| The country attaches great importance to the development of intelligent agricultural machinery and equipment technology,Unmanned agricultural machinery is one of the important applications in the future.Agricultural machinery structure needs to have good flexibility to reduce the damage of agricultural machinery to the farmland.Traditional agricultural machinery mostly uses fuel-driven and front-wheel steering mechanical transmission,which has low transmission efficiency and poor flexibility.The four-wheel independent drive(4WID)agricultural machinery equipment can provide sufficient driving force and control freedom,which can effectively overcome the influence of the side slip of the driving wheel and improve the passability of the sprayer in a complex operating environment.The unmanned operation of agricultural machinery equipment integrates environmental perception,planning and decision-making,drive and control.Drive and control mainly realize the start,stop,acceleration and deceleration,steering movement and path tracking of agricultural machinery equipment.The essence of path tracking is to control the longitudinal and lateral movement to make the agricultural machinery equipment drive according to the desired path,so as to meet the needs of agricultural operations.Aiming at the structural shortcomings and low intelligence of traditional high clearance sprayer,this paper proposes 4WID high clearance sprayer with new front-rear-dual-steering-axle.This chassis structure with front-rear-dual-steering-axle and auxiliary push rod device does not require the steering wheel control of traditional agricultural machinery to achieve steering,which is convenient for unmanned operation.Studies the path tracking control strategy of the sprayer.The main contents are as follows:(1)First,4WID high clearance sprayer with new front-rear-dual-steering-axle is introduced.The structure of the sprayer is analyzed and the kinematic model and dynamics model of the sprayer are built.The chassis kinematics of the proposed new high clearance sprayer is established with ADAMS software.The model lays the foundation for the follow-up path tracking control strategy.(2)Based on the established chassis kinematics model of the sprayer and the single-point preview principle,a path tracking controller is designed.In the process of path tracking,the lateral deviation and heading deviation of the sprayer are kept within a certain error range.In a complex operating environment,hydraulic push rods and connecting rod devices are used together to achieve differential steering,which reduces path tracking errors while ensuring the same height of the front and rear wheel tracks to reduce crushing of crop seedlings.(3)Based on the preview model of the kinematics and dynamics model,model predictive control(MPC)path tracking control method is proposed.Adopting a layered structure,the upper controller takes the sprayer rotation angle and acceleration as the control variables and introduces the heading deviation and slip for path tracking control.The lower controller calculates the tire speed according to the obtained rotation angle and acceleration,so as to realize the sprayer’s path tracking.(4)A joint simulation platform is established based on Matlab/Simulink and ADAMS software to verify the correctness of the built model and the single-point preview control and MPC algorithms.Set up different operating environments to verify the tracking performance of the sprayer in straight travel and steering.The simulation results show the effectiveness of the path tracking control algorithm.(5)The A&D5436 hardware simulation experiment platform is built,the path tracking control experiment is carried out on the real vehicle.The experimental results show that the sprayer has good stability and the path tracking control algorithm has good control accuracy. |
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