| Most of the orchards in the south of China are mountainous with relatively large slopes.Because there is no good planning and the distance between plants is small,largescale spray machinery is difficult to enter the orchard for pesticide application.Therefore,in 2011,the team developed a pipeline constant pressure spraying system.(Abbreviated to single-node system),the system uses the pressure of the pump outlet as the input of closedloop feedback,which can ensure the pressure of the outlet is constant and can basically guarantee the normal spraying demand.However,the liquid flow in the pipeline will be lost.The pressure at the outlet of the pump will be different from the pressure at the node.At the same time,the terrain will have a great impact on the pressure of the node.Therefore,the pressure at the node is limited by the terrain.Sometimes,it is impossible to ensure that the pressure of the pump outlet is nearly the same as that of the outlet of the pump,so that the effect of spraying can not be achieved.Therefore,it is of theoretical significance and use value to make a set of pressure values at the monitoring nodes and feedback the pressure values at the nodes back to the control system.This can effectively improve the pressure control system at the nodes.Therefore,this paper develops a multi-node pressure control system and conducts a field spray test from the point of view of reducing the relative deviation between node pressure and pump outlet.This article uses ZigBee wireless communication technology and uses 12 V lithium battery for power supply.A multi-node liquid pressure control system has been set up.The system can realize real-time monitoring of the outlets of various nodes.According to the pressure,farmers can install different numbers of ZigBee wireless nodes according to the orchard area.At the same time,the system uses closed-loop feedback.The average pressure monitored by each node is used as the feedback value of the closed-loop feedback to ensure that the pipeline pressure is stable in the setting work.The pressure can also ensure that the pressure at the outlet of each node is constant and can be set as close to the set working pressure as possible.The multi-node liquid pressure control system makes the spray effect optimal.The research content and results of this paper are summarized as follows.1)The overall design of the multi-point liquid chemical control system: The system consists of two major parts,the spray device and the electronic control system.The spray device includes the frequency converter,variable frequency motor,water pump,main pipeline,branch pipeline,and spray node;the inverter controls the frequency conversion motor and frequency conversion.The motor drives the water pump and the main pipeline to discharge the drug from the pump outlet and reaches the branch pipeline respectively.Finally,several outlets are connected to each branch pipe to fight the drug.2)The electronic control system includes a main control system and a wireless pressure transmission node system.ZigBee wireless communication protocol is used for data transmission between the systems.The main control system plays a central coordination role,and the read data of each node is analyzed and processed as a system.The feedback parameters make the pressure of the branch pipe stable within the set working pressure error range.3)Wireless pressure transmission node system design: 8 wireless pressure transmission nodes are installed at equal intervals in the two branches of the orchard to monitor the pressure of the spray nodes.The experimental results show that the wireless pressure transmission nodes can all make 100% correct response in the wireless transmission mode.4)Field trial study: The test results show that for a single point system,the greater the number of open spray guns,the greater the pressure decay rate,and the greater the node pressure variance.For a multi-point system,the number of open spray guns does not have a significant effect on the spray node pressure,and no matter how many open spray guns are used,the node pressure variance is close to zero.Changing the set working pressure,flat ground and uphill conditions,the node pressure variance of a single-node system will gradually increase.Under the downhill conditions,the node pressure variance of a single-node system will gradually decrease,and the multi-node system can improve this effect.5)The terrain has a great influence on the pressure of the nodes,and the uphill terrain has greater influence on the pressure of the nodes.The designed multi-node liquid pressure control system can simultaneously monitor the data of multiple nodes,and can also process data of multiple nodes at the same time.The pressure data measured in the field spray test can be combined with the actual demand of the orchard,and the tests performed.The research provides reference for further improving the constant pressure spray of orchard pipelines and optimizing the technical parameters of their network management.However,the designed multi-point liquid pressure control system still has some shortcomings.For example,the waterproof and sun-proofing of the pressure node needs to be solved.It is hoped that the design of the multi-point liquid pressure control system can be improved according to the shortcomings. |
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