Parameters optimization and experiment of mechanical wheat shooting seed-metering device

This study aims to optimize the key component and blade in a shooting mechanism using the conflict matrix method of TRIZ, in order to improve the emergence rate of seeding, while, to reduce the seed breaking rate, during planting wheat in a mechanical shooting seed-metering device. The structure of blade was designed as a combined blade using the surface and reverse force method in TRIZ, where the backward blade served as an initial part, while the forward blade as an accelerate part. Compared with the previous blades, a combined parameters of optimal structure was achieved to decrease the wheat breaking rate, where the radius of backward and forwardbladeswere4 mm and 800mm, respectively. The kinematics analysis can be used to clarify the influencing factors related to the internal collision force of wheat seed and shooting performance during the movement of wheat seed inside the shooting device. The specific factors included the rotation speed of seed-metering device, the radius of backward blade, and the install angle of blades. There was also great influence of structural parameters of blades on the movement of wheat seed in the contact process between wheat seed and blades. EDEM software was used to simulate the movement of wheat seed inside the seed-metering device, where the wheat seeds were constructed by a bonding sphere. In a simulation experiment, five blades were designed to explore the shooting performance at different structures and motion parameters. The maximum collision force between wheat seed and blade were determined for the breaking rate of seeds. An orthogonal simulation test was designed to evaluate the experiment indicators, including the average shooting speed, the maximum collision force, and the coefficient of variation for the shooting depth. The test results showed the primary and secondary order of influencing factors for each index. In the maximum collision force, the significance order was the rotation speed of seed-metering device, the radius of backward blade and install angle of blades, whereas, the significance order for the average shooting speed was the rotation speed of seed-metering device, the install angle of blade, and radius of backward blade. Furthermore, the significance order for the coefficient of variation of shooting depth was the rotation speed of seed-metering device, the install angle of blade, and radius of backward blades. The verification bench experiment was performed on the Conservation Tillage Research Center of China Agricultural University, in 2019, where the average shooting speed, seed breaking rate, coefficient of variation of seeding depth were selected as experiment indicators. The power of seed-metering device and forward speed of conveyor belt were provided by an electric motor directly, where the speed was adjusted at five different levels. In the shooting experiment, the average size of wheat seed (Zheng Mai 9023) was 4.1 mm×3.2 mm×2.1 mm, and the average water content was 19.4%. A SF501 high speed camera was used to collect the average shooting speed of wheat seed, with the spotlight and capture frequency was 50 mm and 1000 r/min, respectively. The results show that the maximum collision force, seed breaking rate, average shooting speed, and coefficient of variation of shooting depth were 7.3 N, 1.1%, 32.5 m/s and 8.9%, respectively, while the rotation speed of seed-metering device, radius of backward blade, and install angle of blade were 1 000 r/min, 40 mm and 15°, respectively. This findings can provide new promising techniques and approaches for the optimization design of seed-metering device in mechanical shooting of wheat.