Cassava is one of the world's top three tuber crops, and its harvesting mechanization level is low. Digging- pulling cassava harvester is the main research direction of cassava harvesters. However, the soil-loosening components of the existing digging-pulling harvesters have poor loosening effect, high tuber damage rate, and large pulling force of cassava tubers after loosening. The two-sided loosening shovel that digs and loosens the soil on both sides of the tubers has low working resistance and is not easy to damage the tubers, but there are few reports on the impact of its operating performance. Therefore, this study focuses on three common types of two-sided soil-loosening shovels: the offset-wing shovel (OWS), L shovel (LS), and double-wing shovel (DWS). A two-factor, three-level orthogonal experiment is conducted, taking tillage depth (h) and shovel distance (b) as variables, then range analysis and factor impact analysis are carried out. Finally, through comprehensive comparison and optimization, a shovel type with best operational effects and its optimal working conditions are identified. The results show the LS demonstrated optimal performance when the breakage rate and pulling force were minimized. At the optimal combination of h of 0.25 m and b of 0.6 m, the LS has a breakage rate of 7.576% and a pulling force of 291.608 N. This study can provide basis for optimizing the design of loosening parts of digging-pulling cassava harvester.

In this study, the potato excavator with loosening shovel was designed in order to solve the problems of serious soil obstruction and high excavation resistance during the potato harvest. Using EDEM discrete element simulation software, potato excavation simulation experiments were carried out on soil broken effects and excavation resistance. Through the comparative analysis with loosening shovel and without, the results showed that the increase of soil broken effects was close to 52%, and the excavation resistance decreased by 16.57%. Through the two-factor and three-level field orthogonal experiment with excavation depth and loosening depth as influencing factors, the optimal operating parameters was determined for potato excavators: the excavation depth was 23 cm and the loosening depth was 20 cm. At this time, the excavation potato rate was 98.21%, and the rate of damaged potato was 1.31%. The traction resistance was 1826 N, which met the requirements of relevant industry standards. Through comparative analysis of simulation experiments and field experiment, it was found that when the excavation depth was 23 cm and the loosening depth was 20 cm, the error value of traction resistance was 11.3% between simulation experiments and field experiments. The discrete element simulation analysis can provide a preliminary reference for potato excavation design.