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Deduction and Experiment on the Environmental Control System of an Acclimatization Chamber for Grafted Seedlings



Parallel abstracts

The objective of this paper was to demonstrate how the principles of apsychometric chart could be applied on deducing the procedural and logical issues oftemperature-humidity environmental control.Considering practical applications,anProgrammable Logical Controller(PLC)was developed to accomplish thesestrategies,and the condition-sequence control implementation was adopted as themain control scheme for the system.This paper illustrated that the developedenvironmental control system could be installed in an acclimatization chamber forgrafted seedlings to demonstrate the complete function of this methodology.Firstly,the compound control strategy,upper-lower limit,time-sequence control and freecooling conditional action,was adopted as the main design for the system.Secondly,logic control circuits finished by industrial wiring devices and PLC were created tomodel the temperature;humidity,illuminance and CO2 control processes.The systemsuch designed was suitable to operate in winter,spring(autumn)and summer ofsubtropics.Results indicated that the control system could satisfactorily achieveexpected goals for providing suitable curing conditions and modulating theenvironmental factors such as temperature and relative humidity for graftedseedlings.Regarding power consumption,the system was developed to moderatethe difference among power consumption for the four seasons.As for environmentalcontrol,if the weather conditions(temperature and relative humidity)wereappropriate for grafted seedling curing,the ambient air was directed to regulate thechamber environment.Otherwise,vents in the chamber would be closed to form aclose system,and furthermore the inner environmental control would be activated.In summary,the system was designed for flexible adjustments to environmental,illuminable,heatable and free cooling conditions,so it achieved the goal of powersaving,and it was easy to operate and maintain for users in agriculture.