Assessment of Structural Performance and Integrity for Vibration-based Energy Harvester in Frequency Domain
Round 1
Reviewer 1 Report
The authors have proposed a new method for the evaluation of the vibration-based energy harvesters. The paper is interesting with several hardware-based results. However, the reviewer suggest that the authors should cite and explain the recent research articles in the introduction section. Moreover, the contributions of the paper are not clear to the reviewer. Therefore, contributions should be clearly written. In addition, within the whole manuscript including the abstract, all the acronyms should be defined first before using them. The language of the manuscript also requires careful proof-reading. The result section need more explanation. Discuss and compare your schemes with already published schemes.
Author Response
The authors have proposed a new method for the evaluation of the vibration-based energy harvesters. The paper is interesting with several hardware-based results. However, the reviewer suggest that the authors should cite and explain the recent research articles in the introduction section. Moreover, the contributions of the paper are not clear to the reviewer. Therefore, contributions should be clearly written. In addition, within the whole manuscript including the abstract, all the acronyms should be defined first before using them. The language of the manuscript also requires careful proof-reading. The result section need more explanation. Discuss and compare your schemes with already published schemes.
Ans)
According to your comments, we did proof-reading of entire manuscript. According to your comments, we refered the latest research trends in the introduction as follwong.
“Kang et. al. [18] studied experimentally the structural performance for the vibration-based energy harvester; they just, however, introduced the experimental results for structural performance for VEHs, not discussed the structural integrity and relevant assessment methodology. Accordingly, the methods employed in these studies are hardly applicable to evaluate the structural integrity of the VEH, which utilizes the resonance”
According to your comments, we have amended the conclusion as following.
“In this study, the authors carried out the static performance test, static and frequency response analyses for two versions of vibration-based energy harvesters. Based on these results, the authors proposed procedure to assess the structural performance and integrity for VEHs.
(1) Static performance tests were performed via the incremental sinusoidal sweep test condition at the predefined frequency range and acceleration level.
(2) We carried out static structural analysis to assess the natural frequency and failure critical locations (FCLs) on the leaf spring-shaped moving component of VEHs.
(3) We performed frequency response analysis to identify the stress and displacement responses at the FCL in the frequency domain.
(4) Based on these results, we investigated the structural performance and integrity of VEHs of two versions taking into consideration the resonance between the excitation load and VEHs itself. ”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
I have read the submitted manuscript entitled "Assessment of Structural Performance and Integrity for Vibration-based Energy Harvester in Frequency
Domain" by K.-W. Kang et al to Electronics. The presented work is of interest but unfortunately, authors have published similar results static performance test (particularly, displacement-frequency curve, and stress contour of VEH through FE analysis) in MATEC Web of Conferences 167, 02003 (2018). So, there is no insights available from the current work to publish.
Author Response
I have read the submitted manuscript entitled "Assessment of Structural Performance and Integrity for Vibration-based Energy Harvester in Frequency
Domain" by K.-W. Kang et al to Electronics. The presented work is of interest but unfortunately, authors have published similar results static performance test (particularly, displacement-frequency curve, and stress contour of VEH through FE analysis) in MATEC Web of Conferences 167, 02003 (2018). So, there is no insights available from the current work to publish.
Ans)
Paper on MATEC web of conference evaluated the behaviour at a specific acceleration level, but in this manuscript the frequency response behavior of the VEH was evaluated for various acceleration levels. In addition, paper on MATEC web of conference did not take into account any changes in the role of the rubber stopper and the resulting VEH response and structural frequency response. In particular, paper on MATEC web of conference do not present a methodology to comprehensively evaluate the structural performance and structural integrity of the Vibration-based Energy Harvester because it failed to take into account the role of the rubber stopper and its effect.
Author Response File: Author Response.pdf
Reviewer 3 Report
The comments are given in pdf file.
Comments for author File: Comments.pdf
Author Response
The manuscript related to numerical and experimental investigation of reliability and integrity of vibration energy harvester during it operation at resonance and high levels of acceleration. The topic, it self, is interesting and relevant however, there is several serious drawbacks. Firstly, the topic of the manuscript does not corresponds to subject areas of the journal. The investigations proposed in the manuscript are purely related to mechanical, structural or vibration engineering. Also, investigations are focused on very high accelerations i.e. 2-3g. The authors must discus potential vibration energy sources which can generate such acceleration levels in normal operation conditions. And finally, the authors does not introduced energy conversion mechanism which is used in the investigated energy harvesters. According to the manuscript it looks like that it is electromagnetic. My suggestion is to reject and encourage to submit revised manuscript to journal related to mechanical engineering or vibrations of solid bodies. On the other hand, some of my remarks are given below:
Ans) Scope of special issues posted on the journal homepage is as follows.
“This Special Issue is proposed to encourage further research and development of energy harvesters as mobile and remote power sources.
Development of energy harvesting devices should be carefully planned considering their target application. Powering wireless sensor nodes is one of the most attractive applications of energy harvesting technology for various monitoring purposes for large-scale structures and machines such as bridges, railroad, wind turbines, and naval platforms, as well as biosystems, such as the human body and/or animals. An energy harvester needs to be designed to meet the power requirements of the application (e.g. sensor), and integrated with a power management circuit for maximum power conversion and seamless sensor operation.“
Therefore, the topic of this manuscript is consistent with the special issue.
1. The authors neglected possible influence of electrical load to stress/ strain characteristics of the energy harvester. In general, the authors investigated energy harvesting system in open circuit condition. However, typically, the energy harvester is loaded directly by sensor or by energy storage and management system. The electrical load will damp the displacements of the shaft and as a result the maximum possible acceleration will be higher. Also, the potential electrical load will change natural frequency of the energy harvester and as a result strain/stress characteristics will be different.
Ans) As you have commented, electrical loads can generate mechanical damping to relieve the load on the mechanical structure. The main purpose of this manusctipt is not to investigate these effects, but to present structural assessment procedures for VEH design considering resonance effects.
2. The authors investigated energy harvester which consist of rubber based stoppers. In most cases, rubber based stoppers acts as an additional damper of the system. Therefore, usage of such type stoppers is not recommended. My suggestion is to change rubber based stoppers to permanent magnetic field based stoppers and investigate it influence to the reliability and integrity of the system.
Ans) The VEHs used in this study are designed for high-speed railways and are subjected to a very large acceleration of more than 3g, even over 5g, when travelling on high-speed railways. The VEH of this study should be designed to ensure sufficient durability under these highly acceleration conditions. When using the metallic stopper, it was determined that there would be an additional damage caused by the impact of the metal spring and metal stoppers. Therefore, the additional damping effects are desirable from a VEH design process, and the rubber stopper in this study was deliberately employed.
3. Fig. 11. The graphs looks very poor. Only a few points are given. My suggestion is to change the graphs to one common bar based graph or give these results just in table.
Ans) We revised the graph to reflect your opinion.
4. The manuscript lacks detailed explanation of structural design of the energy harvester. My suggestion is give a detailed drawing with section view in order to represent the design and stress the parts which will be investigated in field of reliability and integrity.
Ans) The VEH of this study is protected by international patents and is currently promoting commercialization. Therefore, although we have not explained the structure in detail, we believe that the basic mechanism can be deduced sufficiently because it follows the electro-magnetic mechanism. In addition, the main purpose of this manuscript is to present the structural performance and structural integrity evaluation procedures for electro-magnetic VEH considering resonance effects, so we believe that a detailed description of the structure of the VEH is not essential.
5. Fig. 1. The flow of the investigation is a little bit unusual. The manuscript should consist explanation why firstly were performed experimental investigation and after that finite element model was build. In most cases, first step is finite element model and investigations based on numerical investigations and only after that experimental investigations.
Ans) As your opinion, the general structure design will carry out the initial structural analysis and later experiments. The VEH of this study was also developed through this procedure. However, the purpose of this paper was not to introduce the design or analysis contents, but to present the procedure for evaluating the structural performance and structural integrity of the VEH considering resonance effects, so the initial analysis process was not important. In addition, when the initial analysis process is described in the manuscript, there are many contents that do not contribute significantly to the originality of the manuscript. Because of this, the volume of the paper becomes too long, so we omitted the initial analysis results.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
No more comments.
Reviewer 3 Report
No comments.
