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Donciu et al.

Donciu et al. /Environmental Engineering and Management Journal 6 (2007), 6, 537-540 as purpose a modular administration of incomes (seeds, irrigation water, fertilizers, fungicides, herbicides, insecticides) by adapting the works of the soil, sowing, and fertilizers to the heterogeneity characteristics of the plot. The precision agriculture notion is based on the information provided by the production maps: a combine equipped with a production recorder for instance, connected to a satellite positioning (GPS), allows getting a production map on a certain plot. This information associated with other agronomical data ensures the income modulation with respect to the plot heterogeneity. In order to become e operational, these techniques must be joined with a series of agronomical models, only after this stage the decision can be finalized. The disadvantage of this method is that the investigations can be realized only in the absence of the crops and not during their vegetation period. Nevertheless, in opinion of the precision agriculture supporters, this can replace the side effect of the treatments evenly applied to the plot in the case of the conventional agriculture, through adapting the various actions to the plot characteristics variability. This way the negative impact of intensive treatments upon the environment is avoided. 2. System architecture The present paper proposes the realization of measurement and control modules of distributed data transmission, implemental on automatic irrigation systems so that it may lead to obtaining of an intelligent system of irrigation combined with automatic nutrients injection, relying on the sensory investigation of the environment and soil parameters conditions. The decisional algorithm of the control centre prescribes combined irrigation recipes according to the exploited crop and to its development specificity, and the investigation is carried out at irrigation cell level, modularly. Data flux communication has as a physical support the existent infrastructure of power supply of the automatic irrigation systems and is developed through the Power Line Communications technique (Benzekri et al., 2006). The system architecture is so conceived that it should allow its implementation on the automatic irrigation systems of both circular movement (central pivot), and linear movement. In order to reach the notion of precision agriculture (Yang et al., 2006), which represents a model in progress of implementing in all the very developed countries and has in view a modular administration of incomes in terms of the plot heterogenic characteristics, the project proposes the introduction of a sensory modules network to entail a division of the farming field into characterization (Zhao et al., 2007). The intelligent irrigation system architecture is structured on five main levels, as follows: • the irrigation modules level, which join the automatic irrigation systems on angular or linear movement and which have as main function the controlled command of the electro valves for the admission of the water-nutrients mixture, in accordance with the recipes prescribed by the control; • the sensors modules level, which are fixed and placed at the ground, having as main purpose the sampling through sensors of the surrounding cell characterization data and their transmission towards the control centre; • the nutrients injection batteries level, with the role of injecting nutrients into the irrigation water, in terms of the concentration prescribed by the control centre (Ruiliang et al., 1999); • the data flux transmission through PLC level, has as physical support the network of the power supply of the engines operating on the automatic irrigation systems and water pumps and realizes the data transfer between the control centre on the one hand and the irrigation module and the nutrients injection batteries on the other (Kubota et al., 2006); • the decisional level, based on the data resulted from the sensors modules level and those extracted from its own data basis, of combine irrigation recipe, delivers the execution commands to the injection batteries regarding the irrigation output and the characterization cell geographical localization (Mohan et al., 2003). The general architecture of the intelligent irrigation system is shown in Fig. 1. There can be noticed the existence of two independent circuits, one of water supply and one of power supply. The water supply circuit CAA makes the junction between the water supply source AA and the nutrients injection batteries BIN. This circuit converts into combine supply circuit CLC, after the nutrients injection with the pulverization nozzles of the irrigation module MI. The electric circuit powers up the engines and the pumps afferent to the automatic irrigation system and is the data transmission physical environment. Fig. 1. The intelligent irrigation system architecture 538

Sustainable irrigation based on intelligent optimization of nutrients applications The irrigation module is set up at the level of the mobile arms of the automatic irrigation system and it is made up of the communication interface IPCL, the microchip control device µP, the radio receiver RR and the electro valve EV. On the MI module movement, the identification of the membership to a characterization cell is performed on the grounds of the entering its range of action. The emission power of the sensors modules MS is limited within the cell and towards its detection there interferes the criterion of the emission maximum. Following the communication settlement between the sensors module transmitter and the irrigation module receiver, the data are transmitted by the command device µP to the PLC interface, joined with the supply circuit of the operative electrical engine (Sohag et al., 2005). By the PLC transmission the useful information is received by the control centre CC, on a computer server. As a consequence of the interpretation of the response type data provided by the characterization cells sensors are taken the control decisions of reaching the limits of the nutrients concentrations and relative humidity imposed by the data basis. The quality and quantity commands are transmitted by the PLC system to the nutrients injection batteries, providing the combine irrigation agent to the pulverization nozzles, to the volume controlling electro valves belonging to the irrigation module. By the communication system PLC useful data are delivered as modulated signal. The signal is of the broadband type and the physical environment enables multiple operations roll on the same existent infrastructure. The hardware architecture of the sensors module is shown in Fig. 2 and is com posed by a set of sensors specialized on the climatic parameters detection (temperature, humidity, dew point, speed, direction and movement sense of air masses, precipitations) and a set specialized on the soil parameters detection (conductivity, humidity). For the air relative temperature and humidity measurement it is used an incorporated sensor on digital output STU, made in CMOS technology, which makes it thermally safe and stable. This generates a useful signal of superior quality, has a very quick response time and insensibility at external noises (EMC). The data delivered by this sensor are used to forecast the degree of the water evaporation off the ground. The need to utilize the rain gauge sensor type (SP) comes from that the irrigation procedure interruption, during precipitations, following the data provided by the soil humidity sensor, happens late because of the needed time of water permeating through the ground, up to the depth where the humidity sensor is set up. The data coming from the anemometer SV are used to eliminate irrigation unevenness caused by wind blasts. At the ground level are set the conductivity sensor SC, the humidity sensor SU, on whose account will be supplied the input data for the estimation procedure of the relative nutrients and humidity concentration. The bidirectional communication with the sensors block is performed through the microchip µP and is of the serial type. As the sensors module is an independent system it is equipped with a control keyboard and a LCD screening. The radio data delivery to the irrigation module is done by the transmitter ER, having the transmission force so adjusted that it should not surpass the characterization cell by more than half the radius. The assembly supply is performed by a dry B battery. Fig. 2. Hardware architecture of the sensors module MS The control centre is the physical support of the decisional algorithms which operate, relying on the data resulted from the level of the sensors modules the actions of the executor elements, the actors. The data basis found at this level contains information referring to the leguminous species classification in terms of the water consuming and the absorption capacity and it designs irrigation graphs regarding the cultivated species, zone climatic factors, culture denseness and rows orientation, plant habitus, root system and vegetation stage. Besides, beginning with this level is programmed the time diagram start (the culture initiation) and the spells designated for the maintenance works. The Intervention and Monitoring Centre CIM designates the interface with the human operator in the process of supervision and monitoring the control actions elaborated by CC and allows the effectuation of modifications in the decisional algorithms development. Also, starting with this level can be completed or modified (upgrade software) the data basis with respect to the irrigation networks. Because the control centre is configured by the server, one can access it from any geographical area where there is internet access point. The TCP-IP communication between CC and CIM is provided by two dedicated virtual instruments, server and costumer. For security reasons the login to the server is permitted only on password basis. The problems identification and improvement with respect to the automatic systems irrigation are presented in Table 1. 539

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