Embedded Flight Control Based on Adaptive Sliding Mode Strategy for a Quadrotor Micro Air Vehicle

Round 1

Reviewer 1 Report

An adaptive sliding mode technique based embedded flight control for a quadrotor micro air vehicle subject to uncertainties and perturbations has been designed and implemented. The content of the paper is good. But authors need to clarify a few things as given below.

1) eq (5) not available

2) Please clarify. In eq (2), whether phi, theta, psi denote the Euler angles? If so then eq (7) is not correct. R2 is a function of theta and phi (not theta and psi)

3) Please clarify. Page 6, below eq (40), it is mentioned that Kp>0 and Kd>0. 

But in the experimental  results section Kp = diag[-0.24, 0.24] and Kd = diag[0.1,-0.1]. Why negative gains?

4) Plot of evolution of Ka(t) must be given for the experiments for better understanding. It is not clear how the adaptation of the controller gains resulted in better performance than constant controller gains

5) Need to compare the results with the default PID controller used for rolling spider micro drone to substantiate the advantages of the proposed controller

6) The disturbance given is just like an impulse in the experiment. It would be interesting to give wind disturbances in-order to evaluate the performance of the controller under persistent disturbances

7) It is not clear how the position information of the quadrotor is obtained during the experiments. Is it using any GPS or from IMU or from motion capture? Please clarify.

8) The claim "saving energy" given in CONCLUSIONS is not substantiated by the experiments. It is not clear how the proposed controller can "save energy" as the proposed controller is not based on any optimization. Please clarify

Author Response

We appreciate the time and efforts provided by the reviewer for the high quality of the review of this manuscript. We have addressed all issues indicated in the review report, and we hope that the revised version can meet the journal publication requirements.

Author Response File: Author Response.pdf

Reviewer 2 Report

Title: Embedded flight control based on adaptive sliding mode strategy for a quadrotor micro air vehicle

Summary: This paper addresses the developement of a robust controller subjected to uncertainty and perturbations.

Introduction:

- There is a need to incorporate the review studies conducted in the area of marine robotics towards control and path planning for readers to give them a larger perspective.

Following studies can be incorporated:

Campbell, S., Wasif Naeem, and George W. Irwin. "A review on improving the autonomy of unmanned surface vehicles through intelligent collision avoidance manoeuvres." 

Annual Reviews in Control 36.2 (2012): 267-283.

Singh, Y., Sharma, S., Hatton, D., & Sutton, R. (2018). Optimal path planning of unmanned surface vehicles.

- Provide a separate subsection in the paper towards major contribution. 

- Better explanation required for justifying the contribution.

Mathematical Model:

- Provide a reference for Table 1.

- Actuated and the underactuated system is both mentioned and explained. It creates confusion and needs rewriting in a way.

There is a need to make sure that a clear explanation is available which kind of system is used for the control system design. 

Experimental Results:

- Ensure that Experimental results are compared against Simulation results in the same graph with an Error bar chart.

- Compare the Adaptive Sliding mode controller against an MPC based control strategy to show its quantitative superiority over the other classic control approaches in UAVs.

Author Response

We appreciate the time and efforts provided by the reviewer for the high quality of the review of this manuscript. We have addressed most of the issues indicated in the review report. Authors consider only 2 points not relevant with respect our manuscript, and we hope that the revised version can meet the journal publication requirements.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors have submitted an improved version with all of my previous concerns addressed. The paper can be accepted after a minor revision.

Eq. 6 is not correct. theta should come in the second row instead of psi

Author Response

Thank you for your time and effort to evaluate this manuscript. Sorry for this mistake, now it has been fixed. In fact, in the second row of equation (6) the correct  variable is phi (roll), and you right, the transformation between angular velocities does not depend on psi.

Reviewer 2 Report

The paper can be accepted for publication 

Author Response

We appreciate time and effort to evaluate this paper