Advances in Control Techniques for Rehabilitation Exoskeleton Robots: A Systematic Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

(1) The following referennce was cited twice. "Control Method of Upper Limb Rehabilitation Exoskeleton for Better Assistance: A Comprehensive Review,” J Field Robot, 2024. There are some other significant publications relevant to this topic from the same research group, such as [1] A Brain-Inspired Decision-Making method for upper limb exoskeleton based on Multi-Brain-Region structure and multiodal information fusion[J]. Measurement, 2024, online, DOI:10.1016/j.measurement.2024.115728 [2] Research on Multimodal Fusion Recognition Method of Upper Limb Motion Patterns[J]. IEEE Transactions on Instrumentation and Measurement, 2023. 72, 1-12. doi: 10.1109/TIM.2023.3289556

(2)The picture presented in this manuscript are not significant, some more meaningful pictures should be prepared and compared about the control methods.

(3)  In section “2. Current Review”, over seven pages of this article are taken to discuss existing review articles one after another, and only in form of text. It’s suggested that the section should be condensed and refined, and provide general and conclusive figure(s) or table(s) if possible.

(4) In section “5. Overview of Robot Control System”, several kinds of controllers are studied by cases that are discussed separately, but there is no in-depth compare of these cases.

Author Response

1. The following referennce was cited twice. "Control Method of Upper Limb Rehabilitation Exoskeleton for Better Assistance: A Comprehensive Review,” J Field Robot, 2024. There are some other significant publications relevant to this topic from the same research group, such as [1] A Brain-Inspired Decision-Making method for upper limb exoskeleton based on Multi-Brain-Region structure and multiodal information fusion[J]. Measurement, 2024, online, DOI:10.1016/j.measurement.2024.115728 [2] Research on Multimodal Fusion Recognition Method of Upper Limb Motion Patterns[J]. IEEE Transactions on Instrumentation and Measurement, 2023. 72, 1-12. doi: 10.1109/TIM.2023.3289556

       At this point it is very challenging to add more references.

2. The pictures presented in this manuscript are not significant, some more meaningful pictures should be prepared and compared about the control methods.

     We are not clear about meaningful figures, more explanation needs to be addressed

3. In section “2. Current Review”, over seven pages of this article are taken to discuss existing review articles one after another, and only in form of text. It’s suggested that the section should be condensed and refined, and provide general and conclusive figure(s) or table(s) if possible.

        Reviewed rewrote using 2 pages

4. In section “5. Overview of Robot Control System”, several kinds of controllers are studied by cases that are discussed separately, but there is no in-depth compare of these cases.

        All of the controllers mentioned were compared and contrasted, the whole section was rewrote

Reviewer 2 Report

Comments and Suggestions for Authors

In this review manuscript, the authors have examined the recent literature on rehabilitation exoskeleton robot control. The exhaustive literature reviewed highlights the potential for improving rehabilitation exoskeleton functionality and provides future recommendations for improving functionality. 

However, as a systematic review, it would be inappropriate for this manuscript to provide an introduction to the referenced literature and list their strengths and limitations point by point.

I don't consider it a review to introduce all 100+ references one by one, as if you were a curator at a children's museum. I think the authors should categorize the references that achieved similar goals and functions, and suggest the strengths and weaknesses, limitations and strategies for further development between each category.

Comments on the Quality of English Language

 The English could be improved to more clearly express the research.

Author Response

1. I think the authors should categorize the references that achieved similar goals and functions, and suggest the strengths and weaknesses, limitations and strategies for further development between each category.

      We revised and addressed the issue

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents a systematic review analyzing various control techniques used in rehabilitation exoskeletons.

The paper seems well structured and generally well written.

BUT it is far too long. Which is why I strongly recommend shortening it. It has far too many details which only confuses the reader, distracting from the main goal of the paper.

Please have a look at section 2, which analyses different other review articles. I don’t think it is necessary to justify in such a way the current review, since it merely can focus on different aspects of the control strategies and techniques. Probably the same applies in the case of other included articles in this paper. For example, why is it important to mention what is the future direction of the research in the referenced articles, since it represents merely an intention?

Please check the references within the manuscript, sometimes errors appear: Error! Reference source not found. (on page 38)

I would expect a summarization of such a thorough study, presenting the main findings of the literature review, what are the current trends in rehabilitation and human-machine interaction. It would be nice to summarize especially the conclusions regarding those devices and control strategies which have been clinically tested (if there are any in this paper, since most papers have mentioned clinical validation as future work), which might have strong impact on the utility and usability of the robotic rehabilitation.

Author Response

1. The paper seems well structured and generally well written BUT it is far too long. Which is why I strongly recommend shortening it. It has far too many details which only confuses the reader, distracting from the main goal of the paper.

       We rewrote and shortened the size of the article

2. Please have a look at section 2, which analyses different other review articles. I don’t think it is necessary to justify in such a way the current review, since it merely can focus on different aspects of the control strategies and techniques. Probably the same applies in the case of other included articles in this paper. For example, why is it important to mention what is the future direction of the research in the referenced articles, since it represents merely an intention?

         Section 2 was revised and rewrote

3. Please check the references within the manuscript, sometimes errors appear: Error! Reference source not found. (on page 38)

        Revised and reference problem was fixed

4. I would expect a summarization of such a thorough study, presenting the main findings of the literature review, what are the current trends in rehabilitation and human-machine interaction. It would be nice to summarize especially the conclusions regarding those devices and control strategies which have been clinically tested (if there are any in this paper, since most papers have mentioned clinical validation as future work), which might have strong impact on the utility and usability of the robotic rehabilitation.

        Revised and rewrote to address the comment

Reviewer 4 Report

Comments and Suggestions for Authors

Based on reviewing the manuscript, here are some critical comments and questions should be addressed before proceeding with the publication. The manuscript identifies gaps in prior reviews but does not clearly demonstrate how it uniquely addresses these. Including a focused comparison table or diagram highlighting these gaps could strengthen its contribution.

Questions for Clarification

- Could the authors elaborate on how their systematic review specifically fills the gaps left by prior reviews? What are the actionable insights derived?

- The manuscript mentions neural networks but lacks clarity on how specific architectures (e.g., CNNs or RNNs) outperform traditional methods. Can the authors provide more examples or data?

- Given the focus on adaptability and safety, how does the review address potential psychological factors or user acceptance in rehabilitation exoskeleton use?

- What standardized metrics were used to evaluate the effectiveness of the discussed control techniques? Can the authors provide a consolidated view of these metrics across studies?

- The manuscript proposes future research opportunities, but can the authors prioritize these recommendations based on clinical need or feasibility?

Critical Comments

- While the manuscript provides an extensive review of control techniques, it lacks a clear roadmap connecting theoretical advancements with practical clinical applications. Strengthening this link could enhance the relevance for practitioners.

- The organization of content is comprehensive but could benefit from more concise section transitions to improve readability.

- While various control strategies (e.g., adaptive, sliding mode, MPC) are discussed, the technical comparisons are uneven. Some methods, such as robust control, are explained in more detail than others, like neural network-based techniques. Balancing the depth of discussion would improve the paper.

- The reliance on simulation data and the absence of robust experimental validations on impaired participants reduce the impact of the findings. Incorporating or referencing studies with real-world validations could address this issue.

- Discussion on the challenges of implementing these techniques in standard clinical settings (e.g., cost, ease of use, and adaptability) is limited. Adding a dedicated section on clinical feasibility would make the study more applicable.

- To enhance the manuscript's relevance and provide a broader perspective, suggest incorporating insights from recent articles. Here are some recommendations that align well with the manuscript's focus on control strategies for rehabilitation exoskeletons:

Belal, M., Alsheikh, N., Aljarah, A. and Hussain, I., 2024. Deep Learning Approaches for Enhanced Lower-Limb Exoskeleton Control: A Review. IEEE Access.

Luo, M., Wu, X., Yu, N., Wang, K. and Cao, W., 2024. Biomechanics, sensing and bio-inspired control in rehabilitation and wearable robotics. Frontiers in Bioengineering and Biotechnology, 12, p.1487075.

Narayan, J., Kalita, B. and Dwivedy, S.K., 2021. Development of robot-based upper limb devices for rehabilitation purposes: a systematic review. Augmented Human Research, 6, pp.1-33.

Major Concerns

It can be found the authors have a publication on the similar topic as ” Alam, N., Hasan, S., Mashud, G.A. and Bhujel, S., 2025, January. Neural Network for Enhancing Robot-Assisted Rehabilitation: A Systematic Review. In Actuators (Vol. 14, No. 1, p. 16). MDPI.” Hence, it will be great if the authors can provide clarification on ensuring that each manuscript provides unique contributions is crucial to avoid self-plagiarism or redundant publication concerns.

Author Response

1. Could the authors elaborate on how their systematic review specifically fills the gaps left by prior reviews? What are the actionable insights derived?

        We tried our best to contribute, we revised and rewrote to highlight the novelty

2. The manuscript mentions neural networks but lacks clarity on how specific architectures (e.g., CNNs or RNNs) outperform traditional methods. Can the authors provide more examples or data?

       We revised and tried to address the above-mentioned issue

3. Given the focus on adaptability and safety, how does the review address potential psychological factors or user acceptance in rehabilitation exoskeleton use?

         The issue was addressed in the revised version

4. What standardized metrics were used to evaluate the effectiveness of the discussed control techniques? Can the authors provide a consolidated view of these metrics across studies?

         It is very difficult to use any specific metric to validate all the control techniques

5. The manuscript proposes future research opportunities, but can the authors prioritize these recommendations based on clinical need or feasibility?

         It is out of the scope of this article

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been reviesed according to the comments.

Reviewer 3 Report

Comments and Suggestions for Authors

Although the paper is still too long, the authors has shortened it considerably. From my side it is ok.