Characteristics and Analysis of an Eddy Current Shock Absorber Damper Using Finite Element Analysis^†

Round 1

Reviewer 1 Report

Interesting article but needs supplementing:

Formulas 1 and 2 require supplementation and improvement.

The dimensions given in table 1 do not match the results shown in figures 4, 5, 6 and 7.

Please explain what is a car displacement? (Figures 9, 10 and 11).

It should also be noted that shock absorbers in motor vehicles have non-linear characteristics. And the same should be assumed for other types of damping in the suspension.

Table 3 shows that replacement of the traditional shock absorber with the proposed solution may be considered. This should be clarified. The mathematical model shown shows that the hydraulic shock absorber is still there. Has the extra ECD mass been included in the simulations (in the simulink model)?

Author Response

Both I and my co-authors agree with the reviewer remarks and suggestions and have done every effort to implement them. More specifically, the following items list the remarks, suggested modifications or inquiries as well as responses and/or action(s) taken to implement them:

Reviewer #1 (Remarks): 

Formulas 1 and 2 require supplementation and improvement.

Response: Done.

2) The dimensions given in table 1 do not match the results shown in figures 4, 5, 6 and 7.

Response: Done. The Table was corrected (1 cm instead of 0.1 cm).

3) Please explain what is a car displacement? (Figures 9, 10 and 11). 

Response: It’s the vertical displacement resulted from a road disturbance.

4) It should also be noted that shock absorbers in motor vehicles have non-linear characteristics. And the same should be assumed for other types of damping in the suspension.

Response: The road disturbance could be step or gradual, but the step disturbance was chosen since it causes the most extreme disturbance.

5) Table 3 shows that replacement of the traditional shock absorber with the proposed solution may be considered. This should be clarified. The mathematical model shown shows that the hydraulic shock absorber is still there. Has the extra ECD mass been included in the simulations (in the simulink model)?

Response: No it was not added, but the added weight of the ECD is negligible compared to the quarter car weight (about 466 kg compared to about 6.7 kg). 

Finally, we would like to thank the reviewer very much for his/her sincere and thorough review of our manuscript and we believe that the paper quality has been strengthened by his/her comments.

My best regards and please let me know in case I could be of further help.

Sincerely,

Tamer M. Abdo

Reviewer 2 Report

The reviewed paper does not contain any significant achievements. It largely overlaps with the work [17]. The part concerning the FEM simulation is described in a rather brief way. No data is given on the materials used. The method used to calculate the field distributions is not specified. The quasi-stationary method is only valid if the core is infinitely long. For the case of a short core, an transient analysis should be used. However, if the quasi-stationary method is used for the short core, it is necessary to discuss how big are the differences in relation to the correct method. The distributions of fields B and J are in my opinion incorrect. In the central part of the core, the distribution of field B should be homogeneous (Models 1, 2 and 4). The concentration of induced eddy currents should occur mainly near the outer poles of permanent magnets. Incorrect field distributions are probably due to improper finite element meshes used for calculations that do not take into account the penetration depth of the field. Model 3 is unrealistic because it is very difficult to place two oppositely magnetized permanent magnets side by side without taking into account the air gap between them. In addition, the presented results concern a model other than the one defined in Table 1. The thickness of the aluminum coating according to Table 1 is equal to 0.1cm, whereas in the presented field distributions it is equal to 1cm! Table 1 also gives the dimensions of the stator, which is not included in the simulations. Additionally, because the Lorentz damping force is only dependent on the Br component of the magnetic flux density and the Jphi component of the eddy current density, there is no point in visualizing the module |B|. Since in my opinion FEM simulations are incorrect, it is also difficult to assess the quality of the presented models.

Author Response

Both I and my co-authors agree with the reviewer remarks and suggestions and have done every effort to implement them. More specifically, the following items list the remarks, suggested modifications or inquiries as well as responses and/or action(s) taken to implement them:

Reviewer #2 (Remarks): 

The reviewed paper does not contain any significant achievements. It largely overlaps with the work [17]. The part concerning the FEM simulation is described in a rather brief way. No data is given on the materials used. The method used to calculate the field distributions is not specified. The quasi-stationary method is only valid if the core is infinitely long. For the case of a short core, an transient analysis should be used. However, if the quasi-stationary method is used for the short core, it is necessary to discuss how big are the differences in relation to the correct method.

Response: The reviewer’s comments are correct regarding ref [17]. In [17] the model was quasi-static with 3-phase windings to simulate the relative motion between the magnetic field and the actuator, but in this paper the model used is a 2D axis-symmetric model (i.e. 3D) with permanent magnets and motion so it’s more accurate.

The distributions of fields B and J are in my opinion incorrect. In the central part of the core, the distribution of field B should be homogeneous (Models 1, 2 and 4). The concentration of induced eddy currents should occur mainly near the outer poles of permanent magnets. Incorrect field distributions are probably due to improper finite element meshes used for calculations that do not take into account the penetration depth of the field.

Response: The asymmetry at the edges is due to the using coarse mesh size, while there is symmetry at the center.

Model 3 is unrealistic because it is very difficult to place two oppositely magnetized permanent magnets side by side without taking into account the air gap between them.

Response: Correct. It’s a hypothetical case that was studied for the case of more understanding.

In addition, the presented results concern a model other than the one defined in Table 1. The thickness of the aluminum coating according to Table 1 is equal to 0.1cm, whereas in the presented field distributions it is equal to 1cm!

Response: Done. The Table was corrected (1 cm instead of 0.1 cm).

Additionally, because the Lorentz damping force is only dependent on the Br component of the magnetic flux density and the Jphi component of the eddy current density, there is no point in visualizing the module |B|.

Response: Correct. We chose to show the magnitude of the current density and the magnetic flux density for more clarification.   

Finally, we would like to thank the reviewers very much for his/her sincere and thorough review of our manuscript and we believe that the paper quality has been strengthened by his/her comments.

My best regards and please let me know in case I could be of further help.

Sincerely,

Tamer M. Abdo