Design and experiment of test bench for garlic bulbil adjustment and seeding based on bilateral image identification

Garlic is one of the most important cash crops in China. Single grain sowing in garlic planting needs to follow the agronomic requirements of the upward bulbil and downward root. Since foreign garlic planters cannot be used for hybrid garlic sowing in our case, it becomes necessary for domestic garlic planters to adjust the direction of various garlic bulbils using mechanical devices. These garlic planters have a good effect on the sowing of Cangshan garlic, but not good on that of the hybrid garlic. The reason is that the irregular shape of the hybrid garlic cannot meet the condition of the center of gravity locating at the lower half of the garlic clove. In this case of the irregular garlic, the mechanical directing device also fail to adjust the direction of the garlic bulbil. Here a test bench for the garlic seeding was designed to solve the sowing of the hybrid garlic. The test bench of garlic sowing is mainly composed of a seed taking device, a garlic sorting device, an image acquiring machine, a detecting system of garlic bulbil direction, a device of garlic seed directing, and a box for the garlic seeds. The motor with adjustable speeds can serve as the power source for the test bench of the garlic seeding. The following procedure will be performed on this test bench. The power of the motor via the chain drive can first be input to the single-grain taking device with large/small scoops, which can take the single-grained garlic out from the storing box. A large scoop can take one or more garlic seeds in one time, where the single-grain spoon can be turned 90o counter clockwise to transfer the garlic into the small volume of the spoon. Since the small spoon can hold only one garlic, the rest of garlics fall back into the seed box. The device of the single-grain picking transports the garlic and flips the spoon at the top of the garlic channel. Due to the movement of the garlic baffle and various gravity-center of garlics, the garlic seeds that fell into the garlic channel can be arranged horizontally to move linearly with the downward baffle. When the garlic reached to the location of the image collection, the photoelectric sensor can be triggered to control each of the USB cameras on the both sides of the garlic channel to take an image. Based on the collected image showing the bulbil/root of the garlic, the detecting device can identify the direction of the garlic bulbil, whereas the directing device of garlic seed can adjust timely the direction of the garlic. In the course of the garlic seeding, it is necessary to optimize the operating parameters of the test bench. Therefore, the test factors can be selected as the motor speed, the width of the garlic channel, the shooting distance, and the recognition threshold, while the test index as the directing rate of garlic seed. The performance test for the test bench of garlic seeding was carried out by using Box-Behnken analytical method to obtain the influence of the seed directing rate on the sowing of hybrid garlic. The primary and secondary factors in order were the width of the garlic channel, the motor speed, the shooting distance and the recognition threshold. These parameters can then be optimized in the data-processing software Design Expert 10. The optimum parameters can be achieved as the index of the seed directing rate: the motor speed was 18.34 r/min, the width of the garlic channel was 38 mm, the shooting distance was 8.64 mm, and the recognition threshold was 178.36. The seed directing rate was reached 91.67% predicted by the model. Under the condition of modified optimum working parameters, the garlic seed directing rate in the physical test can reached 90.56%, showing that the experimental results were consistent with the optimized simulation. The average identification time of a garlic was 0.29 s, which can meet the requirements of the sowing speed of the garlic planter. These findings can provide insightful application for the vertical planting technology of hybrid garlics.