LED Lighting Control System Based On Chlorophyll Fluorescence

Artificial light sources are the main means by which plant factories regulate the light environment of crops,but the energy consumption of artificial light sources accounts for more than40%of the total energy consumption of plant factories.In addition,the traditional light supplement strategies are based only on temperature,humidity,CO2,etc.The environmental factor setting and fill light strategy does not detect the physiological information of plants,and cannot achieve real-time and dynamic feedback control.Moreover,blindly focusing on the growth rate of plants does not consider economic costs and other factors.Chlorophyll fluorescence can be used as a rapid detection method to obtain the photosynthetic status of plants conveniently.By measuring the chlorophyll fluorescence,the photochemical quantum efficiency of the PSII system can be known,which reflects the utilization efficiency of light energy by plants.Under the premise of ensuring the photosynthetic rate of plants,it is an effective means to maximize the utilization efficiency of light energy by developing LED light control system based on chlorophyll fluorescence.The main research contents and achievements of this article are as follows:（1）LED dimming method selection for plant fill lightIn order to select the LED dimming method suitable for plant growth,the experiment was compared and analyzed from the aspects of life span,dimming linearity,luminous efficiency,energy consumption,and effects on plant growth for PWM dimming and linear analog dimming.The experimental results show that under the two dimming methods,the LED lifespan calculated by the Arrhenius model is basically phase;under the PWM dimming method,the LED luminous intensity and the average current have a linear relationship;as the average current decreases,The luminous efficiency of both dimming methods is increasing,but the linear analog dimming is better than the PWM dimming,and the luminous efficiency is about 6%higher.From the perspective of the energy consumption of the entire system,the PWM dimming is more energy-saving than the linear analog dimming.In the PWM dimming mode,lettuce has more efficient use of light energy,ETR and Yield parameters are better than the linear analog dimming method,when PAR is300μmolm^-2s^-1,Fv/Fm maintains above 0.81,and With the increase of the PWM dimming frequency,lettuce utilization efficiency of light energy is also increasing.（2）Development of LED measurement and control system based on chlorophyll fluorescenceAn LED measurement and control system based on chlorophyll fluorescence was designed.According to the design requirements of the measurement and control system,the selection of the sensor and the construction of the hardware circuit were completed.Through the development of the SDI-12 and MODBUS communication protocol,the collection of chlorophyll fluorescence parameters and light temperature parameters was completed;and according to the PSII chlorophyll fluorescence parameter Ft,FM,Yield measurement process and acquisition cycle,designed the automatic acquisition mode and manual acquisition mode;through the design of the PWM dimmer to complete the LED luminous intensity of the precise control,through the design of man-machine interface,the realization of the temperature and temperature parameters Display of fluorescence parameters and human-computer interaction.（3）LED fill light control based on real-time chlorophyll fluorescenceTaking lettuce as the research object,the changes of chlorophyll fluorescence parameters of lettuce under different sampling periods and long-term supplemental light conditions were studied;the photosynthetically active radiation from 100μmolm^-2s^-1 to 600μmolm^-2s^-1 was studied at 15°C to 30°C.At 1 o’clock,the change law of chlorophyll fluorescence parameters of lettuce was established,and PSII photosynthetic electron transfer rate（ETR）and actual photochemical quantum efficiency（Yield）were modeled with changes of temperature and photosynthetically active radiation（PAR）,and NSGA-II multi-objective optimization algorithm was used.The Pareto optimal solution sets of optimal light intensity and ETR at different temperatures are obtained.The Pareto optimal solution set is used to verify the dimming system.The experimental results show that through the feedback control of the chlorophyll fluorescence parameters,the stable control of ETR and Yield can be achieved,and the utilization efficiency of lettuce can be increased.