Review of Fault-Tolerant Control Systems Used in Robotic Manipulators

Round 1

Reviewer 1 Report

A good review paper. Some revisions are required. 

1. What is the methodology for selecting the papers?

2. Which robotic systems were included and excluded?

3. References for the equations are required.

4. Please check the overall english style. 

5. Please add more write-up in the discussion section and provide clear future challanges. 

Author Response

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a review paper that covers fault tolerant control systems for robot manipulators from 2003 to 2022. 

In my opinion, this is a well organized paper that presents the recent advances in fault tolerant systems in a comprehensive manner.

I did notice grammatical mistakes and strange sentence structure on a few occasions. For example, this sentence in the abstract could have been phrased better: "The use of fault-tolerant control systems allow to reduce robots downtime."

I think this paper can be accepted after correcting such grammatical mistakes.

Author Response

Reviewer 2

This is a review paper that covers fault tolerant control systems for robot manipulators from 2003 to 2022.

In my opinion, this is a well organized paper that presents the recent advances in fault tolerant systems in a comprehensive manner.

I did notice grammatical mistakes and strange sentence structure on a few occasions. For example, this sentence in the abstract could have been phrased better: "The use of fault-tolerant control systems allow to reduce robots downtime."

I think this paper can be accepted after correcting such grammatical mistakes.

 

Dear Reviewer,

Thank you for your comments and suggestions on the article.

Linguistic correctness was checked again. Sentences about which there were doubts were changed, e.g., the sentence in Abstract:

The use of fault-tolerant control systems allow to reduce robots downtime, which usually bring the production to very costly standstill.

Is replaced with:

The use of fault-tolerant systems in robotics can prevent the production line from being immobilized due to minor faults.

The work was checked again for language. A dozen sentences were added for better understanding of the work.

 

We hope this answer is satisfactory for you.

Yours faithfully

Andrzej Milecki, Patryk Nowak

 

 

Reviewer 3 Report

The font style in Figure 3 should be revised.

Please check if the first letter of each word of every figure's caption is capitalized.

 

Author Response

Reviewer 3

The font style in Figure 3 should be revised.

Please check if the first letter of each word of every figure's caption is capitalized.

 

Dear Reviewer,

Thank you for your comments and suggestions on the article.

 

In the revised work, Figure 2 is removed and therefore the Figures numbering in the paper has been changed. The styles and font size in the figure have been corrected. Other drawings are checked for the style and font size. Descriptions of drawings were also checked in terms of starting captions with a capital letter. Similar problems were found and corrected in the Figure 10.

 

We hope this answer is satisfactory for you.

Yours faithfully

Andrzej Milecki, Patryk Nowak

 

 

Author Response File: Author Response.pdf

Reviewer 4 Report

The review work in "Review of Fault Tolerant Control Systems Used in Robotic Manipulators" is a good review that can help the community to get a broad knowledge about the FTCS.

However, the comparison is not complete without an analysis of the strength and weaknesses of each in more depth. The comparison is scattered in the paper. Also, the improvements are not quantified. It makes it difficult to follow. Some good points about computational complexity have been mentioned in the paper, but it is not clear the impact of the computational delay on the overall performance. 

I suggest the authors summarise all the controllers in a table and present the comparison quantitatively if it's possible or qualitative if it is not possible for the below topics

- Accuracy

- Robustness

- Dependency on accurate modelling 

- Dependency on training data or training in general

- Robustness in model or environment inaccuracies and disturbances

- Complexity in implementation and tune.

- Computational cost 

- Dependency to the bounds in the disturbances, uncertainty and noise

- Can cope with match and un match uncertainty at the same time

- Limits in practical use

I see merit in this work; however, without a conclusive conclusion as suggested, the aim of the work is not fulfilled, in my opinion.

Moreover, I suggest to short list the front runners of the above table and do simulation applying the selected controllers on the same model (discuss the model and the condition of the test). Then the results can be a good review.

Author Response

Reviewer 4

The review work in "Review of Fault Tolerant Control Systems Used in Robotic Manipulators" is a good review that can help the community to get a broad knowledge about the FTCS.

However, the comparison is not complete without an analysis of the strength and weaknesses of each in more depth. The comparison is scattered in the paper. Also, the improvements are not quantified. It makes it difficult to follow. Some good points about computational complexity have been mentioned in the paper, but it is not clear the impact of the computational delay on the overall performance.

I suggest the authors summarise all the controllers in a table and present the comparison quantitatively if it's possible or qualitative if it is not possible for the below topics

- Accuracy

- Robustness

- Dependency on accurate modelling

- Dependency on training data or training in general

- Robustness in model or environment inaccuracies and disturbances

- Complexity in implementation and tune.

- Computational cost

- Dependency to the bounds in the disturbances, uncertainty and noise

- Can cope with match and un match uncertainty at the same time

- Limits in practical use

I see merit in this work; however, without a conclusive conclusion as suggested, the aim of the work is not fulfilled, in my opinion.

Moreover, I suggest to short list the front runners of the above table and do simulation applying the selected controllers on the same model (discuss the model and the condition of the test). Then the results can be a good review.

 

Dear Reviewer,

Thank you for your comments and suggestions on the article. We added following text in the Summary:

The purpose of the work was to present the issue of FTC in the context of manipulators, particularly to control a robot in case of one or two axis failure. It was decided to collect work from the last 20 years and then try to group them. In this way, 3 chapters were created: AI-based methods, SMC-based methods and others which numerically constituted a similar number to the first two groups. The goal of the article was to collect and systematize what has been done so far on the topic of FTC in manipulators. The reader, after reading the paper, is expected to gain a general understanding of FTC in manipulators. We believe that the topic of FTC is very subjective and depends strictly on the application, e.g., if we have a robot connected on very long wires, it may turn out that using FTC algorithms for the communication line is a much better solution than using an AI or SMC-based controller. For manipulators with a large number of degrees of freedom, a computationally simple SMC-based controller is probably better, but this may also depend on the required motion speeds or positioning accuracy. The article is intended to direct the reader to the solution and to urge the reader to read the valuable in our opinion, works of the cited authors. Therefore, as suggested by the Reviewer, the methods described in the cited articles are compared in Table 1. Each of the proposed methods is valid for a different type of application and their comparison could only be done for detailed boundary conditions.

Table 1. The comparison of FTC methods described in cited articles used for robots control

 

We hope this answer is satisfactory for you.

Yours faithfully

Andrzej Milecki, Patryk Nowak

Round 2

Reviewer 1 Report

Paper can be accepted as authors have made significant revision.

Reviewer 4 Report

Thanks for the updates, the paper has a good summary. 

I'm satisfied with the current version.