Analysis of Intelligent Control Technology for Greenhouse Plant Semiconductor Lighting
In China, the facility horticultural cultivation area is up to 4 million hectares, including natural light cultivation systems (arch sheds, plastic greenhouses, solar greenhouses, glass greenhouses, etc.) and artificial light cultivation systems (plant factories, tissue culture rooms, incubators, etc.). The greenhouse is the most important type of natural light cultivation system. By the end of 2014, the greenhouse area has exceeded 1 million hectares and played a leading role in the anti-season cultivation of vegetables, flowers and fruit trees. The greenhouse mainly includes solar greenhouses and multi-span greenhouses. The greenhouse fill light is the main place for facility agricultural semiconductor lighting applications. Studies at home and abroad have shown that greenhouse light supplementation is very necessary and plays an important role in ensuring the healthy growth and development of crops.
First, greenhouse fill light is the essential requirement of facility agriculture.
The essence of facility agriculture is to promote the production mode, that is, to promote or delay the growth and reproduction of agricultural organisms through environmental control, to obtain higher yield and quality. Illumination is the most important environmental factor, and regulation plays a key role. Modern greenhouse production must achieve on-demand adjustment of lighting conditions.
Second, greenhouse fill light is a realistic demand for greenhouse production.
In actual production, weak light and illuminating stress caused by rain, snow, haze, dust pollution, etc. occur frequently, causing serious damage, resulting in crop yield reduction or even failure (filling light); Moreover, high-latitude areas have short sunshine and cannot meet long-day horticultural crops. The photoperiod needs to be supplemented by artificial light.
Finally, LED fill light equipment is the necessary actuator for greenhouse environmental control.
The illumination environment in the greenhouse changes instantaneously with the change of external natural light. In addition, the wall, the greenhouse beam support structure, and the occlusion of the thermal insulation cover shading mechanism, the internal illumination conditions are reduced in light intensity and photoperiod, and also on the light quality. Change. These changes are particularly serious under the conditions of low light and illuminating weather, and light environmental stress has become a bottleneck restricting the physique and efficiency of China's greenhouse horticultural industry, which needs to be solved urgently. According to the theory of factor comprehensive action rate, the implementation of intelligent control of greenhouse light environment not only can guarantee the high quality and stable yield of greenhouse crops, but also improve the utilization efficiency of greenhouse production resources (water and fertilizer, CO2, etc.), which can improve the level of greenhouse automation and save human resources. As a powerful horticultural country, the Netherlands has pushed the research of fill light technology to a high level and achieved fruitful results. It has been at the forefront of LED fill light, and China's greenhouse semiconductor lighting has just started.
The necessity of intelligent control of greenhouse plant semiconductor lighting
In general, greenhouse factory production requires intelligent control of environmental factors and even production factors, based on intelligent control to enable the greenhouse to have annual production capacity. The difficulty in achieving intelligent control of greenhouses is related to the type of greenhouse. Depending on the type of external protection structure and its material types, the input-output ratio is different from the greenhouse type. Moreover, the performance of intelligent control systems is continuously optimized and improved with the development of power electronics technology and computer network communication technology. In fact, China's plastic greenhouses and solar greenhouses are far from achieving intelligent control and management, and only the multi-span greenhouses and glass greenhouses have high levels of equipment. Nowadays, most greenhouses in the world do not really realize smart fill light, and most multi-span greenhouses use only HPS to achieve regular fill light. The emergence of LED light source and the development of technology have fundamentally solved the problem of lack of actuators for greenhouse smart fill light, and are advancing the intelligent process of greenhouse light environment regulation. In fact, the greenhouse light supplement is essentially different due to the type of greenhouse, and it is also related to the type of cultivated crops and seasonal factors. The spatial and temporal variability of this fill light demand leads to the implementation of intelligent control of greenhouse fill light, which can save energy and high efficiency. Moreover, the artificial light supplementation of greenhouses is a natural light-oriented regulation mode, which requires intelligent control to achieve the goals of energy conservation, high yield, stable production, high quality and improved resource utilization efficiency. The design and development of LED lighting systems are aimed at maximizing their photoelectric conversion efficiency and spatio-temporal bio-efficiency to ensure the benefits of horticultural light environment regulation. At the same time, the temperature in the greenhouse is not only controlled by the ambient temperature, the greenhouse insulation performance, but also controlled by the light conditions. The light stress caused by the low light and illuminating weather is often accompanied by the occurrence of low temperature stress. In addition, compared with greenhouse temperature, greenhouse crop root zone temperature changes have hysteresis, which needs to be considered when filling light. The quality and quantity properties of the light environment in the greenhouse are instantaneously changing and seasonally changing. If the constant light filling system is used for light environment regulation, it is not suitable, and it is difficult to obtain good biological benefits. Therefore, the greenhouse fill light system must adopt intelligent control, fully consider the use of natural light conditions, reduce the energy consumption of artificial light, fill light as needed. Greenhouse semiconductor lighting is highly feasible, and photovoltaic power generation technology can be adopted for LED lighting in areas without electricity.
Intelligent control refers to the use of computer, wireless communication data transmission, spread spectrum power carrier communication technology, computer intelligent information processing and energy-saving electrical control technology to form a distributed wireless telemetry, remote control, to find control system to achieve lighting equipment Intelligent control. Intelligent control methods can be divided into two categories, wired control wireless control. At present, greenhouse fill light should adopt intelligent control system based on sensor and PLC system, instead of IoT system based on WiFi communication and Zigbee networking, the practical application of the latter is still far. In addition to intelligent control of lighting formula, intelligent control needs to pay attention to the differences in lighting technology based on the plant production field, the growth and development stages of plants, the control targets and the utilization of natural light resources, which should be adapted to local conditions and vary depending on the type of greenhouse.
The connotation of intelligent control of greenhouse plant semiconductor lighting
Modern facilities and gardening must be developed to achieve intelligent control of the light environment, to create suitable growth conditions for crops, and to ensure high yield, stable yield and high quality. Greenhouse plant semiconductor lighting intelligent control refers to the space-time change and demand law of the facility light environment dominated by the production season, facility type, crop type and production priority target, and the LED light source is used as the light source actuator, and the light source action is implemented according to the principle of energy saving and high efficiency. Automated management of the operating mode. The intelligent control of greenhouse plant semiconductor lighting is a multi-dimensional, multi-factor, multi-objective management mode with rich connotation. The core of it is to establish a model of light environment regulation and implement intelligent control according to the model. One of its connotations, the intelligent control of greenhouse plant semiconductor lighting, including light quality, light intensity and photoperiod and its coupling adjustment, has special requirements for the performance of LED light source; its connotation, the intelligent control of greenhouse plant semiconductor lighting is time and space. The dual-scale coupling regulation should take into account the daily changes of the light environment, as well as the seasonal changes and crop growth changes, and need to be coordinated. The third connotation, the intelligent control of greenhouse plant semiconductor lighting is related to other environmental factors and water and fertilizer elements of the greenhouse. Coupling control process, necessary interaction design; its connotation 4, greenhouse plant semiconductor lighting intelligent control is to make full use of natural light, maximize the effectiveness of artificial light, organically combine artificial light and artificial light resources Overlay effects and complementary effects, not alternative relationships. In short, the intelligent control of light environment is a complex system engineering, and it is only a necessary component of the greenhouse intelligent control. How to optimize the greenhouse fill light intelligent control and organic nesting into the greenhouse intelligent control system is the most effective. The essential.
Technical strategy for intelligent control of greenhouse plant semiconductor lighting
Liu Wenke and Yang Qichang (2014) proposed a strategy for intelligent control of light environment in artificial light plant factories, emphasizing the establishment of lighting recipe (LR) based on the characteristics of plant light environment requirements, and establishing a light enviro nment co ntrol strategy. , LECS) is an effective method to achieve maximum utilization of light energy and reduce energy consumption of light sources under the premise of ensuring high quality and high yield. In fact, the factors that need to be considered in the intelligent control of the greenhouse light environment are more complicated than the intelligent control of the light environment of the artificial light plant factory, and the control model and strategy are more complicated (see Figure 1 for the specific technical system). First of all, the greenhouse plant semiconductor lighting intelligent control technology needs to make full use of the solar energy and resources in the facility, adjust the natural light contribution part of the lighting formula in real time, adjust the lighting strategy, and reduce energy consumption. Secondly, the intelligent control technology of greenhouse plant semiconductor lighting needs to follow the space-time law of horticultural crop growth in the facility. According to the plant growth and development stage, considering the factors such as crop canopy distribution, fruit distribution and leaf angle, the matching relationship between irradiation area and crop canopy is emphasized. Adjust the control parameters such as the light source suspension position and illumination angle. Finally, the greenhouse plant semiconductor lighting intelligent control technology requires a high-power red-blue LED light source device as an actuator. The light source device has a wide light intensity control range, a large illumination area, good heat dissipation performance, and is adjustable. Suspension ability. From the perspective of energy saving, Liu Wenke (2015) discusses the composition of LED lighting system equipment (LED light source and LED light, LED light suspension device and control system, light environment intelligent control system) and its light efficiency improvement approach, focusing on LED The technical approach of chip light quality construction, LED lamp bead illumination angle, LED array arrangement, luminous surface design, heat dissipation system design, light environment intelligent control, suspension device and control system, cultivation platform innovation and regulation. Specifically, the greenhouse plant semiconductor lighting intelligent control technology should fully detect and utilize artificial light on the basis of natural light, and perform dynamic real-time fill light based on the greenhouse environment (light intensity and photoperiod).
Fig.1 Construction of intelligent control technology system for greenhouse plants
Generally, the light energy utilization rate of the blade is only 5%, and the angle of the complementary light irradiation and the angle between the blades are important. At present, the greenhouse fill light has the technical modes of fill light in the canopy, fill light on the canopy, fill light between rows and stereo fill light, which can maximize the proportion and intensity of light received by the canopy and leaves, and try to make up The coverage area cannot cover the entire canopy. In the case of incomplete coverage, the fill light should be concentrated on the site with the highest physiological activity and the largest leaf area index, and the focus should be taken as the fill light focus. The best fill light effect.
Greenhouse plants fill light biological response mode
As an important environmental factor for greenhouse crop production, light is the only energy source for plant photosynthesis and a key environmental signal for regulating crop light form. On the one hand, people can control plant growth and development by changing the light quality and adjusting its quality attributes; on the other hand, controlling plant growth and development and its rate by changing the light intensity and photoperiod and regulating its quantitative properties. The regulation of light on plants is carried out by the action of photosynthetic pigments and photoreceptors in leaves [4], which in turn affects biological processes such as carbon and nitrogen metabolism in plants. Different plant species and even varieties have different requirements for the light environment, so it is necessary to systematically study the establishment of plant LR and LECS. The LR of plant-specific plants is determined to be based on the stage of plant growth and development, with the aim of high quality and high yield, by studying the optimal light environmental parameters required for 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. From the light quality point of view, 400 nm to 700 nm visible light regulates the activity and efficiency of the photosynthetic mechanism through plant photosynthetic pigments, which is photosynthetically active radiation, and 300 nm to 800 nm is physiologically effective radiation. Red blue light is the spectral type with the highest photosynthetic requirements of plant leaves, and is the main body of artificial light supplementation. Second, far red light and UV light regulate leaf, stem and plant morphology through plant photoreceptors. From a plant biology perspective, plants respond to changes in the light environment from different scales, including morphological responses, physiological responses (primary and secondary metabolism, edible part yield and quality indicators), and molecular biological responses (gene expression), each The responses complement each other and influence each other.
Conclusion
Greenhouse semiconductor lighting achieves intelligent control of lighting and light environment in the greenhouse, and has a milestone significance in the history of greenhouse environmental management technology. The artificial light plant factory intelligent control system based on LR and LEMS technology is the basis of intelligent control of greenhouse fill light. Intelligent control of greenhouse semiconductor lighting will play a key role in high-quality, high-yield, energy-saving and stable production of greenhouses, which needs to be realized and promoted.
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