# Influencing Factors Analysis and Simulation Calibration of Restitution Coefficient of Rice Grain
## 3 Results and Discussion
### Discussion  
According to the influence of contact materials on the restitution coefficient of rice grain, the greater the hardness of materials, the greater the restitution coefficient of rice grain. To reduce the splash loss and breakage rate of rice grain in the harvesting process, rubber protection devices can be set on the header of the combine harvester. In addition, rubber type flexible threshing elements can be used in the threshing drum to reduce the breakage rate and ensure rice grain harvest quality. For the working parts that need to increase grain rebound to improve the material circulation, such as the cleaning screen of the combine harvester and seed metering plate, the material with the larger recovery coefficient can be used. According to the influence of spring compressions (initial velocity of rice grain) on the restitution coefficient of rice grain, the greater the spring compression, the greater the initial velocity, and the smaller the restitution coefficient, that is, the greater the velocity difference. In the design and development of the key components of the high-speed precision metering device, such as seed filling, seed protection, seed cleaning, and seed feeding, the initial speed of rice grains should be minimized to maintain the stability in the process of migration. At the same time, how to design the structure of the seed meteringdevice to achieve zero speed seeding, reduce the collision of seeds in the seed guide tube, so as to achieve the goal of low multiples and leak index and high qualified index, is one of the directions. According to the effect of moisture content on the restitution coefficient of rice grain, the higher the moisture content was, the smaller the restitution coefficient was. In the process of rice harvest, rice should be harvested under the condition of appropriate moisture content. Rice grains are directly contacted with the rigid material of the combine harvester in the process of conveying, threshing, and cleaning. When the moisture content of rice grains is high, the deformation of rice grains is large, and the restitution coefficient is small, which is easy to increase the grain breakage rate. At the same time, the moisture content of the rice stem is relatively high, which is easy to block in the screw pusher, inclined conveyor, and threshing chamber of the combine harvester, affecting the quality and efficiency of harvesting working. In addition, high-moisture-content rice is not easy to store after harvest. It needs an additional drying process, which increases the production cost. However, the moisture content during harvesting should not be too low. When the combine harvester is working, the rigid and hard contact between the reel on the header assembly and the upright rice is easy to cause a large loss of header and a large area of grain loss. Therefore, the best harvest time is from the late waxy stage to the early mature stage of rice, and the moisture content is generally 15-21% [32]. Because of the randomness of the rotation speed of rice grain, it cannot be calculated quantitatively. At the same time, the rotation also led to the contact parts of rice grains not to be accurately controlled, and the influence of air resistance was ignored in the process of the test, resulting in certain errors, which is also the deficiency of this study. In the later stage, the calculation of the moment of inertia of rice grain and the analysis of the rotational state after collision will be studied in depth. At the same time, the measuring device of the  
Figure 12: Comparison of motion state of rice grain before and after collision. (**a–d**) is the bench test; (**e–h**) is the simulation test: (**a**) before collision (0.10 s Y state); (**b**) after collision (0.11 s Y state); (**c**) after collision (0.12 s Y state); (**d**) after collision (0.13 s Y state); (**e**) before collision (0.10 s Y state); (**f**) after collision (0.11 s Y state); (**g**) after collision (0.12 s Y state); and (**h**) after collision (0.13 s Y state).