| The paddy wheel as the driving wheel of the plant protection sprayer whose structual parameters have a great influence on the trafficability of sprayer.At present,there are more researches on the impact of dryland tires on the trafficability of tires and less researches on the impact of paddy wheel on the trafficability.Therefore,this study is started from the interaction between paddy wheel and paddy soil,improving the trifficability of the sprayer by optimizing the structural parameters of the paddy wheel.1.Based on the fundamental theories of vehicle ground mechanics and soil mechanics,this paper analyzes the soil mechanical properties related to the trifficability in paddy field environment.The shear properties of paddy soil is described by the Mohr-Coulomb criterion.The cohesion and internal friction angle of the paddy soil are measured.2.Based on cohesion and internal friction angle measured above and soil,a simulation model of the interaction between paddy wheel and paddy soil is established by using the finite element and Smoothed Particle Hydrodynamics(SPH)methods.The previously measured values are used as parameters of the soil SPH model.The changing curve of the paddy wheel subsidence and the cloud diagram of the change of shear stress generated by the applied soil during walking are obtained by Ls-Dyna explicit dynamics solver.After analyzing the force changes of the paddy wheel during the simulated walking process,the interactive mechanism between the paddy wheel and the soil during the walking is obtained,that is,the paddy wheel shears the soil under the action of torque,and relies on the adhesion to overcome the adhesion resistance and compaction resistance to drive the plant protection sprayer.According to the above conclusion,the optimized parameters and indicators are determined.3.Taking pattern depth,pattern tilt Angle and pattern length as factors,and hook traction and traction efficiency as trafficability indicators,this paper concludes the influence of each factor on the index under a single variable.Through the orthogonal test method,the index value under each factor combination is calculated by simulation.The results show the major and minor influence of the sprayer paddy wheel structure factors on the hook tractive force and tractive efficiency by range analysis and variance analysis.Multi-objective optimization is analyzed based on analysis results from response surface,it is concluded that the overall index is optimized extremely at a pattern depth of 50 mm,a pattern inclination angle of 80 °,and a pattern length of 50mm.Compared with the performance indicators under the original parameters,the optimized drawball pull has increased by 23%,and the tractive efficiency has increased by 5.3%.The simulation and optimization is verified by the paddy field experiment.The results show that the simulation value is consistent with the overall trend of the overall drawball pull curve measured by the test under different slip rates.The maximum error is 10.1%and the minimum error is 1.6%,all within the allowable range of error.It indicating that the optimization results have certain accuracy and applicability.The drawball pull test value with optimized structure is 22.2%higher than the calculated value with original parameter,which is closed to the 23%increased in simulation optimization results,which proves the optimization results is reasonable.This paper provides a certain reference for the structural design of the sprayer paddy wheel,and has certain significance for the research of self-propelled sprayer and the improvement of trafficability. |
PDF Full Text Request