A Single-Anchor Cooperative Positioning Method Based on Optimized Inertial Measurement for UAVs

Round 1

Reviewer 1 Report

In this paper, a method for the single-anchor cooperative positioning problem using optimal estimation of inertial data is presented. The experiment results showed that it could effectively improve the positioning accuracy of the UAVs. This manuscript is well-written and well-structured, I would recommend acceptance if the authors can response the following comments.

 

1. The parameters in the 3.5 subsection should be correspondent to the parameters in the cooperative positioning model. The definitions of the variable x and the set X need to be more explicit.

2. I noticed that there is no additional discussion on observability in this paper. The single-anchor positioning is often considered unobservable when the vehicle moving along the extension line of the anchor. However, in the real-world experiment, the position along the extension line can be estimated. Please explain the reason.

3. The subfigures (b) and (c) in Figure 12 are different from each other in size. Similar subfigures in a figure should have the same size.

4. The constant term C in (28) and (29) should be written in bold, as it is a constant vector rather than a constant scalar.

5. Please further discussed the advantages and limitations of the proposed cooperative method and the future promising improvement measurement.

6. Please further discussed the challenge of positioning in single-anchor environment compared to multi-anchor environment and what difference between observability in them. Also, explain the applicability of the proposed method in environments with more anchors, such as two anchors and three anchors, and explain what type of layout is effective.

 

In this paper, a method for the single-anchor cooperative positioning problem using optimal estimation of inertial data is presented. The experiment results showed that it could effectively improve the positioning accuracy of the UAVs. This manuscript is well-written and well-structured, I would recommend acceptance if the authors can response the following comments.

 

1. The parameters in the 3.5 subsection should be correspondent to the parameters in the cooperative positioning model. The definitions of the variable x and the set X need to be more explicit.

2. I noticed that there is no additional discussion on observability in this paper. The single-anchor positioning is often considered unobservable when the vehicle moving along the extension line of the anchor. However, in the real-world experiment, the position along the extension line can be estimated. Please explain the reason.

3. The subfigures (b) and (c) in Figure 12 are different from each other in size. Similar subfigures in a figure should have the same size.

4. The constant term C in (28) and (29) should be written in bold, as it is a constant vector rather than a constant scalar.

5. Please further discussed the advantages and limitations of the proposed cooperative method and the future promising improvement measurement.

6. Please further discussed the challenge of positioning in single-anchor environment compared to multi-anchor environment and what difference between observability in them. Also, explain the applicability of the proposed method in environments with more anchors, such as two anchors and three anchors, and explain what type of layout is effective.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Interesting article submitted.

The authors performed theoretical modeling and practical experiments.

Inaccuracies observed in the work:

  - I missed the reference to literature sources (formula 1 and 2);

  - In the part of simulations (Chapter 5), I missed a clearer plan for conducting experiments. For example, whether the UAV will be controlled manually or automatically. Also, what is the planned flight path? Weather conditions are also uncertain. Looking at Figure 7, it is not clear how the flight is performed: manual control or automatic control. Unclear flight plan. What are those black squares? The same questions for Figure 8.

  - Since there is no flight plan provided, it is not clear whether the information in Figure 10 is correct.

  - Experiments with UGV are carried out in chapter 6. Are their results valid with an operational UAV?

  - In the conclusions, you would like to see how much the considered method is better or worse than analogous methods based on inertial navigation.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Authors present an UAV positioning technique for single-anchor scenarios relying on intertial and range sensors. They detail an optimization algorithm that improves inertial measurements made for the UAVs by using inertial and range ones. Before updating UAV positions, the output of the optimization step is filtered. 

The paper is well motivated, and the background provided in sections 1 and 2 is appropriate. The optimization and filtering process is formally presented.

Results show an improvement in accuracy in almost all cases over non-cooperative methods, although real-world experiments should also have been performed with UAV (instead of UGV). 

I believe that the comparative study should be extended to other state-of-the-art cooperative localization mechanisms (or at least justify why this has not been done).

I also believe that it should be better explained how the cooperation between the agents/UAVs is carried out. What is the communication involved in this cooperation, what is the overhead associated with this communication, and so on.

Finally, a discussion on the applicability of the mechanism in scenarios where real time is key is necessary, including its computational complexity.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf