Active Load-Sensitive Electro-Hydrostatic Actuator for More Electric Aircraft

Round 1

Reviewer 1 Report

The paper presents a novel electro-hydrostatic actuator, called active load-sensitive electro-hydrostatic actuator, analyzing its characteristics in terms of motor heating, dynamic characteristics, stiffness, and power matching by means of mathematical models. Given the complexity and numerousness of the contents presented, the paper is not always easy to read. It would be advisable to use a more schematic approach, presenting and justifying at the beginning of each paragraph all the points that will be deepened in the following in order to guide the reader in the contents proposed from time to time. At the end of the introduction, the organization of the article in the following sections should be presented. Not all figures are adequately described in the text and it should be checked if all symbols appearing in the formulas are explained. The English translation should also be checked. I suggest to deepen the part relating to the experimental results which are very important and must be adequately discussed and highlighted.  The conclusions are too short and future developments should also be included. Finally, I would suggest to the authors to highlight more in the introduction and in the conclusions the importance and novelty of the proposed method.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

!) I think it's an exaggeration to say that "the ALS -EHA has huge advantages ..."

2) The problem of actuator rigidity is treated by the authors leisurely. In airplane flight controls, the dynamic rigidity, also called dynamic impedance, would deserve even more attention, as seen in the article I. Ursu (2012), The kinematics of the rigid feedback linkage, the impedance of the hydraulic servomechanism and the flutter occurrence, INCAS Bulletin, vol. 4, no. 3, pp 63-70.

3) I suggest to the authors to see the article "I. Ursu, G. Tecuceanu, A. Toader, C. Calinoiu (2011), Switching neuro-fuzzy control with antisaturating logic. Experimental results for hydrostatic servoactuators, Proceedings of the Romanian Academy, Series A, Mathematics, Physics, Technical Sciences, Information Science, 12, 3, 231-238", in which the attention was paid to the synthesis of the control, in that case, a neuro-fuzzy comanuscript, namely a Romanian Patent no. 127329/30.07.2014 granted by the State Office for Inventions and Trademarks OSIM, Holder INCAS Bucharest, title of invention: "Aviation hydrostatic servoactuator".

I make this reference because the authors talk on page 9 only in passing about the need for control.

4) In other words, the formulas should be rendered more carefully, and all notations should be described in the text. For example, in the relations (2) - (4) the notations are not introduced, and this is just an example. Relationship (5) has been rewritten in (6), but (6) is not used anywhere in the text.
And another example of careless writing: after various relationships, when making descriptions of the notations used, we must not continue with "Where", but with "where".

5) The conclusions should be more nuanced, in the sense that they should emphasize the contributions of the article.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

I found the paper interesting and fitting the journal scope. Unfortunately, there are several errors in the paper organization, methodology and discussion. Thus, I must advise a major revision. Please address my specific comments:

1. The title is too long. Each scientific paper must present novelty, thus there is no point in including the word novelty in the title. From my point of view “Active Load-Sensitive Electro-Hydraulic Actuator for More Electric Aircraft” would be enough to present the paper content

2. The abstract sound like approach justification and does not reflect the paper content. In fact only the last two sentences refer to the paper directly. The abstract must be rewritten.

3. The English in the paper is good, but I noticed several issues.

3a. The authors should revise the text to eliminate repetitions if possible e.g. in the first sentence of the article (line 30-31) the second use of the word “aircraft” can be replaced by using “its”. Multiple repetitions of the world “use” in the second sentence are not necessary (lines 31-34). This can be observed in the whole paper, e.g. “leaks” in line 51.

3b. The paper suffers from using too many acronyms. They should be eliminated when possible (e.g. PBW and PFV are used only few times, so no need for using the acronym). Using to many acronyms leads to another issue – double use of the same words e.g. in line 103 authors wrote “EHA actuators” which means Electro-Hydraulic Actuators Actuators. This does not make sense and the second word must be skipped. This happens in the whole article.

3c. In the paper some typos and grammar error can be found, e.g. in line 200: “… rang of 0 to …”. Another example can be found in line 238 – authors refer to section IV, but in the paper there is no section IV (but there is section 4).

3d. The authors should check their interpunction, e.g. in line 231 the dot between “known” and “equation (5)” should not be used. In line 475 a capital letter is used after a comma “, i.e. Simultaneously”. In line 461 a dot between words “area” and “so” should not be used. Again, this type of error happens in the whole article.

3e. The authors should also focus on the overall text consistency. Again, in the line 231 – word “and” is of a different style without reason. Moreover, they refer to equations as “equation (5)” (line 231) and “the equation 24” (line 362). The lack of consistency is also present in the equations, e.g. in (5) “x dot” stands for time derivative and “dy/dt” stands for time derivative in (7). Either x dot or dx/dt should be used in the whole paper. In (16) the scalar multiplication symbol is used, but why? If this is a simple multiplication a symbol should not be introduced as it is used only in this place. The inconsistency is observed across the whole paper.

3f. When authors present equations and their explain the symbols indentation before word “Where” should not be present and the word should be written without the capital letter as this is a part of the sentence (not a new one). Again, this can be found in numerous places.

Summarizing, the authors should check their text more carefully when resubmitting it.

4. The paper should be organized in a better way. First, the authors should present the text and then refer to it, and not the opposite way (e.g. in section 2, when referring to explanations shown in section 4, or when explaining the equations)

5. The authors should not write the article from their country perspective, as this is a global problem and not a regional one. In line 128 they use the phrase “foreign countries”. Foreign countries from whose perspective? Their or the reader? This solution is not region-dependent. It can be said that “the idea of using high-speed motors and high pressure systems … is often used” but not to regionalize this topic.

6. The article lacks of qualitative analyzes and reference values, e.g. in lines 177 and 191 authors use large or medium/heavy. The authors should be more specific and explain what means large or medium when referring to their problem.

7. When presenting the equations authors do not explain all variables (or at least they do this in an non ordered way), e.g. in eq. (1). i_m and ω are not explained. They should be explained after eq. (1) and not later. This is true for all equations in the text.

8. When presenting eq. (9) and (10) authors say that those are obtained by assuming that M_T+M₀=0. This is true for eq. (9), but I cannot see how this fact leads to eq. (10). Please explain this in a greater detail.

9. Obtaining eq. (14) requires using eq. (11)-(13) and not only (12) and (13) as it is written in line 278. Moreover, in eq. (14) authors multiplied by γ and not y as shown in eq. (12).

10. In line 305 the authors wrote that P_A has negative correlation with the control current. This cannot be concluded without evaluations (e.g. from Figure 7). As correlation is a quantitative measure please express it through numbers or rephrase the text.

11. In Figure authors present the curve matching and explain it in lines 451-452. From Figure 7 it can be seen that it is a very poor estimate. Even if a polygonal chain is used, a cost function should be defined for that purpose e.g. RMS minimization. As power matching is one of the key aspects of the paper, this (at least) must be discussed in a greater context. This can be done by comparing it with nonparametric approach in frequency responses matching presented in e.g. [R1] and parametric approach shown in e.g. [R2]. Without, at least, the qualitative discussion like this - the paper sounds like an engineering note and not like a scientific paper in a well-recognized journal.

[R1] Berger T., Tischler M. B., Hagerott S. G., Cotting M. C. and Gray W.: "Identification of a Full-Envelope Learjet-25 Simulation Model Using a Stitching Architecture", Journal of Guidance, Control and Dynamics, doi: 10.2514/1.G005094

[R2] Grauer J. A., Boucher M.J.: "Identification of Aeroelastic Models for the X-56A Longitudinal Dynamics Using Multisine Inputs and Output Error in the Frequency Domain", Aerospace 2019, 6(2), 24; doi: 10.3390/aerospace6020024

12. In line 509 the authors write about reasonable match, but what does it means. This should be explained through a quantitative description (e.g. RMS) as explained earlier.

13. Conclusion 2 must be rewritten according to my previous remarks.

14. Conclusion number 3 (lines 574-575) is a general conclusion, not a conclusion discussed through the paper. Thus, it should be deleted or explained better.

For now, this is all for me. I hope that the authors will address all my comments in the revised manuscript.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Thank you for responding to my comments. In my opinion the paper can be published in its current form.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.