Modeling and Theoretical Analysis of Zero-Flowrate-Switching Control Method for a Dynamic Load System to Reduce Switching Power Loss of Control Valves

Round 1

Reviewer 1 Report

The paper is interesting. In the introduction, mention should be made of the proportional control technique commonly used for soft starts in hydraulic systems. References should be completed. The method of experimental testing should be clearly described. As it stands, it is not clear whether the experiment was carried out and, if so, under what conditions. See attached manuscript for detailed comments.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Overall comment

The paper presents the zero-flowrate switching control method for reducing valve switching power losses in digital hydraulic system. The concept is indeed a very interesting one and addresses one of the main concerns of digital hydraulics technology and thus this concept should advance the digital hydraulics technology.

However, the author has presented this concept in their previous publications:

·      S. Peng. The concept of a zero-flowrate-switching controller, Proc. of Eighth Workshop on Digital Fluid Power. Tampere, Finland, 559 2016.

·         Peng, Shuang. "An Zero-Flowrate-Switching (ZFS) Control Method Applied in a Digital Hydraulic System." In Proceedings of 15th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden, no. 144, pp. 172-177. Linköping University Electronic Press, 2017.

The author has not cited their second publication in this article which is concerning.

From aforementioned paper to this one, there is very little difference, namely the rod side of the cylinder is also connected to ZFS control system. Most of the sections of the paper are just repetitions of their previous publication. Thus, I am concerned about the novelty of this work.

The authors should remove the contents in this paper that have been already presented in aforementioned publications and include novel content in this paper to justify its publication.

Language comment:

The quality of English language needs significant improvement.

Other comments:

·         Line 41: provide citation for Johnston and et. Each sentence referring a work should have a citation at the end of it.

·         Eq. (3)-(5), (16), (17) should have proper rationale/citation

·         Line 202: the linear assumption of valve flow is a critical one. Valve flow is almost always turbulent and thus, the relationship is quadratic.

·         In figure 15: measuring flow is always difficult (involves heavier equipment and has trouble capturing the dynamics).

·         Eq (33) shows a quadratic relationship between flow and pressure, but Eq. (8) showed a linear one.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The present document “Modeling and Theoretical Analysis of a Novel Hydraulic Control Method for Reducing Switching Power Loss of Control Valves” deals with the modelling of a particular sort of hydraulic device, used as valve control.

It is an interesting contribution due to energy implications, but some comments are proposed by this reviewer before publication.

Abstract. This section is well presented, depicting the main achievements of the work. Nevertheless, in this reviewer opinion, the novelty of the work should be here pointed out.

1.    Introduction. This section is well presented, with adequate references and presenting the organization of the paper. In this reviewer opinion, the main objectives of the work should be indicating here in order to review later if they have been achieved

2.     Statement of the problems/ 3Principle of ZFS Control Method. These both sections are well presented, with clear figures and description. In this reviewer opinion both epigraphs should be summed in a Materials and methods section.

4.    Mathematic Model of a ZFS Control System. This is an interesting section, presenting the model and the principles of control. In this reviewer opinion, it is not clear if this is a result of the proposed methodoly for modelling, or it is already part of the model and which is the novelty of the proposed equations.

5.    System Evaluation. This is an interesting analysis section of results, presenting application of the described model. It is not clear for this reviewer if this theoretical analyses depicted has been validated in any real system

6.    Conclusions. In this case, conclusions are a resume of the presented work. Two questions are proposed to authors. In which proportion the objectives have been achieved? What is the novelty of the presented research?

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I am mostly satisfied with author's replies. Few suggestions:

Line 38: "Johnston and et" should be "Johnston et al."

The flow meter used by the author is indeed fast, however is heavy (2 kg). They should think of lighter alternatives.

Overall, the paper is acceptable for publication.