Research On Intelligent Water-saving Irrigation And Decision-making Model Of Expert System In Litchi Orchard Based On Wireless Sensor Network

The cultivated area of litchi orchard is about 555.3 thousand hm² and the annual output of litchi is about 2.2 million tons,respectively accounting for 80%of the cultivated area of litchi orchard and 75%of the annual output of litchi in the world approximately.And according to past investigations,the level of orchard management level in China is still very low.Lacking relevant infrastructures,middle and small orchards suffer a low level of modernization in facilities.Flooding or canal irrigation are main methods of fruit trees irrigation,which water supplement time are decided by personal experience or meteorological conditions.Nutrients needed in the fruit trees growth process usually are fertilized at a fixed time with agricultural fertilizer,consuming a lot of resources and manpower but having poor effect.Wireless Sensor Network combines multidisciplinary technologies including modern Sensor technology,microelectronics technology,communication technology and embedded computer technology and so on,which is considered as one of the most important technology in the 21st century.With great values,it does become a concerned emerging frontier hot research field around the world.WSN,a new kind of information acquisition and processing technology applied in agriculture,enjoys the benefits such as low power consumption,low cost,high reliability,and already has many successful cases at home and abroad.Applying wireless sensor technology to monitor litchi growth process has important significance in both boosting the degree of agricultural production automation as well as informatization,and predicting drought,pests and other diseases of litchi.Taking litchi as an example,this paper studied the decision model of expert system,constructed a decision-making model of intelligent water-saving irrigation and expert system in litchi orchard based on wireless sensor network,designed hardware and software for system,built the networks and tested the system in litchi orchard environment.The main contents and achievements show as follows:?1?Set up designing principles and key technologies of wireless sensor network system,investigated intelligent water-saving irrigation technology based on wireless sensor network in orchard and irrigation model of expert system,which provided theoretical basis to build a suitable decision-making model.?2?According to requirements of monitoring the environment in litchi orchard,the system was designed to monitor water-saving irrigation in orchard intelligently,with special designs of hardware and software and optimization of fuzzy control algorithm.Hardware design consists of general structure and the node hardware structure of system,on which based to complete selection of sensors and electronic components,research method to realize the function of each module hardware and design circuit schematic diagram,PCB layout,circuit boards,experimental debugging and so on.Software design consists of node embedded software structure.Firstly,embedded software design and programming methods were researched and components of program including the main program,system initialization,data acquisition,time synchronization algorithm and so on are developed gradually.Secondly,a remote database server was designed to save real-time environmental data of the litchi orchard,providing source data for the expert system and monitoring sites.Thirdly,an expert system was designed to provide different irrigation methods.Fourthly,monitoring sites was designed and real-time environmental information about litchi orchard was displayed,helping administrator monitoring,querying and managing data.Lastly,a mobile phone client was designed for administrator to monitoring real-time situation of litchi orchard even outdoors.Optimization of fuzzy control algorithm was completed after studying the fuzzy control theory and system,including choosing input and output variable domain and fuzzy language variables,creating the fuzzy rules,making defuzzification,etc.This paper using Matlab to simulate the algorithm,and then optimizing the module of the controller.?3?Through the research and design of irrigation model of litchi orchard expert system,including irrigation forecast model,quantitative irrigation model,irrigation rules and the most water-saving irrigation model,to solve the actual litchi production management to determine the irrigation interval,irrigation water per irrigation and how to improve the yield of litchi and other issues.With help of a model of expert system software,the users can choose different irrigation methods according to the actual situation of litchi orchards.Each method has their own advantages and disadvantages.?4?Tested power consumption of different nodes to verify nodes is low power consumption.Designed node life cycle test to verify the nodes can work in litchi orchard field for a long time.Tested interior network to verify the network performance can meet the needs of litchi orchard field monitoring.Designed sensor calibration experiment to verify the monitoring accuracy of environmental parameters in litchi orchard.?5?Furthermore,integration and performance tests was carried out and the network was deployed in litchi orchard environment.Effective communication distance of the nodes,network packet loss rate,intelligent irrigation performance of the system and decision accuracy of expert system was measured and assessed.The analysis and summarizes of the test results show as follows:a)In the test of effective communication distance of the nodes,the six different height--0.25m,0.5 m,0.75m,1.0 m,1.25m,and 1.5 m--where nodes installed was compared.When the nodes were in the open field,all of their effective communication were 1205 m.When the nodes were in the litchi orchard,the longest effective communication distance was 81.5m which belongs to 1.0m,larger than distance of 0.25m,0.5m 0.75m,1.25m and1.5m.b)In the test of network packet loss rate,soil moisture had been collected by sensors in nodes every 30 minutes using the strategy of dormancy awakening for 15 days.The result showed that a single node packet loss rate was 2.63%at least,loss rate of whole network 3.87%on average and 4.03%at most.Packet loss rates were low enough to satisfy stable and reliable requirement of communication.c)During the performance test period,the soil moisture content in A zone and B zone was compared.On one hand,the average of the soil moisture content of A zone was17.85%,higher than the lower threshold of litchi growth--15.55%and achieved expected effect using intelligent irrigation.On the other hand,the average of the soil moisture content in B zone without been irrigated was 7.75%,much lower than 15.55%.In conclusion,the performance of intelligent irrigation system was better.d)The results of system test of decision accuracy was measured in two scenarios.When only a parameter was input to system,it predicted litchi drought level would be 4 or5 at the next irrigation time,which meant litchi trees were in wet or humid condition now.Meanwhile,soil moisture content was still in the best level of litchi trees growth--15.55%¹9.14%,demonstrating that prediction ofdecision-making system was conflict with actual situation.When multiple parameters was input,the prediction of drought level would be 3 at the next irrigation time,litchi,which meant litchi trees were in a suitable growth state now.At the same time,soil moisture content was in the best level of litchi trees growth,proving the litchi drought condition predicted by decision-making system matched the actual situation.Therefore the accuracy of the irrigation decision could be improved by inputting multiple parameters.