Identification of Close Modes on Frequency in Rotating Systems

Round 1

Reviewer 1 Report

In my opinion, the manuscript is suitable for publication in Applied Sciences journal but Authors must complete a major revision.  Therefore, reviewer suggested authors to do revising according to following general comments:

1. Introduction must be improved.
On the basis of literature, Authors should explain the need of scientific research which is presented in the manuscript. 
Has this method: “the joint use of the imaginary sensor technique and a Modal Parameter Extraction tool (EPM)” been used by other researchers? If so, what problems did they encounter? 
Authors should describe in detail the research gap that will be filled with their research. What's new in this manuscript?

2. Research object must be described.
Authors wrote (line 222): “the technique proposed for the study was applied in a field turbogenerator”, but any description of this turbogenerator is not presented in the manuscript. 

3. Discussion of results must be improved.
The obtained results must be discussed in relation to the results of other authors.

4. Conclusions must be improved. 
Presented conclusions look like an abstract of the article. Conclusions should briefly described how to fill the research gap which described in introduction.   

Author Response

The all corrections was done and are presented in attach file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors focused on the presentation of identification methodology through the use of coordinate transformation and a modal parameter extraction tool. This approach allowed them identification of characteristic patterns of close modes in frequency. It creates logical scientific research and that is why in my opinion could be published in "Applied Sciences" after introducing some corrections. Some of the comments on the manuscript are listed below.

1) Line 22; some keywords have been already used in the title of your manuscript. Please change them into different ones (to avoid the keywords repetition with the words used in the title).

2) What do asterisk (*) mean in equation (3) and (4)?

3) Table 1; what is the difference between “horizontal mode damping ratio (ᴟ_rx)” and “horizontal mode damping ratio (ᴟ_ry)”?

4) Instead of Kg probably Authors should use kg.

5) Please consider inserting the radius R and the locations of sensors in Figure 1 mentioned in the manuscript.

6) It is not clear for the Reviewer what does sen(ωt) mean in equation (5)? Do the Authors mean sin(ωt)?

7) Line 224 and 225; “…the second bearing at 45° and 135°, and whose corresponding polar diagram is presented in the figure below.” According to the Reviewer below there is nothing.

8) Please consider adding some more explanations concerning the mathematical models presented in your manuscript.

9) For the Reviewer it is not quite clear what is new in this manuscript in comparison with the published earlier Authors’ articles?

Author Response

The all corrections was done and are presented in attach file.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

It was a pleasure to review your paper. Find below some observations regarding it:

1. The state-of-the-art review provided is adequate as concerning the methods published previously. Unfortunately, that proposed by you is not sufficient compared with these and its advantages over those are not sufficiently highlighted in your paper.

2. The theoretical background is satisfactorily clear.

3. In table 1 you are providing the natural frequency in rpm, but upon its name, it should be given in Hz. Or the "frequency" name is not correct. Anyway, the revolution per minute should be abbreviated as r/min (upon SI standards) and not rpm.

4. You should use a unitary measurement unit for the angular velocity since by now you are using both rpm and rad/s.

5. Fig 6 and 7: the quantities on the y-axis do not have measurement units

6. The conclusion section must be rewritten since now it is only a recapitulation of what you performed, and it does not contain true conclusions upon your findings.

Author Response

The all corrections was done and are presented in attach file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Accept in present form.