Design of Manual Handling Carts: A Novel Approach Combining Corrective Forces and Modelling to Prevent Injuries

Round 1

Reviewer 1 Report (New Reviewer)

Comments and Suggestions for Authors

This study introduces a novel method to adjust pushing force measurements for resilient floor coverings incorporating corrective force models based on floor hardness and wheel characteristics. The approach is validated by testing 44-wheel designs across various floor types. The language is clear and easy to understand with no obvious language issues. 

The main drawback of this study is that it is conducted based on the fact that design standards for manual handling equipment often overestimate maximal loads by relying on tests conducted on smooth steel plates, rather than realistic floor coverings. This means that the reason for this study is not well justified. The paper is not supported by medical reports, worker injury data, legal claims, or a detailed review of the literature and the development process of existing standards to demonstrate that the forces defined in the existing standards are excessive and inadequate. . Therefore the introduction should be widely rewritten covering the literature to justify the research study.  

Another significant drawback of this paper is the lack of comparison between existing standards (at least in the authors’ own country) and their proposed method in %, which takes floor stiffness and wheel types into account. Providing such a comparison would give readers a better sense of how much operators are, in a way, overburdened, making the study easier to understand even for non-expert readers. Additionally, this calls for an assessment of the likelihood of injuries arising from these factors.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

Review of the Manuscript: Design of manual handling carts: a novel approach combining corrective forces and modelling to prevent injuries

 

1. Summary of the Paper

The paper presents a novel approach to modeling the pushing forces required to move manually handled carts on various floor coverings. The authors developed a corrective force model and to account for real-world conditions that differ from traditional testing methods, such as those on smooth steel plates. The methodology combines corrective forces with a basic Newtonian mechanics model to provide practical predictions for industrial applications. This work has significant implications for reducing workplace injuries associated with musculoskeletal disorders.

I appreciate the study novelty and rigor. However, there is need to address some weaknesses to improve the paper generalizability, practical relevance, and applicability.

 

2. Strengths

·      The study addresses a practical issue with real-world implications (modifying design standards to account for real usage conditions), and therefore has applications in improving occupational safety.

·      The experimental design includes robust data collection across a big variety of wheel types and multiple floor coverings, leveraging a custom-built test bench.

·      The model was validated experimentally, achieving an average deviation of only 5.1%, which demonstrates strong accuracy.

·      The use of corrective force abaci simplifies the application of the findings, making them accessible for practitioners in ergonomics and equipment design.

 

3. Weaknesses and Flaws

·      The study tested only four types of floor coverings, which limits generalizability. Many other floor materials used in industrial settings were not included.

·      The Newtonian mechanics model, while practical, does not account for dynamic factors such as variable load distributions or surface inclinations, which could affect accuracy in real-world scenarios.

·      There is limited exploration of how variations in input parameters (e.g., wheel diameter, load distribution) influence the model’s predictions.

·      The presentation of results is overly technical, with insufficient discussion of their practical implications for non-specialists in ergonomics.

·      While potential extensions to additional floor coverings and swivel motion are mentioned, these ideas are not developed in detail, leaving the reader unclear on the next steps.

 

4. Recommendations for Improvement

While the paper is well-written, a few suggestions could help with improving the study and its presentation:

 

1.    If possible, include additional floor type(s) to improve the generalizability of the findings. I suggest conducting additional experiments or simulations to validate the applicability of the proposed model across a wider range of floor coverings. If not available due to lack of resources, it should be explained as a limitation of the study.

 

2.    Extend the model to consider variations in load distribution, acceleration, and cart motion. I recommend either modifying the model to account for these complexities or explicitly acknowledging its limitations and discussing the conditions under which the model is most valid. If not available due to lack of resources, it should be explained as a limitation of the study.

 

3.    Conduct validation trials with a more diverse set of operators to account for ergonomic variability. If not available due to lack of resources, it should be explained as a limitation of the study.

 

4.     For sensitivity analyses, explain clearly for the audience to understand how variations in key input parameters (for example the wheel diameter, tread type, load distribution, etc.,) affect the model’s predictions. I think including a detailed discussion or additional experiments to demonstrate the robustness of the model under varying conditions can significantly help.

 

5.    The study assumes uniform pushing techniques and does not account for inter-operator variability in strength, posture, or technique. I suggest incorporating a section on the ergonomic implications and how operator-specific factors might influence the findings.

 

6.   Provide more actionable recommendations for equipment designers and facility managers, including threshold values and guidelines. This could be also done through a comparative study with available guidelines and other research.

 

7.   Simplify figures and include practical examples to make the findings accessible to a wider audience.

 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

Comments on the submitted paper entitled Design of manual handling carts: A novel approach combining corrective forces and modelling to prevent injuries.

This submission describes laboratory testing to obtain data on forces required to push wheeled carts on a steel plate—the standard method—as input data for estimating forces required in workplace. The laboratory testing was conducted on an apparatus for testing a single wheel on a simulated moving cart equipped with instrumentation for obtaining data on force, acceleration, and other parameters. My comments are numbered.

1. My fist comment is the paper is an excellent fit for the MDPI journal Safety.

2. The Abstract is informative while being concise. I have a concern about the third line of the Abstract where it says tests on a flat steel plate “overestimate maximum loads”. My understanding is this refers to psychophysical tests using loads the subjects consider acceptable. Therefore, it would be clearer to say “maximum loads acceptable to the test subjects”.

3. The first sentence in the Introduction says across occupational setting, 50% of tasks involving manual handling equipment consist of pushing and pulling on wheel mounted equipment. I  have not visited References 1 and 2 to check on where those authors reached that claim, however, based on the article titles, one citation was about manual handling on ramps and the other on a transportation company. I am skeptical about either source justifying “across occupational settings”. I recommend providing more on the basis of that claim.

4. Presentation is facilitated by using the standard IMRD sections. Results are presented by extensive graphs along with equations. I like the use of appendices for placing extensive technical material. I am not qualified to critique the content of the appendices.

5. My recommendation is the paper is acceptable with the minor modifications numbered 2 and 3 above.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report (New Reviewer)

Comments and Suggestions for Authors

Dear authors,

thank you for your cooperation and for following some of the instructions given. I believe that the paper quality is improved at least a little.  

Kind regards

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

Thanks for addressing the comments. 

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

The author has adequately addressed my prior concerns. I have no more concerns.

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.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper offer readers to understand the resistive forces and corrective force for manual handling of carts based on experimental results. But I have some suggestions below for authors to consider.

1) Figure 2, Figure 3, Figure 4, Figure 5 and Figure 8 did not clear to read for low quality illuatration, please to redraw.

2) The exprssions for hardness values A/15 in this paper were not consistant, pleased to ammend. (see Table 2; p7, L207-209; p11, L329; p13, L395-411)

3) It should be explained whether the pushing force model established in this study is applicable to the situation of carrying fluid materials on an inclined surface.

4) All the equations in this paper (include Appendix B) should be checked or corrected to meet the format. Delete the comma in equation 1 (p2, L80).

5) The glossary in the Table 4 did not matched Scheme 1 (eg. inertia force for an acceleration and ground reaction force), and without definition of h_G and L_D.

6) Correct the "air pressure" to "tire air pressure". (p1, L35)

7) Correct the table description in the content to "Table #". (p4, L137; p8, L238)

8) Delete the wording of "and so too can" in p13, L379.

9) The cited references no.23, 26 are different from the format. And the cited references no.13 is incorrect, pleased to check.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This paper presents a method for estimating the pushing force of a cart in a longitudinal motion on various floor coverings, which combines corrective forces with a pushing force model to help reduce the incidence of musculoskeletal disorders. A mean deviation between experimental results and model predictions of 5.1% is obtained for pushing forces, which account for the real conditions in which manual handling equipment is used and help in reducing the incidence of musculoskeletal disorders. The following issues need to be addressed.

1. The article does not provide enough detail on the current state of research on traditional testing methods, and it is suggested that this should be supplemented in the introduction section, which will lead to the innovations of the new testing methods.

2. The introduction of the thrust model in section 2.2 of the article is not detailed enough, and the definition and application of the model are not described in detail, so it is recommended that the authors add the relevant content. For example, a. adaptive human-robot interaction torque estimation with high accuracy and strong tracking ability for a lower limb rehabilitation robot. b. finite-time observer based variable impedance control of cable-driven continuum manipulators. c. structural design and stiffness matching control of bionic variable stiffness joint for human–robot collaboration.

3. The experimental content of the article lacks comparative experiments and application experiments of the proposed model. It is suggested that the authors design relevant experiments to supplement the description.

4. The hierarchy of the article is not clear, for example, section 2.2 and section 3.4 have the same title but different introductions. There is a mishmash of content and the authors are advised to make changes.

5. Equation B.23, Equation B.51, and Equation B.52 in the article are not aligned, and the authors are advised to make changes.

6. The alignment format of Picture 1 and Picture 8 of the article is incorrect, and the clarity of the pictures in the article is not high, so the author is advised to confirm and revise them.

Comments on the Quality of English Language

 Moderate editing of English language required.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Very interesting work written in a good English. Nice and truly specialistic images. References are adequate. 

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Please correct ref.13. (IDC-11 change to ICD-11). No further comment.

Reviewer 2 Report

Comments and Suggestions for Authors

The English of response is hard to read. The author did not answer the comments, and it seems that this paper lack contribution and novelty. It needs to be revised thoroughly.

Comments on the Quality of English Language

Extensive editing of English language required.

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

It seems that this paper lack contribution and novelty.

Comments on the Quality of English Language

Extensive editing of English language required.