Flight Tracking Control for Helicopter Attitude and Altitude Systems Using Output Feedback Method under Full State Constraints
, Yulong Huang 1,†, Dongping Li 3,*, Yuan Sun 4,*, Han Liu 1 and Yongze Jin 1
Round 1
Reviewer 1 Report
This paper presents an output feedback control scheme for the altitude and attitude system of the unmanned helicopter, wherein full-state constraint issues are addressed by employing BLF method in the framework of backstepping control. Overall, this paper is well-organized, and some suggestions are as follows:
1. There are some typos in the current manuscript. Please double check the whole paper to improve the English.
2. The expression in the paper are not unified, for example: $f_1(x_1(t))$ in Eq.(5).
3. In line 103, the yawing inertia moment should be $J_{zz}$, there is a symbolic error here.
4. Some punctuations should be consistent throughout the text, for example, the end of Eqs.(12), (15) and (16) have no punctuation “.”, which are different with others.
5. Moreover, some future works should be further showcased using the techniques developed in the manuscript.
I have no more comments. It can be accepted.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Title: Flight Tracking Control for Helicopter Attitude and Altitude Systems Using Output Feedback Method under Full State Constraints
11 The authors proposed an output feedback flight tracking control scheme for small-scale helicopter 1attitude and altitude systems with
22 The authors claim to construct a state observer based on the measured output signals, which seems wrong, it is based on the error between the actual states and the estimated states.
Comments to the authors:
11 More clarification about the type of the observer as explained in the introduction above. See Equations 5, 6, and 7. The state observer usually depends on the output and the control signal. Only the estimated error depends on the output.
2.2 The mathematical model given in Equations (1) and (2) describes the motion of the helicopter in the z-direction only (i.e. take off vertically). I cannot see the motion in the x and y directions. Any explanations?
33 In the inequality before equation (20), the symbol appeared, but not defined or explained before.
44 In the inequality before inequality (25), M1I and M2I are not defined, nor the term containing them explained how it is derived. The values of M1 and M2 are not given in the simulation section.
55 In the results, it is strange to obtain L1 and L2 be diagonal. Could the authors have explained why?
66 The authors should include the values of all matrices and parameters mentioned in Theorem 1.
77 There are many works on Unmanned Ariel vehicle (UAV), the authors are required to add a paragraph explaining the differences between them and the small-scale helicopter.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Previous Revision Comment: “In the results, it is strange to obtain L1 and L2 be diagonal. Could the authors have explained why?”
Authors’ Response: Thanks for your comments. Theorem 1 of this paper is a sufficient condition to design the state observer and flight controller. Indeed, L1 and L2 are the gains of state observer, which have been proved to satisfy the conditions of Theorem 1. Yes, normally, the solvable matrices of Theorem 1 are non-diagonal. While, in order to guarantee the conciseness of the observer gains and well control performance of closed-loop systems, we choose L1 and L2 are the diagonal matrices
Here, the authors are saying in their previous response they “choose” L1 and L2, while in the paper they wrote “, …the state observation gain matrices are obtained as:”. They should write “we choosed” instead of “obtained”.
Author Response
Thanks for your comments. We have amended “the state observation gain matrices are obtained as” as “the state observation gain matrices are chosen as” under the line 186 in the present version according to your suggestions.
