Statistical analysis of threshing characteristics of Impact-type rice plant threshing device

An impact-type threshing device that applies perpendicular force to rice ear was developed in this study. Threshing experiment was performed for a single ear and to a bundle of rice plants. Crop properties and collision conditions were used as input parameters in this experiment to perform multiple regression analysis, thereby estimating threshing rate and percentage of grains with rachis branch. Optimal regression model for estimating threshing rate and percentage of grains with rachis branch was obtained for both single ear and bundle of rice plants. Although all four regression models had low analytical error and verification error, but relative error was high due to insufficient number of datasets and accuracy was low as a result. However, certain extent of estimation was possible for threshing rate. Observing that threshing rate was highly correlated with transverse threshing force and transverse displacement, it was inferred that threshing of rice plant by impact-type threshing device is from perpendicular force acting on rice ears. Although estimation of percentage of grains with rachis branch had low absolute error, accuracy was low because of relative error that is enlarged due to low rate of occurrence. Since percentage of grains with rachis branch was negatively correlated with net's mesh size, we concluded that the mesh size must be made as low as possible to reduce percentage of grains with rachis branch.