Investigation of the Mounting Position of a Wearable Robot Arm

Round 1

Reviewer 1 Report

This paper explores the possible mounting points and some aspects of synthesis for an assistive robot arm.  Most of the assessment is based on workspace properties, and the paper also includes experiments with feedback from human subjects.  Comments on the details of the paper are as follows.

The indexes of cooperativity, scalability, and invasiveness used in [20] should be defined/described in more detail if they are to be used as a basis for evaluation.
Even though the blue areas in Figure 4 are not intended to be accurate representations of workspace, it would be better if they were closer approximations (i.e., not just elliptical shapes); in this regard, Figure 5 is more accurate.
In line 175, it seems like “maximum length” should be “preferred total length”.  Similar in line 190.
In line 202, “L2 and L3” should be “L1 and L2” to be consistent with nomenclature used up to that point in the paper; a similar issue exists in Table 2.  However, it is strange that the selected values of 30 and 250 mm are not shown in Figure 6.
Figure 6 should appear before Figure 7 and closer to the text in which it is mentioned.
The paragraph starting on line 217 seems to take the paper off course.  Figures 1 and 3 imply a robot with only rotational joints, not with a prismatic joint as shown in Figure 7.  Even the terminology (“spherical robot”) is confusing.  Typically a spherical robot is one which achieves spherical motion (3 rotational DOF of the end effector and no translational DOF).  Here the authors have used this term to describe a robot whose position workspace is a spherical shell.  Line 223: “In addition, a robot arm that uses a spherical coordinate system has the ability to perform only a limited range of tasks…” – any robot can use a spherical coordinate system; it seems that the authors are referring specifically to Figure 7a here.  Line 225: “A spherical robot arm can have one to three DoFs.” – with 1 DOF, the workspace would only be a circle, with 2 DOF a ring, and with 3 DOF a spherical shell (these are all fundamentally different).  Line 227: “If the robot arm has more than three DoFs, it becomes an articulated robot arm depending on the joint configuration. An articulated robot arm has a three-dimensional range of motion.” – Neither of these statements is quite true, and again there is an issue with terminology.  Any arm with a joint is articulated by definition.  An articulated arm has a 3-dimensional range of motion if it has at least 3 DOF without redundancy.
It is unclear how the determinations in Table 3 were evaluated.  If this table is to be retained, probably more details are needed.
Line 265: “As a result, when all lengths of the active-joint links are set to 0.317 m, the most comprehensive movement is obtained.”  Where is this shown in Figure 8?  Line 268: “With a link length of 0.073 m, it is possible to ensure the broadest range of motion while retaining a large cooperative workspace.”  Same question.
Line 292: “If the invasiveness in the middle range is high, the robot arm will interfere with the user’s hand and affect the work.” – Is this based on an assumption that more tasks occur in the middle range?
Discussion of experiments: What were the survey questions?  Was the order of mounting points randomized?  Did the subjects rest in between experiments?  Overall, more details on the experiments and their evaluation are needed.
Line 364: “In terms of operability, there is no significant difference between the robot arm with all the joints controlled by actuators and the AOA” – this is not a claim/conclusion supported by the information presented in this paper.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

General Comments:A combination of passively driven passive joints and dynamically driven active joints was considered in this paper.The paper also investigated the optimal configuration of DoFs, link length, and mounting position for the wearable robot arm. Although the overall mechanical structure of the wearable robot arm is relatively simple, it still needs some necessary theoretical analysis and experimental verification.

1.It is not precise to obtain the total workspace of the robot arm only by superposition of passive joint space and active joint space. Therefore, it is suggested to analyze the kinematics theory of the robot arm to explore its workspace.

2.It is suggested to use the interaction force between human body and installation position to evaluate the user burden, and the results should be more objective than questionnaire survey.

3.There are some format errors in the text and figures.

1)Figure 6 and figure 7 are out of order.

2)There are some spelling mistakes in some words in the paper, please check them carefully.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have presented an Assist Oriented Arm (AOA) which is a wearable robotic arm. They have already discussed the design of AOA in their previous work [1]. In this work, they investigated the mounting position, as well as, the optimal link lengths of the wearable arm. They also discuss about the weight burden of this wearable arm while the used mounted it at the chosen positions.

Minor Comments:

1) The paper is well written. There are a few writing mistakes that you can improve. For example; in line 220, there is space in the word robot "robo t", in line 374, wearable robotic arm "was" been considered.... there should be "has" instead of "was".

2) Please check notations L1, L2, L3 carefully. In section 4.1, it is mentioned "L2" and "L3" but in figure 6 it is "L1" and "L2".

3) Figure 6 comes after figure 7. You can interchange them. 

4) Explanation of selection of Articulated robot over Spherical robot on page 7 is confusing. Please re-write that.

Major Comments:

1) You have selected the optimal lengths as L1 = 50 mm, L2 = 30 mm, L3 = 250 mm. This range of lengths can not be seen in the x-axis of figure 6. Please explain that.

2) Please add mechanisms used for passive joints. Where is the switch attached? how is the mechanism works? I saw some information regarding passive joint mechanisms in your previous work [1]. But in this work, you changed the joint configuration and the link lengths. So, it is better to mention how passive joints work.

3) Figure 4 shows the effect of the passive joint link length on the range of motion. In this figure, the passive link is shown as two different links in black color. You have varied lengths of these two links in the step size of 10 mm to find the optimal lengths. But did you vary the angle between these two links or did you fix the angle between them? In figure 4, it seems these links are at some angle to each other. 

4) It would be good if you can add some real-time use of this wearable robotic arm in this paper. For example, a few daily life activities showing lifting and placing a few different objects placed at different distances from the person wearing it to show the effectiveness of the use of this arm. It can also show if there is any interference of the wearable arm with the human arm during its operation.

[1] Kojima, Akimichi, Hirotake Yamazoe, and Joo-Ho Lee. "Wearable Robot Arm with Consideration of Weight Reduction and Practicality." Journal of Robotics and Mechatronics 32, no. 1 (2020): 173-182.

Author Response

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Round 2

Reviewer 1 Report

The authors did a good job of addressing previous concerns. 

In Figure 8 the line should be removed, because these are measurements at discrete settings.  It may be more appropriate to go back to a bar graph.

The methods leading to Figure 13 have not been adequately described.  What software was used, what boundary conditions were applied, etc.?

Author Response

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Reviewer 2 Report

The article has been carefully revised.There are no comments now.

Author Response

Thank you very much for your valuable comments and suggestions.

Reviewer 3 Report

I would like to thank the authors for thoroughly addressing my comments. I am comfortable with the changes made to the manuscript. I believe that the paper is now suitable for publication.

Author Response

Thank you very much for your valuable comments and suggestions.