Design And Development Of A Fertilizer Flow Measurement System Based On Single-Line Lidar

At present,in order to alleviate the pressure of per capita arable land,the overuse of chemical fertilizers is widely used to increase the yield of grain in most parts of china.It has caused a significant decrease in the organic matter content of the arable land,soil compaction and acidification,and serious damage to the microbial system.It has severely damaged China's agricultural resources and environment.In view of the above phenomenon,in order to ensure the sustainable development of China's agriculture,variable fertilization has gradually become the academic frontier and research hotspot in the agricultural engineering field.In recent years,scholars at home and abroad put forward a lot of technical means.But it is difficult to achieve the actual fertilizer flow as feedback signal.As a result,the accuracy of variable fertilization closed-loop control system is generally low.Therefore,in order to overcome the technical bottleneck that the measurement accuracy of fertilizer flow is difficult to improve,this paper designs a fertilizer flow measurement system based on single-line lidar.The system realizes the actual amount of fertilizer discharged as a feedback amount,and significantly improves the measurement accuracy of the fertilizer flow.The main research content of this article is as follows:(1)The lidar motion control mechanism and hardware control system are designed in this paper.They have the main functions of interval sampling,reciprocating periodic motion and high precision based on the imaging characteristics of single-line lidar.The lidar motion control mechanism is mainly composed of synchronous belt linear slide module,Omron photoelectric switch and motion controller SMC606.The synchronous belt linear slide module has high-speed uniform motion capability(position accuracy: 0.1mm).The photoelectric switch can control the lidar to achieve reciprocating motion.And the SMC606 controls and monitors the lidar motion state in real time.Based on the DLL of the SMC606,the lidar motion control system software is written.It can realize the functions of human-computer interaction and real-time control of lidar motion state.(2)The point cloud algorithm of the measurement system is analyzed and designed.Firstly in this paper.First,by studying the characteristics of point cloud on the surface of fertilizer,the basic data pre-processing procedures such as point cloud coordinate system conversion,median filtering,external point processing,abnormal local point processing,linear interpolation,Gaussian smoothing and dynamic area extraction are proposed.In the second step,Delaunay triangulation and volume integration are performed on the pre-processed dynamic area for volume calculation of the fertilizer flow.Finally,,the software for calculating the amount of fertilizer is programmed based on QT.And combining multi-thread technology,a main thread,a data preprocessing thread,and a volume integration thread are written.By above research,the measurement system designed in this paper has the functions of basic function parameter configuration,point cloud processing and calculation of fertilizer flow.(3)In order to explore the regression relationship between the system response time,the optimal scanning speed and the measurement accuracy of the system,the measurement volume of the fertilizer flow,and to determine the optimal value of each parameter,the parameter optimization test was performed on the measurement system.In this paper,the curve between sampling speed and measurement error was obtained by simulation software.The influence law of sampling speed on average effective error is clear.And according to the sampling speed error curve,it is determined that the scanning speed factor level range is 200 mm/s to 500 mm/s.Through the single factor experiment,the optimal scanning speed was determined as 500mm/s,and the system response time was determined as 1154 ms.The linear regression formula for phosphate fertilizer,potash fertilizer and nitrogen fertilizer are respectively obtained as 1 0166 0 0313NM(28).V(10).,1 2961 0 1391kM(28).V(10).and NM =0.6862V+0.0159.2R are 0.9958,0.9966 and 0.9948,and the average effective error are 2.67%,2.71% and 2.64%.(4)In this paper,field experiments were performed to verify the results of parameter optimization experiments and the actual operation effectiveness of the measurement system.The field test results show that the average effective error of phosphate fertilizer,potash fertilizer and nitrogen fertilizer in the actual operation is 2.79%,2.81% and 2.83%,respectively.And the effective error increases with the increase of fertilizer flow within a certain range.The system effective error is stable within 3.91% when the fertilizer flow exceeds 1.75 kg.The fertilizer flow measurement system designed in this paper can significantly improve the accuracy of variable fertilization.It can reduce the effective error by about 35% compared with the variable fertilization system based on CPLD developed by Jilin University.Therefore,this study can provide technical and equipment support for variable fertilization operations.