Joint Stiffness Identification Based on Robot Configuration Optimization Away from Singularities
Ganesan Kanagaraj
Round 1
Reviewer 1 Report
Thank you for sharing valuable findings and taking action to improve your original article.
The topic is original and relevant in the field. It proposes a new identification method for a robot joint stiffness.
It is convenient to apply in the field since it couples translational and rotational displacements.
Thus, it is somewhat interesting but not a game changer since the traditional ways are not difficult to apply and accurate.
One last comment is that an uncertainty analysis would help the readers to understand the accuracy of the model.
Author Response
Dear Reviewer 1,
Thank you very much for your letter and the comments about our paper submitted to Applied Sciences-Basel (Manuscript ID: applsci-2319771 entitled ‘Joint stiffness identification based on robot configuration optimization away from singularities’).
We have checked the manuscript and revised it according to the comments. We submit here the revised manuscript.
If you have any questions about this paper, please don’t hesitate to let me know.
Sincerely yours,
Xiaoqin Zhou, Prof. in mechanical engineering
School of Mechanical and Aerospace Engineering, Jilin University, P. R. China
Response to Reviewer 1:
Thanks for your comments on our paper. We have revised our paper according to your
comments:
- Thus, it is somewhat interesting but not a game changer since the traditional ways are not difficult to apply and accurate.
Answer: According to the suggestion, we would like to answer your questions as follows.
Compared with the traditional robot joint stiffness identification method, the method proposed in this paper does not require an expensive laser tracker. Therefore, a low-cost robot joint stiffness identification method is proposed to simplify the experiment and reduce the number of tests. This means that the method can be convenient to apply.
In this paper, a new index is proposed to evaluate the robot's posture away from the singularities which can increase the accuracy of robot joint stiffness identification.
- One last comment is that an uncertainty analysis would help the readers to understand the accuracy of the model.
Answer: As shown in Fig. (10), the convergence of joint stiffness values becomes better as the number of tests increases and the results are more reliable. When the number of tests is higher than 5, the joint stiffness identification method is considered to be robust.
The validation experiment is realized by a random set of 5 poses in the Cartesian workspace. The errors are less than 10%, which proves that the calculated displacement values are close to the measured displacement values. Therefore, the joint stiffness identification method is feasible.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This is a well-designed and structured paper focusing on the robot stiffness identification aspect. The overall quality of the paper is excellent except for some English language and format issues, for which I list a few in the following for the reference of the authors:
Line 20-21: please rephrase the sentence as 'have advantages of dexterity, low price...'
Line 23: '1,2' is not an appropriate citation format...please change through the paper.
Line 25: I thought industrial robots have relatively good repetition accuracy compared to their poor absolute position accuracy?
Line 27-29: Are all these mentioned topics to do with the target problem (joint stiffness) to be solved in this paper? Please make it more clear in the text.
Line 31: please put citations after 'scholars'
Line 32: please put the definite article 'the' before a noun such as 'machining robot' and 'spindle' - this language error exists throughout the paper - please check.
Line 60-62: these sentences could be merged to make the text neater
Line 64: delete 'of'
Line 65: delete 'on'
Line 149: 'wildly' -> 'widely'
Line 154: please rephrase the sentence as 'means the robot is closer to...'
Line 161: inset ''is solved' before 'using'
Line 172: the sentence format is different from the context
Line 183: put 'is' after 'change'
Line 184: put 'is' after 'influence'
Line 190-191: rephrase the sentence as '...a larger absolute value indicates a greater degree of influence'
Line 208: it's strange for the read to see a sudden '3D scanner' here as there's no mention of this in the above context.
Author Response
Dear Reviewer 2,
Thank you very much for your letter and the comments about our paper submitted to Applied Sciences-Basel (Manuscript ID: applsci-2319771 entitled ‘Joint stiffness identification based on robot configuration optimization away from singularities’).
We have checked the manuscript and revised it according to the comments. We submit here the revised manuscript.
If you have any questions about this paper, please don’t hesitate to let me know.
Sincerely yours,
Xiaoqin Zhou, Prof. in mechanical engineering
School of Mechanical and Aerospace Engineering, Jilin University, P. R. China
Response to Reviewer 2:
Thanks for your comments on our paper. We have revised our paper according to your
comments:
- Line 20-21: please rephrase the sentence as 'have advantages of dexterity, low price...'
Answer: According to the suggestion, we have rewritten this part as follows.
'Industrial robots have advantages of dexterity, low price, and large operating range in milling, drilling, and grinding compared with traditional machine tools'.
- Line 23: '1,2' is not an appropriate citation format...please change through the paper.
Answer: According to the suggestion, we have rewritten this part as follows.
'In the fields of automotive parts manufacturing, shipbuilding, and aerospace industry 1-2'.
- Line 25: I thought industrial robots have relatively good repetition accuracy compared to their poor absolute position accuracy?
Answer: According to the suggestion, we have rewritten this part as follows.
'…industrial robots have disadvantages such as poor absolute position accuracy'.
- Line 27-29: Are all these mentioned topics to do with the target problem (joint stiffness) to be solved in this paper? Please make it more clear in the text.
Answer: According to the suggestion, we have rewritten this part as follows.
'…industrial robots have disadvantages such as poor absolute position accuracy, poor stiffness performance, and poor compliance due to the open-chain and serial structure'.
- Line 31: please put citations after 'scholars'.
Line 32: please put the definite article 'the' before a noun such as 'machining robot' and 'spindle' - this language error exists throughout the paper - please check.
Answer: According to the suggestion, we have added references and re-written this part as follows.
' (i) optimize the compliance of the spindle holder in the machining robot by controlling the position and orientation of the spindle at end-effector 18, (ii) increase the systematical stiffness of the machining robot by using serial-parallel hybrid structures 19, and (iii) optimize the robot machining stiffness by determining robot performance indices based on stiffness model 13'.
- Liao ZY, Li JR, Xie HL, et al. Region-based toolpath generation for robotic milling of freeform surfaces with stiffness optimization. Robotics and Computer-Integrated Manufacturing 2020; 64. DOI: 10.1016/j.rcim.2020.101953.
- Denkena B and Lepper T. Enabling an Industrial Robot for Metal Cutting Operations. 15th Machining Innovations Conference for Aerospace Industry (MIC) 2015; 35: 79-84. DOI: 10.1016/j.procir.2015.08.100.
- Line 60-62: these sentences could be merged to make the text neater.
Answer: According to the suggestion, we have rewritten this part as follows.
'Therefore, it is necessary to propose a low-cost method to simplify the experiment and reduce the number of tests'.
- Line 64: delete 'of'. Line 65: delete 'on'. Line 149: 'wildly' -> 'widely'.
Answer: According to the suggestion, we have deleted 'of' in line 64 and deleted 'on' in line 65. We have changed 'wildly' to 'widely' in line 149.
- Line 154: please rephrase the sentence as 'means the robot is closer to...'.
Answer: According to the suggestion, we have rewritten this part as follows.
'…means the robot is closer to the singularities'.
- Line 161: inset 'is solved' before 'using'.
Answer: According to the suggestion, we have added 'is solved' before 'using'.
- Line 172: the sentence format is different from the context.
Answer: According to the suggestion, we have modified the sentence format.
- Line 183: put 'is' after 'change'. Line 184: put 'is' after 'influence'.
Answer: According to the suggestion, we have added 'is' after 'change' in line 183 and added 'is' after 'influence'.
- Line 190-191: rephrase the sentence as '...a larger absolute value indicates a greater degree of influence'.
Answer: According to the suggestion, we have rewritten the sentence as '...a larger absolute value indicates a greater degree of influence'.
- Line 208: it's strange for the read to see a sudden '3D scanner' here as there's no mention of this in the above context.
Answer: According to the suggestion, we have deleted 'the 3D scanner'.
Author Response File: Author Response.docx
Reviewer 3 Report
Equation numbering is repeated.
Table 3. Measuring area unit is to be corrected
Page 2 line no 64 . In section 3, a new index is presented to evaluate the distance of from ... grammer to be corrected
scope for future research direction to be elaborated
Author Response
Dear Reviewer 3,
Thank you very much for your letter and the comments about our paper submitted to Applied Sciences-Basel (Manuscript ID: applsci-2319771 entitled ‘Joint stiffness identification based on robot configuration optimization away from singularities’).
We have checked the manuscript and revised it according to the comments. We submit here the revised manuscript.
If you have any questions about this paper, please don’t hesitate to let me know.
Sincerely yours,
Xiaoqin Zhou, Prof. in mechanical engineering
School of Mechanical and Aerospace Engineering, Jilin University, P. R. China
Response to Reviewer 3:
Thanks for your comments on our paper. We have revised our paper according to your
comments:
- Equation numbering is repeated.
Answer: According to the suggestion, we have removed the repeated equation numbering.
- Table 3. Measuring area unit is to be corrected.
Answer: According to the suggestion, we have rewritten this part as follows.
Measuring area(mm2) 50×38-450×342
- Page 2 line no 64 . In section 3, a new index is presented to evaluate the distance of from ... grammar to be corrected.
Answer: According to the suggestion, we have rewritten this part as follows.
In Section 3, a new index is presented to evaluate the distance from the singular pose, and the effect of each joint is analyzed.
- Scope for future research direction to be elaborated.
Answer: According to the suggestion, we have rewritten this part as follows.
In future work, the link stiffness will be considered to complete the joint stiffness identification method, and the complementary stiffness matrix (CoSM) will also be analyzed for its effect on the identification of the robot joint stiffness.
Author Response File: Author Response.docx
