| With the improvement of people's living standard and the change of life style,fruit has become the third largest crop in our country and fruit industry occupies an important position in our national economy.However,the low degree of orchard mechanization and the shortage of labor force restrict the further development of fruit industry in our country.Therefore,it is considered as an effective way that robots enter orchards and finish the production work instead of person.Based on the project of "Research and Development of Multifunctional Self-propelled Orchard Management Robot",this paper does the following main work on the autonomous navigation system of Orchard Operating Robot:(1)Briefly introduce the research background and significance of this topic,the paper investigates and analyzes the research status of autonomous navigation system for agricultural robots at home and abroad.Then,list the existing problems and challenges of autonomous navigation system of Orchard Operating Robot.(2)The functional requirements of autonomous navigation system of Orchard Operating Robot are analyzed,including global positioning function,global trajectory planning function,trajectory tracking function and remote operation function.Based on the analysis of application environment,the overall design of software and hardware of the robot system is carried out,and the selection of key hardware and the design of software framework are completed.(3)A global positioning method is designed for orchard semi-structured environment.Based on the LOAM algorithm of three-dimensional laser SLAM,a re-location algorithm based on prior map is designed,which increases in numbers of feature points and improves the accuracy and stability of location.Then the data of RTK-GNSS are fused with 3D SLAM,and the estimated value of 3D SLAM algorithm is corrected by the observation value of RTK-GNSS,which solves the problem that 3D SLAM algorithm is easy to fail in feature points matching in the turning stage,and makes the global positioning accuracy of the robot meet the requirements of autonomous navigation in orchard.(4)Based on the global positioning of the robot,the autonomous navigation requirements of Orchard Operating Robot are analyzed,and the autonomous navigation modes of path teaching,trajectory optimization and trajectory tracking are determined.Then the system modeling of Orchard Operating Robot is carried out,including kinematics modeling and coordinate system modeling.A trajectory optimization algorithm is designed to smooth the initial path obtained by the teaching,plan speed of the robot and obtain the optimal trajectory.(5)On the basis of global positioning and trajectory planning,an autonomous navigation controller of Orchard Operating Robot is designed.Based on the idea of hierarchical control,the trajectory tracking controller and speed tracking controller are designed respectively.Firstly,the tracking error of tracked mobile robot is modeled,and the trajectory tracking control law is verified.Secondly,the speed loop sliding mode controller and the cloud model cross-coupling controller of DC motor are designed to reduce the speed tracking error and compound tracking error.(6)The autonomous navigation system of Orchard Operating Robot is implemented and tested.Based on the hardware platform,the subsystem of the robot is programmed in ROS system and the subsystem of upper computer is programmed in Aliyun platform.Through the test of global positioning function and trajectory tracking function of the robot,the feasibility and effectiveness of the autonomous navigation system designed in this paper are proved. |
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