Review Reports - Motion Planning for Vibration Reduction of a Railway Bridge Maintenance Robot with a Redundant Manipulator

Round 1

Reviewer 1 Report

This paper proposes a method to reduce vibrations of a railway bridge maintenance robot. A piecewise quintic polynomial S-curve with a smooth jerk profile is used to calculate the angular positions for a collision avoidance trajectory. Simulations have been carried out to show that the proposed method can reduce the vibrations in the end-effector of the robot. Following minor suggestions are recommended to improve the paper.
- Discuss the real implementation-related details and insights to the paper. It would be beneficial for the community.
- Provide the details of the actuators of the robot considered for the simulations which allow the replication of the experiment.
- Discuss the extendibility and the generalizability of the method to other robots
- Add more references of robots developed for maintenance applications (e.g., “A self-organizing fuzzy logic classifier for benchmarking robot-aided blasting of ship hulls”, “Design of an adhesion-aware façade cleaning robot”)

Author Response

Dear Reviewer,

We would like to express our sincerest thanks for your valuable comments on our paper Electronics-1432821 “Motion Planning for Vibration-reduction of a Railway Bridge Maintenance Robot with a Redundant Manipulator”. Below are our replies to your comments.

Point 1: Discuss the real implementation-related details and insights to the paper. It would be beneficial for the community

Response 1: Thanks for your valuable suggestion. The picture of the prototype of the CMBOT in Figure 1(b) and the performance descriptions related to the prototype of the CMBOT have been added in the revised manuscript. Please kindly refer to Figure 1 and the paragraph above Figure 1 highlighted in the revised manuscript.

Point 2: Provide the details of the actuators of the robot considered for the simulations which allow the replication of the experiment.

Response 2: Thanks for your valuable suggestion. We have added the torque bound of joint i i.e. actuator i in the fifth row of Table 3 in the revised manuscript, then the kinematic and dynamic constraints of i th actuator in the simulation such as velocity bound, acceleration bound, jerk bound and torque bound of i th actuator can ben found in Table 3. Please kindly refer to Table 3 highlighted in the revised manuscript.

Point 3: Discuss the extendibility and the generalizability of the method to other robots

Response 3: Thanks for your valuable suggestion. We have added the extendibility and the generalizability of the method to other robots in the conclusions of the revised manuscript. Please kindly refer to conclusion highlighted in the revised manuscript.

Point 4: Add more references of robots developed for maintenance applications (e.g., “A self-organizing fuzzy logic classifier for benchmarking robot-aided blasting of ship hulls”, “Design of an adhesion-aware façade cleaning robot”)

Response 4: Thanks for your valuable suggestion. We have supplemented some references about developed for maintenance applications which include “A self-organizing fuzzy logic classifier for benchmarking robot-aided blasting of ship hulls”, “Design of an adhesion-aware façade cleaning robot”, Please refer to the Introduction and Reference in the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Very interesting research in a well drafted manuscript that needs some mild revisions.
Abstract is okay but is not likely to entice the readership to continue reading the rest of the manuscript.
1. Use of acronyms/abbreviations in an abstract is unlikely to attract readers not already aware of the manuscript’s content. Please consider more general terminology to attract potentially very intelligent readerships unfamiliar with (for example) CMBOT, DOF, quintic polynomial S-curve, etc.
2. 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. In lines 28-29, “…results show that the proposed algorithm can effectively reduce…” is very weakly stated compared to “…xxx percent performance improvement over conventional methods was achieved….”. Abstract improvement should be a relatively easy for the authors, since the reviewed manuscript presented many very interesting comparisons throughout the document’s sections: without optimization versus with optimization.
Introduction is decently done with some omitted very recent literature and some mild abuse of multi-citation without elaboration.
1. Some recommended additional literature includes:
  - Akin the cited example of Huang’s proposal for climbing robot for ship inspection, in 2021 Eldred et al. proposed undersea ship inspection robots in https://doi.org/10.3390/jmse9030320. The work would enhance the comprehensive nature of the pre-existing literature review for autonomous robot relief of human-tasks in dangerous or complex environments. An example in space would be nice as well….particularly an example where the proposed solution method includes a similar optimization formulation.
  - Chang, et al. (2019)’s cited redundant manipulator’s flexibility indeed compounded complexity of controlling the end effector as claimed in lines 46-47. Formulation of the optimization problem for minimum time, jerk, or energy are logical approaches as described in lines 51-92, but an alternative solution approach was also proposed in 2019 as a constrained optimization problem for highly flexible space robots demanding zero vibration residual (as a constraint’s final conditions) and minimum control energy (as a cost function) as described in https://doi.org/10.3390/aerospace6090093.
2. Please elaborate a reason for the reader to investigate each of the sextuple cited references [2-7] in the introduction or alternatively choose the key single reference or two and discard the others as superfluous.
3. Please elaborate a reason for the reader to investigate each of the triple cited references [25-27] in the introduction or alternatively choose the key single reference or two and discard the others as superfluous.
Equations are scientifically sound and well presented, enhancing the manuscript quality.
Figures are decently done with some mandatory improvements to ensure the readership has access to the content.
a. Internal font size is (very) occasionally too small, but generally done very well. Please notice the smallest font size permissible in the manuscript template (to ensure legibility by the reader) is the figure caption which provides a conveniently proximal prototype for sizing figures. Figures that would benefit from improvement include the abscissa and ordinates of figure 8-14, and 16.

b. Line styles and sizes are identical in figures 7, 9-14, 16,17,19-24, and 26 rendering the disparate data indistinguishable when the manuscript is read in printed hardcopy (particularly in black and white) negating the value of the figures due to reliance on colors. Please consider using additional measures to distinguish sets of data, e.g., varied line thicknesses and styles (e.g. dotted, dashed, use of markers, etc.).

Tables are decently done to introduce problem formation (aiding repeatability), e.g. Denavit-Hartenberg parameters, but quantitative results are neglected completely in favor of qualitative results presented in many excellent figures. Key qualitative figures should have representations of means and standard deviations presented in tables of results, and these results will aid the improvement of the manuscript’s abstract with definite “percent performance improvement” statistics. Figure 24’s presentation of torques and figure 26’s presentation of tracking errors is highly recommended as sources of tabulated results.
Inclusion of a table defining variables and acronyms in an appendix is welcome and effective. Please add such.
Please consider eliminating first-person tense throughout the manuscript in favor of a neutral presentation of the scientific development.
Please consider adding a “future research” section to advise the reader on the immediately next steps recommended to follow the developments presented in the review manuscript.

Author Response

Dear Reviewer,

Point 1: Abstract is okay but is not likely to entice the readership to continue reading the rest of the manuscript. Use of acronyms/abbreviations in an abstract is unlikely to attract readers not already aware of the manuscript’s content. Please consider more general terminology to attract potentially very intelligent readerships unfamiliar with (for example) CMBOT, DOF, quintic polynomial S-curve, etc. 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. In lines 28-29, “…results show that the proposed algorithm can effectively reduce…” is very weakly stated compared to “…xxx percent performance improvement over conventional methods was achieved….”. Abstract improvement should be a relatively easy for the authors, since the reviewed manuscript presented many very interesting comparisons throughout the document’s sections: without optimization versus with optimization.

Response 1: Thanks for your valuable suggestion. Your recognition of our work is motivating. According to your suggestion, the abbreviations in the abstract have been replaced by the unabbreviated ones and the main results of the simulations have been described more accurately and attractive. Please kindly refer to the abstract in the revised manuscript.

Point 2: Introduction is decently done with some omitted very recent literature and some mild abuse of multi-citation without elaboration.

Response 2: Thanks for your valuable suggestion. We have added some references about human-tasks in dangerous or complex environments and constrained optimization for highly flexible space robots. In addition, the multi-citation has been simplified to one single reference. Please kindly refer to Introduction and Reference highlighted in the revised manuscript.

Point 3: Figures are decently done with some mandatory improvements to ensure the readership has access to the content. a. Internal font size is (very) occasionally too small, but generally done very well. Please notice the smallest font size permissible in the manuscript template (to ensure legibility by the reader) is the figure caption which provides a conveniently proximal prototype for sizing figures. Figures that would benefit from improvement include the abscissa and ordinates of figure 8-14, and 16. Line styles and sizes are identical in figures 7, 9-14, 16,17,19-24, and 26 rendering the disparate data indistinguishable when the manuscript is read in printed hardcopy (particularly in black and white) negating the value of the figures due to reliance on colors. Please consider using additional measures to distinguish sets of data, e.g., varied line thicknesses and styles (e.g. dotted, dashed, use of markers, etc.).

Response 3: Thanks for your valuable suggestion. Your recognition of our work is motivating. We have modified the figures carefully according to your suggestion: the figures have been zoomed to the appropriate scale, and the thicknesses and styles of the lines in the figures have been adjusted for better identification. Please kindly refer to figures highlighted in the revised manuscript.

Point 4: Tables are decently done to introduce problem formation (aiding repeatability), e.g. Denavit-Hartenberg parameters, but quantitative results are neglected completely in favor of qualitative results presented in many excellent figures. Key qualitative figures should have representations of means and standard deviations presented in tables of results, and these results will aid the improvement of the manuscript’s abstract with definite “percent performance improvement” statistics. Figure 24’s presentation of torques and figure 26’s presentation of tracking errors is highly recommended as sources of tabulated results. Inclusion of a table defining variables and acronyms in an appendix is welcome and effective. Please add such.

Response 4: Thanks for your valuable suggestion. We have added Table 4 and Table 5 to express the mean deviation and stand deviation of the tracking errors that presented in Figure 16 and Figure 26. And we also added Appendix A with Table 6 to describe the variables and acronyms at the end of paper according to your suggestion. The explanation of torques in Figure 24 also presented in the paragraph above Figure 3. Please kindly refer to Table 4 Table 5 and Table 6 highlighted in the revised manuscript.

Point 5: Please consider eliminating first-person tense throughout the manuscript in favor of a neutral presentation of the scientific development.

Response 5: Thanks for your valuable suggestion. We have eliminated first-person tense in the paper. Please kindly refer to the related position in the revised manuscript.

Point 6: Please consider adding a “future research” section to advise the reader on the immediately next steps recommended to follow the developments presented in the review manuscript.

Response 6: Thanks for your valuable suggestion. We have added the future research about prototype experiment and the wind pressure’s influence on the vibration of the manipulator which caused by the passing train. Please kindly refer to the “future research” section in the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

I believe that this article is better submitted to another MDPI magazine. Abstract does not accurately reflect the essence of the article.
1. Introduction is too long and obvious.
Figure 1 is not new information. "Figure 3." too simple algorithm, describe what is innovative here. Formulas 29 and 30 require more explanation. Figure 12,24,26. It is necessary to provide a clearer and more complete explanation.

add more Q1 level journals

Author Response

Dear Reviewer,

Point 1: Introduction is too long and obvious.

Response 1: Thanks for your valuable suggestion. We have simplified and improved the introduction according to your comment. The introduction about the biped climbing robot was shorten and the introduction about current research was optimized. Please kindly refer to the introduction highlighted in the revised manuscript.

Point 2: Figure 1 is not new information. "Figure 3." too simple algorithm, describe what is innovative here.

Response 2: Thanks for your valuable suggestion. We have added the picture of the prototype of the CMBOT in Figure 1. The innovation of the algorithm presented in Figure 3 is to solve the obstacle avoidance and vibration-reduction problems of the manipulator in the motion planning by using nonlinear optimization, and this description has been added in the paragraph above Figure 3. Please kindly refer to Figure 1 and Figure 3 highlighted in the revised manuscript.

Point 3: Formulas 29 and 30 require more explanation

Response 3: Thanks for your valuable suggestion. Explain the Formulas 29 and 30 more detailed according to your comment. Please kindly refer to Formulas 29 and 30 highlighted in the revised manuscript.

Point 4: Figure 12,24,26. It is necessary to provide a clearer and more complete explanation.

Response 4: Thanks for your valuable suggestion. We have added more complete explanation about Figure 12,24,26 through text description and adding tables. Please kindly refer to Table 4 and Table 5 highlighted in the revised manuscript.

Point 5: Add more Q1 level journals

Response 5: Thanks for your valuable suggestion. We have adjusted the reference in the manuscript, related papers of top journals in the field of robotics such as IEEE. T. Robot. and IEEE. T. Ind. Electron. have been cited in this revised manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors indicated a goal in vibration reduction. This magazine does not correspond to the subject of the given one. The article is interesting, but I think it is for another magazine or just submit it to a special issue.