Design And Experiment Of A Bionic Subsoiling Mechanism For Hilly And Mountainous Farmland Based On DEM

As an important content of conservation tillage,soil subsoiling technology could break the plow pan soil,ameliorate the soil structure,and improve the soil water storage and moisture retention capacity.The hilly and mountainous farmland in China is characterized by complex terrain and scattered distribution,which makes it extremely inconvenient to conduct subsoiling with large tractor.Combining bionics theory and agronomic requirements,this paper designed a six bar subsoiling mechanism that can achieve the specific trajectory.The excellent performance of the six bar subsoiling mechanism has been verified using discrete element method,and the accuracy of the discrete element method has been verified through soil tank tests.This provides a reference basis for the design of the executive components to small and medium-sized subsoiling machines suitable for hilly and mountainous farmland.The main research contents and conclusions of this paper are as follows:(1)Combining multiple factor test methods,the soil accumulation test was designed to calibrate the micro parameters of the tillage layer soil,and the soil direct shear test was designed to calibrate the micro parameters of the plow pan soil.A dual contact model coupled discrete element soil model was established.(2)Image processing technology was used to extract the point cloud data of the inner and outer contour for the largest toe of a mole cricket’s forefoot,and the polynomial functions were used to fit the point cloud data.A bionic subsoiler was designed based on the optimal fitting function.Using the ADAMS-EDEM coupling simulation method,the discrete element simulation analysis of the interaction process between the four bar subsoiling mechanism equipped with a bionic subsoiler and a common subsoiler mechanism and soil was conducted.The results showed that the bionic subsoiler had the advantages of resistance reduction,greater damage to the bottom pan,and better soil disturbance effects.(3)The digging trajectory of mole rats’ forelimb was mapped into a desired subsoiling trajectory.A comprehensive optimization model for the high-dimensional path generation without prescribed timing,with the goal of minimizing the square sum of Euclidean distances between the target trajectory point and the set of positions of the coupler of the designed four-bar mechanism,was established.An improved difference algorithm was used to solve the optimization model,and a bionic four bar subsoiling mechanism capable of reproducing the moles’ digging trajectory was designed using the optimal solution.The discrete element method was used to verify that the comprehensive tillage performance of the bionic four bar subsoiling mechanism has improved,but the soil disturbance effect is not good.(4)Aiming at the problem of poor soil disturbing effect for the bionic four bar subsoiling mechanism,the bionic trajectory was optimized to serve as an ideal subsoiling trajectory based on the agronomic requirements.A six bar subsoiling mechanism capable of reproducing the ideal trajectory was designed.The tillage performance of the bionic four bar subsoiling mechanism and the six bar subsoiling mechanism were compared using the discrete element method.The results showed that the six bar subsoiling mechanism had resistance reduction performance,and the soil disturbance effects were more in line with the requirements of subsoiling agronomy.(5)An indoor soil tank test of the physical prototype for six bar subsoiling mechanism was carried out.The variation data of tillage resistance for the subsoiler were obtained using a strain testing system.The soil disturbance process was observed and analyzed.And a discrete element simulation was conducted under the same conditions.The results show that the relative error between the simulated and measured values of the average tillage resistance is 8.67%.The damage range and depth of the plow pan,the disturbance range of each soil layer,and the soil discharged condition of the subsoiler in the experiment are basically consistent with the simulation results.