| Edible mushrooms are characterized by their delicious taste and high nutritional value,which makes them extremely popular among consumers.The greenhouse cultivation industry of edible mushrooms is an important carrier of rural revitalization strategy.However,there are still some issues that need to be addressed,such as difficulty in cooling the greenhouse during the summer,poor environmental uniformity,and low level of intelligence in the greenhouse,resulting in low greenhouse utilization efficiency,poor monitoring effects of single-point configured sensors,and high labor intensity for mushroom farmers.To solve these problems,this paper proposes a cooling method for greenhouse airconditioning using air-bags,provides theoretical guidance for sensor configuration using CFD technology,and designs a fuzzy control system for the internal environment of the greenhouse,which provides technical support for realizing the intelligent control of annual production and growth environment of edible mushrooms.The main research work of this paper includes:(1)Research on performance of cooling method for greenhouse air-conditioning using air-bags.Based on field measurements and existing theoretical models,two transient CFD simulation models are established for an empty greenhouse and a mushroom greenhouse,respectively.The temperature and water vapor distribution inside the greenhouse after the air-conditioning and air-bag system is turned on are studied.The measured results show that the relative error of CFD simulation value and measured value is less than 12.5%,and the normalized root-mean-square difference is less than 0.011,which indicates that the CFD model and the boundary conditions used are reliable.The average temperature of the empty greenhouse can be reduced from 26 ℃ to 22 ℃ within 5 minutes,and the average temperature of the mushroom greenhouse can be reduced below 24 ℃ after 50 minutes and remain stable.The average non-uniform coefficients of the two greenhouse temperatures are 0.0062 and 0.0073,and the average non-uniform coefficients of water vapor mass fraction are 0.0087 and 0.0102.This indicates that the air-conditioning and air-bag ventilation system can meet the temperature requirements of mushroom growth and provide good uniformity of temperature and humidity inside the greenhouse.(2)Determination of the number and location of greenhouse sensors.Based on numerical simulation results and previous research experience,considering the buoyancy effect of air in enclosed spaces,a typical greenhouse temperature control scheme is determined for sensor placement.In edible mushroom greenhouses,sensors are placed in the middle column tier 1.5 m above the ground,3 m from the door,and at the middle position of the top tier in the middle column.In an empty greenhouse,sensors are placed in the middle column tier 0.14 m above the ground and at the middle position of the top tier in the middle column.This achieves optimal greenhouse environmental monitoring with a small number of sensors and provides theoretical guidance for sensor configuration during greenhouse environmental control system construction.(3)Analysis of the effects of different control measures on greenhouse environment.The effects of natural ventilation,shading net,sprinkling,and air conditioning with ducts on indoor environmental factors are analyzed.Based on mushroom farmer production experience,control measures for greenhouse environmental factors are determined: natural ventilation and air conditioning with ducts for temperature control;natural ventilation and sprinkling for humidity regulation;shading nets and supplemental lighting for light regulation;and natural ventilation for carbon dioxide regulation.This lays the foundation for greenhouse environmental control system design.(4)Design of a fuzzy control system for greenhouse environment.Combining practical production and spider technology,a greenhouse environmental control system is built consisting of an indoor and outdoor environmental monitoring system,a host computer,and greenhouse actuators.By designing fuzzy logic controllers for temperature,humidity,light,and carbon dioxide,and considering crop management requirements,the control capabilities of actuators,and climate characteristics,a fuzzy control strategy that considers the impact of outdoor environment on greenhouse environment is proposed.A dual-stage fuzzy control process that takes into account environmental changes over time is designed.(5)Control system testing and analysis.Through software debugging and field communication testing,it is verified that the greenhouse environmental control system can accurately control greenhouse actuators.Performance testing of the control system shows that the proposed fuzzy control strategy can effectively regulate greenhouse temperature,humidity,and light intensity.Temperature can be controlled within the target range throughout the day,with the optimal interval accounting for 36.99%.The greenhouse provides good humidity regulation compared to the outdoor environment,and light conditions meet crop growth requirements.The greenhouse control is relatively stable,and the executing mechanisms can operate steadily for a certain period of time,which verifies the reliability of the fuzzy control system. |
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