Fault-Tolerant Control Scheme for the Sensor Fault in the Acceleration Process of Variable Cycle Engine

Round 1

Reviewer 1 Report

This work is laboriously designed and of good quality.

Author Response

Dear reviewer:

Thank you very much for your recognition and encouragement of the work of this paper, as well as your valuable suggestions.  Please feel free to contact me if you have any questions.

Li Lingwei

[email protected]

Reviewer 2 Report

Review: applsci-1595295

Title: Fault-tolerant Control Scheme for the Sensor Fault in the Acceleration Process of Variable Cycle Engine  

The paper deals with a fault-tolerant control approach for the sensor fault in the acceleration process of the variable cycle engine. The suggested control approach is based on MIMO adaptive equilibrium manifold model and Kalman filter, in order to reconstruct engine signals in case of sensor faults.  The description of the controllers appears to be well designed and results appear to be coherent. I obviously did not redo their work. Generally, the manuscript is well-written and the language level is good. The complete controller design is highly appreciated. I generally believe the paper is an interesting approach.

However, there is one major comment I want to highlight in order for me to properly review this paper:

The engine model is poorly presented; In section 2 for the modeling part, all the dynamic models are generic, such as eq(1-5). Then suddenly eq (6) appears with a new set of variables (not defined). Then, equation (7) is presented with new undefined variables such as α₁₁ - α₂₂ without disclosing the partitioning process. 

The dynamic model of the studied system should originate from physical governing equations or can be imported from another article with citation, of course, it should be explained thoroughly in order for the reader to understand the presented problem.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

it's good with more comparisons with the others

Author Response

Dear reviewer:

Thank you very much for your recognition and encouragement of the work of this paper, as well as your valuable suggestions.  Please feel free to contact me if you have any questions.

Li Lingwei

[email protected]

Reviewer 4 Report

The paper is well written. The results are satisfactory.

Author Response

Dear reviewer:

Thank you very much for your recognition and encouragement of the work of this paper, as well as your valuable suggestions.  Please feel free to contact me if you have any questions.

Li Lingwei

[email protected]

Reviewer 5 Report

1. Interesting research in a decently drafted manuscript that needs some mild revisions. General comments follow:
   • The manuscript is clear, relevant for the field and presented in a well-structured manner.
   • References are generally quite old with merely two references being within the last 5 years with no issues of self-citation. Consider adding newer references particularly of virtual sensoring, since it is a key feature needed for FTC. The reviewer recalls seeing very recent publications in MDPI Sensors on virtual sensoring for temperature by Brunello, et al; for pressure by Shin, et al. and also for vehicle motion mechanics using Pontryagin’s treatment of Hamiltonian systems (makes a nice companion alternative to the numerical NLP approach to constrained optimization used by the authors).
   • The manuscript is scientifically sound and is the experimental design appropriate to test the hypothesis.
   • The manuscript’s results are reproducible based on the details given in the methods section, allocating the topology in section 1 to section 2.
   • The figures/tables/images/schemes are appropriate, properly show the data, they are they easy to interpret and understand, and the data is easily interpreted appropriately and consistently throughout the manuscript. Statistical analysis and figure of merit data must be improved to make the presently qualitative presentation of data in plots have more quantitative value (e.g. means, standard deviations, or other significant quantitative measures). This is done very well in lines 440-441.
   • The conclusions are consistent with the evidence and arguments presented.
   • Please evaluate the ethics statements (lacking conflict of interest) is sufficient. Data availability statements is missing.
   • The manuscript is clear, comprehensive and of relevance to the field, although the gap in knowledge should be more strongly identified with modern citations.
2. Abstract is okay but is not likely to entice the readership to continue reading the rest of the manuscript. It is a short paragraph outlining the aim of the paper, to introduce a fault-tolerant control (FTC) scheme for the sensor fault in the acceleration process of the variable cycle engine (VCE). The main contributions and strengths, namely, to propose a sensor FTC scheme in the acceleration process of VCE which uses the rotational speed for the closed-loop control, and then the control plan of the acceleration process is optimized based on the target shooting method.
   • Use of acronyms/abbreviations so early in an abstract is unlikely to attract readers not already aware of the manuscript’s content. Many scientifically inclined readers will simply become uninterested in continuing to read the manuscript beyond the abstract. Already in the abstract the reader is burdened with the expectation to quickly become fluent using new words, FTC, VCE, AEMM, and HIL. A better place to introduce such is the introduction and Materials and Methods only in the instance the authors feel it enhances reading by using acronyms.
   • Results are only presented in weak, qualitative fashion. Highest quality expression of main conclusions or interpretations is quantitative results discussed in the broadest context possible, e.g., percent performance improvement compared to a declared benchmark. “…results show that the FTC scheme can accurately diagnose the fault…” and “…ensures the reliability of the acceleration process….” are very weakly stated results compared to “…xxx percent performance improvement over conventional methods to overcome sensor faults was achieved….”, where comparison is made to any of the several methods described in the lit review. Some meaningful figures of merit are listed in the manuscript’s body, e.g. KF estimation errors (means and standard deviations of figure 6, 10, and 11 would be nice to add). Percent differences (or other meaningful quantitative figure of merit) from figure 20(a) and 25 would tell the reader a lot.
3. Introduction is modestly done with significant omissions of very recent literature but no mild abuse of multi-citation without elaboration. The lit review is quite well done in this regard.
4. Materials and Methods is solid. Equations are scientifically sound and well presented, enhancing the manuscript quality.
5. Presentation of results is mildly acceptable but can be improved. Figures are decently done with some mandatory improvements to ensure the readership has access to the content.
   • Internal font size is marginally small, but quite acceptable and likely to ensure legibility by the reader, even when archival copies are printed on poor, black and white printers. Great job.
   • Line styles and sizes are disparate in figures rendering the disparate data very distinguishable when the manuscript is read in printed hardcopy (particularly in black and white) rather than reliance on colors. Great job. Consider increasing the line thickness of dashed or dotted lines to amplify their difference from the identically sized solid-lines in figure 4.  Great inset in figure 20 and annotation of figure 22 and 27…very effective.
   • Addition of figure 23 is very effective to lend enhanced credibility, although the reader (at least this one) would like to have the photo be large enough to discern features to aid my attempt to reproduce the results in the manuscript
   • Tables are neglected. The review recommends a summary table of acronyms and variables in an appendix, but also recommend a small table of quantitative results (figures of merit) proximal to each plotted data set to enhance the qualitative presentation of the data produced.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 6 Report

In the paper should be added a Nomenclature inside which will be listed and explained all abbreviations, symbols and markings used throughout the paper text. A Nomenclature will notably improve reading experience because all abbreviations, symbols and markings will be placed in one place.

Author Response

Dear reviewer:

Thank you very much for your recognition and encouragement of the work of this paper, as well as your valuable suggestions.  Please feel free to contact me if you have any questions.

Li Lingwei

[email protected]

Round 2

Reviewer 2 Report

Review: applsci-1595295

Title: Fault-tolerant Control Scheme for the Sensor Fault in the Acceleration Process of Variable Cycle Engine.   The authors cleared the ambiguity regarding the model used and also cited a reference regarding the parameter identification technique that they have used. The article is suitable for publication in the Applied science journal.