Design and experiment of the flexible baffle-type conveying and separating device for multiple taro harvesting machine

Taro is one of the three major export specialty aquatic vegetables in China (along with lotus root and water chestnut), and it plays an important role in promoting the national strategy of rural revitalization. However, currently, the harvesting process of taro mainly relies on manual labor, with the labor cost accounting for 40% to 50%. The technical difficulty lies in that taro grows in a wet and sticky soil environment, and during harvesting, the root system is entangled and adhered to the soil, forming a conical spherical root-soil composite structure, making it difficult to separate the taro from the soil. At the same time, the moisture content of taro during the harvesting period is as high as 73.70%, and it is prone to mechanical damage when subjected to impact. Therefore, exploring the root-stem soil separation technology and optimizing the separation mode of transportation is an important scientific issue that urgently needs to be solved in the current mechanized harvesting of taro. When transporting taro using the traditional rod-bar type lifting chain, there are problems such as the root-soil composite body rolling back and falling, low transportation efficiency, and high damage rate of taro. This study designed a flexible baffle-type transportation separation device. It is mainly composed of rods, rubber baffles, vibrating wheels, frames and chain drives. By analyzing the collision and disintegration characteristics and throwing effect of the flexible baffle on the root-soil composite body, the main factors affecting the transportation separation performance were identified as the height of the flexible baffle, the lifting line speed, the inclination angle of the screen surface, the vibration frequency and amplitude of the vibrating wheel. The coupling method of discrete element - finite element - multi-body dynamics (DEM-FEM-MBD) was used to analyze the influence laws of the height of the flexible baffle, the inclination angle of the conveying screen surface, the lifting line speed, the vibration frequency and amplitude on the average transportation time and soil screening rate of taro. Through single-factor simulation experiments, the results showed that the flexible baffle could effectively prevent the root-soil composite body from rolling back, and the maximum impact force of the flexible baffle on the taro was 55.66% lower than that of the rigid baffle. The flexible baffle spacing was determined to be 300mm. Grid convergence verification was carried out, and the mesh size of the flexible baffle was determined to be 4mm.The relative error between the fitting curve and the physical experiment was 1.78%. Through the Box-Behnken response surface bench test, the influence laws of the transportation screen inclination angle, lifting line speed and vibrating wheel frequency on the average transportation time and soil screening rate of taro were explored. After multi-objective optimization, the optimal parameter combination was determined to be: a transportation screen inclination angle of 18°, a lifting line speed of 0.62 m/s, and a vibrating wheel frequency of 2 Hz. The soil screening rate was 88.76%, and the taro transportation time was 1.91 s. The relative errors of the two with the regression model predictions were 0.15% and 2.10% respectively. The relative errors between the coupled simulation tests and the bench tests were 0.20% and 3.08% respectively, which verified the reliability of the coupled model. Field verification results showed that the soil screening rate and transportation success rate of the flexible baffle-type transportation separation device were increased by 4.72 and 17.97 percentage points respectively, while the damage rate and harvest loss rate of taro were reduced by 12.11 and 0.97 percentage points. The separation effect and harvest quality were superior to those of the traditional rod-bar type transportation separation device, meeting the requirements of multi-sub-taro transportation separation operations. The research results can provide a reference for the optimization design of efficient and low-loss harvesting equipment for taro and other root and tuber crops.