Contribución a las redes de sensores inalámbricas. Estudio e implementación de soluciones hardware para agricultura de precisión.
[SPA] En las regiones áridas y semiáridas, como el sureste español, la escasez de los recursos hídricos está causando importantes problemas de abastecimiento que afectan principalmente a la agricultura. Además, las predicciones sobre los efectos de cambio climático en estas regiones auguran un progresivo empeoramiento de la situación actual. Por tanto, uno de los objetivos prioritarios en el manejo y gestión de los recursos hídricos destinados al riego, debe ser el desarrollo e incorporación de nuevas tecnologías, así como de métodos que permitan conseguir una mayor eficiencia del uso del agua. Uno de los métodos más conocidos, y utilizados, para estimar, evaluar y entender las variaciones existentes en los cultivos es la agricultura de precisión. Este método se beneficia de numerosas tecnologías, entre las que se pueden citar los sistemas de posición global, las comunicaciones inalámbricas y los sistemas de instrumentación. Estas tecnologías permiten realizar tareas de monitorización de los cultivos almacenando los datos adquiridos, junto con las coordenadas geográficas del punto en el que se realizó la medida. Las redes de sensores inalámbricas constituyen una tecnología emergente de adquisición de datos que recientemente está atrayendo gran interés gracias a sus posibilidades, siendo aplicadas en numerosos ámbitos científicos e industriales para la realización de estudios y control de procesos. El uso de comunicaciones inalámbricas permite que los dispositivos sensores que la forman sean emplazados, así como reubicados, fácilmente sobre el terreno. Esta tesis se plantea con el objetivo global de estudiar, diseñar e implementar una arquitectura hardware, basada en redes de sensores inalámbricas, que pueda servir de herramienta a los ingenieros agrónomos para monitorizar, y así estimar, evaluar y entender las variaciones existentes en los cultivos, con objeto de determinar con mayor exactitud las necesidades de fertilizantes y riego, las fases de desarrollo y maduración de los productos, así como los puntos óptimos de siembra y recolección, que son los principales objetivos del método de la agricultura de precisión. Teniendo en cuenta las premisas de la arquitectura propuesta, durante el desarrollo de esta Tesis se han diseñado y construido diferentes prototipos de dispositivos inalámbricos (motes), los cuales han sido progresivamente depurados y mejorados a lo largo del transcurso de este trabajo, para poder ser validados en despliegues de redes de sensores, ubicadas en plantaciones agrícolas con diferentes cultivos. El resultado de este proceso ha concluido con el diseño de un dispositivo inalámbrico multi-entorno (MEWiN), con objeto de disminuir el número de elementos necesarios para configurar una red determinada y poder realizar tareas de monitorización mediante un único dispositivo. Los resultados que se derivan del desarrollo de esta tesis pueden ser aprovechados en nuevos trabajos de investigación aplicada, no sólo en el ámbito de la agricultura de precisión, sino también en contextos más diversos, como la monitorización en entornos marinos, o la vigilancia preventiva de partículas nocivas en ambientes industriales. [ENG] Water and food are the main resources that meet the needs of human beings. Agriculture provides most of the food but it also consumes most of the Earth’s available fresh water. In arid and semiarid regions, as Southern Spain, the water supply is an important factor that considerably affects agriculture. Development of innovative irrigation systems that efficiently use water is a high priority. In these regions, farmers must irrigate their crops efficiently; therefore, they must find new solutions and methods that improve the irrigation programming systems, taking into account not only the state of the soil and the plants but also information relating to the climate. All these data must be properly interpreted to decide the most suitable actions to carry out. Precision Agriculture is a set of techniques that provide a suitable solution to these problems because it aims to optimize field-level management with regard to crop science by matching farming practices more closely to crop needs. Economic advantages are also obtained by boosting competitiveness through more efficient practices (e.g. better management of water usage and costs). On the other hand, Information and Communication Technologies (ICT’s) are used to acquire information about the crop needs. Precision Agriculture techniques use this information to achieve the proposed objectives, in particular, intensive monitoring of crops, data analysis, decision making and application of control actions. Sensor Networks is a technology to carry out the intensive monitoring of crops using both wired and wireless nets. Wired solutions have been used since the 90s, whereas Wireless Sensors Networks (WSNs) are more recent (from the year 2000). In Agriculture, WSN‟s are more suitable because costs are reduced and the final solution is more reliable, since wires can be damaged by farming machinery in the crop. The simple redeployment of the devices provides high network versatility, so it is also another advantage to consider. Furthermore, WSN’s are proving to be a promising technology, and many WSN solutions are being successfully designed in several areas. The interest aroused by WSN technology has prompted the appearance on the market of various hardware platforms (sensor nodes or motes) for the development of new applications (hospitals, unfriendly environments and mobile control applications, among others), and research works (e.g. energy-efficient optimization or target tracking). Worth noting among these platforms are MICAz, TelosB, IRIS, Imote2 and others. It should be noted that these motes, and others not mentioned here, are devices that normally include embedded low-cost sensors whose specifications (precision, resolution, drift, etc.) are not the same as those of the instruments that are normally required in Precision Agriculture applications. For instance, the TelosB that includes the temperature sensor Sensirion SHT11 has no protection level. Moreover the temperature accuracy of this sensor is very dependent on environmental conditions compared to the HMP41 Vaisala sensor, widely used in precision agriculture. Moreover, many of these motes have only been used in laboratory or research applications and are not robust enough for use in real agricultural environments. In fact, many theoretical references about WSN based applications in Precision Agriculture can be found in scientific literature, but very few real deployments had been carried out, due to the scarcity of resources and the high cost of technology in the agricultural sector. Therefore, cost reduction is necessary to guarantee the success of WSN based applications in Precision Agriculture. Another important aspect of the motes is their capacity for connection to external instruments. There is a large group of external outdoor sensors used in the field of Precision Agriculture. Consequently, if motes are to be used in real agricultural applications, they first of all need to incorporate the necessary electronic interface to connect with external quality instruments. This feature together with robustness, autonomy and the possibility of connecting different types of instruments must be prioritized, as Geographic Information Systems (GIS), have been frequently used in Precision Agriculture. However WSN’s are not yet popular. Therefore, the development of new low cost hardware devices (motes) is necessary because they can measure the state of the crops in real time and provide the essential support to Precision Agriculture. Furthermore, these devices must be reliable in both indoor and outdoor conditions. They must be designed using an open architecture to facilitate the connection between different sensors and actuators required by the farming application. The main objective of this Thesis is the study and implementation of a hardware architecture based on WSN’s and their application in Precision Agriculture, particularly in real-time crops monitoring. Specifically, using Precision Agriculture to get an optimal crops production involves carrying out the following stages: Monitoring crops by acquiring data from sensors, analyzing obtained data, making decisions, applying control actions.
Redes inalámbricas, Dispositivos inalámbricos (motes), Plantaciones agrícolas, Dispositivo inalámbrico multi-entorno (MEWiN), Agricultura de precisión, Irrigation systems, Precision Agriculture, Information and Communication Technologies
Networked Digital Library of Theses and Dissertations