Julián Sánchez-Hermosilla

Field evaluation of a self-propelled sprayer and effects of the application rate on spray deposition and losses to the ground in greenhouse tomato crops

BACKGROUND In the greenhouses of south-eastern Spain, plant protection products are applied using mainly sprayers at high pressures and high volumes. This results in major losses on the ground and less than uniform spray deposition on the canopy. Recently, self-propelled vehicles equipped with vertical spray booms have appeared on the market. In this study, deposition on the canopy and the losses to the ground at different spray volumes have been compared, using a self-propelled vehicle with vertical spray booms versus a gun sprayer. Three different spray volumes have been tested with a boom sprayer, and two with a spray gun. RESULTS The vehicle with the vertical spray boom gave similar depositions to those made with the gun, but at lower application volumes. Also, the distribution of the vertical spray boom was more uniform, with lower losses to the ground. CONCLUSIONS The vertical spray booms used in tomato crops improve the application of plant protection products with respect to the spray gun, reducing the application volumes and the environmental risks of soil pollution.

A Mechatronic Description of an Autonomous Mobile Robot for Agricultural Tasks in Greenhouses

Today, greenhouses are one of the main productive sectors of many areas of the world (Spain, the Netherlands, Australia, Morocco, etc.). One extraordinary area is the province of Almeria (SE Spain), where production exceeds 2.7 million tn on a surface area of 48000 ha of greenhouses (Camara Oficial de Comercio, 2007). This constitutes not only economic wealth but also a source of research and innovation.

Mechatronic Description of a Laser Autoguided Vehicle for Greenhouse Operations

This paper presents a novel approach for guiding mobile robots inside greenhouses demonstrated by promising preliminary physical experiments. It represents a comprehensive attempt to use the successful principles of AGVs (auto-guided vehicles) inside greenhouses, but avoiding the necessity of modifying the crop layout, and avoiding having to bury metallic pipes in the greenhouse floor. The designed vehicle can operate different tools, e.g., a spray system for applying plant-protection product, a lifting platform to reach the top part of the plants to perform pruning and harvesting tasks, and a trailer to transport fruits, plants, and crop waste. Regarding autonomous navigation, it follows the idea of AGVs, but now laser emitters are used to mark the desired route. The vehicle development is analyzed from a mechatronic standpoint (mechanics, electronics, and autonomous control).

Volume application rate adapted to the canopy size in greenhouse tomato crops

The application rate of plant-protection products is indicated as a concentration or amount of product per area. Greenhouse crops grow swiftly, and an application rate based on a fi xed amount of product per hectare can result either in large losses and overdoses when the plants are small or to be insuffi cient when the plants are fully developed. To solve these problems, the application rates of plant-protection products need to be adapted to the plant mass present in the greenhouse when the spray is applied. Two models were developed to estimate the leaf area based on easily measured geometric data of the vegetation in a greenhouse tomato crop. The model based on the PRV (Plant Row Volume) had that best results. The calculation of the vol- ume application rate from the PRV has resulted in a reduction of more than 30 % of the quantity of plant protection product sprayed, without decreasing yield. The PRV of a greenhouse tomato (Lycopersicon esculentum Mill.) is an easily measured parameter that enables the estimation of the leaf area index and the use of application strategies adapted to the changes in the plant canopy, saving major amounts of plant protection product used, compared to the conventional system.

Fast nonstationary filtering for adaptive weighing system

In this work, a practical evaluation of the filtering method for weighing system is provided. The analyzed system form a part of the horticultural fruits sorting machine, which requires a fast and reliable weight measurements. Dynamic weighing of moving objects requires fast and adaptive signal processing techniques in order to guaranty a timely response. Thus, applied signal filtration technique must ensure that the constant component remains free of noise, transient responses of load cell as well as mechanical vibrations. In this paper fast nonstationary filtering method is applied, providing optimal tradeoff between response time and settling time of steady state value. The implementation method uses the distributed approach, where an intelligent sensor captures raw signal and applies adaptive filter. Subsequently, obtained value is transmitted to central unit, that applies weight compensation function to improve the measurement accuracy. All presented results use the real signal acquired in industrial conditions from the tests of sorting machine prototype. The analyzed approach obtains promising results for all sorting modes. Moreover, classical filtering approach is used for comparison purposes and performance evaluation.

Potential dermal exposure to operators applying pesticide on greenhouse crops using low-cost equipment.

During pesticide application, operators are exposed to chemical products. Dermal exposure has been reported as the principal means of exposure for growers. In the present work, potential dermal exposure (PDE) has been assessed when using new low-cost equipment (a knapsack with a vertical spray boom) and compared to a hand-held spray lance, which is the equipment most widely used by growers in greenhouses. Two sprayers were used, a hand-held spray lance with four twin flat-fan nozzles and a knapsack fitted out with a vertical spray boom containing 3 pairs of twin flat-fan nozzles. Three applications were carried out and compared, one with the spray lance walking backwards (the reference application), and two with the spray boom - the first stopping at the turns and the second with no stopping. The patch method (19 position on the body) and tartrazine (the tracer) were used to assess de PDE. Each application tested was replicated three times. The results show that the knapsack with the vertical boom should not be used walking continuously along the greenhouse rows because the total PDE (1637.12mL 1000L-1) is greater than in the rest of the configurations tested. If the operator stops at the turns for a few seconds, allowing the previously sprayed droplet cloud to dissipate, the level of exposure decreases significantly (324.63mL 1000L-1), providing similar results to the reference application with the spray lance walking backwards (292.25mL 1000L-1).

A Frequency Domain Quantitative Technique for Robust Control System Design

Most control techniques require the use of a plant model during the design phase in order to tune the controller parameters. The mathematical models are an approximation of real systems and contain imperfections by several reasons: use of low-order descriptions, unmodelled dynamics, obtaining linear models for a specific operating point (working with poor performance outside of this working point), etc. Therefore, control techniques that work without taking into account these modelling errors, use a fixed-structure model and known parameters (nominal model ) supposing that the model exactly represents the real process, and the imperfections will be removed by means of feedback. However, there exist other control methods called robust control techniques which use these imperfections implicity during the design phase. In the robust control field such imperfections are called uncertainties, and instead of working only with one model (nominal model), a family of models is used forming the nominal model + uncertainties. The uncertainties can be classified in parametric or structured and non-parametric or non-structured. The first ones allow representing the uncertainties into the model coefficients (e.g. the value of a pole placed between maximum and minimum limits). The second ones represent uncertainties as unmodelled dynamics (e.g. differences in the orders of the model and the real system) (Morari and Zafiriou, 1989). The robust control technique which considers more exactly the uncertainties is the Quantitative Feedback Theory (QFT). It is a methodology to design robust controllers based on frequency domain, and was developed by Prof. Isaac Horowitz (Horowitz, 1982; Horowitz and Sidi, 1972; Horowitz, 1993). This technique allows designing robust controllers which fulfil some minimum quantitative specifications considering the presence of uncertainty in the plant model and the existence of perturbations. With this theory, Horowitz showed that the final aim of any control design must be to obtain an open-loop transfer function with the suitable bandwidth (cost of feedback) in order to sensitize the plant and reduce the perturbations. The Nichols plane is used to achieve a desired robust design over the specified region of plant uncertainty where the aim is to design a compensator C(s) and a prefilter F(s) (if it is necessary) (see Figure 1), so that performance and stability specifications are achieved for the family of plants. 17

Adaptive Weighing System With Fast Nonstationary Filtering and Centrifugal Force Compensation

In this paper, a dynamic fruit sorting machine weighing system has been studied and optimized to improve weight measurement precision. This new approach relies on the combination of a fast nonstationary filtering technique with a centrifugal force compensation method. The proposed architecture uses the distributed approach, where an intelligent sensor captures a raw signal and applies an adaptive filter. Subsequently, the value obtained is transmitted to a central unit that applies a weight compensation function to improve measurement precision. The second stage considers regression models to capture the existing relationship and introduces the correction compensating working principle of the sorting machine. All provided analyses used the real signal acquired under industrial conditions from testing the sorting machine prototype. Moreover, the classical filtering approach has been used for the purposes of comparison and performance evaluation. The application of the developed scheme allows one to achieve an average absolute error of about 3 g and standard deviations do not exceed 1 g for any of the operating modes in the range up to 1 kg.