Research on the Jet Distance Enhancement Device for Blueberry Harvesting Robots Based on the Dual-Ring Model

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript designs a jet separation device tailored to the densely packed nature of blueberry fruits. It combines finite element technology for fluid simulation analysis and conducts practical experiments for validation. However, the manuscript mainly focuses on the selection of structures, lacking in-depth research on aspects such as structural design, which needs to be further strengthened.

1. The abstract needs to highlight the experimental results. Please rewrite the abstract.
2. Equations should be edited in italics.
3. Figure 1, the overall structural diagram, should not be placed in the introduction. Moreover, the introduction of this section is too brief and needs to be expanded with multi-angle graphics for a detailed explanation.
4. There is an error in the correspondence of the nozzle structure in Figure 3b. Please correct it.
5. The paper should use simulation technology to optimize the nozzle structure and parameters such as the number of holes. The existing nozzle structure may not meet the technical requirements, so it is recommended to add content on structural design and optimization.
6. The grid structure in the simulation experiment needs further optimization.
7. The results of the simulation experiment should be compared and deeply analyzed with the actual experimental results. Please strengthen this part.
8. When the paper uses airflow to conduct separation tests on blueberries, whether the separation effect will be affected by the obstruction of other objects needs to be thoroughly explained.

Comments on the Quality of English Language

The English language needs polishing.

Author Response

Response to Reviewer 1 Comments

Dear reviewer：

Thank you for taking the time to thoroughly review this paper and provide valuable suggestions. Your professional insights and constructive feedback have helped us further improve the quality and rigor of the article. We have carefully considered all your suggestions and made the necessary revisions. We sincerely appreciate the time and effort you have dedicated to this review! Here are our responses to your comments and questions.

Comments 1: The abstract needs to highlight the experimental results. Please rewrite the abstract.

Response 1: Thank you very much for your valuable feedback, which has greatly helped us in our work. As you pointed out, our abstract lacked a clear emphasis on the experimental results. Following your suggestion, we have revised the content. The specific change was made on page 1, lines 25-28.

The original text was: [Finally, field experiments confirmed the effectiveness of separating clusters under different interference conditions.].

The revised text is: [The final field experiments show that the mean distance for Type I (mature fruit) is 5.41 mm, for Type II (red fruit) is 6.42 mm, and for Type III (green fruit) is 5.43 mm. The short, curved stems of the green fruit are less effective, but the minimum distance of 4.71 mm is greater than the claw wall thickness, meeting the design requirements.].

Comments 2: Equations should be edited in italics.

Response 2: Thank you very much for pointing out the issue. The formatting problem with the equations was an oversight on our part, and we apologize for this. We have made the necessary revisions according to your feedback. All equations have been re-edited in italics, and the font size of the equations has been standardized to match the characters in the text. The specific locations of the equations are as follows: page 6, line 179; page 7, line 212; page 8, lines 247-262; and page 15, lines 443-452.

Comments 3: Figure 1, the overall structural diagram, should not be placed in the introduction. Moreover, the introduction of this section is too brief and needs to be expanded with multi-angle graphics for a detailed explanation.

Response 3: Thank you very much for your questions. This paper focuses on the research of the air jet device, so the content of other modules was not particularly emphasized. The overall structural diagram was placed in the introduction to explain the specific functions and workflow of the module studied in this research. Following your suggestions, we have adjusted the structure of the paper. We added a " Designing scheme " section in Chapter 2, where the overall structural diagram and related workflow are now described. Additionally, since the research content of other modules is currently being submitted for publication, we did not provide much detail on those areas in this paper. The added section and workflow description can be found on page 3, lines 107-128.

The specific content introduced is as follows: [As shown in Figure 1, the blueberry-picking robot must complete five basic actions in sequence during each picking cycle: identification, positioning, air jetting, gripping, and separation. First, the recognition device identifies the mature fruit and determines the picking target's location, issuing the corresponding commands. The recognition system assesses the pre-grip force based on the maturity and external characteristics of the fruit to prevent damaging the fruit during gripping. Next, it checks for the presence of interfering fruits; if any are detected, the air jet device separates them from the target fruit. Then, the system determines the spatial position of the picking target by identifying its X, Y, and Z coordinates. The control system moves the robotic arm to the working area, where the air jet device operates to separate the target fruit from interfering fruits. The mechanical claw grips the target fruit, and the end effector's linkage mechanism then separates the fruit from its stem. Finally, the robotic arm follows an optimized path to place and store the blueberries. Since this study's primary goal is to provide an air-jetting solution for separating clustered fruits (using specially designed nozzles to apply high-speed jets to the fruit cluster, allowing accurate separation and enabling the mechanical claw to reach in), the specific functions of other modules are not discussed. Additionally, major components of the air jet device, such as the air compressor and regulating valves, are installed within the chassis of the picking robot, while the nozzle is connected to the robot's small arm.].

Comments 4: There is an error in the correspondence of the nozzle structure in Figure 3b. Please correct it.

Response 4: Thank you very much for identifying the issue in our article. The incorrect correspondence in the structure was due to our oversight when creating the figure. We have corrected this part. The specific location of the figure is on page 5, line 157.

Comments 5: The paper should use simulation technology to optimize the nozzle structure and parameters such as the number of holes. The existing nozzle structure may not meet the technical requirements, so it is recommended to add content on structural design and optimization.

Response 5: Thank you very much for your questions and suggestions. Most commonly used nozzles are single-hole designs, such as columnar nozzles, conical columnar nozzles, and fan nozzles. These nozzle structures do not meet the needs of our research, so multi-hole nozzles are the focus of our design, research, and application. Based on the recommendations from manufacturers, we studied flat-head and round multi-hole designs. The goal is to create a fluid with a dual-ring working area: a strong-force region for dispersing interfering fruits and a weak-force region to create a gap that allows the mechanical claw to reach in. I have also added content to the paper regarding this topic. The additional text can be found on page 4, lines 147-152.

The added content is: [This study aims to effectively separate the target fruit from the interfering fruit and to design dual-ring working area as described earlier. Commonly used single-hole nozzles (cylindrical or conical) do not meet our requirements. Therefore, we have chosen multi-hole nozzles for this study. Considering the difficulty of manufacturing and the need to achieve the dual-ring working area, we focused on studying and applying standard flat-tip and round-tip nozzles.].

Comments 6: The grid structure in the simulation experiment needs further optimization.

Response 6: Thank you for raising this question. The nozzle model used in the simulation analysis is the model constructed in Section 2.1.3. The mesh structure is also described in this section. The fruit model is imported through the fluid-solid coupling module, and the mesh structure is divided within this module. The fruit model has an indented thick pancake shape, which is irregular and has significant curvature changes at the edges. Therefore, we chose an unstructured mesh, which provides high resolution near wall surfaces and shear layers but requires more memory and has a slower computation speed. We believe that computation speed and memory usage are not obstacles to our design. In terms of the mesh, this type of mesh has a random direction and size distribution, which is not advantageous for fluid domains. However, in fluid-solid coupling, this unstructured mesh has advantages for the solid domain (the force exerted by the fluid on the solid surface). It allows better boundary resolution and, under the same conditions, is smaller and more numerous than other mesh types, resulting in better distribution of external forces. In the fluid-solid coupling analysis of the fruit model, we used this unstructured mesh. Additionally, the main variable area in our study is the fruit stem, so we use a smaller mesh structure in this region. The mesh is slightly larger on the windward side, while the mesh inside the fruit, including the skin and flesh, is smaller due to issues like viscosity. We also use a higher-order differential scheme for greater accuracy. Additional explanations have been included in the paper. The supplementary text can be found on page 15, lines 467-471.

The added content is: [The fruit model is imported through the fluid-solid coupling module and uses an unstructured mesh method. This approach has advantages in fluid-solid coupling for the solid domain (force exerted by the fluid on the solid surface). Smaller and more numerous meshes allow for better resolution of boundaries and analysis of external fluid forces].

Comments 7: The results of the simulation experiment should be compared and deeply analyzed with the actual experimental results. Please strengthen this part.

Response 7: Thank you for your questions and comments. In the comparison of the two results in the paper, we only calculated the error magnitude without a detailed analysis. Based on your suggestion, we have made revisions and additions, including the error analysis and influencing factors. The additional text is located on page 17, lines 525-530.

The added content is: [With forward air jetting on the target fruit, the side fruit spacing is approximately 5.08 mm. A 0.3 mm error, corresponding to a relative error of 5.9%, arises due to differences between the real blueberry cluster and the simulation. This error is caused by discrepancies in fruit size, stem length, and simulation settings, as well as the fruit's orientation in actual conditions. Despite the errors, the overall results still meet the requirements for the mechanical claw to reach in.].

Comments 8: When the paper uses airflow to conduct separation tests on blueberries, whether the separation effect will be affected by the obstruction of other objects need to be thoroughly explained.

Response 8: Thank you for your questions and comments. In our experiments, branches and leaves do not have a significant impact. With this strong and weak zone design, the diameter of the dual-ring model ensures that the fruit does not come into direct contact with surrounding objects. Additionally, in 30 subsequent experiments, we observe that the contact and compression between surrounding fruits have minimal effect on the separation process.

Thank you again for your thorough review of our manuscript and for providing your valuable feedback. Your guidance and suggestions have greatly helped us improve our work and writing skills. We are very grateful for your hard work and professional expertise.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents a study on a jet device designed to enhance the picking efficiency of a blueberry-picking robot. The proposed device aims to improve the operational space for mechanical claws by using a jetting mechanism to separate fruit clusters. The research is interesting and significant; however, several issues need to be addressed:

1.Ensure that Table 5 is formatted correctly, as its current layout may cause confusion.

2.For the type of simulation, I'm not sure an ANSYS fluent or CFX could answer these questions. The fouling cannot be studied, maybe with a meshless software.

3.The accuracy of the simulation results can be significantly affected by the refinement of the mesh. Did you perform a mesh independence study? This is a critical step that must be included to validate the simulation results.

4.To further elaborate on the simulation analysis conditions, it is crucial to indicate whether a transient analysis or a steady-state analysis was performed.

5.The manuscript mentions the jetting step, which could be influenced by various factors. Besides the orientation of the fruit, what other environmental factors (e.g., wind speed, temperature, humidity) might significantly affect the effectiveness of spray separation? How can these factors be modeled and experimentally validated to design a more comprehensive spray separation system?

6.In the experimental validation section of the manuscript, it is recommended to include images of the experimental setup, including the test apparatus and the nozzle installation angles. This will help readers better understand the experimental design and procedures.

7.The conclusion section repeats the same or similar results multiple times. For example, several points describe the effectiveness of the jet device in separating blueberry clusters. While these points are approached from different angles, the core result remains the same. Consider consolidating these to avoid redundancy.

8.The text in Figure 1 is too small to be legible, which is a common issue in other figures as well. These need to be corrected to improve the manuscript’s overall clarity.

Author Response

Response to Reviewer 2 Comments

Dear reviewer：

Thank you for taking the time to thoroughly review this paper and provide valuable suggestions. Your professional insights and constructive feedback have helped us further improve the quality and rigor of the article. We have carefully considered all your suggestions and made the necessary revisions. We sincerely appreciate the time and effort you have dedicated to this review! Here are our responses to your comments and questions.

Comments 1: Ensure that Table 5 is formatted correctly, as its current layout may cause confusion.

Response 1: Thank you for identifying the issues in our article. We sincerely apologize for our oversight, which led to formatting errors in the paper. We have corrected these errors based on your feedback. The specific changes were made on page 18, lines 552-553.

Comments 2: For the type of simulation, I'm not sure an ANSYS fluent or CFX could answer these questions. The fouling cannot be studied, maybe with a meshless software.

Response 2: Thank you for your questions and comments. The software used in this study is ANSYS Fluent. ANSYS Fluent features the globally renowned ICEM high-end meshing tool, known for its top-notch geometric repair and hexahedral meshing capabilities, leading all CFD pre-processing software. Additionally, it includes the highly automated Ansys-Meshing tool on the Workbench platform (Ansys-Meshing fully replaces the functions of Gambit and CFX-Mesh and now essentially integrates the tetrahedral meshing capabilities of ICEM and Fluent-Meshing). The meshing in this study was done using the Ansys-Meshing tool with Mosaic technology. Mosaic technology is the latest mesh generation technology introduced by ANSYS Fluent, allowing various mesh types to connect, including hexahedral, tetrahedral, pyramid, wedge, and polyhedral meshes, forming a conformal body mesh. The Mosaic technology enables mesh generation that fully utilizes the advantages of various mesh types, achieving fast, high-fidelity, and high-precision CFD simulations. The fluid-solid coupling analysis in this study uses the fluid-solid force analysis module within Workbench and employs an unstructured mesh for the fruit model. We used smaller mesh sizes and higher-order precision difference schemes. This unstructured mesh has advantages for the solid domain in fluid-solid coupling (the force exerted by the fluid on the solid surface). It provides good boundary resolution and, under the same conditions, is smaller and more numerous than other mesh types, resulting in better external force distribution. Our team has consistently used ANSYS Fluent and STAR CCM+ software, with mesh generation being an essential part of our research. The quality of the mesh is critical in the analysis process, as when the mesh is discontinuous or does not meet pre-processing requirements, the mesh-based solving and iteration process becomes challenging. The meshless method you mentioned can be effectively applied to address this issue, which is why it is a popular research topic in this field. Our team has also discussed this approach, and everyone agrees on the advantages of this approach. In future work, we will explore and apply meshless software and compare the advantages and disadvantages of the two methods. We also believe that more meshless methods will be integrated into commercial software to solve complex numerical simulation problems that traditional meshes find difficult to analyze.

Comments 3: The accuracy of the simulation results can be significantly affected by the refinement of the mesh. Did you perform a mesh independence study? This is a critical step that must be included to validate the simulation results.

Response 3: Thank you for your question and critique. In our study, we conducted a mesh independence analysis. However, due to space limitations in the paper, we did not elaborate on all aspects, which led to this part being overlooked. We used the Mosaic method for meshing, mainly including hexahedral, tetrahedral, pyramid, and polyhedral meshes. We analyzed and compared six setting schemes: 64,000, 75,000, 88,000, 101,000, 112,000, and 125,000, using the relative deviation between schemes as an indicator to evaluate the effect of the grid number settings. We used the results of 125,000 as a reference baseline and plotted based on the relative errors in velocity and pressure. The results show that the relative error between 112,000 and 125,000 is less than 0.5%, within an acceptable range. Therefore, we chose the 112,000 scheme to set the grid number. We have supplemented this part of the content in the paper, which can be found on page 5, lines 163-171.

Comments 4: To further elaborate on the simulation analysis conditions, it is crucial to indicate whether a transient analysis or a steady-state analysis was performed.

Response 4: Thank you for raising this question. In the paper, we provided the boundary conditions and setup parameters for the simulations, but we did not provide a more detailed analysis of the conditions and methods used. For example, the question of whether to use transient or steady-state analysis was not clarified; we used the steady-state analysis method, which was not reflected in the paper. We appreciate your suggestion and have further elaborated on these analysis conditions in the paper. The specific location of this addition is on page 6, lines 185-188.

The added content is: [The solution method used is the SIMPLE algorithm, which requires solving the pressure field through the Poisson equation and uses a steady-state solver. To ensure consistency, the same simulation conditions are applied to all structural models once they are determined.].

Comments 5: The manuscript mentions the jetting step, which could be influenced by various factors. Besides the orientation of the fruit, what other environmental factors (e.g., wind speed, temperature, humidity) might significantly affect the effectiveness of spray separation? How can these factors be modeled and experimentally validated to design a more comprehensive spray separation system?

Response 5: Thank you for your questions and comments. Regarding the impact of environmental factors, we have considered this in our study. Most blueberry varieties in northern China are rabbit-eye blueberries, typically grown in greenhouses due to climatic and growth characteristics. This was mentioned in the introduction of the paper. Under the harvesting conditions in greenhouses, there are generally no significant environmental influences. Therefore, our modeling and experimental validation did not include analysis related to environmental impacts. Since the goal of our air jet device is to achieve fruit separation, wind speed, as you mentioned, might be a crucial factor, while temperature and humidity do not affect the content of this study. Since we are targeting high-quality blueberry automatic harvesting in greenhouses, with the primary goal being the initial market release of high-quality fruit without damage, we plan to optimize our design in future research. For field applications, the stability of branches is an issue that needs to be addressed in the future. Overall, applying this system in multiple scenarios requires improving and designing a more comprehensive air-jet separation system. The specific location of this addition is on page 4, lines 131-142.

Comments 6: In the experimental validation section of the manuscript, it is recommended to include images of the experimental setup, including the test apparatus and the nozzle installation angles. This will help readers better understand the experimental design and procedures.

Response 6: Thank you very much for your questions and suggestions. In the experimental validation section, the experimental conditions we used are the same as those in the modeling simulation and theoretical analysis described in Chapter 2, including parameters such as compressor working conditions and working distance. Since we are still in the design and development phase, the nozzle installation is the same as in the Chapter 2 modeling simulation, directly aimed at the target fruit using a bracket. Due to the camera angle and the need for a clear display of the vernier caliper, not all experimental equipment was shown. We sincerely apologize for this oversight. To better understand the nozzle's working angle, we have marked the airflow direction and the target and interfering fruits in the figures.

Comments 7: The conclusion section repeats the same or similar results multiple times. For example, several points describe the effectiveness of the jet device in separating blueberry clusters. While these points are approached from different angles, the core result remains the same. Consider consolidating these to avoid redundancy.

Response 7: Thank you for pointing out the issue. As you mentioned, some redundant content appeared in our conclusions. We have revised them based on your suggestions, removing the redundant parts and merging the conclusions of the same research sections. With these changes, our conclusions are now more concise and professional. The specific changes can be found on page 20, lines 594-613.

The revised conclusions include: [

2. We established a circular model of the working end face in the spatial flow field. By designing high-pressure and low-pressure zones, we achieved functional separation of the airflow. Finite element analysis shows that the effect of air jet separation is directly related to the nozzle structure type and parameters. A solution using an 8-hole 40° round-head nozzle effectively meets the needs of dispersing clustered blueberries.

3.Fluid-solid coupling simulation indicates that the fruit's orientation significantly affects the air jet separation effect. For example, for fruit with a stem length of 15 mm, the horizontal deformation is about 1.74 mm, the total vertical deformation is approximately 9.68 mm, and the deformation at a 53° horizontal angle is about 7.12 mm, with a minimum gap of about 5.38 mm. Therefore, to achieve more accurate results, it is necessary to consider the mechanical parameters of the fruit stem and the impact of gravity. Additionally, the target fruit in the low-pressure area should be kept as horizontal as possible, and the horizontal orientation angle of the fruit in the high-pressure area should be maximized.

4.Experimental data comparison shows a 10.0% error in theoretical calculations and a 5.9% error in simulation calculations, with the fluid-solid coupling model being more accurate. These errors are due to differences in fruit size, stem length, simulation parameters, and the impact of the fruit's orientation in actual working conditions. Despite these errors, the overall results meet the design requirements.].

Comments 8: The text in Figure 1 is too small to be legible, which is a common issue in other figures as well. These need to be corrected to improve the manuscript’s overall clarity.

Response 8: Thank you very much for your questions and suggestions. We apologize for not comparing the text sizes in the images inserted in the paper. Based on your feedback, we have adjusted all the images and compared them after inserting them into the paper. We believe this change will significantly improve the clarity of our presentation. However, we are unable to change the text and number sizes of the scale in the simulation image of Figure 15 due to software limitations. We sincerely apologize again for this limitation. To compensate for this shortcoming, we have increased the image resolution and uploaded high-resolution images separately in the journal submission system.

Thank you again for your thorough review of our manuscript and for providing your valuable feedback. Your guidance and suggestions have greatly helped us improve our work and writing skills. We are very grateful for your hard work and professional expertise.

Reviewer 3 Report

Comments and Suggestions for Authors

The title can be improved, it is not very scientific or editorial.

In scientific papers, we provide the Latin names of plants and animals that are the subject of the research. This is missing here. There is also no indication of its species, of which there are dozens. It may turn out that the developed model is only a study of a specific case and cannot be generalized to all varieties and species. How were the optimal harvest phase and boundary conditions (environment) determined?

The idea of ​​using a pneumatic system for blueberry harvesting is quite interesting, but there are also shortcomings. The air stream will also pick unripe fruit. For this reason, mechanical shaking systems, such as the Polish Jagoda 300 combine, are better. Additionally, this combine can harvest raspberries and blackberries in addition to blueberries. Poland has extensive experience in this area. It is also worth analyzing other designs, such as the OSKAR 4WD Plus combine with hydraulic drive of the working units. This self-propelled harvester is designed for harvesting many different berries (black, red and white currants, chokeberries, gooseberries, Kamchatka berries, autumn raspberries).

The advantage of pneumatic harvesting is obtaining a clean harvest, free from contamination. This means one less operation in the production chain. The disadvantage is the distortion of the air flow by external factors, e.g. strong wind.
The pressure of 0.5 MPa is quite high for such small and delicate fruits. The blast can damage those that are already very ripe.

Comments on the Quality of English Language

no specifics

Author Response

Response to Reviewer 3 Comments

Dear reviewer:

Thank you for taking the time to thoroughly review this paper and provide valuable suggestions. Your professional insights and constructive feedback have helped us further improve the quality and rigor of the article. We have carefully considered all your suggestions and made the necessary revisions. We sincerely appreciate the time and effort you have dedicated to this review! Here are our responses to your comments and questions.

Comments 1: The title can be improved, it is not very scientific or editorial.

Response 1: Thank you very much for your questions and suggestions. First, to address the challenge of precise, non-destructive picking of blueberries that grow in tight clusters, we propose adding an air-jet step during the picking process. This step separates the berry clusters to increase the working space for the mechanical gripper. In this study, we combine flow field analysis and pressure-sensitive experiments to optimize the nozzle design. We establish design guidelines for the number, diameter, and angle of both flat and round nozzles. Additionally, for berries with stems, we use fluid-structure interaction methods to calculate stem deformation. We also perform a mechanical analysis to quantify the relationship between the airflow characteristics and the separation gap. Finally, we conduct experimental tests to validate the air-jet method. Based on this workflow and our design goals, we initially titled the paper " Research on Jet Device of Blueberry Picking Robot: Dual-Ring Model and Distance Enhancement Experiments." After considering your suggestions, we have changed the title to " Research on the Jet Distance Enhancement Device for Blueberry Harvesting Robots Based on the Dual-Ring Model "

Comments 2: In scientific papers, we provide the Latin names of plants and animals that are the subject of the research. This is missing here. There is also no indication of its species, of which there are dozens. It may turn out that the developed model is only a study of a specific case and cannot be generalized to all varieties and species. How were the optimal harvest phase and boundary conditions (environment) determined?

Response 2: Thank you very much for your questions and comments. The rabbit-eye blueberry variety originates from North America. It is popular among blueberry enthusiasts worldwide because of its adaptability, large fruit size, and balanced sweet-tart flavor. The fruit is round, resembling a rabbit's eye, which is how it got its name. Rabbit-eye blueberries have firm flesh and a rich taste, making them irresistible whether eaten fresh or dried. In China, they are considered a premium variety and are gaining attention from growers. This variety is adaptable and can thrive in various environments, offering stable yields. This study focuses on rabbit-eye blueberries grown in greenhouses in northern China. The experimental site is located at Qingdao Wolin Blueberry Fruit Industry Co., Ltd. (latitude 119°89'N, longitude 35°75'E), where the blueberry plants are of the low-bush type. Greenhouses provide an ideal climate for this variety, making it one of the first to be available in the market each season. Additionally, manual picking inside greenhouses is more expensive, so non-destructive harvesting and bringing the first batch of high-quality fruit to market are the main goals. The main harvesting period is usually from June to July, but the earliest high-quality fruits can be harvested around May. Regarding environmental factors, our current study focuses on manually grown fruit inside northern greenhouses. These greenhouses offer advantages like insulation, wind resistance, and durability, which are mentioned in the introduction of our paper. Therefore, we have not extensively considered environmental impacts in this study. However, in future research, we plan to optimize our design for open-field picking tasks, taking environmental factors into account. We aim to develop a more comprehensive air-jet separation system to enable non-destructive sorting and picking in various scenarios.

Comments 3: The idea of using a pneumatic system for blueberry harvesting is quite interesting, but there are also shortcomings. The air stream will also pick unripe fruit. For this reason, mechanical shaking systems, such as the Polish Jagoda 300 combine, are better. Additionally, this combine can harvest raspberries and blackberries in addition to blueberries. Poland has extensive experience in this area. It is also worth analyzing other designs, such as the OSKAR 4WD Plus combine with hydraulic drive of the working units. This self-propelled harvester is designed for harvesting many different berries (black, red and white currants, chokeberries, gooseberries, Kamchatka berries, autumn raspberries).

Response 3: Thank you for recognizing and commenting on our research. Unlike large-scale harvesting machinery, our air-jet device is designed for precise picking by separating clustered fruits. Our air-jet device is specifically designed to separate clustered fruits. Due to the difficulty of inserting a mechanical gripper into tightly clustered blueberries, we propose adding an air-jet process during harvesting. This air jet separates the ripe fruit from others, allowing the gripper to target the desired berries. Concerning the potential loss of unripe fruit due to airflow, we address this in our paper as well. The airflow velocity in the work area must be sufficient to achieve separation but not so high as to blow the berries off the bush or damage the fruit skin. We provide a detailed description of the airspeed required to avoid fruit drop and skin damage at the end of the field experiment section of the paper. Regarding the Polish Jagoda harvester, it is mentioned and analyzed in the introduction section of our article. Although this type of harvesting equipment is quite advanced, it is not suitable for greenhouse conditions or the staggered ripening of blueberries. Moreover, such vibration equipment has not yet considered the issue of sorting and selective picking, which differs from our goal of precise, non-destructive harvesting of high-quality fruit. Additionally, the Polish OSKAR 4WD Plus harvester, which combines hydraulic drives with working units, also has the issue of not distinguishing between ripe and unripe berries. Although this equipment is not suitable for our study's growing conditions and blueberry varieties, we found its technology to be mature and worthy of analysis. We have also included an analysis of this equipment in our introduction, located on Page 2, lines 49-60.

Comments 4: The advantage of pneumatic harvesting is obtaining a clean harvest, free from contamination. This means one less operation in the production chain. The disadvantage is the distortion of the air flow by external factors, e.g. strong wind.

Response 4: Thank you for your questions and comments. We have considered the impact of environmental factors. Since our air-jet device is designed to separate fruits, the external factors you mentioned (such as strong winds) could indeed be crucial. In northern China, most blueberries are of the rabbit-eye variety, which, due to its climate and growth characteristics, is typically grown in greenhouses. Our study focuses on the automatic harvesting of high-quality blueberries in greenhouses, with the main goals being non-destructive harvesting and bringing the first batch of high-quality fruit to market. In future research, we plan to further optimize our design to account for environmental factors in open-field picking tasks. We aim to improve the air-jet separation system to handle various external conditions, such as strong winds, high temperatures, and rain, making the system more comprehensive.

Comments 5: The pressure of 0.5 MPa is quite high for such small and delicate fruits. The blast can damage those that are already very ripe.

Response 5: Thank you for your questions and comments. The working pressure we mention specifically refers to the compressor. The compressor directs air jets at fruit clusters over a specific working distance, achieving separation through the jet stream. We measure the air velocity at different pressures and use these measurements to model and study the nozzle design. Because of the multi-hole nozzle structure and the energy loss of the jet stream, the fluid does not damage the fruit when it contacts it. To further explore the issue of fruit damage, we provide a detailed description at the end of the field experiment section in our paper, covering the airspeed that causes fruit drop and skin loss. You can find this information on Page 18, lines 540-548.

Thank you again for your thorough review of our manuscript and for providing your valuable feedback. Your guidance and suggestions have greatly helped us improve our work and writing skills. We are very grateful for your hard work and professional expertise.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript revision was completed of high quality.