Experimental Assessment of Semi-Active ECS Under Low-Friction Conditions with Integrated Roll–Yaw Control

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Controlled dampers, and in particular continuously controlled dampers, are dominated by MR dampers. Such dampers use MR Fluid in a more or less conventional damper configuration and then current control dictates asymmetric damper forces if that is desired, or ON-OFF damper forces if that is desired, or any damper forces desired where the forces are generated by the relative velocity across the damper. Additionally, MR dampers can be adjusted in 1-3 ms.  MR dampers are currently on about 50 models of vehicles in the world. The authors should justify the time and effort spent on developing and using a solenoid valve, mechanical flow control for their dampers.  

The authors never describe how or why controlled dampers effect vehicle handling. This is due to the nonlinearity of the tires. When a vehicle rolls due to a steering input, the outside tire load increases and the inside decreases. The increased normal force on the outside tire generates an increased lateral force at the contact patch and the decreased normal force on the inside tire reduces that tire's ability to generate a lateral force. Due to the nonlinearity of tire force generation, the increase on the outside tire is not a large as the decrease on the inside tire and that axle experiences an overall decrease in cornering ability. Thus by controlling the dampers one can generate transient oversteer or understeer. 

Why was a model not used to develop and demonstrate control philosophies for vehicle handling in low mu conditions? A relatively simple model incorporating the Pacejka or Dugoff tire model would allow for easier and understandable development of the emperical relationships in this paper.   

The authors should discuss these concerns and justify their approach.

Author Response

Dear Reviewer,
Your comments and corrections have been included in the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The study is interesting, and its results might have promising applications in automotive engineering in designing new suspension systems. The authors have done extensive tests and analyzed a series of test results demonstrating the consistency of the proposed damper design. However, the manuscript has several major flaws that the authors need to address.

1) Elaborate on the test setup - sensors, data acquisition, data sampling, sensor calibration/installation, and so forth.

2) Explicitly show graphically with arrows how the proposed damper system - reverse mode semi-active damper operates and how its control works. As shown in Fig. 1, not much information can be obtained.  

3) Show how the characterization of the proposed damper was obtained - Fig. 2 is insufficiently explained and poorly prepared (low resolution). Show the theoretical formulation of the characteristics of the damper. 

4) Why was a 1 Hz sampling rate (line 211) used for the damper responsiveness test? This value is too small. In general, cars experience 1 to 20 Hz vibrations.

5) What is along the y-axis in Fig. 3?

6) How are the measurement data shown in Fig. 5 obtained? The quality of Fig. 5 is very poor.

7) Some equations need to be corrected - (3), (4), (5), (9), (10), etc.

8) Why is Vch = 79 km/h in Eqn (11), but the tests were run at 70 km/h?

9) The sources of the given formulations need to be cited explicitly. Otherwise, there is a plagiarism issue.

10) Where is eqn (16)?

11) Authors should show numerical assessment metrics (values) in addition to the bare-bone results to show the outperformance characteristics of their proposed damper, e.g., % improved damping, improved stability, reduced vibration, or improved comfort ride, etc.

12) Test results - Fig. 13 - 25,  need to be compared with the "conventional" damper performances. Clarify what a "conventional" damper is used as a benchmarking indicator.

13) Rewrite the summary based on your quantitative assessment analyses of your proposed damper vs. "conventional" damper. 

 

Author Response

Dear Reviewer,
Your comments and corrections have been included in the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Good job. The only point that needs to be fixed is the information on your used sensors: Model, manufacturer, and country of origin. Add this information while finalizing your manuscript. 

All the best!