Grote uitdaging is het brein automatiseren

Het belang van agrotechnologie is groot, gezien de toenemende wereldbevolking. Daarnaast worden natuurlijke hulpbronnen schaarser, emissiereductie-eisen aangescherpt en neemt de arbeidsparticipatie in de agrosector af. Mechanisatietechnologie wordt steeds meer een combinatie van software en hardware. Samen met mechanisatie-, elektronica- en informatietechnologiebedrijven is de WUR betrokken bij de ontwikkeling van precisielandbouw, voertuignavigatie, robotica en managementondersteuning

Optimal greenhouse cultivation control: survey and perspectives

Abstract: A survey is presented of the literature on greenhouse climate control, positioning the various solutions and paradigms in the framework of optimal control. A separation of timescales allows the separation of the economic optimal control problem of greenhouse cultivation into an off-line problem at the tactical level, and an on-line problem at the operational level. This paradigm is used to classify the literature into three categories: focus on operational control, focus on the tactical level, and truly integrated control. Integrated optimal control warrants the best economical result, and provides a systematic way to design control systems for the innovative greenhouses of the future. Research issues and perspectives are listed as well

Open-loop optimal temperature control in greenhouses

Earlier research has revealed that considerable energy savings can be achieved by maintaining an average temperature in the greenhouse in stead of maintaining rigid pre-defined temperature `blue-prints¿. A model based optimal control approach has proven to be a suitable framework to tackle these kind of control problems and it has been shown that these algorithms can be implemented on-line. But, when on-line optimal temperature control is considered, interesting questions arise, some of which are still unresolved. The issue tackled in this paper concerns the relation between the resolution of the control strategy (sample time) and energy savings of the control strategy. One would expect that an accurate and frequent anticipation to changing outdoor climate conditions might result in reduced energy consumption. It was indicated in the literature that a sample-time of 0.25 h or 1 hour should be sufficient, but these choices were hardly motivated. In this research, the relation between the control resolution and energy savings was quantitatively investigated using a dynamic greenhouse climate model and measurements of Dutch outdoor climate conditions containing high-frequency components. The results indicate that for an open-loop optimal control problem concerning the realization of an average temperature during a fixed period of one day using a minimum amount of energy with full a-priori knowledge of the outdoor weather, a resolution of the heating profile between half an hour and a hour suffices to produce accurate results in terms of energy conservation. These results were not much affected by parameter variations (heat capacity of the air, the solar heating efficiency) or opening and closing of thermal screens

Proceedings of the 4th field robot event 2006, Stuttgart/Hohenheim, Germany, 23-24th June 2006

Zeer uitgebreid verslag van het 4e Fieldrobotevent, dat gehouden werd op 23 en 24 juni 2006 in Stuttgart/Hohenhei

Use of supplementary lighting top screens and effects on greenhouse climate and return on investment

Discomfort caused by light pollution from greenhouses that apply supplementary lighting is an issue in Dutch society nowadays. At this moment Dutch legislation requires an opaque screen that reduces light transmission of the greenhouse wall by 95%. In 2008 also the light transmission of the greenhouse roof must be reduced equally and supplementary light will be limited to 15,000lx(180¿mol/m2/s), unless light emission is totally prevented. The objective of this research was to calculate the economic consequences of installing reflecting, light emission reducing or blocking screens by considering crop yield and costs. A mathematical correction equation was developed to approach the light gain for the crop as a result of internal reflection. Greenhouse climate and tomato crop growth were simulated for a reference greenhouse with supplementary lighting and without an emission blocking screen and for a low-light-emission greenhouse with a blocking screen. The supplementary lighting level was set at 180¿mol/m2/s. Results show that the greenhouse climate below the screen remained manageable, but that the desired DIF of 2°C was affected. The light gain was on average about 3% and resulted in production increase. A small net yearly profit resulted based on direct and indirect effects of the screen. In conclusion, the simulation suggested that stopping light emission at the source with help of reflective opaque screens is economically feasible if screen operation is included in planning the lighting scheme

The combined effects of cover design parameters on tomato production of a passive greenhouse

The objective of this paper is to demonstrate the need of a multiple design parameter approach to greenhouse design. To illustrate this need, we determined the combined effects of cover design parameters on tomato production of a passive greenhouse, that is a greenhouse with only natural ventilation and seasonal whitewash for climate management. The design parameters investigated in this research were the transmission of the cover for photosynthetically active radiation (PAR) and near infrared (NIR) radiation, the emission coefficient for long wave radiation of the cover and the ventilation area. First, we developed a model to link the tomato yield to the cover design parameters, through their effects on greenhouse climate. The model was validated by comparing the simulated greenhouse climate and yield with data obtained from field studies conducted in Almería, Spain. Thereafter, the sensitivity of the yield to the cover design parameters was analysed for three greenhouse configurations. This analysis gave insight into the effects of the cover design parameters on crop yield. Results showed that the sensitivity of the yield to a single design parameter depended on the absolute values of the other ones. For example, the yield in a greenhouse with a high ventilation capacity was the most sensitive to PAR transmission (0.45 % more yield for each 1% increase of PAR transmission) while in a greenhouse with a low ventilation capacity the crop yield is most sensitive to the ventilation area (0.63 %) and NIR transmission (-0.56 %). In addition, the yield sensitivity to the design parameters also varied over time because of changing outdoor climate conditions. In conclusion, a significant improvement of greenhouse design can be attained only through a multifactorial approach that accounts for the joint effect of design parameters, local climate and desired production period upon crop yield