Design and experiment of an intra-row weeding end in paddy fields based on discrete element simulation

High-efficiency weeding is often required for the low seedling injury in paddy fields. In this study, an intra-row finger weeding end was designed for such environments. The weeding end also included an inter-row hoeing roller and an inter-plant finger weeding end, according to the hoeing conditions of the paddy field. Initially, the working principle of the end was explained to determine the dimensional parameters of the inter-row and inter-plant hoeing end. The motion equation was established for the finger-weeding end. The motion trajectory was then plotted with the Matlab software. Subsequently, a systematic investigation was made to explore the influence of flexible finger lengths (65, 85, and 100 mm) on the motion trajectory. The finger weeding end of the motion trajectory map indicated that a significant impact was observed in the length of the finger employed for weeding at the finger end of the operation on the trajectory of motion. The results show the greater the length of the finger employed for weeding at the finger end of the operation was, the greater the area covered by a single finger was, and the greater the length of the finger was. Therefore, the inter-plant weeding area depended mainly on the length of the finger; The longer the finger was, the greater the area covered by a single finger at the end of the finger weeding was. Furthermore, a correlation analysis was performed between the finger length and the coverage of the inter-plant weeding area. The optimal working parameters of the finger weeding end were further determined to clarify the effects of different parameters on the soil disturbance, weeding effect, and soil structure. The simulation was also carried out on the weeding end–paddy field soil interaction. The optimal number of finger rods was then selected. A systematic evaluation was also made on the inner and outer stresses and the soil structure of the finger weeding end. There were critical forces on the inner and outer sides of the finger-wearing end and the velocity field of soil particles. The capacity of the finger weeding end was obtained to rotate stably and passively during weeding. Thereby, the roots of rice seedlings were protected from damage during operation. The performance of the finger weeding end was optimized to investigate the primary and secondary influencing factors on its working. Four parameters were utilized for optimization, namely the forward speed, the depth of entry into the soil, tilt angle, and bending angle. A four-factor three-level orthogonal test was conducted for the optimal parameters, with the weed removal rate as the primary objective during optimization. The optimal combination of parameters was the forward speed of 1.00 m/s, the soil penetration depth of 40 mm, the tilt angle of 30°, and the bending angle of the finger bending angle of 60°. The weed removal of the weeder end was validated in the real paddy. A weeder prototype machine was constructed. Among them, the rice transplanter was taken as the power platform machine, a finger weeding end was as the inter-plant weeding end, and a weeding roller was as the inter-row weeding end. The field test demonstrated that the average inter-row and inter-plant weeding rates were 80.76% and 78.57%, respectively, while the average seedling injury rate was 4.70%, indicating a better performance than before. The inter-plant weeding end was achieved as an effective inter-plant weeding to fully meet the demand of inter-plant weeding operations with less seedling injury.