| Precision control irrigation technology is an important part of precision agriculture.At present,the most obstacle of precision agriculture is still the research on high density,high speed,high accuracy and low cost acquiring technology of farmland information.As the development of successful application of Wireless Sensor Networks(WSN) in occasions,the WSN technology has been applied in large-scale farmland irrigation control system abroad, while such research is at the beginning stage in China.During application of WSN on acquiring farmland information,specific application feature must be taken into consideration to solve key issue in data transmission,thus,research on key technology of WSN data transmission regarding specific case of farmland irrigation control system is significant for establishment of WSN theory in precision agriculture and promotion of precision irrigation in China.Based on requirement of precision irrigation,combined with feature of WSN,taken sprinkler irrigation system as an example,a precision irrigation oriented WSN data transmission system was introduced and key issues regarding data transmission was further studied.The main research and innovative achievements includes:1.Create a WSN irrigated area soil moisture data acquisition/transmission method to make further development on the process of realizing "high density,high speed,high accuracy and low cost" precision agriculture information acquisition.Via analyzing requirements of precision irrigation and features of WSN based on arrangement of sprinkler irrigation system,taking sprinkling area into consideration,and studying classification methods of sprinkling area,a WSN with layer structure was designed, which adopted irrigated plot as irrigation unit and took data acquiring area of irrigated plots nearby as basic object to study constructing method of overall WSN data transmission system.2.Establish optimal deployment models of sensor nodes and aggregation nodes to realize low cost nodes deployment.To meet requirements of precision irrigation for completely acquaint of farmland information,pertaining theories have been discussed theoretically.Placement of equilateral triangle mesh was proposed for irrigated plots.Via analyzing relationship between sprinkler range and sensing radius of sensor node,optimized coverage placement model for sensor nodes of irrigated plots was introduced.Shortage of equilateral triangle mesh was analyzed, and proper revised placement was proposed as well,which was compared with that of equilateral triangle mesh.To meet requirement of full connectivity of sensor nodes,an optimal deployment model of aggregation nodes was established with equilateral triangle mesh.3.Create a node dynamic power management method to realize low power consumption data transmission.To reduce nodes communication consumption and prolong network life,a dynamic power management based on data flow grey prediction was proposed according to time varied soil moisture,which adopted aggregation node in data collection area to predict data flow of each cluster,and created prediction model using grey theory to realize dynamic switching of operation mode with limited WSN nodes and reduce communication consumption between WSN nodes.Operation status of nodes was studied and two operation modes of node were defined as well.Simulation results show that over 63.63%of communication consumption can be saved using this dynamic power management method.4.Establish a node fault diagnosis model to realize reliable data transmission.A spatial correlated fault diagnosis model was introduced according to spatial correlation of each sensor node data of irrigated area,and then Variance Theory was adopted to carry out the 1 st stage judgment to get parts of normal nodes;fault diagnosis of second stage can be realized for the other nodes according to data deviation.Experiments show the effectiveness of fault diagnosis method.
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