Research On Navigation Control Of Orchard Sprayer Based On Lidar And Satellite Positioning

Orchard planting area is large in China.With the decrease of rural labor population,the demand for unmanned orchard operation is increasing,among which spraying operation is an important part of orchard management.In order to realize unmanned spray operation,this paper developed an experimental prototype of autonomous navigation sprayer in orchard,and realized the function of autonomous navigation and spraying operation between fruit trees.This requires accurate detection and positioning of orchard environment,operating object and operating machine itself.In non-standard orchard,fruit trees were planted irregularly,leading twists and turns of road and fruit trees,thus causing a great difficulty for orchard autonomous navigation.In order to make the experimental prototype have the flexibility to adapt to the road and orchard rows,three-dimensional lidar combined with GNSS-IMU integrated navigation system was used to detect the orchard environment,and the laser point cloud processing method and navigation control algorithm were studied.The main work is as follows:(1)Navigation detection and control system was designed and implemented.According to the functional requirements,the idea of modular design was adopted and the design scheme for satellite positioning system,laser radar detection system,chassis control system and spray system was given.The control circuits for chassis and spray system were designed.And satellite positioning data analysis and coordinate conversion were carried out.The point cloud data and positioning data time synchronization was realized.(2)The detection and recognition of fruit trees in orchard environment and the navigation path calculation of spray were realized.The coordinate transformation of point cloud data was completed.According to the characteristics that the density of point cloud decreases with the increase of distance,the existing algorithm was improved to adapt to the clustering of different point cloud density by adding distance factor;The point cloud filtering algorithm and sub regional ground fitting algorithm were designed to realize the filtering,noise reduction and ground segmentation of point cloud.Through adaptive point cloud clustering,the point cloud information of fruit trees was obtained,and the fruit trees could be accurately detected and identified at the distance of 16.4m.Then,the geometric center coordinate of point cloud after clustering was used as the location of fruit trees,and the fruit tree row curve was fitted according to the location distribution of fruit trees,and the navigation path adapted to the zigzag changes of road between fruit trees was calculated.(3)The kinematic modeling and path tracking algorithm of sprayer chassis are studied.According to the sliding steering principle of four-wheel chassis,the chassis kinematics model was established,and the pure tracking control algorithm was improved to increase its control accuracy in curves.Curvilinear path tracking and linear path tracking experiments were carried out respectively,and the results showed that:At the speed of 0.5m/s,the maximum lateral error of curve driving is 0.056 m and the average error is 0.023 m,and the maximum lateral error of straight driving is 0.045 m and the average error is 0.019 m.Therefore,it can be seen that the spray machine can track both straight path and curve path with high precision.(4)The experiment and research on the autonomous navigation and spraying of the orchard navigation sprayer were carried out.Under the experimental conditions,curvilinear tree rows were arranged,autonomous navigation and spray tests of orchard sprayer along the tree rows were carried out,and spray effects of linear walking and curvilinear walking were compared.The experimental results show that when driving along the straight path,the maximum difference between the sprayer and the left and right fruit trees is 0.57 m,and the standard deviation is 0.180 m.The distance between the sprayer and the fruit trees varies greatly.The average difference of fog drop coverage between the left and right fruit trees is 29.93%,and the spray is not uniform.Compared with the straight line driving and the curve path driving,the maximum difference between the sprayer and the fruit trees on the left and right sides was 0.06 m,and the standard deviation was 0.084 m.The average difference between the fog drop coverage of the fruit trees on the left and right sides was7.11%,decreasing by 22.82%,indicating a significant improvement in spraying uniformity and spraying effect.The above results show that the orchard sprayer developed in this paper has the function of autonomous navigation between orchard rows,adapt to the curve road between orchard rows,and spray medicine evenly.