Discussion on Intelligent Control Strategy of LED Plant Lighting

The plant factory has been recognized internationally as the most advanced development stage of facility agriculture, and is an inevitable trend in the future development of facility horticulture. It is one of the important indicators to measure the level of agricultural high-tech development in a country. Plant plant production systems have greater controllability and stability than open field farm systems, and are of great value in addressing world resource, environmental and food security issues, and addressing climate change and extreme weather hazards. Plant factories can be divided into artificial light plant factories and solar plant factories according to the light source. But the internationally narrow definition of a plant factory refers to an artificial light plant factory. The intrinsic essential technical features of the artificial light plant factory include four points: (1) the environmental factors required for plant growth and development are intelligently controllable, such as temperature, humidity, CO2 concentration, light, airflow, etc.; (2) plant cultivation using soilless solid Multi-layer cultivation mode, generally adopts DFT, NFT, mist culture and semi-hydroponics for integrated supply and control of water and fertilizer; (3) artificial light illumination technology for electric light source, providing photosynthesis energy and light environment signals for plants through electric light source; The maintenance structure is fully enclosed, with strong airtightness, opacity and good heat insulation. The intelligent control of production factors is the most essential feature of plant factories. It takes the fourth point as a precondition and covers the essential technical characteristics of the first three points mentioned above. Of course, the development of plant plant technology is not a short-term development, it is the result of the joint development of industrial technology and agricultural technology. In summary, the technical basis for the development of plant factories includes the following three points. First, the introduction of mineral nutrition theory and the development of chemical fertilizer industry, the three-dimensional soilless culture technology produced by the birth; second, the development of computer and sensor technology, making environmental factors and nutrient monitoring control become a reality; third, semiconductor electric light source technology The development has promoted the development of artificial lighting technology and expanded the connotation of light environment control. At present, automatic detection, storage analysis and intelligent control are realized as all environmental factors of plant factories, and the time has come to develop intelligent plant factories. 1. The necessity of intelligent control of light environment in plant factories The production and operation of intelligent plant factories not only requires automation of environmental factor control, water and fertilizer supply and blending control, but also automatic operation in the production of seedlings, transplanting, harvesting, etc., and reduction of human activities. Interference and pollution to the production space. Intelligent management and control of plant plant operations and production consumes electrical energy. The energy consumption of the artificial light plant factory includes light source, air conditioner, pumping system, pneumatic system, detection control system and so on. In the case of artificial light plant plants, the most energy-consuming is the lighting system, which accounts for more than 60 of the total energy consumption; the second is the air-conditioning system, which accounts for more than 30. The remaining control systems consume relatively little energy. At present, the operating energy cost has become the main component of plant plant operating costs, and is an important reason for the high operating costs of plant factories. Therefore, reducing the energy consumption of the lighting system has become the main way to save energy and increase efficiency in plant factories. Light-emitting diode (LED) is a semiconductor solid-state light source, which is an ideal substitute for traditional plant factory light sources such as fluorescent lamps, and has obvious energy-saving effects. Importantly, the development of LED semiconductor lighting technology provides hardware conditions for plant plant light source energy saving and environmental intelligent control. Its maximum energy saving potential is to achieve intelligent control of light quality, light intensity and photoperiod. At the same time, light is an effective environmental factor regulating plant growth and development and yield quality. Light environment regulation is essential to improve the production efficiency of artificial light plant factories. At present, plant factories have outstanding problems such as high energy consumption of LED light source, low utilization rate of light energy, and lack of precise control technology for light environment. Research on optimization parameters and control mode of light environment for plant horticultural crops in plant factories is to reduce energy consumption of LED lighting systems and increase The only way to produce efficiency. 2. Plant factory light environment intelligent control strategy The plant factory light environment control is realized by the control system composed of LED light source, sensor and computer, and its target is two. First, energy conservation; second, high quality plants. Plant yield quality response is the core of plant plant environmental control and regulation. Therefore, the light environment parameters required for plant growth and development are the basis of plant factory illumination technology, and also the biological basis of light environment intelligent control. Therefore, based on LED semiconductor lighting technology, the main method of plant factory lighting energy efficiency is to establish a targeted lighting recipe (LR) and Lightenvironment control strategy (LECS) based on the plant's light environment demand characteristics and time and space characteristics. Automatic control through the computer, which can not only maximize the productivity of the plant, but also enable the light to be targeted, avoiding the waste of energy caused by blind ineffective lighting. Increasing the productivity of plant factories is the main way to increase the productivity of plant factories. LR refers to the parameter set of the light quality composition and quantity attribute necessary for the growth and development of specific plant species and varieties in the artificial light plant factory with the aim of high quality and high yield. LECS refers to a method of directly controlling and switching light environmental parameters by computer based on the LR of specific plant species and variety growth and development in artificial light plant factories with the aim of high quality and high yield. The types of light contained in LR include visible light, UV and far red light, among which red light and blue light are the large amount of light required by plants, while other visible light is the trace light quality required by plants, while UV and far red light are plants. The beneficial light quality required. The core of LR is the composition of light quality and its quantitative properties. The reasonable combination of the three types of light quality constitutes an LR. The light environment regulates the growth and development of plants by changing the quality of light quality, as well as the quantity of light intensity and photoperiod, and regulating photosynthesis. The role of pigments and photoreceptors in affecting carbon and nitrogen metabolism is shown in Figure 1. Different plant species and even varieties have different requirements for light environment. Therefore, systematic research is needed to establish plant LR and LECS. Plant factory specific The LR of the plant is determined by taking the stage of plant growth and development as the center, aiming at high quality and high yield, and obtaining the optimal light environmental parameters required by plants at different stages. LR is the basis for intelligent control of light source and light environment. Establishing LR and LR libraries is the prerequisite for energy efficient production of plant factories. Based on LR, develop LED light source, establish LR space-time conversion control strategy and time node, namely Light Environment Control Strategy (LECS), to coordinate the conversion of light quality, light intensity and photoperiod, which is the premise of achieving high quality and high yield of plant factory (Figure 2). The implementation of LECS requires LED light source luminaires and control system hardware and software conditions to support. Based on the LED lighting technology, the intelligent control of the plant factory light environment is realized, and the last level of environmental factor control of the plant factory is solved. The intelligent control of lighting marks the reality that intelligent plant factories and their intelligent production have become a reality. 3. Conclusion The intelligent control of lighting and light environment is an environmental factor finally realized by the artificial light plant factory, which has a milestone significance. The establishment of LR and LEMS not only provides technical parameters for energy saving of light sources, but also provides a means of light environment regulation for high quality and high yield of plants. The establishment of LR and LEMS technology provides new technical support for the sustainable development of artificial light plant factories. The establishment and LECS are important technical support for the energy-efficient and efficient production of plant factories. At the same time, combined with LED light source space management technology, such as vertical and horizontal light source movement technology, as well as light reflection technology on the upper surface, lower illumination surface and side of the lamp, can effectively improve the light energy utilization efficiency of the plant. The organic combination of the two technologies will greatly improve the utilization of light in plant factories.