Model-Based Design and Testbed for CubeSat Attitude Determination and Control System with Magnetic Actuation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The purpose of this research work is a model-based framework designed for the verification and validation of Attitude Determination and Control Systems in nanosatellites.

The topic is relevant and original. In introduction the authors evidenced the wide variety of available testbeds and considering the technical and economic advantages of using techniques such as: Model-in-the-Loop, Software-in- the-Loop, Processor-in-the-Loop, and Hardware-in-the-Loop.

The authors made a good introduction concerning, for i.e., the CubeSats, small satellites with their diverse applications, the low-cost techniques such as Software-in-the-Loop, Processor-in-the-Loop, and Model-in-the-Loop that have been developed. Then they highlight the research contribution for nanosatellite developers that, depending on their requirements and verification objectives.

In section 2 the utilized mathematical methods for both attitude estimation and control were described.

For attitude and orbit dynamics was described and deduced the mathematical model taking in consideration the following torques: the interaction of the forces of gravity and the CubeSat body; the aerodynamic force produced by drag; the interaction between a magnetic dipole and a magnetic field.

For attitude determination algorithm a method was developed for both sunlight and eclipse zones. Then, in order to maintain safety conditions and reach good initial conditions to apply the nadir controller, detumbling control was applied.

In Simulation environment and approaches section were presented the research work concerning: the model-in-the-loop used (sun sensor model, magnetorquer model), software-in-the-loop (SIL simulations were executed and evaluated using the Monte Carlo analysis), software and hardware configuration for Processor-in-the-Loop and Hardware-in-the-Loop

The results section, based on the proposed methodology, the specific roles of the different approaches and the results obtained were described. Additionally, the contribution of each approach was detailed according to its specific contribution.

The analysis of the obtained results is clearly and comprehensively presented.

In conclusions ‘section the authors emphasise their contributions and future possible applications.

The references are appropriate and recent.

Final recommendation:

The subject is well within the scope of the journal, and the paper fulfils all the requirements to be published.

Author Response

The purpose of this research work is a model-based framework designed for the verification and validation of Attitude Determination and Control Systems in nanosatellites.

The topic is relevant and original. In introduction the authors evidenced the wide variety of available testbeds and considering the technical and economic advantages of using techniques such as: Model-in-the-Loop, Software-in- the-Loop, Processor-in-the-Loop, and Hardware-in-the-Loop.

The authors made a good introduction concerning, for i.e., the CubeSats, small satellites with their diverse applications, the low-cost techniques such as Software-in-the-Loop, Processor-in-the-Loop, and Model-in-the-Loop that have been developed. Then they highlight the research contribution for nanosatellite developers that, depending on their requirements and verification objectives.

In section 2 the utilized mathematical methods for both attitude estimation and control were described.

For attitude and orbit dynamics was described and deduced the mathematical model taking in consideration the following torques: the interaction of the forces of gravity and the CubeSat body; the aerodynamic force produced by drag; the interaction between a magnetic dipole and a magnetic field.

For attitude determination algorithm a method was developed for both sunlight and eclipse zones. Then, in order to maintain safety conditions and reach good initial conditions to apply the nadir controller, detumbling control was applied.

In Simulation environment and approaches section were presented the research work concerning: the model-in-the-loop used (sun sensor model, magnetorquer model), software-in-the-loop (SIL simulations were executed and evaluated using the Monte Carlo analysis), software and hardware configuration for Processor-in-the-Loop and Hardware-in-the-Loop

The results section, based on the proposed methodology, the specific roles of the different approaches and the results obtained were described. Additionally, the contribution of each approach was detailed according to its specific contribution.

The analysis of the obtained results is clearly and comprehensively presented.

In conclusions ‘section the authors emphasize their contributions and future possible applications.

The references are appropriate and recent.

Final recommendation:

The subject is well within the scope of the journal, and the paper fulfils all the requirements to be published.

Reviewer 2 Report

Comments and Suggestions for Authors

This paper presents a comprehensive framework for the verification and validation (V&V) of Attitude Determination and Control Systems (ADCS) in nanosatellites using magnetic actuation. Employing a variety of methodologies like Model-in-the-Loop (MIL), Software-in-the-Loop (SIL), Processor-in-the-Loop (PIL), and Hardware-in-the-Loop (HIL), the authors offer a systematic approach to testing and validation. The paper is detailed and well-structured, demonstrating a good understanding of CubeSat ADCS and the challenges associated with their validation.

 

The inclusion of Monte Carlo simulations to optimize control gains and the use of comprehensive sensor suites, including sun sensors, magnetometers, and gyroscopes, are particularly impressive.

 

However, there are areas that could benefit from further enhancement.

1. The introduction should include recent advances and uses of CubeSats in fields such as interferometry and Quantum Internet, consider reviewing references such as

i) "Celestial bodies far-range detection with deep-space CubeSats." Sensors 23.9 (2023): 4544.

ii) "The quantum internet: A synergy of quantum information technologies and 6G networks." IET Quantum Communication 4.4 (2023): 147-166.

iii) "Quantum cryptography—A simplified undergraduate experiment and simulation." Physics 4.1 (2022): 104-123.

iv) "Quantum gas mixtures and dual-species atom interferometry in space." Nature 623.7987 (2023): 502-508.

  

2. Captions in figures 1, 2, 3, 4, 7, 8, 10, 11 need to explain the process and include a definition of all the elements presented.

 

3. In line 385, What specific steps should be taken to ensure that both Simulink and STM32 Cube IDE are properly configured to use the ISO C99 standard in the code generation workflow?

 

4. In line 739, What are the main advantages of using a sequential approach in the simulation environments for ADCS verification and validation, according to the conclusions of the article?

 

5. In general, some of the technical details and assumptions made in the simulations, particularly in the Monte Carlo simulations, could be further elaborated. Can you provide more insight into the selection of parameters and their impact on the simulation results?

 

 

Comments on the Quality of English Language

Minor spell check.

Author Response

This paper presents a comprehensive framework for the verification and validation (V&V) of Attitude Determination and Control Systems (ADCS) in nanosatellites using magnetic actuation. Employing a variety of methodologies like Model-in-the-Loop (MIL), Software-in-the-Loop (SIL), Processor-in-the-Loop (PIL), and Hardware-in-the-Loop (HIL), the authors offer a systematic approach to testing and validation. The paper is detailed and well-structured, demonstrating a good understanding of CubeSat ADCS and the challenges associated with their validation.

 

The inclusion of Monte Carlo simulations to optimize control gains and the use of comprehensive sensor suites, including sun sensors, magnetometers, and gyroscopes, are particularly impressive.

 

However, there are areas that could benefit from further enhancement.

Comment 1: The introduction should include recent advances and uses of CubeSats in fields such as interferometry and Quantum Internet, consider reviewing references such as

i) "Celestial bodies far-range detection with deep-space CubeSats." Sensors 23.9 (2023): 4544.

ii) "The quantum internet: A synergy of quantum information technologies and 6G networks." IET Quantum Communication 4.4 (2023): 147-166.

iii) "Quantum cryptography—A simplified undergraduate experiment and simulation." Physics 4.1 (2022): 104-123.

iv) "Quantum gas mixtures and dual-species atom interferometry in space." Nature 623.7987 (2023): 502-508.

Response 1: The information from the papers "Celestial bodies far-range detection with deep-space CubeSats" and “The quantum internet: A synergy of quantum information technologies and 6G networks” were added to the introduction as a proof of CubeSat’s versatility for integrating advanced technologies.

Comment 2: Captions in figures 1, 2, 3, 4, 7, 8, 10, 11 need to explain the process and include a definition of all the elements presented.

Response 2: Corrected. Now captions include a more detailed description and definition of all elements presented.

Comment 3: In line 385, What specific steps should be taken to ensure that both Simulink and STM32 Cube IDE are properly configured to use the ISO C99 standard in the code generation workflow?

Response 3: To ensure this configuration in Simulink, the process involved accessing "Model Settings," selecting "Code Generation," and choosing "C99 (ISO)" under "Language Standard." Activating C99 in STM32 Cube IDE required navigating through "File," then "Properties," selecting "C/C++ Build," accessing "Settings," and choosing "Toolchain Settings," with "GNU99 (ISO C99+gnu extensions)(-std=gnu99)" selected under "Language Standard".

Comment 4: In line 739, What are the main advantages of using a sequential approach in the simulation environments for ADCS verification and validation, according to the conclusions of the article?

Response 4: The sequential approach in space projects is crucial for ensuring the correct design and implementation of the project itself. Therefore, this sequence is constrained into a dynamic cycle of continuous improvements and design changes that would involve more economical and time resources. Hence, a model-based sequential approach implies the use of fewer resources for potential design changes. Additionally, the sequential approach enables the isolation and differentiation of errors generated during the sequential system integration and development, such as errors in mathematical modeling, physical implementation of sensors, or computational limitations of the controllers.  

Comment 5: In general, some of the technical details and assumptions made in the simulations, particularly in the Monte Carlo simulations, could be further elaborated. Can you provide more insight into the selection of parameters and their impact on the simulation results?

Response 5: To clarify the technical details about the Monte Carlo simulation, Table 4 and 5  were included to specify the variation parameters for each test. Additionally, a more detailed explanation of the insights and impacts of varying each parameter is provided in the results and discussion sections.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents a robust model-based framework integrating MIL, SIL, PIL, and HIL methodologies. This comprehensive approach allows for thorough verification and validation of the ADCS, which is crucial for ensuring the reliability of CubeSat missions. The authors have meticulously detailed the simulation environments, including the use of various sensors and the integration of astrodynamics perturbations. This enhances the fidelity of the simulations, making the results more reliable and applicable to real-world scenarios. Also, the inclusion of Monte Carlo simulations to optimize control gains and evaluate pointing accuracy under different conditions is a notable strength. I like this paper, but here are a couple of general comments and suggestions.

1.         While detailed modeling is a strength, it also introduces complexity. Is it possible for the author to simplify some aspects without losing significant accuracy? It could make the framework more accessible to a broader range of researchers and practitioners.

2.         The paper focuses on a 1U CubeSat. It would be beneficial to discuss how the proposed methodologies and models can be scaled to larger CubeSat platforms since it provides larger volume and potential mass capacity for more complex instruments and payloads.

3.         Is there any possibility of comparing it with other methods? Including a comparative analysis with other existing ADCS verification and validation methods could provide a clearer context of the advantages and limitations of the proposed framework.

Author Response

The paper presents a robust model-based framework integrating MIL, SIL, PIL, and HIL methodologies. This comprehensive approach allows for thorough verification and validation of the ADCS, which is crucial for ensuring the reliability of CubeSat missions. The authors have meticulously detailed the simulation environments, including the use of various sensors and the integration of astrodynamics perturbations. This enhances the fidelity of the simulations, making the results more reliable and applicable to real-world scenarios. Also, the inclusion of Monte Carlo simulations to optimize control gains and evaluate pointing accuracy under different conditions is a notable strength. I like this paper, but here are a couple of general comments and suggestions.

Comment 1: While detailed modeling is a strength, it also introduces complexity. Is it possible for the author to simplify some aspects without losing significant accuracy? It could make the framework more accessible to a broader range of researchers and practitioners.

Response 1: Previous works in the literature have already implemented simplified modeling processes for both attitude/orbit mathematical models and actuator/sensor models. Our approach seeks to include as many relevant models as possible that were not considered in previous studies. For instance, we integrate the electronic behavior of magnetorquers and sun sensors. These models are challenging to simulate, but utilizing Simscape/Simulink features, which is a graphical modeling environment, has considerably simplified the modeling process without requiring the quantification of overly complex circuit models. Although Simulink provides some libraries to facilitate the modeling process (e.g., World Magnetic Model), other models, such as sun vector behavior (for which we use the DE405 model), may require a custom model. One significant way to simplify the modeling process may be by restricting the testbed’s verification and validation features. For instance, neglecting the attitude estimation measurements could eliminate the need for the DE405 model.

Comment 2: The paper focuses on a 1U CubeSat. It would be beneficial to discuss how the proposed methodologies and models can be scaled to larger CubeSat platforms since it provides larger volume and potential mass capacity for more complex instruments and payloads.

Response 2:  In principle, the proposed framework is applicable for the validation of any control system that includes a magnetometer as an attitude sensor. Moreover, the scalable potential of this framework allows its adaptation to validate systems of higher volume and complexity due to the modularity and flexibility of the proposed system, allowing developers to include in the simulation the dynamics of the analyzed spacecraft and mathematical models of sensors or actuators, or even to physically implement other sensors, which also involves modifying the controlled environment to obtain reliable results. In addition, the versatility of the proposed approach provides the necessary tools to implement code generation using SIL and PIL in embedded systems with low computational resources, assuming that the sensor readings are performed directly by the controller and considering the restrictions discussed in the  “Software In The Loop” section, such as the alignment of sampling times between the simulation and the controller, as well as that the controller board supports C99 (ISO), to ensure the consistency of the model and its corresponding code.

Comment 3: Is there any possibility of comparing it with other methods? Including a comparative analysis with other existing ADCS verification and validation methods could provide a clearer context of the advantages and limitations of the proposed framework.

Response 3: Currently, the advantages and limitations of the proposed framework are primarily highlighted in the discussion and conclusion sections. Implementing comparisons with other methods may be difficult to replicate, as discussed in the introduction section, because the mathematical models for the space environment and the software-hardware facilities vary considerably across different testbeds. Moreover, our proposed framework for magnetic control verification attempts to encompass all previous model-based verification methods, allowing for a more systematic approach from Model-in-the-Loop to Hardware-in-the-Loop.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have made substantial improvements to the manuscript. These revisions significantly enhance the clarity and relevance of the work. Therefore, I support the acceptance of this article for publication.