بهینه سازی پوشش هوایی در مدیریت کشاورزی دقیق: رویکرد الهام گرفته از هارمونی موسیقی

Aerial coverage optimization in precision agriculture management: A musical harmony inspired approach

Abstract

The coverage path planning (CPP) problem belongs to a sub-field of motion planning where the goal is to compute a complete coverage trajectory from initial to final position, within the robot workspace subjected to a set of restrictions. This problem has a complexity NP-complete, and has no general solution. Moreover, there are very few studies addressing this problem applied to aerial vehicles. Previous studies point out that the variable of interest to be optimized is the number of turns. Thus, by minimizing the number of turns, it can be ensured that the mission time is likewise minimized. In this paper, an approach to optimize this cost variable is proposed. This approach uses a quite novel algorithm called Harmony Search (HS). HS is a meta-heuristic algorithm based on jazz musician’s improvisation through a pleasant harmony. Finally, the results achieved with this technique are compared with the results obtained with the previous approach found in the literature.

1 Introduction

Coverage path planning problem is the computation of a path that passes through all the required points in the workspace from a starting point to a final point. This problem has been mostly addressed to Unmanned Ground Vehicles (UGVs) applied in cleaning, farming, de-mining, etc. The

problem of covering a determinate area with an Unmanned Aerial Vehicles (UAVs) is directly related to the aforementioned problem. However, the aerial coverage path planning (CPP) problem is subjected to harder restrictions. Typically, UAV’s have limited working cycles compared with ground robots (i.e. the mission time has to be carefully optimized). Furthermore, they are not able to take off or land in random places (initial and final positions are usually pre-defined).

Depending on the application, the problem restrictions can slightly change. Herein, the problem of covering a wide area with an irregular shape is considered for mosaicking purpose. Mosaicking is the technique of mapping an overall area by stitching a set of geo-referenced images acquired. In order to achieve this objective with an UAV, the workspace is sampled by using a regular grid (kind of Sukarev grid), where each cell corresponds to an image sample. Then, a complete coverage trajectory must be generated ensuring that no points are revisited, taking into account pre-defined take off and landing positions, a required minimum number of turns. In this way, the coverage time is minimized.

The study case presented is based on a vineyard parcel (see Fig. 1), since irregular shape fields are more challenging for addressing the related problem. Mosaicking procedures can be applied in vineyards parcels for weeding, frost monitoring, fruit maturity, as well as for measuring other biophysical parameters of interest.

The organization of the paper is as follows: After this brief introduction, Section 2 reviews some related works. Section 3 introduces the HS algorithm and shows how the CPP problem is addressed by employing this optimization technique. Section 4 presents the results obtained and makes a comparison with other techniques. Finally, Section 5 provides the concluding remarks of this work.

متابولیسم و تجمع قندهای انتقال یافته به میوه و تنظیم آنها

Metabolism and Accumulation of Sugars Translocated to Fruit and Their Regulation

Photoassimilates needed for fruit development are supplied from leaves, converted in fruit to substances relating to the specific quality of the fruit, then accumulate in the fruit. There are various regulation steps in the process from photoassimilate synthesis in leaves to sugar accumulation in fruit: photosynthesis, synthesis of translocation sugars, loading of translocation sugars, their translocation, their unloading, their membrane transport, their metabolic conversion, and compartmentation in vacuoles. Thus, it is important to clarify the mechanism and regulation of each step in fruit development. In this review, mainly the metabolic conversion of translocation sugars and their regulation at the genetic level in fruit are described because the metabolic conversion in fruit contributes greatly to produce the sink activity needed for fruit development.

1 Introduction

Photoassimilate in fruit depends mainly on supply from leaves, but some fruits in their early stages of development can supply it by their own photosynthesis. Fruit is a heterotrophic organ. However, specific substances in some fruits are generated in the fruit by themselves from photoassimilates etc., and can accumulate in fruit. Therefore, they depend on sugars translocated from leaves. The force attracting translocation sugars in fruit is called the sink strength. If the sink strength of the fruit is weak, the fruit can not grow sufficiently: growth is retarded or sometimes the fruit shrinks because of sugar deprivation. This review discusses the physiological conditions influencing sink strength during the various steps between photoassimilate synthesis in leaves and its accumulation in fruit (Fig. 1). 1.

Photosynthesis: Photoassimilate is synthesized by photosynthesis in leaves. 2. Synthesis of translocation sugars: Photoassimilate is converted to translocation sugars, such as sucrose and sorbitol. 3. Loading: Sucrose and sorbitol are carried in the phloem by a transporter. 4. Translocation: Sugar can flow from high to low sugar concentration according to the pressure flow theory. 5. Unloading: Sugars translocated in fruit tissue are carried out from phloem tissue. 6. Membrane transport: Sugars unloaded apoplastically are taken up in cells by a transporter on the plasma membrane. 7. Metabolic conversion: Translocation sugars unloaded in fruit by the symplasmic or apoplastic pathway are converted to various substances; first, invertase and sucrose synthase metabolize sucrose, sorbitol dehydrogenase metabolizes sorbitol, and then sucrose phosphate synthase synthesizes sucrose. 8. Compartmentation: Sugars in cells are mainly compartmented in vacuoles. High accumulation of sugars in vacuoles produces a high osmotic pressure that stimulates influx of water into vacuoles, leading to a high turgor pressure that is the driving force for cellular enlargement. Physiological steps for controlling the sink strength of fruit are mainly unloading, membrane transport, metabolic conversion, and compartmentation, if sufficient photoassimilate is supplied. Among these four major steps, the role of enzymes in metabolic conversion seems to be the most important for producing the sink strength of fruit because this step correlates closely with unloading and compartmentation of sugar. Thus, in this review, I want to describe mainly “metabolic conversion”.