Abstract
Psychrometer sensors are widely used for monitoring greenhouse air humidity because of its simplicity, low cost and accuracy. For proper operation the wick, which is immersed in a water reservoir, must maintain a continuous supply of water to the wet bulb temperature sensor. This implies the need to refill periodically the water reservoirs, which is the major limitation of these sensors. To avoid this problem an electronic psychrometric sensor was developed. A microcontroller is used to read the wet and dry bulbs temperatures and compute the vapor pressure and relative humidity. In addition, it controls a micro heat pump to supply continuously water to the reservoir.

Abstract
This paper presents an on-chip silicon bulk-micromachined Soil Moisture Sensor (SMS) for irrigation control in greenhouses. The system-on-a-chip includes the SMS, readout electronics, self-test, calibration facilities and a digital bus interface for external data transmission. Moreover, this low-cost device can be applied in several locations (e. g. per each plant root), and networked together with the 1-wire bus. The heat-pulse technique is used (for measuring the maximum temperature on a distant point) to determine the volumetric heat capacity and hence the water content of a porous media, such as soil. In order to validate this method, experimental results were achieved with a macrosensor based on the heat-pulse and capacitance methods. The capacitance method relates the volumetric water content with the capacitance change (dielectric properties) of a probe, inserted in the soil. Several tests were performed for different type of soils and water contents. These results are compared with the measurements achieved using the conventional thermogravimetric method.

Abstract
In the recent past, the distance between the sensing and processing points imposed critical constraints on the application of most PC-based data acquisition and control systems. Nowadays, it is possible to access the control systems installed in remote sites over the Internet. The World Wide Web has revolutionised the Internet by providing a medium for the dissemination of information, and the use of this technology can have a great impact on Agricultural Systems as well. These technologies allow almost any PC with a browser and a communication link to the Greenhouses to be used as an operator workstation, which gives benefits to the users who need remote access to greenhouses. Besides this, modern systems for agricultural applications are based on interconnection and integration of several Local Area Network (LAN) technologies combining data connectivity with user mobility. With a browser, the user is able to download a set of web pages, review information about the status of the system in real time, by running Java Applets, and display it in a browser window. Also, in this way it is possible to remotely configure any network node.

Abstract
Improvement of crop quality and yields is a demand in modern greenhouse production systems. Also, production costs must be kept as low as possible to guarantee market competitiveness. The achievement of these goals implies the use of complex management and control systems to regulate, in an efficient way, a large amount of interactive physical variables. Recent developments in hardware and software tools, namely microprocessors and microcontrollers, lead to the integration of complex control and management tasks in agricultural exploitations. In this paper is presented a data acquisition and control network that was implemented with the aim of being applied to any agricultural environment. The network has three main operating levels. At the lower level, a set of remote microcontroller stations perform data acquisition and radio frequency transmission to a collecting and control station. The control station, which generates actuating signals, is linked to a higher-level network based on PC's. The management and supervision of the entire greenhouse system is performed at this lever. Also, the results achieved with its application to the environmental control of a set of greenhouses located in the north of Portugal are described. The proposed architecture is now being installed in several commercial exploitations in order to evaluate its performance and introduce any improvements required by the growers. After this phase, the network will be available commercially through a joint Venture between UTAD University and a Portuguese greenhouse constructor.

Abstract
A multivariable predictive controller was implemented to regulate the air temperature, humidity and CO(2) concentration for a greenhouse located in the north of Portugal. The controller outputs are computed in order to optimise the future behaviour of the greenhouse environment, concerning the set-point accuracy and the minimisation of energy inputs. This is accomplished by using an optimisation module that minimises a cost function proportional to the sum of the squared errors between the simulated and desired outputs plus the square of the incremental and absolute energy inputs over a prediction horizon of one hour. Since the controller must be able to predict the greenhouse environmental conditions over the specified time interval, it is necessary to use mathematical models that describe the greenhouse climate, as well as to predict the outside weather. The experiments showed that second order ARX and tenth order ARMA models are well suited to simulate the inside and outside climate conditions, respectively. Since the model parameters are time-varying, recursive identification techniques were applied to estimate in real-time their values. The models employ data from the air temperature and humidity, inside and outside the greenhouse, solar radiation, wind speed and control inputs. To minimise the cost function a sequential quadratic programming method was used to solve the constrained optimisation problem. The results achieved with the proposed controller proved to be suitable for this application. Moreover, the controller performance, when compared to other control techniques such as commercially available PID controllers, was greatly improved.

Abstract
This paper proposes a genetic algorithm to generate trajectories for robotic manipulators. The objective is to minimize the ripple in the trajectory time evolution and to minimize the actuator energy requirements without colliding with any obstacles in the workspace, The article presents the results for several redundant and hyper-redundant manipulators.