Design of a High Torque Density Robot Joint and Analysis of Force Control Method Applied for a Light Exoskeleton

Round 1

Reviewer 1 Report

Dear Autors,

The manuscript is written clearly and understandably. The main reason for using a common motor and reducer is spatial optimization to maximize the output torque.

This manuscript is well edited and provides a lot of relevant information about the OR-SPM FSCW engine. The authors designed this motor with 2.4 N torque control and high overload capacity. Designed with a 10-speed planetary gear, it further enhances the torque. It was then designed and analyzed using an interface and an impedance force control algorithm. At the end of the tests, there are experimental validations.

The missing element of this manuscript is the scant amount of scientific considerations included. This is especially true for the designed motor, its connector and the control algorithm. A few formulas are not enough to assume that the manuscript brings new ideas to the world of science in this field. The prototype developed under the grant is, of course, a very well-executed engineering project, but it does not bring much benefit to scientists.

Therefore, in addition to the engineering project, the scientific quality should be improved by introducing innovative design solutions for the motor and connector as well as simulation solutions for the control algorithm.  

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors present an article that apparently tries to explain a new high torque density robot joint, as well as an analysis of force control method for it. 

However, my first comment is that the title is not completely appropriate, unless you include some experiments on a robotic joint.
The presented work is, in fact, a set of a different motor and a common type of motor gear, however throughout the article, this system is never applied to a robot, nor is there any indication that this will ever happen, even if it were via assembly in 3D simulation.
Thus, my first recommendation is to change the title of the article, to become more suitable and not mislead the readers.

Across the introduction, several literature references are presented, which focus on robotic joints and their control. However, considering that one of the major contributions of this article is the motor, there should be more bibliographic references that include this theme. 

In the next section - motor design - all mechanical and electrical aspects of the motor are presented. However, although there is a figure that shows the 3D explosion of both the rotor and the stator, there is no physical image of these parts that shows the similarities between the designed and the obtained.

This problem no longer arises in section 3 - reducer design - for example, where the gearbox is presented with actual photographs. However, I think that section 3 should be englobed in section 2, since its scientific contribution is not relevant. 

Section 4 presents the theoretical foundations for force control, and the block diagrams associated with it. In addition, representative graphs of the results obtained are presented. Again, given the limited scientific contribution of this section, I would include everything in section 2, which I would call Prototype Design.

Throughout section 5 the reader can understand that the real scientific contribution of this work is indeed an innovation in motor construction, considering all the attention that is given to this component. 
Both the gearbox and the controller are simply tools to demonstrate that this motor has scientific contributions. Thus, this part can be more explored.

I also think that Figure 21 should be changed, since every electrical engineering student knows what an oscilloscope and a DC source are, and everyone knows what a PC is. I think it is more relevant to describe the peripheral equipment that is used for control (namely microprocessor, programming language, ...), among others. There should also be a block diagram showing the connections between the components of this setup. 

The conclusion section is poor, considering the conclusions that can be drawn from this work, namely improvement over the state of the art. There are results that should be analyzed and presented in this section. 

Considering all of the above, the article should undergo quite a few changes in order to be published, starting right away by changing the title to ensure that it does not mislead any reader interested in robotics.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors

The changes introduced significantly increased the scientific value of the manuscript.

In the future, please consider the scientific dimension of publications related to engineering applications.

Author Response

We would like to thank the reviewer for the very kind suggestions, and will consider to present the scientific research work on the user experience and applications of the exoskeleton in the future, when the battery package that powering the exoskeleton is fully optimized.

In addition, the links of two videos showing the exoskeleton in use are added to Supplementary Materials. It should be emphasized that the exoskeleton shown in these videos is a previous version, since the exoskeleton system shown in this paper is not fully accomplished. The exoskeleton system will be presented in the future as a new product, when the battery package that powering the exoskeleton is fully optimized. Nevertheless, these two videos demonstrate the functions and applications of the designed exoskeleton. We also explained this situation in the revised paper, near the links of the videos.

Reviewer 2 Report

I want to thank the authors for following all the recommendations. I think that now the article is a lot better and will be excellent for the scientific community. As a final remark, if you have a video of the experiment shown on Figure 27, please upload it and put the link on the paper. 
Congratulations on the excellent work!

Author Response

First of all, we would like to thank the reviewer for the very kind comments and suggestions.

 

In the revised paper, the links of two videos showing the exoskeleton in use are given, as in the Supplementary Materials. It should be emphasized that the exoskeleton shown in the videos is a previous version, since the exoskeleton system shown in this paper is not fully accomplished. The exoskeleton system will be presented in the future as a new product, when the battery package that powering the exoskeleton is fully optimized. Nevertheless, these two videos demonstrate the functions and applications of the designed exoskeleton. We also explained this situation in the revised paper, near the links of the videos.