this phenomenon can be attributed to experimental errors, which may have influenced the observed results.
In our experiments, when the NFC gap and length are small, the electromagnetic force characteristics of the EDS system change more drastically with displacement, making the influence of the NFC geometry more pronounced. However, as the NFC length increases, the system behavior becomes more sensitive to small errors in the experimental setup. Specifically, the test platform uses TBCs (Test Bed Coils) with rounded corners rather than square TBCs, which introduces some error. These errors become more significant when the NFC gap and length are small, leading to the irregular fluctuations in the lift-to-drag ratio that were observed in the experimental results.
We have revised the manuscript to provide this explanation for the unusual trend in the lift-to-drag ratio. Thank you again for your valuable feedback.
Comments 4: Figure 7 mentions the effect of different NFC lengths when the NFC gap is 400mm. However, such a large NFC gap value has never been mentioned earlier in the text. Please provide a reasonable explanation for this discrepancy.
Response 4: Thank you for pointing this out. The value of 400 mm was a mistake; the actual value should be 40 mm. We have corrected this in the manuscript accordingly.
Comments 5: The keyword “geometric optimization” appears in the manuscript, but there is no mention of any optimization processes throughout the text. This keyword is therefore inaccurate.
Response 5: We agree with your assessment. Since no optimization process is conducted in this study, we have removed the keyword “geometric optimization” to ensure accuracy.
Comments 6: The NFC structure presented in Figure 2(b) is overly simplistic and lacks a detailed description of the specific structure of the NFC. Please provide more explanation in the figure.
Response 6: We have revised Figure 2(b) to include a more detailed depiction of the NFC structure and have provided additional explanation in the text.
Comments 7: Equation (4) mentions the coil U and coil L, but no explanation of these terms is provided in the surrounding text. Please provide their specific definitions.
Response 7: We have added the missing definitions of coil U and coil L in the surrounding text to enhance clarity. The revised explanation of the variables in the equations is as follows, with the added text appearing in lines 112 to 113 of the article.
“ represents the mutual inductance between the upper (or lower) coil of a given NFC and the upper (or lower) coil of the th adjacent NFC.”
Comments 8: Equation (6) refers to a matrix that contains many zero elements. Please explain the reason for this.
Response 8: Thank you for your insightful comment regarding the matrix in Equation (6). As the distance between the NFC coils increases, the mutual inductance between them decreases significantly. When the NFC spacing exceeds a certain threshold, the mutual inductance becomes negligible, meaning the coils no longer exert significant influence on each other. To simplify the calculations and improve computational efficiency, we have made the approximation that the mutual inductance between coils separated by more than n NFCs (where n = 2 in this study) is effectively zero. This simplification is reflected in Equation (6), where several elements of the matrix are zero, indicating the negligible mutual inductance between distant NFCs.
We hope this explanation clarifies the reasoning behind the presence of zero elements in the matrix. Thank you again for your valuable feedback.
We appreciate your insightful feedback, which has helped improve the clarity and completeness of our manuscript. Thank you again for your valuable time and suggestions.
Best regards,
Jun Zheng, Prof.
E-mail: jzheng@swjtu.edu.cn
Reviewer 3 Report
Comments and Suggestions for AuthorsThis work refers to NFC coil optimization. However, the optimization carried out shows obvious and well-known results, such as increasing the gap reducing the force or mutual inductance between NFCs increasing with closer NFC coils. These are well-known in magnetism.
The experimental procedures should be explained. How did they change the distances between the coils? Are they adjustable? How did they conduct experiments with various coil lengths? Did they use different coils?
Can the author add a novel contribution to their work? Can optimization for energy consumption be performed?
Author Response
Comments 1: This work refers to NFC coil optimization. However, the optimization carried out shows obvious and well-known results, such as increasing the gap reducing the force or mutual inductance between NFCs increasing with closer NFC coils. These are well-known in magnetism.
Response 1: Thank you for your valuable feedback. We agree with your observation that some of the optimization trends in our study, such as the influence of NFC coil gap on mutual inductance and the effect of closer NFC coils on inductance, are indeed well-established principles in magnetism. However, we believe that although the impact of geometric changes on self-inductance is evident, it is still crucial to compute both self-inductance and mutual inductance when analyzing NFCs. This analysis is key to drawing accurate conclusions in the context of an EDS system.
We appreciate your comment, and in light of your suggestion, we have reduced the emphasis on self-inductance and mutual inductance in the manuscript. Our work now focuses more on the practical implications of these factors, especially in relation to their role in the design and optimization of NFC configurations for real-world applications.
The shortened text is as follows, appearing in lines 181 to 183 of the article.
“The self-inductance and resistance of the NFC are intrinsic parameters of the NFC itself and are independent of the distance between the NFCs. Both the self-inductance and resistance increase as the length of the NFC increases.
Comments 2: The experimental procedures should be explained. How did they change the distances between the coils? Are they adjustable? How did they conduct experiments with various coil lengths? Did they use different coils?
Response 2: Thank you for your thoughtful comment regarding the experimental procedures. We would like to clarify that the NFCs used in our experiments are virtual NFCs, which have identical geometric parameters in the vertical direction. However, both the length and gap of the NFCs can be adjusted as needed for different experimental conditions. The electrical parameters of these virtual NFCs are calculated based on the desired configuration.
In our experimental setup, TBCs (Test Bed Coils) are used to replicate the electromagnetic forces and torques generated by the virtual NFCs when subjected to the magnetic field sources of the test platform. These TBCs allow us to simulate the behavior of real NFCs within the experimental system. More information about the experimental methods can be found in reference [19], which has not yet been published. You can find it in the supplementary materials.
The added description of the experimental process is as follows, with the new text appearing in lines 160 to 167 of the article.
“In the experiment, we are able to define virtual NFCs with any length and gap, and use the testbench to reproduce the electromagnetic force and torque generated by the virtual NFCs with given parameters when passing through the magnetic field source of the testbench. To achieve this, we need to pre-calculate the electrical parameters of the virtual NFCs, including resistance, self-inductance, and the mutual inductance with other NFCs. These calculations will provide the necessary foundational data for further experiments and simulations, allowing us to accurately simulate the variations in electromagnetic force and torque under different configurations.”
We appreciate your helpful suggestion, and we have added these details to the manuscript to provide a clearer explanation of the experimental procedures.
Comments 3: Can the author add a novel contribution to their work? Can optimization for energy consumption be performed?
Response 3: Thank you very much for your valuable suggestion. We believe that the innovation of this study lies in the use of a novel experimental platform to test and study the NFC parameter design in electric suspension systems. This research method allows for the convenient simulation of the electromagnetic force generated by NFCs with different parameters as they pass through a magnetic field source, without the need to measure the magnetic field. Moreover, since the electromagnetic force characteristics are based on measured values, the results are closer to actual operational conditions. Besides, we appreciate your recommendation regarding the optimization of energy consumption.
In response to your comment, we would like to highlight that, according to thermodynamic principles, the work done by the magnetic resistance during train operation is almost entirely dissipated as Joule heat generated by the current in the NFCs. Additionally, due to the self-adaptive nature of the levitation height in electrodynamic suspension systems, the levitation force remains constant for a given train mass, regardless of the track type. As a result, the lift-to-drag ratio provides an excellent indicator of the energy loss during train operation.
We have taken your suggestion into account and added a discussion on energy loss in the manuscript, using the lift-to-drag ratio as a reference. We hope this addition contributes to the novelty and practical relevance of the work. The added section on energy consumption is as follows, appearing in lines 244 to 251 of the article.
“According to the laws of thermodynamics, the work done by the magnetic resistance when the train moves are almost entirely dissipated as Joule heat generated by the current inside the NFC. Meanwhile, due to the self-adaptability of the levitation height in the EDS system, the levitation force experienced by the train remains unchanged regardless of the track type, as long as the train’s mass is constant. Therefore, the lift-to-drag ratio of the train serves as an excellent indicator of energy loss during its operation and can be considered an important metric for assessing the operational efficiency of the train.”
We sincerely appreciate your constructive feedback, which has helped improve the clarity and completeness of our manuscript. Thank you again for your valuable time and suggestions.
Best regards,
Jun Zheng, Prof.
E-mail: jzheng@swjtu.edu.cn
