Comments on abstract, title, references

Abstract: The problem statement must be reformulated to reflect the contribution of the research. Also, all the abstract must be rewritten in clear and concise statements.

Title: I suggest changing the title to: Reducing the parameters of high order models by approximation to fractional order models.

References: For such research topic (fractional calculus and its application in system modeling), I suggest adding the most recent papers (from 2015-now) .

Comments on introduction/background

1- A brief introduction to fractional calculus is needed. 2- Reducing the number of parameters by approximating the high order transfer function by a fractional order transfer function introduces difficulties in implementation. These difficulties must be discussed and investigated; otherwise, the contribution of the paper is questionable.
3- In the last sentence of the last paragraph of the introduction, the recent technologies of implementation technologies must be (at least) mentioned.

Comments on methodology

The methodology is based on finding the inverse relations between the parameters of the approximations between the high order system and fractional system; this can be considered an interesting contribution in fractional order systems.

Comments on data and results

1-One numerical example was considered. Can the obtained results be generalized for other cases. The authors must clarify this issue. 2- How was the step response (Fig. 3) obtained? This must be achieved by certain approximation, hence contradict the contribution of the paper. The authors must states this clearly.

Comments on discussion and conclusions

1- The authors must give "general conclusions" for each system, not only for the special case that was considered by the numerical example. 2- For integer models having only poles without zeros, the approach of the paper is not applicable; hence, the authors must suggest solutions, or leave it for future work.