Kinematic Analysis and Verification of a New 5-DOF Parallel Mechanism

Round 1

Reviewer 1 Report

Dear authors,

This is a well-written paper. This paper discusses on the design of the parallel robots. However, this paper lacks the novelty even though the authors included the detailed design methods with DoF and robot movements.

I hope the authors can add scientifically novel flavors to the current devices. With the device updated, the manipulator can contribute to the MDPI society.

Regards,

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

In this paper, the authors proposed a 5-DOF parallel mechanism with 5PUS-UPU for a multi-directional 3D printer. Using Grubler-Kutzbach and screw theory, their parallel mechanism was analyzed to have 5-DOF such as 3 translation and 2 rotations. When building and testing the experimental setup of their mechanism, they improved their mechanism and analyzed its kinematics. Also, Mote Carlo method was used for analyzing and improving the workspace of the mechanism. However, there are several recommendations that would improve this paper.

1) In introduction, the advantages of using multi-directional 3D printing should be clearly demonstrated.

2) It should be explained in detail why the values of the parameters are used for the mechanism as n = 14, g = 18, summation of fi =35.

3) In line 136, more explanations for the specific situation of the degree of freedom should be provided in detail. It would be better to elaborate why screw theory was used additionally.

4) In section 2.2, there are subsections 2.2.3 and 2.2.4 describing the experimental setup and singularity problems of the proposed parallel mechanism. Since the descriptions of the prototype are repeated in section 5 and a singularity problem can be theoretically evaluated before building an experimental setup, it would be better to merge subsection 2.2.3 with section 5 Experiment and subsection 2.2.4 with subsection 2.3 Singularity.

5) In section 2.4.1, the process of determining the shape of a moving platform as a quadrilateral are needed to be elaborated in detail. This is because the slight change of the location of a spherical hinge may improve singularity problem and the shape chosen in Figure 16(a) is a isosceles trapezoid which is different from a rectangular structure.

6) In lines from 260 to 262 of section 2.4.2, it should be demonstrated in detail how the moving platform cannot move to the specific position due to the restriction of the spherical hinge angle.

7) In equation 8, the font of symbol x,y,z of Trans(x,y,z) should be italic to be identical to the same symbols in matrices.

8) Section 3.3 and the paragraph mentioning section 3.3 in conclusions may be removed because it seems that the section is not closely related to kinematic analysis or the verification of the mechanism.

9) In figures(15, 17, 18, 19, 20) of workspace analysis, the scales of x, y axes should be equal so that the shape of workspace is properly recognized. For example, the distance between the ticks of x, y axes should be the same as 20 mm in Figure 15.

10) In figures(15, 17, 18, 19) of workspace analysis, the workspaces may be approximately drawn by using the outline(outer contour) of the workspace and can be overlaid within one graph for better comparison.

11) It does not look like that the 3D model in Figure 21 and the profile in Figure 22 are needed to be demonstrated because the difference in the 3D model in Figure 21 compared to Figure 4 is the moving plate and the shape of the profile in Figure 22 is not quite relevant to verification of the mechanism. Instead of the shape of the profile, it would be better to show the dimensions of the outer frame of the protype, such as height, width, and depth.

12) It looks like that the mechanism followed a circle trajectory twice as indicated as R and r. It would be better that the R and r cases are compared and explained in section 5.

13) English in this paper should be improved.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

In this work, a kinematic analysis was conducted for a new 5-DOF parallel mechanism and experimental verification was also carried out. Although the results of kinematic analysis are well presented, the presentation of experimental results is somewhat  insufficient. Followings are comments for this paper.

1. Equation (1) is not a complete equation. It would be better to express it as a complete expression with an equal sign, or insert it into the text.

2. Only one experimental result using the fabricated system is presented in Figure 23. More experimental results should be presented. It would be good if the results for the 3D workspace obtained through the experiment could be added and compared with Figure 20.

3. 

Author Response

We would like to thank you very much for the valuable comments from the reviewers. The comments have been very helpful in improving our manuscript. We have attempted to address all the comments and suggestions in the revision, polish the language, as well as improve several pictures quality. 

Point 1: Equation (1) is not a complete equation. It would be better to express it as a complete expression with an equal sign, or insert it into the text. 

Response 1: Thank you for pointing out our errors.

We have been inserted Equation (1) into the text. (line121)

Point 2: Only one experimental result using the fabricated system is presented in Figure 23. More experimental results should be presented. It would be good if the results for the 3D workspace obtained through the experiment could be added and compared with Figure 20. 

Response 2: The purpose of using the experimental results in Fig. 23 is to verify that the mechanism can realize multidirectional motion. We also try to obtain its 3D workspace through experiments, but it seems to be a little difficult.

Round 2

Reviewer 2 Report

For improving this paper, all the comments from Point 1 to Point 13 has been addressed by the authors.