In this study, the discrete element method was used to optimize the bucket size for the metering device in a garlic planter for enhancing the productivity of garlic farming according to the garlic size. Statistical information concerning the actual shape of garlic cloves was incorporated, and the mechanical properties of garlic were determined using the bulk density, sliding test, and repose angle test for enhancing the fidelity of the simulation model. The optimal bucket size achieving the target plant rate of 97.5% was determined using the developed discrete element model for the three garlic size groups. The linear search method was used for optimization, and batch simulation was performed to validate the optimized results and confirm the performance index of the metering device. A Gaussian distribution based on statistical information accounted for the various garlic sizes in each group. Finally, a metering test verified the reliability of the optimization technique. The differences between the simulation and test results were within 10% for all performance indices, including missing plant rate, multi-plant rate, and planting rate, indicating the high reliability of the analysis model. Subsequently, the larger garlic groups (Groups 2 and 3) exhibited metering performance close to the target plant rate.

The gearbox has the advantage of being able to change the torque and rotational speed according to the gear ratio and has high power transmission efficiency by transmitting power through the contact of the gear pair. When evaluating the strength and fatigue life of a gearbox using a design load or an equivalent load, there is a possibility that the results will be very different from the actual ones. Therefore, in this study, the load duration distribution (LDD) constructed based on the actual workload was used to evaluate the strength and fatigue life of the gearbox reliably. As a result of evaluating the strength and fatigue life of the gearbox using LDD, it was confirmed that the existing gearbox did not satisfy the target lifespan in the operating environment. Therefore, the reasons for these results were analyzed, and design modification was performed based on the analyzed results. As a result of design modification, shaft deflection decreased by rearrangement of the bearings, from an overhung type to a straddle type, thereby improving the fatigue life of gears and bearings. Finally, the load distribution acting on the gear tooth surface was improved through micro-geometry modification of the gears.

A gearbox is a power transmission system consisting of various machine elements such as gears, bearings, shafts, and housings. The gearbox has the advantage of being able to change the torque and rotation speed according to the gear ratio and has high power transmission efficiency by transmitting power through the contact of the gear pair. Although improvement and optimization of gearbox performance was researched in various fields, it is being conducted using an equivalent load condition rather than an actual workload. If the gearbox is evaluated using the equivalent load condition, the evaluation results are less reliable. Therefore, the gearbox must be evaluated under the actual workload condition in which the gearbox is operated. In this study, the evaluation of the gearbox was performed based on the actual workload measured in the environment in which the gearbox operates, and design modifications were made to improve and optimize the gearbox performance. As a result, shaft deflection was reduced by rearrangement of the bearing, from an overhung type to a straddle type, thereby improving the fatigue life of the bearing. Finally, the load distribution acting on the gear tooth surface was improved through micro-geometry modification of the gear.