Evaluating the Efficiency of Connected and Automated Buses Platooning in Mixed Traffic Environment

Round 1

Reviewer 1 Report

This study developed a speed planner based on the model predictive control (MPC) to minimize the total platooning energy consumption, and HVs were programmed to maintain a long enough distance from the preceding vehicle to avoid collision. The problem is interesting and valuable. The organization is well.  I suggest it can be accepted after minor revision.

The authors needs to explain how the energy consumption reduction by 4% was obtained. In addition, it needs to give units for each line in the tables .

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Reviewer 2 Report

In this paper, a speed planner based on model predictive control is proposed to minimize the total energy consumption of queue driving, and HV is programmed to keep a long enough distance from the vehicle in front to avoid collision. Now, the following suggestions are put forward:

1.      It is hoped that the location of the figures and tables will be consistent with those mentioned in the text.

2.      The author should add corresponding symbols to the numbers appearing in the text.

3.      The quality of Figure 5 needs to be improved. It is hoped that the author can select appropriate image size and curve color to better reflect the meaning of the image.

4.      The format of equation 8 and equation 4 should be unified.

5.      It is hoped that the author can explain the meaning of "s.t" between equations (9a) and (9b).

6.      The conclusion is relatively simple. The author can make a detailed summary of the advantages and disadvantages of the method proposed in this paper on the original basis.

Author Response

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Reviewer 3 Report

Dear Authors,

thank you very much for the contribution. Overall, the paper is very well described, yet I have a few comments on the presentation.
-> Can you give more information about the simulation (software etc.) and how the MPC was implemented algorithmically (solver, how were the maps considered, etc.)?
-> Is it not possible with the presented setup that a HV pushes a CAV virtually in front of it? This is very questionable for safety reasons.
->l.104: a and b --> a_i and b_i?--> a also used for acceleration
-> l.122: SOC --> abbreviation not introduced
-> How were W_1 and W_2 tuned?--> There are systematic approaches for this, e.g., A. Gharib, D. Stenger, R. Ritschel and R. Voßwinkel, "Multi-Objective Optimization of a Path-following MPC for Vehicle Guidance: A Bayesian Optimization Approach," 2021 European Control Conference (ECC), 2021, pp. 2197-2204, doi: 10.23919/ECC54610.2021.9655125.
-> l.160: Here x_k+1 is introduced as velocity. Since velocity was previously described by v, I would recommend introducing the state space model first and then defining the state as velocity.
-> Please check the references, there seem to be some copy/paste errors, e.g. 28

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Reviewer 4 Report

The paper deals with a problem of optimization of platooning of a special case of the set of vehicles, namely mix of autonomous an man-operated traditional trucks.

The reasoning, problem formulation and the proposed solution brings no major concerns, I have therefore little comments.

As usual, the conclusions could be better developed , better outlining the future directions of research.

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Round 2

Reviewer 2 Report

Due to the limitation of battery capacity of pure electric vehicles (BEV), in order to improve the energy efficiency of automobiles, exhaust gas technology has attracted the attention of many automobile manufacturers. This paper develops a Model Predictive Control (MPC)-based speed planner to minimize total platoon energy consumption and program HVs to maintain a sufficient distance from the preceding vehicle to avoid collisions. And the energy consumption of various forms of platooning in mixed traffic is analyzed. The experimental results show that the energy efficiency of the MPC-based CAVs controller is higher than that of the HVs controller. Especially on slope roads, CAVs have a more obvious performance in energy consumption than HVs. And by simulating multiple different platooning scenarios, the SOC results of platooning are analyzed. It is more powerfully proved that the design of this paper has a realistic basis and can be reliably applied in a variety of scenarios. Suggestions below:

1.     Is there a realistic reference for the fitting parameters in Table 1?

2.     Please check the battery capacity unit in Table 2 and the calculation relationship with the maximum capacity of the battery mentioned above.

3.     It is recommended to adjust the position of the legend in Figure 5.

4.     The quantitative analysis of the simulation is commendable in this paper, but the overview in the conclusion is relatively sparse and not forward-looking.

Author Response

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Round 3

Reviewer 2 Report

In this paper, a method to improve the energy efficiency of vehicles is designed for the battery life of pure electric vehicles. A model predictive control (MPC)-based speed planner was developed to minimize the energy loss of vehicle platoons while ensuring a safe distance between vehicles. Finally, the multi-scenario and multi-angle experiments verify that the energy efficiency of the MPC-based CAVs controller proposed in this paper is higher than that of the HVs controller. Suggestions below:

1.     The actual application scenarios of the car queue mentioned in the article can be briefly introduced.

2.     Please check the punctuation in formulas 1-3 and unify the full text formula format.

3.     The vehicle in this article is a passenger car, so whether the influence of the change in the quality of the car has been considered.

4.     Vehicles will inevitably encounter various disturbances in the process of driving. Whether the control scheme designed in this paper has the ability to deal with disturbances.

Author Response

Thank you for your valuable suggestions to improve the paper quality. We carefully reviewed your constructive comments and reflected to the fullest extent in the revised paper. Please find the attached our response letter.

Author Response File: Author Response.pdf