Development of a model to predict the throwing trajectory of a rice seedling

[Display omitted] •Propose a trajectory prediction model based on experimental and numerical method.•Measure the trajectory and forces of a thrown rice seedling using experiments.•Use the model to predict the trajectory dynamic parameters of rice seedlings. Understanding the trajectory parameters (e.g., distance and angle) and dynamic behaviors (e.g., velocity and acceleration) of a thrown seedling is paramount important for the design and operation of rice seedling throwing equipment. In this study, a trajectory prediction model based on Runge-Kutta algorithm was developed. The model considered the drag and lift forces at different wind velocities which were measured using a wind tunnel test. Two different motion analysis models were proposed for the rising and falling stages of the trajectory. The equations of motion were solved using the Runge-Kutta algorithm. The modeling results were in good agreement with the experimental results as shown by the relative errors of 0.16%, 3.61%, and 6.16% for the throwing distance (D), final angle (θF), and final velocity (vF) respectively. The validated model was used to examine the effects of the throwing height (H) and the initial angle (θI) on the D, θF, and vF. Generally speaking, the effects of θI on both D and θF were more dominant as compared to H, but in certain situations, the results were the opposite. The relationships between the working parameters (H and θI) and the throwing parameters (D, θF, and vF) were quantified using regression equations with R2 values greater than 0.96. The equations could be used to determine the appropriate working parameters of a rice seedling thrower to meet specific requirements on the trajectory and associated parameters of the throwing process. The proposed model would be useful in understanding the working mechanism and predicting the throwing trajectory of rice seedling throwing equipment for accurate replanting operations.