Review Reports

Round 1

Reviewer 1 Report

This paper conducts a comprehensive survey of mobile manipulators for smart maintenance of railway track. Generally, the content of this review is rich, and the perspectives are objective. The writing is quite good and logical. I recommend the publication after addressing the following issues:

1) It is recommended to include some perspectives for futher technonogical development and scientific research in the abstract, which would be interesting for readers in this community.

2) In the first paragraph of introduction, it is recommended to included several literature review to indicate the necessary of track maintenance from different angles. The quality of track also matters for the vehicle-overhead infrastructure performance [1], and the passenger comfortability [2]. These can be solid motivations for performing a regular track maintenance.

[1] Song, Y., Wang, Z., Liu, Z., Wang, R. (2021). A spatial coupling model to study dynamic performance of pantograph-catenary with vehicle-track excitation. Mechanical Systems and Signal Processing, 151, 107336. https://doi.org/10.1016/j.ymssp.2020.107336

[2] Azzoug, Adam, and Sakdirat Kaewunruen. "RideComfort: a development of crowdsourcing smartphones in measuring train ride quality." Frontiers in Built Environment 3 (2017): 3.

 

 

3）It is a bit confusing to see the application of UAV to bridge monitoring. Is the maintenance of bridge relevant to the topic of this paper? Please consider this issue.

Author Response

This paper conducts a comprehensive survey of mobile manipulators for smart maintenance of railway track. Generally, the content of this review is rich, and the perspectives are objective. The writing is quite good and logical. I recommend the publication after addressing the following issues:

1) It is recommended to include some perspectives for further technological development and scientific research in the abstract, which would be interesting for readers in this community.

Response: Thank you for your suggestion. Abstract has been modified (line 24 to 27).

2) In the first paragraph of introduction, it is recommended to included several literature review to indicate the necessary of track maintenance from different angles. The quality of track also matters for the vehicle-overhead infrastructure performance [1], and the passenger comfortability [2]. These can be solid motivations for performing a regular track maintenance.

[1] Song, Y., Wang, Z., Liu, Z., Wang, R. (2021). A spatial coupling model to study dynamic performance of pantograph-catenary with vehicle-track excitation. Mechanical Systems and Signal Processing, 151, 107336. https://doi.org/10.1016/j.ymssp.2020.107336

[2] Azzoug, Adam, and Sakdirat Kaewunruen. "RideComfort: a development of crowdsourcing smartphones in measuring train ride quality." Frontiers in Built Environment 3 (2017): 3.

Response: Thank you for pointing out important literatures. Text and citation have been added in the introduction (line 43).

 3）It is a bit confusing to see the application of UAV to bridge monitoring. Is the maintenance of bridge relevant to the topic of this paper? Please consider this issue.

Response: Thank you for the feedback. The review focus on the mobile manipulator and railway track. There are diversified robotic solutions available for inspection. But very few robotic solutions are available for repair tasks. UAV in bridge monitoring has been mentioned to show the diversification of robotic inspection. Moreover, maintenance for the structure of railway bridge and tunnels are important as they carry the railway track.  

Reviewer 2 Report

The strength of this paper is its in-depth analysis of the prospects for the application of mobile robots in railway maintenance, including a detailed examination of related technologies and best practices. The article introduces a mobile robot that consists of a commercial unmanned ground vehicle and an industrial robotic arm, discussing its advantages, challenges, and requirements in railway maintenance. Additionally, this paper provides references to related research, which is convenient for readers who wish to conduct further in-depth research. The author's review papers are interesting and valuable. However, the manuscript could be improved in the following areas:

• The article focuses too much on mobile robotics itself, ignoring the problems that may arise in practical applications.
• The paper does not provide sufficient data to support the efficiency and safety advantages of mobile robots in railway maintenance.
• The discussion only covers mobile robots composed of commercial unmanned ground vehicles and industrial robotic arms, and there is a lack of discussion on other types of mobile robots.

Moreover, as artificial intelligence (AI), machine learning (ML), and deep learning (DL) are hot research areas for the future, the author should increase the analysis and discussion of AI in mobile manipulators and intelligent maintenance of railway tracks. Therefore, the suggested discussions are in the following areas:

1. Environmental perception: Mobile robots need to sense the surrounding environment when performing railway track maintenance, including the state of the railway track, the position of the switch, and foreign objects on the track. Using deep learning technology to process perception data such as images and sounds can achieve a fast and accurate perception of the environment.
2. Track detection: Mobile robots can use sensors such as laser scanning and cameras to detect tracks. By training machine learning models, functions such as the classification of track status and detection of anomalies can be realized.
3. Operation control: The motion control of the mobile robot needs to be adjusted in real-time, and dynamic calculations should be performed according to changes in the current environment. The application of machine learning and control theory can realize the optimization of motion trajectory, dynamic control, and other functions.
4. Fault detection: Faults and problems may occur when mobile robots are performing railway track maintenance. Using machine learning and deep learning technology, faults and problems can be automatically detected and diagnosed, improving the efficiency and accuracy of fault handling.

In summary, AI, ML, and DL have broad application prospects in railway track maintenance with mobile robots.

l   Other considerations for mobile robots in railway maintenance include safety risks, cost issues, and legal and regulatory restrictions.

l   When performing railway track maintenance, mobile robots need to follow corresponding safety regulations and standards to ensure the safety of staff and users.

l   The R&D, production, and use costs of mobile robots are relatively high, and factors such as business model innovation and sustainable development need to be considered.

l   Finally, the use of mobile robots needs to comply with relevant laws and regulations, such as restrictions on intellectual property rights, environmental protection, and privacy protection.

Author Response

Response: Thank you for your detailed feedback and suggestions. Please find my responses below:

• problems that may arise in practical applications: few problems and challenges from the practical applications has been discussed in section 7.1. These problems and challenges arise from the railway track design, related infrastructures, access points, communications, power, data budget.  
• insufficient data to support the efficiency and safety advantages: I have found very few railway maintenance robot related research which discuss about the efficiency and safety impact. Hence, efficiency and safety related research from other industries are also included in section 6.1. But more research is required to find the efficiency and safety impact in numbers.
• lack of discussion on other types of mobile robots: though other types of robots can be used for railway track inspection and repair, but this research article focuses on the usage of mobile manipulator because of dexterity and mobility

A discussion on the usage of AI, ML and DL has been added in 7.2 (e) (line 790-798). Also, standards and regulations related discussion has been added in 7.2 (f) (line 799-804).

Reviewer 3 Report

This paper describes the overview of the mobile manipulator in the intelligent maintenance of railway track, the direction of the argument is very good. But I would like to make a few suggestions:

1. In line 234: ‘’A computer vision-based approach was developed by Mazzeo et al‘’ you need to specify which specific algorithm.

2.  Figure 11（a） needs to be in the form of (b) , and the two diagrams should be identical in style.

3. In the conclusion section, add two sentences to the last paragraph (lines 805-810) about the future of mobile manipulator.

Author Response

This paper describes the overview of the mobile manipulator in the intelligent maintenance of railway track, the direction of the argument is very good. But I would like to make a few suggestions:

1. In line 234: ‘’A computer vision-based approach was developed by Mazzeo et al‘’ you need to specify which specific algorithm.

Response: Thank you for your comment. Specific algorithms have been mentioned.

2. Figure 11（a） needs to be in the form of (b) , and the two diagrams should be identical in style.

Response: Thank you for pointing out the mismatching style. Figure 11(a) has been updated to match Figure 11(b).

3. In the conclusion section, add two sentences to the last paragraph (lines 805-810) about the future of mobile manipulator.

Response: Thank you for the suggestion. A new paragraph has been added (line 837 - 843) regarding future research of mobile manipulator.

Round 2

Reviewer 2 Report

The manuscript has undergone revisions in accordance with the reviewers' suggestions, resulting in significant improvements. As a result, it now meets the criteria for publication in Applied Sciences.