Contributions to the Development of Tetrahedral Mobile Robots with Omnidirectional Locomotion Units
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper introduces two tetrahedral robot prototypes with omnidirectional locomotion. The first prototype exhibited challenges in stability and efficiency, prompting a redesign. The second, improved prototype features a refined structure, enhanced material strength, and an MPU6050 orientation sensor for spatial stability. Comparative testing showed superior performance in the second prototype due to an optimized design, stable center of gravity, and improved omnidirectional mobility using Omni-Ball wheels. The paper concludes with suggestions for future enhancements, such as miniaturization, mobility upgrades, and the addition of sensors for navigation in complex environments. This paper is well-structured and well-written. Before publication, there are some questions to be solved.
1. The author mentioned “Their utility is demonstrated in a variety of applications, such as search and rescue operations, interventions in hazardous environments, medical assistance, and more.”, more state-of-the-art can be cited: DOI: 10.34133/cbsystems.0128; DOI: 10.34133/cbsystems.0096; DOI: 10.34133/cbsystems.0120.
2. What criteria or thresholds were used to determine the "optimal performance" of the second prototype in various movement tests, such as lateral movement and ramp climbing?
3. Could the authors elaborate on the material selection for the second prototype? Specifically, how do the chosen materials improve the durability and rigidity compared to the first prototype's PMMA construction?
4. In the comparative analysis, what specific design features of the Omni-Ball wheels contributed to improved contact with the ground surface, and how did this impact the robot's movement efficiency and control?
5. The authors mention the potential integration of lighting and video systems. Could they specify how these additions might affect the robot's weight distribution and power requirements, and what adjustments would be needed to accommodate these changes?
6. For future research directions, could the authors clarify the challenges they foresee in miniaturizing the robot while maintaining its functionality, and what strategies are planned to address them?
Author Response
Point 1: The author mentioned “Their utility is demonstrated in a variety of applications, such as search and rescue operations, interventions in hazardous environments, medical assistance, and more.”, more state-of-the-art can be cited: DOI: 10.34133/cbsystems.0128; DOI: 10.34133/cbsystems.0096; DOI: 10.34133/cbsystems.0120.
Answer 1: Thank you for the recommendations.
We have analyzed these materials, and the references [1], [2], [3] have been added to the paper. (line 30)
Point 2: What criteria or thresholds were used to determine the "optimal performance" of the second prototype in various movement tests, such as lateral movement and ramp climbing?
Answer 2: Thank you for your question.
The paper focused on improving the second prototype from multiple perspectives, such as a more robust structure, an enhanced design, and most importantly, the integration of the MPU 6050 sensor, which enables the robot to move even in the event of rolling over.
However, in terms of movement performance, considering the travel velocity, it slightly favors the second prototype. Additionally, the functionality, rigidity, and design of the second prototype are significantly superior.
Point 3: Could the authors elaborate on the material selection for the second prototype? Specifically, how do the chosen materials improve the durability and rigidity compared to the first prototype's PMMA construction?
Answer 3: We appreciate your question. The lines 348-352 have been added to the paper in response to your question.
“Compared to PMMA, PMA is much more durable and resistant to rigid mechanical clamping conditions. While PMMA can break or crack when subjected to mechanical stress or rigid clamping, PMA enables durable mechanical clamping without the risk of cracking, thanks to its greater rigidity and improved structure. Therefore, PMA is much better suited for applications requiring mechanical strength and long-term durability.”
Point 4: In the comparative analysis, what specific design features of the Omni-Ball wheels contributed to improved contact with the ground surface, and how did this impact the robot's movement efficiency and control?
Answer 4: Thank you for this question, which highlights an extremely complex issue. The lines 363-365 have been added, and lines 371-375 have been replaced.
“Considering the two locomotion units developed, the first unit has a complex structure, and due to the discontinuous contact during movement (caused by the gaps between the rollers), it may introduce vibrations.” (lines 363-365 have been added)
Lines 356-358 have been replaced with: “Regarding the Omni-Ball units, the specific design characteristic is their spherical shape. This contributes to improving contact with the locomotion surface by ensuring that they maintain constant contact with the surface, regardless of the rotation position.
Thus, this unit provides a stable and continuous contact surface, which enhances the robot's motion control .”
However, we are focused on improving the existing locomotion units and, if necessary, developing new ones.
Point 5: The authors mention the potential integration of lighting and video systems. Could they specify how these additions might affect the robot's weight distribution and power requirements, and what adjustments would be needed to accommodate these changes?
Answer 5: Thank you for your question. The lines 442-452 have been added.
“The addition of lighting systems and video cameras can affect the weight distribution and increase the robot's power requirements, necessitating adjustments to maintain balance and energy efficiency. Since the balance of a tetrahedral robot is crucial for stability and efficient movement, careful placement of the new components within the robot is proposed to prevent imbalance and achieve optimal counterbalancing of the entire system.
Regarding power requirements, the new lighting equipment and video cameras impose additional energy consumption. The proposed solutions include using a higher-capacity battery capable of supporting the entire system, thus optimizing energy reserves, and implementing intelligent management of the lighting and video systems, activating them only when necessary.”
Point 6: For future research directions, could the authors clarify the challenges they foresee in miniaturizing the robot while maintaining its functionality, and what strategies are planned to address them?
Answer 6: Thank you for your suggestions and the question you raised. The lines 428-436 have been added according to your suggestions.
“Reducing the structural dimensions of the robot is a major challenge that can be addressed by using new materials, such as carbon fiber or lightweight metal alloys. These materials reduce weight while ensuring increased strength for the robot's structure.
Another challenge involves the miniaturization of electronic components. This can be achieved by selecting smaller microcontrollers or by consolidating the circuitry into a single compact unit.
Regarding power supply, the solution is to use lithium-polymer batteries, which are characterized by high energy density while having reduced size and weight, making them ideal for this type of application.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors present a reasonable and clear description of the development of the 2 prototype tetrahedral robots. There is more detail than needed in some areas (such as inclusion of pictures of the printing of components for the second model), and limited detail in others (comprehensive testing of the performance of the prototypes).
I would recommend the following revisions.
- Create a detailed objective set of performance metrics to use for all models / prototypes and collect sufficient data to show significant differences in device performance.
- Do not present subjective comparison of potential design as part of the paper. It lacks rigor and is of little interest to the reader (this is just my opinion, others may disagree).
- Identify specific applications for the tetrahedral robots you are developing. As mentioned in the literature a lot of different robot configuration exist. Development of the metrics of performance in alignment with the desired tasks is critical.
Author Response
Point 1: Create a detailed objective set of performance metrics to use for all models / prototypes and collect sufficient data to show significant differences in device performance.
Answer 2: Thank you very much for your suggestion. In this regard, the paper mentions (lines 369-392):
„To correctly analyze the two prototypes, the authors use metrics that allow for an objective comparison [25], [26], [27].
In this context, we use the existing information to evaluate the metrics associated with the two tetrahedral robot prototypes with omnidirectional locomotion units.
The first relevant metric in comparing the two robots is structural stability. In this regard, the symmetrical distribution of weight is a crucial factor for the tetrahedral structure. The electronic components of the first prototype are concentrated on a central board located at the center of the robot's body, which may cause instability, while the second prototype has the electronic components distributed across all faces of the robot's body, helping to maintain its stability.
The second relevant metric for the two prototypes concerns energy consumption. The addition of the MPU 6050 orientation sensor in the second prototype contributes to the efficient operation of the locomotion units. The first prototype, lacking this sensor, has deficiencies in this regard, as all four locomotion units at the pyramid's tips are active simultaneously during movement, resulting in higher energy consumption.
In contrast, after integrating the sensor into the second prototype, the robot gains the ability to detect orientation, so only the three locomotion units at the base of the robot are activated, automatically reducing energy consumption.
The last metric used in the comparison of these robots is maneuverability.
The omni-ball locomotion unit used in the second prototype represents a superior solution in terms of maneuverability, featuring a design that allows the robot to move easily in any direction without interrupting contact with the locomotion surface.
The double universal locomotion unit used in the first prototype is based on rollers and may cause vibrations during operation due to the gaps between the rollers.”
Point 2: Do not present subjective comparison of potential design as part of the paper. It lacks rigor and is of little interest to the reader (this is just my opinion, others may disagree).
Answer 2: Thank you for your observation and the feedback provided.
Indeed, the main goal of the paper is to analyze in detail the characteristics of the two prototypes, and the comparisons included are meant to highlight the differences and advantages of each solution.
We believe that these comparisons are important to provide the reader with a complete understanding of the impact of each approach, which is why we have also included models in the paper that are part of the modeling process, even though they were not ultimately realized.
Point 3: Identify specific applications for the tetrahedral robots you are developing. As mentioned in the literature a lot of different robot configuration exist. Development of the metrics of performance in alignment with the desired tasks is critical.
Answer 3: Thank you for the feedback provided. According to your suggestions, lines 39-45 have been added.
“Tetrahedral robots with omnidirectional locomotion units are designed specifically for applications in areas where the risk of rolling exists. Due to their symmetrical structure, they achieve a stable position even in the event of falls and rolls.
The robots proposed by the authors will be able to perform inspections/surveillance in both enclosed and open spaces and will transmit information to the human operator. (For example, surveillance inside museums, building inspections, monitoring spaces with potential degradation risks, etc.)”
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper is ready for publication.
