Design And Experimental Study Of Accurate Dry Land Flat System Based On GNSS

Accurate leveling technology can effectively improve farmland irrigation efficiency,save agricultural water,reduce the use of pesticides and fertilizers,improve the overall agricultural production capacity of China,and achieve sustainable agricultural development.The traditional farmland flatland method has low leveling accuracy,time and labor consumption,etc.,and it was difficult to meet the requirements of high standard farmland construction.The laser-controlled flat ground technology had high precision,but the operating radius was small and the degree of intelligence was low.Therefore,this thesis studies and designs a GNSS-based Accurate Dry Land Flat system.The main contents and conclusions are as follows:(1)GNSS-based Accurate Dry Land Flat system design.The system consists of GNSS positioning system,GNSS data processing module,intelligent flat information processing module,level controller and flat shovel.The GNSS positioning system measures the real-time three-dimensional data of the shovel,the GNSS data processing module performs coordinate transformation and extraction on the real-time GNSS three-dimensional data,and the intelligent flat-level information processing module designs and analyzes the flat ground depth,the earthwork distribution and the ground working path according to the three-dimensional data of the leveling operation.The controller automatically controls the blade by hydraulic system.(2)GNSS system elevation positioning accuracy test research.The GNSS system elevation accuracy measurement test was carried out.The test results showed that the mean and standard deviation of the deviation between the elevation value and the reference elevation value of the motion measurement of the platform were 1.29cm and0.92cm respectively,and the data less than or equal to 3cm accounts for 98.7%.The precision of the RTK-GNSS positioning system can meet the precision leveling requirements of farmland.(3)Designed of real-time acquisition system for flat terrain.The displacement sensor was used to measure the elongation of the hydraulic cylinder,and the mathematical model of the positional relationship between the GNSS antenna and the blade is established.The three-dimensional terrain of the rear area of the flat shovel was collected in real time during the ground operation.With the suspension multi-wheel support dryland grader platform,four different vehicle speeds were collected and measured in the dry land.The results showed that the 3D terrain real-time acquisition system can obtain accurate and realistic 3D terrain of farmland under the dynamic conditions(the real-time adjustment of the hydraulic cylinder during the operation of the grader).The difference between the standard and the constructed terrain is mostly concentrated at around 1.1 cm,and the standard deviation was at most 1.527 cm.The acquisition accuracy of the farmland three-dimensional terrain acquisition system in the field can meet the requirements of accurate leveling.(4)Research on flat ground depth and earthwork calculation method.The elevation calculation and the DTM triangulation were used to calculate the earthwork using the elevation weighted average method.The 6×6 raster data was selected from the 3D topographic data of farmland for flat ground depth and earthwork calculation.The comparison with the results of Surfer14 software showed that the weighted elevation average flat ground depth calculation method and Surfer14 software calculated the same result,both were 13.96m;The DTM triangulation earthwork calculation method and the Surfer14 software have a small difference between the fill volume and the excavation volume,and can better reach the earthwork fill and fill balance with an error of less than0.13m~3.(5)Research on intelligent planning of the leveling work path.The dynamic path planning algorithm for flat work was designed.The calculation method of farmland soil distribution trend evaluation was proposed.The flat land depth update method is established based on the relationship between the flat soil distribution and the amount of soil shovel,and the intelligent real-time update path algorithm was realized.(6)Experimental Research.Taking the suspended multi-wheel support dryland grader as the platform,the measurement accuracy test of the farmland three-dimensional terrain real-time acquisition system was carried out.The 3D terrain acquired by the Z+F 3D laser radar acquisition system was used as a reference.The comparative analysis results showed that the three-dimensional terrain distribution method of the farmland and the Z+F three-dimensional lidar acquisition method were similar;due to the Z+F three-dimensional laser radar The information such as weeds could be scanned,resulting in an elevation value of 3.7cm higher than the average elevation of the farmland three-dimensional acquisition system,and the standard deviation phase was 1.02 cm higher.Set the constraints(the actual earthmoving capacity of the shovel and the rated power of the tractor)and the unconstrained two kinds of ground working conditions,and carry out the numerical calculation test of the dynamic path planning algorithm for the horizontal operation and the three conventional working path algorithms,and the test results of the two kinds of flat working conditions.It was shown that the earthwork excavation fill method of the flat ground operation dynamic path planning algorithm was the smallest,which indicates that the flat ground operation dynamic path planning algorithm has the highest level of flat ground after the flat land field.Under the constraint constraint condition,the flat work dynamic path plan is flat after the ground.The path algorithm of earthwork fill and excavation was 1.1m~3 more than that of unconstrained restraint,which indicates that it was difficult to achieve the expected leveling work requirements with a single traversal planing path in the actual leveling operation.Therefore,real-time acquisition of the three-dimensional terrain in the flat area and calculation of updated flat path information,and one or more reciprocating flattening of the Pinghou field in time,was conducive to improving the accuracy and efficiency of the ground.