Study On Monitoring System Of Greenhouse Group And The Spatial And Temporal Distribution Of The Environmental Parameters

Greenhouse cultivation,as a kind of high-efficient and high-yielding,resource-saving agricultural production and management technology,has the unique advantages of controllable environmental information and not affected by seasons.It has become an important production means to improve the utilization rate of land resources,reduce the production cost,and achieve high efficiency and high quality of crop production and income in the cold and dry areas of northern China.The results show that the environmental temperature and humidity,soil temperature and humidity,light intensity and CO₂ concentration in greenhouse play an important role in the growth of crops.In recent years,the research on expert control system,automatic measurement and control technology and intelligent control system,which aims at creating the best environmental conditions for crop growth,has made great progress.However,the interior environment of greenhouse is characterized by strong time-varying,poor linearity,strong coupling,large inertia,obvious lag and so on.And it is easy to be influenced by many uncertain factors such as external environment change,greenhouse building structure,crop growth form and so on,which makes the precise mathematical model difficult to realize,and the overall control effect is not ideal,at the same time,because of the high cost and technical requirements for the operators,it is not practical and difficult to popularize in small greenhouse groups.In order to solve the above problems,a method of combining multi-sensor fusion,greenhouse independent control,lumped monitoring and software simulation analysis based on wireless sensor network and GPRS transmission technology is proposed,and an efficient and intensive intelligent control and management platform for greenhouse groups with the functions of data acquisition and remote centralized monitoring and control of ad hoc networks was established.In order to summarize the effects of different crops,different external environments and different greenhouse structures on the internal environmental parameters of greenhouse,the long-term,real-time and centralized measurement and control of the environmental parameters inside and outside the greenhouse of different types and different structures are carried out,and their changing laws are statistically analyzed.It lays a foundation for the study of the temporal and spatial variation of greenhouse environmental parameters,the rational distribution of crop planting structure,the full utilization of greenhouse space,the improvement of environmental control strategies,the optimization of greenhouse structure and monitoring schemes,etc.By obtaining the growth status of different crops under different growth cycles and environmental parameters,this paper provides a research platform and database support for the research of the optimal parameters matching between greenhouse interior environment and crop growth.The main research results are as follows:1.On the basis of multi-sensor fusion technology and RS485/Modbus protocol,a data acquisition and processing node based on MCU controller,wireless transmission module and multi-sensor is developed,a main multi-slave wired data acquisition network is constructed,and the data transmission function of wireless ad hoc network is realized.The low power consumption data access strategy of nodes and the independent data processing mechanism based on corrosion and expansion algorithm and mean method are studied,and the real-time acquisition and high speed processing of environmental parameters are realized.The node life cycle is prolonged,the interference of all kinds of signals is reduced effectively,and the accuracy and reliability of data acquisition are improved.The experimental results show that the collected values of the sensor group show obvious periodic changes in time,which correctly reflect the changing law of the environmental parameters inside the greenhouse,and the sensor group has higher measurement accuracy and linearity.The measuring accuracy of air temperature and humidity were±0.3?and±2RH,the precision of soil temperature and humidity were±0.2?and±1%RH,the precision of light intensity was±5%and±30ppm.The slope of the quadratic calibration curve of the sensor group was between 0.9 and 1.1,and the fitting degree was above 0.96.At the same time,the cumulative errors of the sensor group for 6 hours of continuous working were not more than 0.1?,2%RH,0.3?,3%RH,100Lx and 70ppm,respectively,which showed excellent stability and consistency.It takes less than 5 seconds for the single chip processor to complete a data acquisition,aggregation and processing process.2.A wireless ad hoc network data transmission network based on star network topology is constructed,which can control the synchronous data acquisition and asynchronous data transmission of all acquisition nodes.This paper designs and studies the data transmission strategy and instruction system of the central node and the packet ad hoc network with the function of wireless ad hoc network data convergence,which reduces the time of data transmission and improves the network monitoring and management ability of the central node.The method of"broadcast communication and fixed-point transmission"is adopted to solve the problem of"congestion"in the process of data transmission,which makes the network run stably and reliably.The experimental results show that the maximum continuous and stable working time of the acquisition node is 73h,the distance of error-free communication between the nodes is not less than300m,the time difference of receiving synchronous acquisition instructions is almost 0,and the time required to complete the acquisition and processing of the data at one time is no longer than that of the other nodes.After 5s,it takes about 1.2s for the central node to complete the data aggregation of a group of?4 collecting nodes?.It takes no more than12s to complete the data aggregation of all nodes?20 acquisition nodes?.The experimental results show that the maximum continuous and stable working time of the acquisition node is 73h,the distance of error-free communication between the nodes is not less than 300m,the time difference of receiving synchronous acquisition instruction is almost 0,and the time required to complete a data acquisition and processing is not more than 5s.It takes about 1.2s for the central node to complete a set of data aggregation?4 nodes?and less than 12s for all the nodes?20 nodes?.3.Based on PLC controller and programmable touch screen,a greenhouse environment information measurement and control system with real-time data gathering and intelligent control function is designed.It realizes real-time data aggregation and centralized display,intelligent control of environmental parameters,remote control instruction receiving,local data storage,data packet recombination and forwarding,etc.The upper computer software system is programmed by MCGS configuration software.The environment information is independently processed,centralized displayed and classified stored,and the real-time change curve is drawn.The controller data processing algorithm and the driver and drive strategy of the actuator are studied,and the autonomous control function of the environmental parameters in the greenhouse is realized.4.The low power GPRS data transmission equipment and network data transmission protocol are developed,and the performance of the system is tested and optimized.The server side data aggregation software,data forwarding software and database storage system are studied.The functions of remote data transmission,database storage and data forwarding are realized.The remote wireless data communication network with the topology of"C/S transmission mode"or"peer to peer transmission mode"is constructed,and its operation stability,accuracy and reliability of data transmission are tested.The experimental results show that the system can connect with two remote servers and realize data transmission at the same time,the connection time is not more than 15s,the maximum data transmission time is 512 bytes,and there is no data packet loss for 56hours.The data received on the server side is normal,the maximum delay of the network reception is not more than 10s,and the database system and the data forwarding software work stably and reliably.5.The remote client data processing software is programmed with Lab VIEW.Through the TCP/IP protocol and remote server,the measurement,control,simulation and analysis system of the spatial and temporal distribution of greenhouse environmental information is constructed,and its basic functions are tested and verified.The functions of real-time collection and processing of environmental information,remote data transmission and lumped analysis are realized.The real-time changing curve of each environmental parameter is drawn by real-time monitoring function,the changing trend is forecasted and the remote control function is realized.Through the simulation analysis function,the environmental information inside and outside the greenhouse is analyzed and processed synthetically,and the variation regularity of the greenhouse with time is counted and the independent and cross analysis are carried out,and then the time space distribution and coupling effects are observed.6.The environmental parameters of typical height plane and typical longitudinal section in greenhouse were monitored for a long time.The overall variation curve of indoor and outdoor environmental parameters was drawn and the daily variation law was determined.The spatial and temporal distribution of the relative environmental parameters on the surface of 0.5m,1 m and 1.5m from the surface,the depth of 0.1m underground and the typical longitudinal section were analyzed,and the distribution of indoor environmental parameters in horizontal and vertical direction was studied.The interpolation method and polynomial fitting are used to process the data,and the 3D image and mathematical model of the spatial and temporal distribution of the main environmental parameters are established.The coupling relationship among parameters and the main factors influencing the distribution and variation of indoor environmental parameters were studied.