Evaluation of a Passive-Assist Exoskeleton Under Different Assistive Force Profiles in Agricultural Working Postures
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors:
This reviewer finds your paper relevant and with important information. However, to improve its quality, please consider the following comments.
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Some equations are presented without impact on the article. This means they appear to be included in the text without any purpose other than their definition. For example, $\tau_{a}. Consider leaving only equations with relevant information; if not, ensure the relationship between them is clearly defined in the text.
- Please include more information related to the experimental results. The answer to the question, "What happens if the user is taller?" is vital. It's worth including additional tests with different body complexions to answer this question. Adding them will support the paper's results and the proposed assistance device.
Please include these comments in a new version of the paper.
Regards.
Author Response
Please refer to the attached file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis paper presents a passive back assistive exoskeleton to aid in half-squatting positions during agricultural labour performed by human workers. The exoskeleton consists of two articulated segments that can rotate relative to each other, one segment is attached to the leg and the other to the breast. Assistive force is provided by a pneumatic artificial muscle. The paper compares using a circular pulley versus a cam, where the latter provides more uniform assistive force even when standing. Experiments with myoelectric potential demonstrate that the proposed exoskeleton reduces muscle activity.
The paper is interesting and well written and illustrated, although some improvements are required:
- Please revise English to correct grammar and typos (for example, sentence in line 102 requires grammar correction).
- Page 5 says contraction rate, whereas the figure and other parts use contraction ratio, which seems more correct. Please use a consistent term everywhere in the paper. Moreover, how is this ratio mathematically defined? l/lw?
- Equation (7) has an error: it says le = lc - r*Delta_phi, whereas this should be lc + r*Delta_phi according to equation (4).
- Please can you provide an explicit expression of Ve in terms of theta and other relevant parameters?
- Lines 242-244 say that Figure 6 shows the contractile force Fc, but what Figure 6 shows is assistive force Fa.
- Line 262 refers to Figure 6, but should refer to Figure 7.
- Please detail how the cam was designed, because this is an important aspect of the paper but page 8 only says that this was designed by trial and error. What logical steps were followed in this trial-and-error design? In principle, it should be relatively easy to find the polar function r = f(theta) defining the profile of the cam (where r is the distance from the center of the cam to its border, and theta is the polar angle measuring from the center of the cam) by setting a desired profile for the assistive force Fa (for example, a straight line with specified slope) and solving the function that specifies the radius of the cam.
- Moreover, Figure 7-right should show coordinates of the cam profile to provide a more accurate description of the cam. Otherwise, it looks just as an irregular line that anyone could trace arbitrarily. Please provide dimensioning of the cam in Figure 7-right.
Author Response
Please refer to the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsIn this study, authors proposed a method to change trend of the assistive force to achieve comfortable and effective assistance using a squatting-assist exoskeleton with pneumatic artificial muscles (PAM) developed by the authors and called "SAEx".
The contributions and novelty must be clearly exposed in the Introduction, in a list fashion style.
In the Section 1, the paragraph before the last repeats the idea from the first two sentences: "As mentioned above, various support exoskeletons have been proposed, but they are not yet widely used in actual work [13]. Although many soft-type exoskeleton products are on the market, they are not widely used."
The reason for using pneumatic muscle instead of other type of muscles, for rehabilitation purposes must be better and more critically analyzed. Please see the more recent works of Myoelectric Control in Rehabilitative and Assistive Soft Exoskeletons: A Comprehensive Review of Trends, Challenges, and Integration with Soft Robotic Devices.
The proposed PAM characterization is sufficient in static mode, however, its most important characterization is in dynamic, mode, i.e. how fast it adapts to human motion. Figures 12-19 are only partially informative in this aspect, as we do not see the supporting force of the exoskeleton being measured and overlapped on the normalized EMG and body flexion angle. It is important to see the force setpoint and the controlled one.
What type of force feedback controller is used for the proposed exoskeleton device?
Author Response
Please refer to the attached file.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for your answer. This reviewer's comments have been answered.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have diligently addressed all my comments from the previous review round.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe innovations list is not explicitly assumed by the authors using a list style, in the introduction: is it the PAM design, or the entire SAEx design concept, or the measurements case studies? The restructured Introduction does not clearly claim the original elements of the study, in a list-like style.
The authors reply have not been well integrated into the revised paper, maybe because the authors chose to reply to multiple comments in a single answer.
Without intelligent posture detection and force control, the proposed passive device is too limited and depends on fitting issues. Its sole advantage may be the reduced cost. However, instead of PAM, a simple spring could be used as well.
