ISHS Acta Horticulturae 406: II IFAC/ISHS Workshop :Mathematical & Control Applications in Agriculture & Horticulture
GREENHOUSE CLIMATE CONTROL WITH A COMBINE MODEL OF GREENHOUSE AND PLANT BY USING ONLINE MEASUREMENT OF LEAF TEMPERATURE AND TRANSPIRATION |
| Author: | U. Schmidt |
| Abstract:
Integration of plant measured physiological data into technical control systems and their use as control variables require algorithms that make allowance for the relationship between plant physiology and process equipment and their dynamic behaviour. The PLANTPUTER process control system is now being developed in view of taking the technical systems (heating, ventilation, energy screen, CO2 treatment, shading, artificial light, irrigation) out of the overall complex of climate and plant physiology. The use of three control variables - air temperature, plant temperature, vapour concentration difference between plant and air - is being discussed and investigated for the main part of the system (heating/ventilation). For heating control purposes these three variables can be used in a system only if a new algorithm - model-based control - was applied. Two models are used for heating and ventilation control. The greenhouse model used beside the plant model shows a differential dynamic behaviour. That is why the two models are applied as quasi-static models. For reasons of adaptation, the greenhouse model gets turned into a dynamic model. For elimination of faulty simulation series, the thus corrected parameters have to be compared with the parameter series. Ventilation control would benefit from use of the vapour concentration difference as a control variable, as locking the ventilation system at excessive vapour concentration differences leads to more intensive transpiration and higher photosynthetic rates in plants that need high levels of moisture. | |
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