Abstract:
To solve the problems of unsatisfactory hole shape, difficult coordination between hole digging and transplanting and decentration of holes during tobacco seedling transplanting, the process, operation resistance, and soil reflux situations of hole digging were analyzed. The soil physical parameters were measured, and the soil parameters were standardized. The results showed that the dynamic and static friction coefficients and collision recovery coefficient of soil and hole digging shovels were 0.14, 0.98 and 0.48, respectively. The accumulation angle regression model was optimized to achieve a target soil accumulation angle of 44.6°. A set of optimal solution resulted in a surface energy between soil particles of 11.8 J/m
2, with collision recovery and static friction coefficients of 0.34 and 0.56, and a dynamic friction coefficient of 0.10. The simulated stacking angle under this solution was 42.9°, with a relative error of 3.8% with the measured value. Three simulation models based on the discrete element contact theory were developed to simulate the interactions between the digging shovel and soil in the tobacco field, and computer simulation of the digging process was performed. The soil box model consistent with the actual situation was determined by comparing the results of field experiments with the results of computer simulation. The analysis results of soil reflux showed that there was less soil reflux in the entry phase and more soil reflux in the exit phase with a soil reflux rate of 4.77% in the central area. Disturbance caused by shovel blade in the exit phase was greater, and the soil reflux rate in this phase was 16.41%. The overall soil reflux rate of the whole digging process was 8.66%. The analysis of the change rule of digging resistance showed that the maximum peak of resistance occurred at 0.7 seconds, the maximum operation resistance was 411.3 N, and the maximum power required during the digging process was 137.2 W.