Analysis of <i>Cyperus esculentus</i>–Soil Dynamic Behavior during Rotary Tillage Based on Discrete Element Method

Considering the problems of low soil fragmentation rates, high working resistance, and high energy consumption in the harvesting process of <i>Cyperus esculentus</i> in China, a method of <i>Cyperus esculentus</i> harvesting based on counter-rotation digging is proposed. The mechanism of interaction between the rotary tillage blade and <i>Cyperus esculentus</i>–soil is systematically investigated, and the vertical and horizontal disturbance performance of the positive and counter-rotating harvesting methods on soil and <i>Cyperus esculentus</i> is compared and analyzed. The results of the experiment showed that the intensity of soil and <i>Cyperus esculentus</i> disturbance by counter-rotation increased by 166.67% and 297.78%, respectively, and the effective disturbance time of soil and <i>Cyperus esculentus</i> increased by 133.33% compared to that of positive rotation. The working depth and rotation speed of the rotary tillage blade were the most significant for soil and <i>Cyperus esculentus</i> disturbance intensity. The working depth increased from 150 mm to 170 mm, and the soil disturbance intensity increased by 17.91% and 21.37% for positive and counter-rotating operation, respectively, and the rotation speed of the rotary tillage blade increased from 270 rpm to 330 rpm, and the soil disturbance intensity increased by 28.85% and 35.29%, respectively. Compared with the positive rotation operation, the <i>Cyperus esculentus</i> counter-rotation soil fragmentation rate increased by 4.09%, the <i>Cyperus esculentus</i> damage rate decreased by 10.69%, and the buried fruit rate decreased by 7.38%. This paper helps to understand the interaction mechanism between the rototiller and <i>Cyperus esculentus</i>–soil and lays a theoretical foundation for the subsequent design and optimization of the <i>Cyperus esculentus</i> digging device.