An Integrated Cyber-Physical Digital Twin Architecture with Quantitative Feedback Theory Robust Control for NIS2-Aligned Industrial Robotics
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe topic of the manuscript is interesting and fits the scope of the Journal. Digital twins and robotics are essential components in Industry 4.0 ecosystems and need relevant research developments. After a careful revision, the following comments are provided for the enhancement of the manuscript.
The type of contribution, Article in this case, should be indicated in the initial statement of the template, removing those types that do not correspond: “Type of the Paper (Article, Review, Communication, etc.)”.
A keyword to include, if the authors agree, is “Communication”, or “Communication protocols” or a similar term, due to the relevance of communications in the developed work.
Certain abbreviations are directly used without the initial decomposition. Some examples are PLC, PID, OPC UA.
Most of figure captions lack the terminal period (punctuation).
The contextualization of the work is well scheduled, nonetheless, given the central role of the PLC, it is suggested to include some recent scientific publication that also deal with digital twins involving PLC, which, in addition, could achieve a wider audience. Some examples, if the authors agree with the suggestion are now provided:
Development and Validation of Digital Twin Behavioural Model for Virtual Commissioning of Cyber-Physical System. Applied Sciences 2025, https://doi.org/10.3390/app15052859
Development and real-world implementation of a Digital Twin-enhanced supervisory system for RES-green hydrogen microgrid. Energy Conversion and Management 2026, https://doi.org/10.1016/j.enconman.2025.120822
Figure 2 is very attractive and illustrative. In a similar sense, Table 3 is also very adequate.
The functional roles are well described in the subsection 3.5. In this regard, using the PLC as master controller and gateway seems adequate given its robust behavior. However, this reviewer has not found the reasons for this choice in the text. Some comment would be desirable.
OPC UA is considered the standard for communication in Industry 4.0, so it could be explicitly mentioned in the manuscript as a reason to choose this protocol, apart from its security features.
The authors comment that use Modbus TCP with TLS, this version is commonly referred to as Secure Modbus. Another aspect concerning this protocol is that Modbus TCP is not a deterministic fieldbus, which should be indicated in the paper, for instance, in Table 1. Even more, given the deterministic feature of the developed approach, as commented in subsections 4.7 and 6.5, this aspect could be mentioned and highlighted as an additional advantage of the proposal.
The timestamp log of the PLC has been probably extracted from the software TIA Portal (or through the DataLog instructions), hence, a brief comment about this aspect could be inserted before Listing 1. A similar issue occurs with the scan cycle time of 42 ms commented in subsection 6.4.
Providing experimental results is a positive feature of the manuscript.
After the references, there are two references of the template that should be removed.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript proposes a Cyber-Physical Digital Twin with QFT & NIS2 Security (CPDTQN) architecture based on QFT and NIS2 compliance, focusing on high-precision trajectory tracking of industrial robots under complex operating conditions. The research topic boasts both industrial practicality and academic innovation, with a relatively systematic experimental design. However, to further optimize the manuscript, the following suggestions are proposed:
1. The manuscript fails to evaluate the computational burden of the proposed architecture, particularly that of the QFT controller, digital twin synchronization, and security protocols. Given that the system is PLC-based and emphasizes real-time performance, it is recommended to supplement the analysis of computational complexity and real-time performance.
2. What are the key steps in the design of the QFT controller and prefilter? Please provide a detailed explanation.
3. Is the simplifying assumption in robot dynamics modeling reasonable? Could the unmodeled nonlinear factors exceed the uncertainty bounds covered by the QFT templates?
4. What is the physical meaning of the intermediate variable \(R_w\) in the inverse kinematics solution (Eqs. (13)-(15))?
5. How were the worst-case dynamics mentioned in the manuscript derived?
6. The current design of disturbance test scenarios is relatively simplistic, as only single-axis disturbance is considered. Could multi-scenario disturbance tests be incorporated, such as multi-axis disturbance and sudden load change scenarios?
7. Several figures in the manuscript have resolution or annotation issues. Please review and enhance their clarity and readability.
8. The titles and captions of figures and tables should be more detailed to ensure that readers can comprehend the content of the figures and tables without relying on the main text.
9. There are some typos and grammatical errors in the manuscript. Please carefully proofread the entire manuscript and correct these mistakes.
10. Some references have formatting inconsistencies. It is recommended to check and unify the reference formatting in accordance with the journal’s specific requirements.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors- Does the introduction provide sufficient background and include all relevant references?
- For clarity, research questions must be listed with focusing more on the academic novelty instead of solely the practical contributions.
- Is the research design appropriate?
- Authors need to add a comprehensive research design so that authors can show the state of the art of this study.
Are the methods adequately described?
- To comprehensively evaluate system performance, it is necessary to formulate relevant test missions, execute them, and analyze their results in the experimental section. Therefore, it is necessary to clarify whether the authors used pre-defined test missions as the basis for evaluating system performance.
- Are the results clearly presented?
- This manuscript does not adequately explain the fundamental references underlying the experimental design. Authors are required to provide clear justification for these references to demonstrate that the experiment was conducted correctly and that the Key Performance Indicators (KPIs) used are appropriate and valid.
- Are the conclusions supported by the results?
- Yes, conclusion supported by the results.
- Are all figures and tables clear and well-presented?
- Lines 208-211: Figure 2 shows that this study shares several similarities with existing state-of-the-art studies. However, the manuscript does not clearly describe the specific parts or aspects of this literature (e.g., concepts, methods, or analytical frameworks) adopted or adapted in this study. To improve clarity and strengthen the scientific contribution, authors should explicitly outline the elements of previous studies used and explain how this study extends or differentiates itself from previous research.
- Quality of English Language
- When writing the title, it is best to write the full form of QFT, then write the abbreviation.
- The abstract should be written without many abbreviations for ease of reading.
- line 1180: What is meant by the numbers in the brackets (e.g., "...based on a B-spline trajectory in the task space (19), inverse kinematics (2)...")?
- When writing the title, it is best to write the full form of QFT, then write the abbreviation.
- The abstract should be written without many abbreviations for ease of reading.
- line 1180: What is meant by the numbers in the brackets (e.g., "...based on a B-spline trajectory in the task space (19), inverse kinematics (2)...")?
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsI have no other suggestions.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have fixed all the revisions I requested, so it is ready to be published.
Comments on the Quality of English Language- When writing the title, it is best to write the full form of QFT, then write the abbreviation.
- The abstract should be written without many abbreviations for ease of reading.
- line 1180: What is meant by the numbers in the brackets (e.g., "...based on a B-spline trajectory in the task space (19), inverse kinematics (2)...")?
