A Direct Contour Control Method for Free-Form Surface Machining Trajectories Based on Coordinate Transformation
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The paper presents a new type of coordinate transformation based direct contour control method for free-form surface machining trajectories. Based on this idea, the proposed solution realizes a decoupled control of the contour error, respectively the feed velocity. The control strategy is validated through simulations and experimental tests, showing that the contour control method effectively improves the system performance. The subject covered is interesting and the paper is relatively well written, with relevant results and conclusions.
Comments, questions and recommendations for the manuscript improvement:
-In figures 3,5,8,9,10, a lot of notations are used, which (not all) are discussed in the body of the article. To be able to follow/understand the presented control schemes more easily, a distinct list with the meaning of these notations would be useful (it could be an appendix to the work, with all the notations explained).
- Why are P controllers (which are simple gain) used and not PI controllers? It is about contour-error P controller (fig. 5), X-axis P controller, Y-axis P controller (fig. 7,8). How is the steady state error problem solved?
- The presented control structures contain several P and PI controllers. How were they tuned (a difficult problem, especially if the same control structure contains two or more controllers)?
- In the article, is there a comparison between the experimental results and those obtained by simulation?
- The paper talks about control period -1 ms. Is it about sample time (specific to discrete systems)? But all presented control structures are in the continuous domain (see Laplace notation s). Can you explain this aspect?
- I think it would be clearer if, instead of the intermediate notations C1...4 (in the legend of fig.18), the acronyms of the compared control types would be used. Without these intermediate notations (which require reading the additional text), the interpretation of the results in the figure would be immediate. And C5 replaced by reference curve and a little highlighted between the other curves presented?
- Related to the specific control systems terminology used in the paper, I think that some corrections should be made. In some cases, the term "command" is used instead of "control”. For example, instead of "the velocity command" I think "the velocity control" is correct (at least in Fig. 4, 6). Also, in the name of figures 7,8,9: Controller or Control system (which can contain many controllers)? I think that a revision of some sentences, using specific terminology of control systems field, would be necessary.
Comments on the Quality of English Language
Minor editing of English language required.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors
The paper deals with a trajectory optimization problem. The introduction of the paper shows the motivítion of the research then discusses the similar research papers to highlight the problems from the area. The end of the introduction contains a very general statement, which should be supported by some citations and some more concrete, open problems mentioned in these sentences to support the novelty of the paper better.
The figures, like figure 3, 4, 5 should be replaced by a higher quality image to improve the readability of the paper.
Please provide some links or cite a manual for the applied servo drive system The motor model was Mitsubishi HC-UFS13 and the servo driver was
Mitsubishi MR-J2S-10A.
The applied “Simulink Desktop Real-Time” library shuold be also cited to the document.
In the Conclusions part the phrase traditional controller is very general, please create a more concrete comparison with some state-of-the art method.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for Authors
Dear Authors,
Thank you for your comments, the article improved a lot, however I don't see how the requested images quality improved, it is still hard to read them.
The bigger problem is that the first two paragraphs of the paper is very similar to a previous paper of the authors, please rewrite this text and include some original sentences, references.
a paragraph between figure 17 and table 8 are also problematic, the text is very similar to this previous paper.
Please check and correct these parts of the paper.
Author Response
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Author Response File: Author Response.pdf
