Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript proposes a composite anti-disturbance control method for CMG gimbal servo systems, combining an adaptive proportional-integral-resonant controller and an adaptive extended state observer. The topic is relevant and the manuscript includes both simulation and experimental validation. However, several important issues should be addressed before the manuscript can be considered for publication.

 

• Section 3 is titled “PIR-ESO Controller”, but Figure 2 and the surrounding text already present the APIR-AESO scheme. The manuscript should clarify more explicitly whether Figure 2 corresponds to the basic controller or the final improved controller, and how the derivation of PIR-ESO relates to APIR-AESO.

 

• The manuscript classifies the disturbance due to the isolator together with rotor imbalance as a fixed-period disturbance handled by the resonant controller. However, the isolator disturbance is also described as being excited during transient operation. The authors should better justify why it can be treated as a fixed-period disturbance in the proposed framework.

 

• The manuscript does not demonstrate that the baseline PIR has been comparably and fairly tuned. Therefore, it is difficult to determine to what extent the reported improvement comes from the adaptive mechanism itself rather than from favorable parameter selection.

 

• In addition to linear ESO-based ADRC, the nonlinear ESO-based ADRC has been extensively studied. The authors should review some of the latest developments, including 10.3390/act13070233 and 10.3390/act14100503, in the introduction section.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. Figures 3 and 4 are not sufficiently clearly labeled. The axes (both x and y) are not properly defined. On the horizontal axis, the notation e_ω should be explicitly introduced to clearly link the relative error to Equation (37). On the vertical axis of Figure 3, the quantity “Gain” should be associated with its corresponding notation. For Figure 4, the vertical axis (“Bandwidth”) should include its physical units (e.g., rad/s).

2. The authors should justify why ESO-based methods are preferred over other observer-based approaches, such as Kalman filtering (including adaptive Kalman methods), particularly in terms of robustness, computational complexity, and noise sensitivity.

3. The adaptive mechanisms introduced in the controller and observer may increase the overall system complexity and require additional tuning. A more detailed discussion on these aspects would improve the clarity and practical applicability of the proposed approach.
4. The manuscript does not explicitly discuss the limitations of the proposed APIR–AESO control strategy. It would be important to clarify under which conditions the method may degrade, as this affects its practical applicability.
5. The manuscript evaluates performance mainly through time-domain characteristics (e.g., settling time and overshoot), but lacks a quantitative analysis of the dynamic tracking error. Including metrics such as maximum error, RMS error, or integral criteria (IAE, ISE) would provide a more complete assessment under transient and disturbance conditions.

6. The manuscript presents a Lyapunov-based stability analysis assuming fixed observer parameters. However, the proposed AESO introduces time-varying adaptation, and it is unclear whether the stability proof remains valid. The authors should clarify whether the Lyapunov function and its derivative hold in the adaptive case, or provide additional justification of stability.

7. The novelty of the proposed APIR–AESO approach is not sufficiently clarified. The authors should clearly highlight the key contribution and distinguish it from existing methods, possibly by expanding the conclusion.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1.The conclusion section should be expanded with more detailed discussion, including clearer practical applications of the findings and a well‑defined outline of potential future research directions.

2.How valid are these assumptions in practical implementations, especially under broadband disturbances or when frequency components are closely spaced?

3.How sensitive is the system performance to deviations in these gain values, and is there a systematic tuning method to ensure robustness against parameter uncertainties?

4. justify the choice of a fixed phase margin, and how does the proposed compensation method perform under varying system delays or unmodeled dynamics?

5.The manuscript would benefit from citing relevant literature on PID-based speed and position control. For instance, the study “Position control and performance analysis of hydraulic system using two pump-controlling strategies” provides useful insights into PID control performance and could strengthen the discussion and comparison of control strategies.

5. How were the specific damping ratios (ζ1=0.01\zeta_1 = 0.01ζ1​=0.01, ζ2=0.07\zeta_2 = 0.07ζ2​=0.07) selected, and is there an analytical or optimization-based approach to balance this trade-off?

6. What is the rationale behind using the product of these metrics as a comprehensive index, and are there alternative multi-objective evaluation methods that could provide a more balanced assessment?

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed the reviewer’s comments and the manuscript has been improved. I have no further comments.