Design and Implementation of a Control System for an Autonomous Reforestation Machine Using Finite State Machines

Round 1

Reviewer 1 Report

This work presents a very interesting robot implementation process for autonomous reforestation. The content presented here is a progression of an ongoing project by the research group. The subsystems of this control platform are described, and the finite state machine is illustrated. Simulations and experiments are conducted for evaluating and comparing the performance of different algorithms and operation strategies. Overall, the manuscript is well-written with thorough background discussion.

Author Response

We gratefully thank reviewer 1 for the time and effort you dedicated to evaluate our work and kind words. We have carefully considered all the review suggestions, including those from other reviewers, and made adjustments to the manuscript accordingly. All updates are visible in the diff-version of the manuscript.

Reviewer 2 Report

Despite the clear efforts of most forestry-developed countries to increase the proportion of natural forest regeneration and decrease the proportion of manual or mechanized planting of seedlings during reforestation, which can be observed in recent decades, this method of forest regeneration is still significantly prevalent. There are many advantages associated with forest regeneration by planting seedlings (e.g. achieving the desired structure of the forest stand, the possibility of certain control over the time of forest regeneration, solutions for the restoration of areas after forest calamities, etc.), but certainly also disadvantages (with manual work, its high physical effort, high consumption of working time, variable planting quality, etc.). The presented article contains findings from a study conducted by the authors with the aim of increasing the degree of automation in mechanized planting of seedlings. They created a control system that should be able to be used when planting seedlings in reforestation in a real environment. If the proposed system is functional (and from the content of the article it can be concluded that it is), it would enable a qualitatively new method of mechanized planting of seedlings during forest restoration. For the stated reasons, I consider the topic of the article to be current and beneficial for forestry science and practice.

In the Abstract part of the article, basic information about the factual content of the article is presented. I have a mixed feeling about the text: the text of the Abstract does indicate what the article is about, but this information is rather imprecise - it should be clearly stated that the authors solved the given issue primarily at the level of theory, using certain methodological procedures, etc. That is, that a real working model of the machine with an automatic way of working was not built. If I have misunderstood the text of the abstract, then that too is evidence that it should be edited - it should be clear and distinct. I have another comment about the abstract, namely that it contains some not generally known abbreviations (e.g. on line 4 "R&D", "ROS" or "SMACH" on line 7). I recommend replacing these abbreviations with the full text of their meaning.

Chapter 1 Introduction characterizes the importance of seedling planting for reforestation in Sweden and mentions the basic principles of existing technological planting procedures, emphasizing the significant importance of land preparation for this activity. Some specific types of betting machines used in Sweden are also mentioned. I believe that for the sake of completeness of this article, it would be appropriate to add a mention of the Hilleshög planting machine, which already provided the possibility of automated planting of seedlings about four decades ago. From the further text of chapter 1, it is clear that the issue of improving the quality of mechanized planting of forest tree seedlings is currently receiving considerable attention in Sweden. However, I recommend to state more clearly whether the study of the authors of the article is related to the cited research activities.

Chapter 2 provides information on the possibilities of the theoretical principles of controlling automated (robotized) machines. This chapter is a bit too abstract for me personally, but I'm not a specialist in the field, so I don't object. However, what I miss in this chapter is the connection of the mentioned principles to the main topic, i.e. to automating the planting of forest seedlings. Therefore, I recommend slightly modifying and supplementing the text.

Chapter 3 Materials and Methods provides information on the properties of the assumed base machine and its equipment for automated seedling planting. It is a four-wheel chassis equipped with a hydraulic crane, on which the Bracke Forest planter is suspended. The expected activities that the machine should provide, especially scarifying and planting, are listed. The picture No. 1 shows the layout of the model machine in an illustrative way. Special attention is paid to the issue of the robotic operating system (ROS) and related software equipment. Unfortunately, some passages (e.g. 3.3.6 or 3.4.1) are processed too briefly, which (at least in my opinion) makes it difficult to understand their substantive content (it is not clear whether the so-called field tests took place in reality or virtually, etc.). It would certainly help to understand the matter if the authors, among other things, staded a photo from the field tests they mention in ch. 3.4.2 and 3.4.4. I think that it should be more clearly described what the experimental device looked like, which (or its parameters) is described in ch. 5.

Chapter 4 The Control system characterizes the algorithms of the automated betting machine. The description is quite thorough and the principles used can be understood from it. I'm just somewhat bothered by the formal aspect of the inclusion of this chapter in the structure of the article, i.e. between chapters No. 3 and 5. What is this chapter No. 4? Is it part of the Materials and Methods issue (i.e. ch. 3) or Results (ch. 5)? A chapter classified in this way is outside the usual formal structure of articles. I therefore recommend adjusting the formal inclusion (marking) of this separate chapter and completing it with chapter 3 or 5.

Chapter 5 Results presents the knowledge obtained during the solution of the study of the automated betting device. It is clear from its content that the authors obtained their knowledge from simulations (apparently computer) of the activities of the assumed automated betting device, but also from experiments (see e.g. Table 3). The principle of simulation was chosen in order to gain knowledge about the operation of the equipment in different conditions. I think that the authors succeeded in this intention and that the presented results are convincing. I have no comments on this chapter.

Chapter 6 Discussion contains the authors' controversy over the achieved results of their study. However, for the most part, authors here discuss "with themselves" and do not compare their results with the results of other authors, as is usually the case in Discussions. I noted only one reference to an external resource here (line 608). From the content of this chapter, I did not gain a clear understanding of whether the authors consider their results to be proven, i.e. whether their assumptions were fulfilled, etc. In this sense, I recommend the text of ch. 6 edit. Subchapter 6.5 outlines the recommended further course of research work. Again, I got the impression (and it was the case in the previous parts of the article) that the authors are more focused on the control and system component of this problem, and the implementation of a functional betting machine in the form of a real prototype was not done. But is that really the case? Therefore, would it not be appropriate to also mention the possible real material output of the research solution, i.e. a working prototype of the automated planting machine, if it has been manufactured and tested, or display it? The most important thing that is certainly expected from every planting machine is that its planting mechanism works as efficiently and reliably as possible and that the plants planted by it grow successfully. However, little is written about this fundamental requirement in the article.

Chapter 7 Conclusions summarizes the factual content of the article and from it it can be concluded that the research on the given problem took place (if I understand correctly) only on an abstract level. Therefore, I recommend, as I stated above, to modify the article slightly in order to avoid possible confusion for readers.

Some of the images, included in the appendices of the article, are rather difficult to read (small font) and quite complicated to understand. In my opinion, it would be expedient to insert them directly into the text where they are mentioned. Apparently, by mistake, some images (A4, A5) ended up among the citations in the References chapter. It itself is arranged in a standard way.

 

I consider the article as a whole to be innovative and interesting for interested readers, so I recommend it for making the edits I mentioned above.

Author Response

We gratefully thank reviewer 2 for the time and effort you dedicated to evaluate our work. It has definitely increased the quality of our paper. All updates and adjustments, including those from other reviewers, are visible in the diff-version of the manuscript. Below we have our comments/answers written in bold. 

Despite the clear efforts of most forestry-developed countries to increase the proportion of natural forest regeneration and decrease the proportion of manual or mechanized planting of seedlings during reforestation, which can be observed in recent decades, this method of forest regeneration is still significantly prevalent. There are many advantages associated with forest regeneration by planting seedlings (e.g. achieving the desired structure of the forest stand, the possibility of certain control over the time of forest regeneration, solutions for the restoration of areas after forest calamities, etc.), but certainly also disadvantages (with manual work, its high physical effort, high consumption of working time, variable planting quality, etc.). The presented article contains findings from a study conducted by the authors with the aim of increasing the degree of automation in mechanized planting of seedlings. They created a control system that should be able to be used when planting seedlings in reforestation in a real environment. If the proposed system is functional (and from the content of the article it can be concluded that it is), it would enable a qualitatively new method of mechanized planting of seedlings during forest restoration. For the stated reasons, I consider the topic of the article to be current and beneficial for forestry science and practice.

In the Abstract part of the article, basic information about the factual content of the article is presented. I have a mixed feeling about the text: the text of the Abstract does indicate what the article is about, but this information is rather imprecise - it should be clearly stated that the authors solved the given issue primarily at the level of theory, using certain methodological procedures, etc. That is, that a real working model of the machine with an automatic way of working was not built. If I have misunderstood the text of the abstract, then that too is evidence that it should be edited - it should be clear and distinct. I have another comment about the abstract, namely that it contains some not generally known abbreviations (e.g. on line 4 "R&D", "ROS" or "SMACH" on line 7). I recommend replacing these abbreviations with the full text of their meaning.

The abbreviations has been replaced with full text when appropriate. The text now better emphasize that both simulations and field tests have been conducted. 

Chapter 1 Introduction characterizes the importance of seedling planting for reforestation in Sweden and mentions the basic principles of existing technological planting procedures, emphasizing the significant importance of land preparation for this activity. Some specific types of betting machines used in Sweden are also mentioned. I believe that for the sake of completeness of this article, it would be appropriate to add a mention of the Hilleshög planting machine, which already provided the possibility of automated planting of seedlings about four decades ago. From the further text of chapter 1, it is clear that the issue of improving the quality of mechanized planting of forest tree seedlings is currently receiving considerable attention in Sweden. However, I recommend to state more clearly whether the study of the authors of the article is related to the cited research activities.

• The HIKO Hilleshög machine is indeed relevant, it has been added to the introduction along with references where it is described.
• In terms of the Plantma-X and Södra Skog project, there are a few AutoPlant project members who have been involved in those projects. However, the authors of this paper have not been a part of those.   
• The final part of chapter 1 now mention field experiments to emphasize the actual experiments. We have also made minor adjustments in Results and in Material and methods to emphasize that both experiments and simulations have been used. 

Chapter 2 provides information on the possibilities of the theoretical principles of controlling automated (robotized) machines. This chapter is a bit too abstract for me personally, but I'm not a specialist in the field, so I don't object. However, what I miss in this chapter is the connection of the mentioned principles to the main topic, i.e. to automating the planting of forest seedlings. Therefore, I recommend slightly modifying and supplementing the text.

We agree this can be more clear and have updated the first part of section 2 to better introduce the reader to the concept of autonomous machines and its need for the presented work.  

Chapter 3 Materials and Methods provides information on the properties of the assumed base machine and its equipment for automated seedling planting. It is a four-wheel chassis equipped with a hydraulic crane, on which the Bracke Forest planter is suspended. The expected activities that the machine should provide, especially scarifying and planting, are listed. The picture No. 1 shows the layout of the model machine in an illustrative way. Special attention is paid to the issue of the robotic operating system (ROS) and related software equipment. Unfortunately, some passages (e.g. 3.3.6 or 3.4.1) are processed too briefly, which (at least in my opinion) makes it difficult to understand their substantive content (it is not clear whether the so-called field tests took place in reality or virtually, etc.). It would certainly help to understand the matter if the authors, among other things, staded a photo from the field tests they mention in ch. 3.4.2 and 3.4.4. I think that it should be more clearly described what the experimental device looked like, which (or its parameters) is described in ch. 5.

• Passage 3.3.6 has been extended.
• Yes, we realise that figure 1 could be mistaken for a photomontage which is misleading. We have added figure 7 and 8 which provide photographs from the sites. The coordinates to field experiment site 1 has also been added. To emphasize the difference between simulation and experiments we have added figure 6 which show the control system during simulation. 

Chapter 4 The Control system characterizes the algorithms of the automated betting machine. The description is quite thorough and the principles used can be understood from it. I'm just somewhat bothered by the formal aspect of the inclusion of this chapter in the structure of the article, i.e. between chapters No. 3 and 5. What is this chapter No. 4? Is it part of the Materials and Methods issue (i.e. ch. 3) or Results (ch. 5)? A chapter classified in this way is outside the usual formal structure of articles. I therefore recommend adjusting the formal inclusion (marking) of this separate chapter and completing it with chapter 3 or 5.

While it can be more clear to use an additional method section for a control system we agree to place the content within section 3.

Chapter 5 Results presents the knowledge obtained during the solution of the study of the automated betting device. It is clear from its content that the authors obtained their knowledge from simulations (apparently computer) of the activities of the assumed automated betting device, but also from experiments (see e.g. Table 3). The principle of simulation was chosen in order to gain knowledge about the operation of the equipment in different conditions. I think that the authors succeeded in this intention and that the presented results are convincing. I have no comments on this chapter.

Chapter 6 Discussion contains the authors' controversy over the achieved results of their study. However, for the most part, authors here discuss "with themselves" and do not compare their results with the results of other authors, as is usually the case in Discussions. I noted only one reference to an external resource here (line 608). From the content of this chapter, I did not gain a clear understanding of whether the authors consider their results to be proven, i.e. whether their assumptions were fulfilled, etc. In this sense, I recommend the text of ch. 6 edit. Subchapter 6.5 outlines the recommended further course of research work. Again, I got the impression (and it was the case in the previous parts of the article) that the authors are more focused on the control and system component of this problem, and the implementation of a functional betting machine in the form of a real prototype was not done. But is that really the case? Therefore, would it not be appropriate to also mention the possible real material output of the research solution, i.e. a working prototype of the automated planting machine, if it has been manufactured and tested, or display it? The most important thing that is certainly expected from every planting machine is that its planting mechanism works as efficiently and reliably as possible and that the plants planted by it grow successfully. However, little is written about this fundamental requirement in the article.

• In this paper, we have focused on the evaluation and ease of implementation of a FSM in ROS while using its packages. Therefore, it is somewhat natural that the discussion is “with ourselves” to a large extent. Having that said, we agree that comparisons should also be made to other efforts of implementation and we have added such parts in the discussion.
• We have now added some remarks regarding the planting machine’s possibilities and an outlook for the future development needed for the planting machine as well as for the scarification and planting functions. Also, images has been added to the methods chapters to show how the machine was equipped durings experiments.

Chapter 7 Conclusions summarizes the factual content of the article and from it it can be concluded that the research on the given problem took place (if I understand correctly) only on an abstract level. Therefore, I recommend, as I stated above, to modify the article slightly in order to avoid possible confusion for readers.

We have added clarifications throughout the paper to have the reader better understand the experimental nature of the evaluations we’ve made. In the conclusions we’ve emphasised that field tests were conducted.

Some of the images, included in the appendices of the article, are rather difficult to read (small font) and quite complicated to understand. In my opinion, it would be expedient to insert them directly into the text where they are mentioned. Apparently, by mistake, some images (A4, A5) ended up among the citations in the References chapter. It itself is arranged in a standard way.

• The images are provided as they are generated by the system. We suggest to move the appendices to "Complementary material" if the editor agrees. This allows the files to be examened and zoomed freely for the reader who is interested in those details. 
• The figure in the references issue has been solved. 

I consider the article as a whole to be innovative and interesting for interested readers, so I recommend it for making the edits I mentioned above.

Again, we would like to express our sincere appreciation for your thorough and inspiring review, thank you.

Reviewer 3 Report

Thank you for your effots. 

I would like to know how much value (benefit, productivity, environment is improved?

Thank you for your effots. 

I would like to know how much value (benefit, productivity, environment is improved?

 

Author Response

We gratefully thank reviewer 3 for the time and effort you dedicated to evaluate our work. 

I would like to know how much value (benefit, productivity, environment is improved?

We have clearified the introduction in terms of ground impact potential and its value. We have also described the energy potential with lighter machines and also clearified the outcome of the planing attempts in the discussion. 

All updates and adjustments, including those from other reviewers, are visible in the diff-version of the manuscript.