Robust Controller Decorated by Nonlinear S Function and Its Application to Water Tank

Round 1

Reviewer 1 Report

The paper matches the Journal's items proposing a robust PID controller decorated by a nonlinear S function testing the level control of water tank.

The nonlinear decoration is shown to be effective in improving robustness and control energy-saving performance, thus proving to be valuable for extensive application in the industry control engineering.

In the paper the features of PID control and the stability analysis of water tank feedback controller are illustrated. The analysis is performed by using Lyapunov stability theorem and robust control theory. The improved PID controller is designed based on the closed-loop gain algorithm and compared with the nonlinear feedback and the fuzzy controller. Thus, the system performance is evaluated with a performance index through three comparing simulations of different scenes. The Simulink toolbox of Matlab is used for simulation experiment.

The manuscript can be accepted after a minor review. The authors are suggested to follow some observations for their revised work:

- In the title of the paper "Robust PID control decorated by nonlinear S function and its 2 application to water tank", PID control should be changed into "PID controller" so to be more suitable to the content of the manuscript.

- In the Introduction section, the final part should include a better reference to the setup of the research to let the reader have a clearer comprehension of the following sections.

- It would be advisable to clarify better the diagram of fuzzy controller and nonlinear robust PID controller riportato in Fig. 2

- In line 40, a space must be introduced after the word feedback.

- In line 117, a space must be inserted between the word “model” and the word “to”.

- In line 275, a space must be introduced between the text and the Fig. 4.

- In line 288, like the previous. The full stop must be black (not red).

- In line 309, replace Table I with Table 1.

- As far as the English language is concerned, authors are invited to modify the parts of the manuscript where the sentences are scarcely linked together (see for example the Introduction section, especially the incipit).

Abstract

- In this manuscript, a concept of modifying the results of the existing robust PID controller decorated by a nonlinear S function is presented to improve the system performance.

- The performance of controlled system is analyzed through Lyapunov stability theorem and robust control theory,

Introduction

- there are hardly any new breakthroughs.

- and the closed-loop control have transferred from process control to state control where the essence is still the linear feedback.

- Yet there is little research based on the orientation of energy efficiency, leading to some prospective potential in this aspect.

- On the basis of the reference [13] and [14], the contributions of this paper are mainly twofold

Section 2

- According to reference [18] and [19], designing a PID controller using robust control theory is paid more attention to, and it will be better to use closed-loop gain shaping method to maintain the robustness of PID controller

- The new PID controller, improved by S function, will be testified for its result in improving the controller performance.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.Thank you very much for considering our manuscript. Thank you again for your help.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments are in attached file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.Thank you very much for considering our manuscript. Thank you again for your help.

Author Response File: Author Response.pdf

Reviewer 3 Report

The proposed PID control method for the second order system is out-of-dated and new advanced method was not found.

The presented method using Lyapunov function is very classical one.

Moreover, there are many English expression typos including equation expressions. Only simulation results for the water tank system are weak to show the proposed method comparing with the fuzzy control system.

More improved control methods or experimental results are required to present the research paper to this journal.

 

Author Response

Please see the attachment.Thank you very much for considering our manuscript. Thank you again for your help.

Author Response File: Author Response.docx

Reviewer 4 Report

Presented here article described modification of the existing robust PID controller decorated by a nonlinear S function. The authors presented simulation studies. The presented method of control is interesting. However, the article has some points that require attention

• Authors should add an additional diagram of the control system or modify figure 2 in such a way that it is more readable (remove unnecessary borders from the Matlab Simulink program),
• no statistical analysis,
• no implementation on a real object (what would be the limitations of the method in this case - parameters of the control system, type of controller, operating frequency),
• Authors only checked step responses. It would be worth checking and showing the frequency characteristics and the response of the object to other signal types (e.g. sinusoidal waveforms) on the charts.

Author Response

Please see the attachment.Thank you very much for considering our manuscript. Thank you again for your help.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The comments are in attached file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

 

Author Response File: Author Response.docx

Reviewer 3 Report

In the revised submission, a lot of questions were answered.

However, to be accepted, more problems in the text are polished. For example,

1. The font size of all equations should be unified.

2. Some typos in English expressions are found yet, i.e.,

  73 put -> puts, 80 reference -> references

  82 controller -> controllers

 Thus, the remained text should be checked.

3. Indentations of the first column in the sentence need to be checked.

Author Response

Please see the attachment.

The authors quite appreciate reviewers’ significant guidance and desire the reviewers’ acceptance for the current manuscript, thank you again.

Author Response File: Author Response.docx

Reviewer 4 Report

Thank You for your answers. I have no more comments.

Author Response

The author is very grateful to the reviewers for accepting the current manuscript, and thank you again.

Round 3

Reviewer 2 Report

please see the attachment

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

The authors quite appreciate reviewers’ significant guidance and desire the reviewers’ acceptance for the current manuscript, thank you again.

Author Response File: Author Response.docx

Round 4

Reviewer 2 Report

Thank you for incorporating my comments.