Carlos Serôdio

A networked platform for agricultural management systems

Greenhouse control computers are an essential part of modern greenhouse operation. Climate, irrigation and nutrient supply must be controlled, in an economical way, to produce the best crop conditions. Current research on CO 2 enrichment and optimal growth strategies implies the use of powerful tools, either based on hardware or software. This paper describes the design and implementation of a distributed data acquisition and control system for computerised agricultural management systems that is being developed at Universidade of Tras-os-Montes and Alto Douro, Vila Real. Different communications platform concepts, such as Controller Area Network (CAN), Wireless Technologies, Ethernet and Internet tools supported by Transfer Control Protocol/Internet Protocol (TCP/IP) and e-mail tools supported by Simple Mail Transfer Protocol (SMTP) were used to achieve a network with a low-cost, flexible, and functional characteristics. The system management and maintenance tasks are divided into two types of performance levels. At a lower supervision level, a Local Controller placed in the greenhouses performs the monitoring/control and communications actions. The management decisions are performed at the higher level. The techniques and tools, which provide to the user a transparent, friendly and intuitive Graphical User Interface (GUI) will be presented.

Virtual Machines Applied to WSN's: The state-of-the-art and classification

In the last few years, various middleware solutions have been proposed for bridging the gap between the complexity of the applications and the low hardware abstraction in order to program and manage the sensor nodes of the wireless sensor networks. The proposed middleware range from market and data- centric approaches to message oriented middleware. This survey discusses the representative state-of-the- art virtual machine (VM) class of middleware for WSNs highlighting the state of the research.

A ZigBee Sensor Element for Distributed Monitoring of Soil Parameters in Environmental Monitoring

This work describes the development and implementation of a grid of self-powered multi-functional probes (MFPz) for small-scale measurements of different soil properties, as being part of a wireless sensor network. The measurement principle is based on the heat-pulse method for soil moisture and water flux measurements and in a Wenner array for soil electrical conductivity. To promote the deployment of these sensing devices across large areas, such as irrigation fields, the ZigBee standard has been adopted as a multi-hop, ad-hoc network enabler. The core of the MFPz device is a wireless microcontroller (with a built-in ZigBee stack) that builds upon an IEEE 802.15.4 radio device. A 7.2 Ah NiHM battery that is charged by a solar panel powers the MFPz device. Experimental results have proofed the reliability of the MFPz, regarding power consumption, connectivity and data agreement with known soil samples, as a cost-effective solution for environment monitoring.

Solar data acquisition wireless network for agricultural applications

This paper describes the implementation of a wireless data acquisition network for agricultural applications based on the Microchip PIC16C71, and the Intel 87C592 microcontrollers. The system uses a set of solar powered wireless data-acquisition stations (SPWAS) linked by radio frequency to a base station (BS). The base station has as main functions the control of the data-acquisition stations and the storage of the data collected by them. The network has been applied to collect outdoor and indoor climate data from a set of greenhouses located at Universidade de Tras-os-Montes e Alto Douro (UTAD), in the northwest of Portugal. Experimental tests have been done since mid June 1996, and the results obtained show that the communications to the BS were performed without errors or loss of data.

Hybrid technique for fingerprinting using IEEE802.11 wireless networks

Location based on fingerprinting comprises two distinct phases: the first phase, off-line phase, is related with two tasks, a site survey to collect data for the Fingerprint Map (FM), and its generation based on the collected data; the second phase, on-line phase, is related with the location of a mobile terminal, by doing the comparison of the data acquired from the wireless transceiver with the data stored in FM. Typically the first phase is very time consuming because multiple samples of the wireless signals, received from the multiple references, must be acquired and stored, for every spatial point to be considered in the FM. In this paper a hybrid approach using propagation models for indoor environments and fingerprinting is presented. In this approach the FM is generated using indoor propagation models and the map of the scenario, instead of requiring a site survey. This makes the generation of the FM faster when compared with the traditional approach. Also when changes occur the FM can be easily recalculated. Several Location Estimation Algorithms were used to test the FM. A precision of 3.118m was achieved using k-Nearest Neighbour and a standard deviation of 0.133m was obtained using Fuzzy Logic.

Indoor Location Using Fingerprinting and Fuzzy Logic

Indoor location systems cannot rely on technologies such as GPS (Global Positioning System) to determine the position of a mobile terminal, because its signals are blocked by obstacles such as walls, ceilings, roofs, etc. In such environments the use of alternative techniques, such as the use of wireless networks, should be considered. The location estimation is made by measuring and analysing one of the parameters of the wireless signal, usually the received power. One of the techniques used to estimate the locations using wireless networks is fingerprinting. This technique comprises two phases: in the first phase data is collected from the scenario and stored in a database; the second phase consists in determining the location of the mobile node by comparing the data collected from the wireless transceiver with the data previously stored in the database. In this paper an approach for localisation using fingerprinting based on Fuzzy Logic and pattern searching is presented. The performance of the proposed approach is compared with the performance of classic methods, and it presents an improvement between 10.24% and 49.43%, depending on the mobile node and the Fuzzy Logic parameters.

A multi-technology framework for LBS using fingerprinting

Due to the present challenges of Ubiquitous Computing, automatic location estimation of a mobile device in wireless networks is becoming increasingly important. Given the complexity of indoor environments, due to factors such as multipath interference, reflections and refractions, fingerprinting scene analysis methodology is presented in this paper. A multi-technology and multi-platform model is presented. After this model a framework for Localization Based Services was implemented. It can be used for analysis of performance of the location estimation, being developed at various levels of abstraction. This model is intended for indoor environment, being presented and tested different location estimation algorithms based on scene analysis with fingerprinting methodology. The framework was tested using IEEE802.11 and IEEE802.15.4 standards and a realtime location estimation with a accuracy of 1m and a precision of 90% was achieved.

CAN based actuation system for greenhouse control

This paper describes an actuation system for greenhouse control. It was built over a previously developed controller area network (CAN) system, based on the P80C592 microcontroller from Philips implementing a hierarchical structure to form a bus topology. In this network a personal computer (PC) is connected through an interface board to stations, located at the greenhouse. These stations are implemented using a serial linked I/O device (SLIO) from Philips, making possible greenhouse control. This choice is based on the SLIOs low price and suitability for applications where no high-speed requirements are needed such as on/off functions. When more complex actuation tasks are needed, more intelligent nodes had been designed, based on the P80C592 microcontroller. The assembling of the actuators within a greenhouse allows the use of a wired architecture. As a means of communication, the CAN protocol is used, which has a great flexibility and robustness needed in real-time control. The system allows easy expansion and configuration without compromising its performance. This is the case when the parameters must be changed whenever the weather conditions (summer/winter), force modification of the set-points of several control variables such as temperature, light and humidity, among others.

Ubiquitous SCADA Systems On Agricultural Applications

Ubiquitous computing and communications concepts are well suited for modern SCADA (supervisory control and data acquisition) systems for agricultural applications, not only to the higher levels, but also to the field level. To obtain a ubiquitous SCADA system, the integration of multiple computing and communications platforms is needed; however it raises the heterogeneity level of the system. A middleware-based environment with platform independence characteristics is then needed and will work like the integrator medium. Such environment is achieved by using the Java and Jini Technologies. Those two technologies are usually applied in the traditional computation resources and networks, utilized on the higher levels of SCADA systems, however it is also possible to use them in field level, where we can find microcontroller based systems, industrial communications such as CAN (controller area network), low cost narrow band RF (radio frequency), IEEE 802.11 and Bluetooth. To support all these features a software deployment framework Jini-based was developed, to deal with the supervision and management layers of the SCADA system. Furthermore, it will manage the applications deployment allowing the automated distribution of Jini implementation files and services remote interfaces.

Embedded Java in agricultural control systems

Embedded systems systems have often unexplored capabilities, which make them able to perform different tasks; furthermore, these systems have usually communication abilities that guarantee the possibility of remote control, supervision and management. In control application the trend is to use a distributed architecture that interconnects different embedded controllers building a wider embedded system. Each of these controllers are usually capable of performing different control algorithms. The concept of a virtual machine using Java is especially useful for this approach, allowing the use of a control strategy independently of the platform of the microprocessor based controller. This methodology has been successfully used in Internet based applications where the real-time constraints of control are avoided. Furthermore, the use of Java for control applications has also the advantage of integrating general-purpose computers with the Internet, to perform supervision and management tasks. Nowadays the embedded systems for agricultural applications are based on the interconnection and integration of several LAN technologies. To achieve the concept of network computing we use the Java technology allowing the combination of a distributed real-time control system with the supervision and management supported by computers linked to the Internet. This paper describes the design and discusses the feasibility of using Java Virtual Machine on 8-bit embedded microcontrollers and the interconnection of these controllers, arranged as a dedicated network, to the Internet.