Research On Local Path Planning And Tracking Control Of Horticultural Electric Tractor

As a small new energy tractor,the horticultural electric tractors can be used in large-scale planting areas such as orchards and forest gardens,which can complete a variety of autonomous operations and intelligent management tasks.It can meet the demands that intelligent agricultural machinery operations have safety and accuracy under the new situation.Local path planning and tracking control is a key part in the research field of autonomous operation of intelligent agricultural machinery.It is one of the important methods to solve the low degree of autonomy and poor tracking performance of current agricultural machinery.This paper takes the horticultural electric tractor as the research object,and conducts in-depth research on local path planning and tracking control.The main research contents include:(1)The theory of navigation and positioning was analyzed.The positioning accuracy and stability of positioning and navigation equipment were analyzed by static test.A two-degree-of-freedom dynamic model of horticultural electric tractor was established.The forward Euler method and the first-order difference quotient method were used for linear discretization,and a linear time-varying prediction model was established,which provided a theoretical basis for the subsequent design of tracking controller and tracking control test.(2)Aimed at the local path planning problem in the obstacle scene,a local path planning algorithm was designed based on the artificial potential field method.By establishing a virtual obstacle function model and an optimized repulsive potential field function model,the problem that the target is unreachable and easy to fall into local optimum was solved.On this basis,the variable ellipse influence area function model of obstacles was designed,and the road boundary constraints and velocity repulsion constraints were added.In addition,the cubic B-spline interpolation was integrated into algorithm,so that the planned path meets the driving requirements of the horticultural electric tractor.(3)Aimed at the problem that the model predictive tracking controller with fixed time domain parameters has poor comprehensive performance under different roads,From the perspective of time domain parameter optimization,the influence of different dual time domain parameters on the controller tracking performance was analyzed,and used genetic algorithm to solve the optimal time domain parameters under different roads,which provide a basis for setting the adaptive adjustment range of time domain parameters.The prediction time domain adaptive control strategy based on fuzzy control,and the control time domain adaptive control strategy based on functional relationship were proposed respectively.Based on this,the adaptive time domain parameter lateral tracking controller was designed for simulation and comparative analysis under different roads.The results show that the controller designed in this paper can ensure good tracking accuracy and possess high real-time performance.(4)Integrated the designed path planner with the tracking controller,and built a visual simulation environment,and conducted simulation analysis based on the Matlab/Simulink and Car Sim co-simulation platform.It was verified that the integrated structure has real-time planning of safe paths and accurate tracking in obstacle scenarios.Based on the horticultural electric tractor real vehicle test platform,the navigation tracking control test was carried out,which further verified the effectiveness of tracking controller in practical applications.