Research On Navigation Control System Of Greenhouse Inspection Robot

The application of greenhouse inspection robots is of great significance to the intelligent development of greenhouse environment and plant detection.Aiming at the problems such as fixed navigation route,high cost of sensor installation and laying and poor satellite positioning signal of the current greenhouse inspection robot.In this paper,by comparing and analyzing the existing navigation control methods of greenhouse mobile robots,a multi-source data fusion navigation scheme based on Lidar SLAM(Simultaneous Location and Mapping)technology is determined,and then finally design a set of autonomous positioning and navigation control system for greenhouse inspection robot based on multi-line Lidar and 2D Lidar SLAM technology which enables inspection robots to have real-time positioning and map construction,multitarget path planning and dynamic obstacle avoidance functions.At the same time,it provides an autonomous operation carrier for the installation of other sensing equipment,which can effectively replace the manual completion of greenhouse inspections operations.The main research contents are as follows:(1)Design of hardware and software of inspection robot navigation system.The design and selection of the hardware and software system of the inspection robot navigation system are completed.The hardware system adopts a modular design method,including sensor module,control module,drive module and power supply module.The inspection robot based on industrial computer realizes timely positioning and map construction of the inspection robot which combines the environmental information collected by the 16-line Lidar,inertial measurement unit information and odometer information.The robot uses STM32 embedded motherboard to complete the underlying control of the inspection robot.The inspection robot software system is developed and designed based on Linux system and Ubuntu 18.04 as a whole,including application layer,control layer and driver layer.The application layer realizes the navigation task scheduling of inspection robot through a graphical interface designed based on Qt Designer;the core control layer is based on ROS(Robot Operating System)development,including environment map construction,multi-target point setting,autonomous positioning of inspection robots and path planning and navigation;the driver layer is used to issue the underlying control commands of inspection robots.(2)Construction of the inspection robot environment map.In order to enhance the safety of the inspection robot during the greenhouse operation and reduce the computational effort during its map construction,this study designed a point cloud conversion node to filter and fuse the 3D environment information collected by the multi-line Lidar into a 2D laser information layer by layer.The fused 2D laser data information includes the information of the closest obstacles to the inspection robot within the height threshold and range threshold set by the node,and then fuses the inertial measurement unit information and odometer information on this basis,and completes the inspection robot with reference to the 2D Cartographer algorithm.Greenhouse navigation raster map build.(3)Design of the positioning and navigation function of the inspection robot.In terms of positioning,the adaptive Monte Carlo algorithm is used to continuously match the environmental information collected by the Lidar with the built grid map,thereby realizing the autonomous positioning of the inspection robot in the navigation map.In terms of path planning of the inspection robot,the Dijkstra algorithm is used for global path planning,and the DWA(Dynamic Window Approach)algorithm is used for local path planning.By designing the target visualization node,the inspection robot adopts the RVIZ-based visualization interface and the Publish Point function to realize the navigation multi-target point setting.(4)Testing the positioning accuracy and navigation accuracy of the inspection robot.Through the design of the inspection robot positioning accuracy test and navigation accuracy test,and the field test in a standard glass greenhouse,the inspection robot moves at a speed of 0.4m/s,the average position deviation from the target positioning point is less than 8cm,and the standard deviation is less than 3cm,the mean deviation of heading is less than 3°,and the standard deviation is less than 1°.When the inspection robot moves at speeds of 0.2m/s,0.4m/s,and 0.6m/s respectively,the average lateral deviation between its actual motion path and the target motion path is less than 10 cm,and the standard deviation is less than 6cm.The average deviation of the heading during the movement is less than 3°,and the standard deviation is less than1.5°.The positioning accuracy and navigation accuracy both meet the mobile navigation and positioning requirements of the inspection robot in the greenhouse environment.