Parametric analysis and numerical optimisation of spinach root vibration shovel cutting using discrete element method

Shovelling the soil and cutting the roots is the first step in harvesting the whole spinach plant, which determines the movement state of spinach plants, the state of soil fragmentation and root soil separation force. Therefore, it is necessary to thoroughly study the process of shovelling the soil and cutting the roots. Firstly, micromechanical and macromechanical models of shovel cutting were built. It was induced that vibration shovel cutting was conducive to soil fragmentation and root-soil separation by the theoretical models. Secondly, a vibration shovel cutting mechanism was proposed. In order to study the interaction mechanism of root-soil-shovel, a root-soil composite discrete element model was established and calibrated. Vibration shovel cutting simulation test was carried out based on the model. The effects of three vibration shovel cutting parameters (vibration amplitude, vibration frequency and cutting speed) on the number of bond by bonding (BOND) breakage, root-soil movement law, soil uplift height and root-soil separation in normal vibration, tangential vibration and non-vibration were analyzed. BOND breakage was conducive to spinach aggregation and root-soil separation by simulation analysis. As determined by response surface analysis, the optimal combination of parameters for the maximum number (80363) of BOND breakage and the minimum soil uplift height (19.4 mm) was vibration amplitude of 3 mm, vibration frequency of 40 Hz and cutting speed of 0.3 m/s. Finally, the vibration shovel cutting model was verified experimentally by field tests. This study provides a method to study the interaction mechanism of rootsoil-shovel.