An Industrial Quadrotor UAV Control Method Based on Fuzzy Adaptive Linear Active Disturbance Rejection Control

Round 1

Reviewer 1 Report

This manuscript claims a controller based on fuzzy adaptive control to be applied on a quadrotor. There are some numerical investigations but the current version of the manuscript still in a very early phase in this research.

0 - The internal disturbance is mostly motivated with a ground effect. I appreciate the justification but it is a quite established and solved problem. However, its counterpart namely the ceiling effect is a more up-to-date problem and more interesting. The authors might want to investigate some research such as Seet - (Nanyang Technological University), Ollero (University of Sevilla) to motivate the problem/method.

1 - I appreciate the effort given for the dynamics in Section II but it is mostly the repetition of what is available in the literature. Furthermore, the internal disturbance could be also added to Eq. (2) to include the ceiling or ground effect.

2 - The third raw in Eq. (4) says that the torque for the yaw dynamics is based on the thrust coefficient. If it is the claim, the authors may need to correct it with the drag coefficient. I think that the authors might check Bouabdallah's Ph.D. thesis for this Section. However, it does not add too much value to the manuscript.

3 - The symbols in Fig. 2 and 3 should match with the equations. If it is italic, please use the exact same symbol with additional characteristics otherwise it could be misleading.

4 - I think that one of the significant parts of this research is to prove the stability. In the current version, there is three main consideration: (i) inner loop; (ii) outer loop; (iii) whole system. I strongly suggest to include the stability proofs considering these.

5 - I assume that PSO is used in an offline manner to find the tuning parameters. One of the questions is based on the dependency of the tuning parameters. If it is changed in a certain range, does the controller still perform well as it is expected?

6 - What is the added value of adding Tables 1, 2, and 3?

7 - Is there any real data to form transfer functions given in (26) - (29)? That could be more valuable.

8 - In Fig. 6, there are two different results are presented, one is for the translational channel with x and z, and the other is for the attitude channel with roll and yaw. However, the block diagram shows that the attitude channel is getting the reference values that are the output of the outer loop controller. How is it possible to get such a reference signal as it appears for the roll and yaw channel? Are the authors only simulating the loops individually?

9 - The step function like reference signals are not very common in practical implementations. Every possible reference signal should be straightforward in this implementation since it is only in a simulation environment. I would suggest to include various reference signals that could be considered in the real-time application.

10 - The tracking results are given but the controller inputs are not presented. One may wonder whether they are applicable in real-time or not. The authors may give the time-based input histories. Additionally, the input energies could be compared for these controllers.

11 - I think that there is a lot to consider to improve the current version of the manuscript.

Author Response

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Reviewer 2 Report

Paper describes the usage of Fuzzy-LADRC controller for UAV. State-of-the-art is well described ad paper is logical continuation of Fuzzy controller applied on UAV autopilot. Paper compares several types of controller and new one has promising result. It will interesting to follow the application on HW. It is question if usage  just only of step function as evidence of control robustness, what about white noise etc.

I have several comment to typography:
Line 95, 96, 103, 106, 169 etc. "T" is not italics.
Eq. (1) not sure that substitution sin, cos to C, S is adequate. It is used in two eq.
Capitalization of sections is not unified.
Eq. (6) "gyro is not italics.
I miss just after Eq. (9) explanation of  χ ζ it is made in the following paragraphs.
Eq. (12) sin a cos are not italics.
Line 150 space between Table_1
Tables 1, 2, 3: Abbreviations NB, NM, ... are not explained.
Eqs (26)-(29) "e" is not italics.

After minor changes, paper should be published.

Author Response

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Reviewer 3 Report

This paper proposed a fuzzy adaptive linear active disturbance rejection control method for strong coupling and nonlinear quadrotor unmanned aerial vehicle (UAV). The problem of disturbance rejection control is very important especially for practical applications, and the proposed method looks promising. However, the quality of the paper should be much improved before the consideration of publication. Please find my detailed comments as follows:

1. The paper is not well written and thus it is difficult to evaluate its contribution. Here are just some examples:

1) Many notations of Eq. (9) are not defined and cannot be understood.

2) Notations of Tables 1-3 are not defined.

3) Figures 5 and 6 are not clear and should be further improved.

2. One key step of the proposed method is to take several nonlinear and uncertain terms as a total disturbance as shown in Eq. (14). My concern is that this step could significantly increase the total disturbance so that the control saturation point is reached. More discussion on this issue is helpful.

3. In the Introduction section, all introduced methods are based on PID control, which is a feedback controller. Another type of controller is feedforward control, which is also commonly used for disturbance rejection. For example, the tube model predictive control method has been investigated by increasing studies, such as [1][2][3]. More discussions about this direction could help further improve the paper.

[1] Lopez, B.T., Howl, J.P. and Slotine, J.J.E., 2019, July. Dynamic tube MPC for nonlinear systems. In 2019 American Control Conference (ACC) (pp. 1655-1662). IEEE.

[2] Feng, S., Sun, H., Zhang, Y., Zheng, J., Liu, H.X. and Li, L., 2019. Tube-based discrete controller design for vehicle platoons subject to disturbances and saturation constraints. IEEE Transactions on Control Systems Technology, 28(3), pp.1066-1073.

[3] Mayne, D., 2016. Robust and stochastic model predictive control: Are we going in the right direction?. Annual Reviews in Control, 41, pp.184-192.

4. I would suggest the authors go through the paper carefully and significantly improve the writing of the paper, which could become a hurdle to the contribution of the paper.

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Round 2

Reviewer 1 Report

Most of the issues are addressed in the resubmitted version of the manuscript. The authors may want to inspect Fig. 11 for the controller actions. The signal values with LADRC and Fuzzy+LADRC are quite high which may not be realistic. I would suggest investigating this to be sure that is applicable experimentally. 

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Reviewer 3 Report

Most of my concerns have been addressed. I would recommend it for publication.

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