Design of a Concentrically Stacked Modular Actuator with Forced Air Cooling for Multi-DOF Robotic Systems

Round 1

Reviewer 1 Report

General remarks:

Essentially, the article makes a positive impression. It is known what the Authors wanted to achieve and what they achieved, as well as how they would like to do develop their design. There are some shortcomings, but they do not reduce the high quality of the article.

Not many current references were recalled. For example, the first paragraph of the introduction refers to sources from 2006, 2008, 1996, and only one is reasonably up to date - 2015. This part is the background for the description of the development of the project, which was implemented in a dynamically developing field, so the reviewer sees here the need to present the current state-of-the-art on the basis of even few slightly newer sources. On the other hand, it should be treated as minor shortcoming rather than a substantial weakness in a generally good article.

In several places, the figure was inserted before the reference in the text. For  example, figure 10 is in section 5.1 and its description in 5.2. It does not look good. The authors are asked to correct this and similar errors.

The technical specification of the prototype actuator is missing (maybe a table?) .

Other detailed remarks:

line 64 there is "it have ", it should be "it has"

lines 98 -112 - mathematical formulas should not be written in the text. Put them separately like formulas are placed usually.

line 164 - there is "airgap", it should be "air gap"

line 171 - there is " forced cooing", it should be " forced cooling "

Figures 6 a b c look a bit blurred. Try to put charts of a higher resolution to avoid that.

line 252 - " was applied for a thermal resistance of 0.5 Ω." - check if everything is fine there.

lines 283 - 284 - something wrong is in this sentence. Reviewer suggests to compose it similar to first phrase in the abstract: "with rotary electric motors" instead of " for a rotary electromagnetic motor". It sounds better.

Authors contribution section is missing - complete it.

Finally, the reviewer would like to wish the authors  all the best during further development of their design.

Author Response

The author would thank to the reviewer for helpful comments and suggestions on the submitted paper. Based on the reviewer’s comments that are in quotation marks in Italic, we revised the submitted manuscript (energies-379429) with the following corrections. Because the authors believe that the revised manuscript is properly updated with improvements that need to be done, we resubmit the new revision. Please see the attached files.

Author Response File: Author Response.docx

Reviewer 2 Report

In this paper, a concentrically stacked modular (CoSMo) actuator with rotary 10 electric motors is proposed to implement multi-degree-of-freedom (multi-DOF) robotic systems with high 11 power densities. The numerical results demonstrate the proposed approach.

This paper contains a lot of abbreviations, please add a nomenclature in the front of the paper.

Can you explain the equation (8) in detail? This is the core of the state equation in row 194, page 7. Please give more information about the control algorithms

In the numerical results, can you give more experiments or result analysis to demonstrate the proposed approach is better than other approaches?

Author Response

The author would thank to the reviewer for helpful comments and suggestions on the submitted paper. Based on the reviewer’s comments that are in quotation marks in Italic, we revised the submitted manuscript (energies-379429) with the following corrections. Because the authors believe that the revised manuscript is properly updated with improvements that need to be done, we resubmit the new revision. Please see the attached files.

Author Response File: Author Response.docx

Reviewer 3 Report

The paper shows designing modular actuator with forced air cooling for robotic systems. Authors say that the actuator presents a new design concept, which enables the actuator module with radiator in order to be combined in series and cooled by one fan. This system has thermal characteristics owing to heatsink sharing effect. What is more, the designing concept decreases a number of components required for cooling. Thermal characteristics were verified by authors using simulation of simplified model. They also verified that maximum continuous current can be applied to the Actuator up to about three times then the rated current in forced air cooling condition.

The introduction chapter is correct. The number of references and used references are proper and well describe the topic of the paper.

17 – “high power density” – what kind of density do you mean? Mechanical, electrical, thermal – W/m3, W/m2, volumetric, surficial?

17 – “The thermal characteristics … was … verified by …”. I think, it should be “The thermal characteristics … were … verified by …” or “The thermal characteristic … was … verified by …”.

67 – “Simulation and experiment is …”. It should be “Simulation and experiment are …”.

129-130 – there is some interline which is not necessary. Please change it like in rest of the text.

170 – “Additionally, due …”. It is not sentence. Please change the grammatical structure.

202 – the unit of heat transfer coefficient “W/m2/C” is difficult to understand and not correct because it means in fact “W∙C/m2”. Please use W/(m2∙C) . Please do not use two slashes in one unit.

Chapter 4 – Verification by simulation – I could not find any assumptions of the simulation. Please clarify what assumptions of the simulations were used by authors. Please clarify how did you verify your results. Also, I could not find any boundary conditions which were used to simulation.

237 – all sentence “(The temperature of the stator was measured through a hole on the red dashed line)” is in brackets? Is it correct? Usually, just part of the sentence is in brackets.

260-261 – see comments to lines 129-130.

284 – “It is consist of …” – please write “It consists of …”.

Author Response

The author would thank to the reviewer for helpful comments and suggestions on the submitted paper. Based on the reviewer’s comments that are in quotation marks in Italic, we revised the submitted manuscript (energies-379429) with the following corrections. Because the authors believe that the revised manuscript is properly updated with improvements that need to be done, we resubmit the new revision. Please see the attached files.

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

The paper shows designing modular actuator with forced air cooling for robotic systems. Authors say that the actuator presents a new design concept, which enables the actuator module with radiator in order to be combined in series and cooled by one fan. This system has thermal characteristics owing to heatsink sharing effect. What is more, the designing concept decreases a number of components required for cooling. Thermal characteristics were verified by authors using simulation of simplified model. They also verified that maximum continuous current can be applied to the Actuator up to about three times then the rated current in forced air cooling condition.

All my suggestions and comments are included in the paper text. I think, the paper i ready to be published in present form.