Research On Variable-rate Spray Targets Laser Scanning Detection Under Simulated Complex Terrain

Spray target detection is an important part of precision variable-rate spray applications.Because of the excellent characteristics of fast scanning speed,high detection accuracy and suitable for outdoor environments,laser scanning sensor has attracted much attention in research and application of precision variable-rate spray.However,potential unknown complex terrain conditions are likely to reduce detection accuracy of target scanning based on real-time sensor of variable-rate sprayer in the actual spray process.The main purpose of this research is to provide more accurate target size information and three-dimensional(3-D)reconstruction images for precision variable spray under complex terrain conditions by exploring how to reduce the adverse impact of laser scanning sensor with attitude angle deviations.First of all,the detection principle of the selected two-dimensional laser scanning sensor has been introduced,and then the data acquisition of target laser detection and the detailed methods of target 3-D reconstruction have been studied.On this basis,an experiment of target laser detection has been designed by linear sliding table target detection platform.The excellent performance of the selected laser sensor and the effectiveness of target 3-D reconstruction method were verified by this experiment.Then,spray target laser detection and correction on linear sliding table and spray target has been studied.The deviations of laser sensor attitude angles in three dimensions were used to simulate complex terrain by adjusting the installation angles of the laser sensor with the linear sliding table target detection platform.Three kinds of attitude angle deviations correction methods were proposed when there were fixed attitude angle deviations of roll,yaw and pitch,respectively.These three methods can be expressed as re-matching trigonometric function and polar coordinate value,correcting coefficient value of depth and re-combinating detection frames and detection points,respectively.And then some experiments were designed to verify the effectiveness of the proposed correction methods when each single kind of fixed attitude angle deviations and the combined fixed attitude angle deviations existed separately.The experiment results showed that the relative errors of width,height and canopy height of tree-shape carving board were all less than 5%,and the relative errors of width,height and canopy height of the artificial tree were all less than 10%.The corrected three-dimensional reconstruction images were greatly improved compared with that before correction.It meets the accuracy requirements of variable-rate spray detection.At last,spray target vehicle-borne laser detection and correction by matching vehicle attitude angle deviations has been studied.A vehicle-borne laser target detection platform with a laser sensor and inertial measurement unit was built to perform target detection experiments.The inertial measurement unit was capable of detecting the real-time attitude angle deviations of test vehicle and saving the data.According to the idea of using the test vehicle dynamic attitude angle deviations to correct the target laser detection data,three kinds of dynamic attitude angle deviations correction methods were put forward to obtain accurate size information of targets and 3-D reconstruction images.These three methods can be expressed as re-matching trigonometric function and polar coordinate value with the fusion of real-time roll angles for dynamic roll correction,re-combinating the detection frames and detection points with the fusion of pitch angle average values segmently for dynamic pitch correction,and correcting coefficient value of depth data with the fusion of yaw angle average values for dynamic yaw correction,respectively.And then some experiments were designed to verify the effectiveness of the proposed correction methods under three kinds of test conditions,which were single dynamic pitch angles,combined dynamic attitude angle deviations of pitch angles and roll angles,and complex terrains,separately.The experiment results showed that the relative errors of height,width of cuboid cabinet were all less than 10% and the relative errors of height,width and canopy height of the artificial tree were also all less than 10%.Good correction effect verified the effectiveness of the proposed correction methods.In this paper,according to the influence of complex terrain conditions on the target laser detection,the study of spray target laser detection and correction with fixed and dynamic attitude angle deviations of laser sensor provided a certain theoretical and experimental basis for the detection of variable-rate spray.