Study On Structure Design Of Autonomous Walking Plant-protection Vehicle And Its Control System

In recent decades,the development of satellite navigation,wireless transmission of information,sensor and control technology supports the intelligent agricultural equipment technically and accelerates the design and development of intelligent agricultural equipment.Intelligent agricultural equipment is increasingly used in the agricultural production.To further improve the intelligent machinery of pest control,an autonomous walking plant-protection vehicle is designed in this study.The study covers the following contents:(1)Targeted the agronomy demand and actual production condition of HuangHuai-Hai region,the performance index of operating platform and overall design scheme are determined.The wheel span and ground clearance chassis of operating vehicle can be adjusted and it is four-wheel drive.Through comparison and analysis on main steering mode of wheeled vehicles,articulated steering is adopted.Innovation design is made to active steering structure and wheel span adjustment structure,wheel span is adjustable from 1m to 1.3m,and ground clearance is adjustable from 0.5m to 1.3m.Kinetic equation of plant-protection vehicle is established,which can be applied to select drive motor model and power supply parameter through computation.Model selection is also conducted to spray system including sprinkler,teat pipette and sprayer controller.(2)In order to verify the rationality of the design of the chassis structure of the work vehicle,the finite element analysis of the chassis of the plant protection work vehicle was carried out,and the stress and displacement distribution diagrams of the chassis under bending and torsion conditions were obtained.Under the two working conditions,the maximum stress is 68.692Mpa and maximum displacement is 0.5284mm,less than yield limit of the material.Modal analysis is also conducted on chassis to get natural frequency(22.367-81.881Hz)and mode of vibration in the first six orders,and the maximum frequency of external excitation is 9.375Hz,without resonating with chassis structure.The analysis result indicates that chassis structure meets the work requirement.(3)Kinematic model of plant-protection vehicle is built,its path tracking method is analyzed,and stability of steering control is also analyzed through establishing Lyapunov function.In addition,analysis and simulation are also carried out on filtering algorithm of sensor and PID control of drive motor,the result of which shows that it is more reliable to use extended kalman filter(EKF)adopting multi-sensor fusion;and PID control can accelerate the system response time.(4)Hardware selection,circuit design and program design of control system are conducted.Hardware selection and circuit design include remote control,communication module,IMU sensor,GPS module and motor drive module,determining the type and completing circuit design of its interface.Following the schematic diagram,PCB model is made.C++is applied in control system,it is developed in Visual Studio 2017,then its basic structure is decided,and program development is completed on the autonomous walking function.(5)Finally,the field test was carried out on the prototype.The performance of the working platform turning radius,straight walking and endurance time was tested.The minimum turning radius of the prototype was 2m,the linear walking deviation of 100m was 5.51cm,and the cruising time was 2.54h.The experiment result indicates that prototype’s performance parameter basically meets the design requirement.