The Design and Analysis of a Lightweight Robotic Arm Based on a Load-Adaptive Hoisting Mechanism
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The paper presents a new design of a manipulator with an integrated gripper mechanism. The development is valuable, the paper is written very well, but I believe that the authors can improve some parts. Specifically:
· Please, provide further information about the mechanism's main parts and working principle in Section 2. This section may be too vague for readers who are not familiar with the authors earlier works.
· The kinematic diagram in Figure 3 has to be redone with greater care to make sure all the parts and connections are clearly defined.
· Increase clarity in Figure 7 (right portion) by accurately defining the arrow's end for angle ϕ4. Readers may become confused by the existing drawing.
· Is using atan in eq. 8 ia appropriate? Perhaps the atan2 function is more suited. Provide details about the workspace of the manipulator, singularities, and other solutions to the kinematic problem.
· One recommendation is to use "conical drum" instead of "reel" to better match its geometry and purpose. It's up to the authors.
· Explain what the reader should focus on in Figure 16. Add explanations and highlight key points. The same for Figure 17.
· Expand the discussion on model validation and compare theoretical and experimental results in more detail to highlight the study's accuracy and limitations.
I recommend major revision of the paper.
Author Response
Comments 1:[Please, provide further information about the mechanism's main parts and working principle in Section 2. This section may be too vague for readers who are not familiar with the authors earlier works.]
Response 1: Thank you for explaining the existing issues. “The load-adaptive hoisting mechanism is mainly composed of a motor, a displacement sensor, a motor base, a variable radius reel, four guide rails, four springs, a slider, a rope and a bottom cover as shown in Figure 2. The motor is fixed on the motor base, The reel is connected with the output shaft of the motor, and the sliders slide along the guide rails. The rope passes through the reel at first and then it passes through the rope winding shaft through the slider, next it passes through the hole on the bottom cover, then it is fixed to the external load. Finally, bolts are used to secure the motor base to a black board as shown in Figure 3. The springs are sleeved on the guide rails and placed between the slider and the bottom cover.”
Comments 2: [The kinematic diagram in Figure 3 has to be redone with greater care to make sure all the parts and connections are clearly defined.]
Response 2: Thanks for pointing out the problem here, the plan view of Figure 3 does tend to confuse the reader because the actual linkages are not in the same plane, the author has now revised Figure 3 to make the positional relationship of the linkages clearer to the reader.
Comments 3:[ Increase clarity in Figure 7 (right portion) by accurately defining the arrow's end for angle ϕ4. Readers may become confused by the existing drawing.]
Response 3: Thanks for pointing out the problem here, the representation of ϕ4 has been modified in Figure 7b.
Comments 4:[Is using atan in eq. 8 ia appropriate? Perhaps the atan2 function is more suited. Provide details about the workspace of the manipulator, singularities, and other solutions to the kinematic problem.]
Response 4: Thank you very much for your guidance, have changed it to atan2 in the paper. During the motion solution, the mechanical limit makes the graph formed by point C convex, so the positive sign is used after parameter Ba(Bb) in eq. 6 and 8. Because of the mechanical limit, the minimum angle of the linkage “l2” is guaranteed to be 0.524 rad, and there is no singular position of the robotic arm within such a range of motion. Currently the farthest reach of the robotic claw from the base is 0.32 m, and the maximum height is 0.15 m.
Comments 5:[One recommendation is to use "conical drum" instead of "reel" to better match its geometry and purpose. It's up to the authors.]
Response 5:Thank you very much for your recommendation, but for the sake of unity with the previous paper, I hope you understand that no changes will be made here.
Comments 6:[Explain what the reader should focus on in Figure 16. Add explanations and highlight key points. The same for Figure 17.]
Response 6: Thank you for your guidance on the problems with Figure 16. Changes have been made to the presentation of Figure 16 and to highlight the purpose of the experiment in the text. “The main purpose of Figures 16 and 17 is to highlight the fact that there is a positive relationship between the gripping force at the end and the displacement of the slider, just like Hooke's law, there are frictional losses in the transmission of tension in the wire drive, but the relationship is more linear within a certain range as fed back by the experimental data.”
Comments 7:[Expand the discussion on model validation and compare theoretical and experimental results in more detail to highlight the study's accuracy and limitations.]
Response 7: Thank you for your advice on the deficiencies in the conclusion section of the paper. The final discussion section has been considerably modified to include a discussion of the mechanism's characteristics in the context of the experimental findings, illustrating the structure's characteristics and advantages, as well as its current limitations.
“In this study, the innovative design of a robotic arm based on an improved load-adaptive hoisting mechanism offers a number of significant advantages. First, by detecting the displacement of the slider, as shown in Fig. 11 and 12, the force of the gripper can be controlled without the need to install a force sensor on the end effector, thus reducing the complexity and weight of the hand gripper. Of course, it is also possible to install angle sensors at the gripper to obtain a more accurate gripper state, as in Fig. 15. Second, the gripper's adaptability to different object shapes realizes flexible gripping, and through the gripping experiments on objects with different stiffness, as in Fig. 13 and 14, the slider's moving speeds of the objects with different stiffness are the same, and the higher the stiffness is, the faster the slider's moving speed is, and such a characteristic can effectively recognize objects with significantly different stiffness. Third, the lightweight design of the robotic arm improves its overall dynamic motion performance. In the experiments of the gripper gripping objects, as shown in Fig. 9 and 10, the articulated motors are able to follow the control commands better. Finally, in the experiments of force transfer characteristics and grasping performance, as shown in Fig. 16 and 17, the heavier the clamped object is, the larger the displacement of the slider is, and they show a linear relationship, which better illustrates the effectiveness of the whole rope - transfer force transfer process.
However, although the proposed design solution achieved good results, further exploration is still needed for the gripping task of a point-footed bipedal mobile platform, especially when the mobile platform is in motion, how to ensure that the manipulator arm can perform the proper gripping task. Future work will focus on refining the control algorithm of the manipulator and further expanding the degrees of freedom of the manipulator arm to improve the performance of the system in unstructured environments.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors
The manuscript deals with the design of a lightweight 3-DOF manipulator with a load adaptive end-effector. Some issues affect the quality of the manuscript:
-In section 2.1 the authors describe only the advancement of the hoisting mechanism in comparison to a previous one; a short paragraph describing the previous mechanism would help in understanding the improvements.
-The sentence in line 124 "that linkage a remains" refers to which linkage?
-In line 125, is it correct to state that "the angle of linkage lp3 remains unchanged during the arm’s movement"? Usually, lp3 is the link that is fixed horizontal, thus limiting the orientation of lp5; however, this sentence seems to allude to the opposite, which should be justified.
-From eq.(1), it is possible to infer that x is equal to F/2k in eq. (2); however, k is not presented in the text, reducing the understanding of the formula.
-Figure 7 should be divided in Figure 7a and 7b to avoid confusion. Moreover, C0 and C1 should be renamed to avoid confusion with eq. 7 and 8.
-The point M of the gripper should be renamed to avoid confusion with the mass matrix in eq. (10); as a consequence, Ma, Mb, Mc, and Md should be renamed accordingly.
Comments on the Quality of English Language
The are several issues with the English style and language of the manuscript, which should be solved:
-In line 132, a dot is missing (" the gripper The entire").
-In several instances, "hoisting" becomes "hositing".
-In line 203, "coriolis" is missing the capital C
-In line 229, "the rope driven gripper adopt" instead of "adopts"
Author Response
Comments 1:[In section 2.1 the authors describe only the advancement of the hoisting mechanism in comparison to a previous one; a short paragraph describing the previous mechanism would help in understanding the improvements.]
Response 1: Thank you for explaining the existing issues. “The load-adaptive hoisting mechanism is mainly composed of a motor, a displacement sensor, a motor base, a variable radius reel, four guide rails, four springs, a slider, a rope and a bottom cover as shown in Figure 2. The motor is fixed on the motor base, The reel is connected with the output shaft of the motor, and the sliders slide along the guide rails. The rope passes through the reel at first and then it passes through the rope winding shaft through the slider, next it passes through the hole on the bottom cover, then it is fixed to the external load. Finally, bolts are used to secure the motor base to a black board as shown in Figure 3. The springs are sleeved on the guide rails and placed between the slider and the bottom cover.”
Comments 2:[The sentence in line 124 "that linkage a remains" refers to which linkage?]
Response 2: Thanks for pointing out the problem, there is indeed an error here, it is not clear which linkage, have labeled the diagram with the connecting rod symbol and corrected “a’’ to ‘lg’.
Comments 3:[In line 125, is it correct to state that "the angle of linkage lp3 remains unchanged during the arm’s movement"? Usually, lp3 is the link that is fixed horizontal, thus limiting the orientation of lp5; however, this sentence seems to allude to the opposite, which should be justified.]
Response 3: Thanks for pointing out the problem here, the plan view of Figure 3 does tend to confuse the reader because the actual linkages are not in the same plane, the author has now revised Figure 3 to make the positional relationship of the linkages clearer to the reader.
Comments 4:[From eq.(1), it is possible to infer that x is equal to F/2k in eq. (2); however, k is not presented in the text, reducing the understanding of the formula.]
Response 4: Thank you for explaining the existing issues. Where k is the stiffness coefficient of the spring, and the selected spring satisfies Hooke's law. Within a certain range of motion, x=0.25F/k.
Comments 5:[Figure 7 should be divided in Figure 7a and 7b to avoid confusion. Moreover, C0 and C1 should be renamed to avoid confusion with eq. 7 and 8.]
Response 5: Thank you for explaining the existing issues. The images and formulas have been modified
Comments 6:[The point M of the gripper should be renamed to avoid confusion with the mass matrix in eq. (10); as a consequence, Ma, Mb, Mc, and Md should be renamed accordingly.]
Response 6: Thank you for pointing out the issue with eq.10. I have modified the symbols in the formula and also addressed the symbol problem in the statement.
Comments 7:[The are several issues with the English style and language of the manuscript, which should be solved: (a)、In line 132, a dot is missing (" the gripper The entire"). (b)、In several instances, "hoisting" becomes "hositing". (c)、In line 203, "coriolis" is missing the capital C. (d)、In line 229, "the rope driven gripper adopt" instead of "adopts"]
Response 7: Thank you to the reviewer for pointing out the sentence errors in the paper. They have all been corrected now.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for Authors
The authors considerably improved the presentation. I recommend accepting the paper as is.
Author Response
Thank you for your guidance！
Reviewer 2 Report
Comments and Suggestions for Authors
The authors have successfully answered my requests.
Author Response
Thank you for your guidance.
