Study on Pulling Dynamic Characteristics of White Radish and the Optimal Design of a Harvesting Device

Abstract

The loss rate is an important index to evaluate the harvesting performance of white radish. To reduce the loss rate, it is necessary to analyze the pulling dynamic characteristics of white radish and then optimize the structure and operating parameters of the harvesting device. In this paper, according to the growth characteristics of white radish in the field, the discrete element method (DEM) was used to simulate the pulling process. The pulling force was calculated using the Edinburgh elasto-plastic adhesion model (EEPA), and the effects of soil bed compactness, pulling speed and angle on the pulling force were analyzed. The tests on pulling mechanics were carried out in the laboratory to verify the accuracy of DEM simulation results. The results showed that in the soft soil bed with compactness less than 2.8 MPa, the pulling force of radish is generally smaller than the leaf breaking force, and it is feasible to pull the radish out directly. While in a soil bed with high compactness, it is necessary to install a loosening shovel to reduce the pulling force thus reducing the loss rate due to leaf breakage. The structure and operating parameters of the harvesting device were designed according to the pulling dynamic characteristics, and the white radish harvesting tests were carried out in different fields. Statistical results show that when the soil compaction was increased from 1.47 MPa to 2.21 MPa, the average loss rate increased from 0.68% to 1.75%, and the average damage rate increased from 2.41% to 2.70%. Similarly, when the forward speed was increased from 0.18 to 0.47 m/s, the average loss rate increased from 1.08% to 1.30%, and the average damage rate increased from 2.34% to 2.74%. Overall, the maximum loss rate and the maximum damage rate could be controlled below 2.0% and 3.0%, respectively. In the hard soil bed, the loss rate can be effectively reduced from 15% to 2.5% by installing a loosening shovel.