Review Reports

Round 1

Reviewer 1 Report

This manuscript described a novel method for oxygen pressure estimator, and described in detail the stability conditions. It is highly recommended to publish. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The objective of developing oxygen pressure estimator is sound useful for fuel cell system diagnostics. However, based on presented methods and results, I suggest to revised or rejected this paper.

1. 21 of V_con is not correct formulation in electrocehmical textbook. 

V_{con =}  RT/nF ln (C_s/C*) = RT/nF ln (1-I/I_{max Limt).}  This will make incorrect and strange results and conclusion.

2. In Table 1, I max current denisty is unit A/cm2, This max current could be function of oxygen pressure (block concentration of oxygen), and not constant.

3. Results of Equation 27 need based on some conditions or constrains. The current density is inverted o oxygen pressure is  physically incorrect. 

4. For purpose of modeling pressure sensor need demonstrate results of potential- current - pressure oxygen, and validated or experimental calibration. It is not Figure 1 results for proof positive partial derivative Φ. The value of current density can not larger than the max current 2.2A. 

5. Results of Figure 7, 8 cell potential is not in practical application of PEMFC  unit cell (0-0.9V). This is due to equations or table parameters.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript proposes a immersion and invariance method to estimate oxygen pressure with other sensor measurements, and investigate its effectiveness using simulation analysis. The topic is interesting and the manuscript is well-organized. It is suggested to be accepted for the publication after addressing the following concerns.

1.Why oxygen pressure sensor measurement is selected in the analysis? How about estimating other sensor measurements like hydrogen pressure? Moreover, as oxygen pressure sensor can be installed at either inlet and outlet of cathode side, is there any significance in using this pressure estimation at practical PEMFC applications?

2.Literature review should be expanded to further clarify the state-of-the-art of sensor estimation method and difficulty in obtaining reliable measurements in practical PEMFC systems;

3.Only simulation results are used in this study to validate the proposed estimation method, experimental analysis should be added to further demonstrate its performance in actual systems.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

No.

Reviewer 3 Report

The reviewer's comments have been addressed, and the revised manuscript can be accepted for the publication in present form.