Design and experiment of missing seed detection and the reseeding device for spoon chain garlic seeders

Abstract: A leakage detection and supplemental inoculation device was designed to deal with the missing garlic seeds during extracting in a spoon-chain garlic seeder. The device included a laser sensor, a rotating spoon-type supplemental inoculation mechanism, and a supplemental inoculation box. Diffuse laser sensors were selected to monitor the seed extraction, further to determine the missing seeds, according to the output pulse. The STM32 processor and electromagnetic clutch were taken as the core in the control system for the missing seed detection and replenishment. A masking pulse acquisition experiment was conducted to obtain the critical pulse width when the seed picker missed the garlic seed. Taking the Ⅰ, Ⅱ, and Ⅲ grade Jinxiang garlic seeds as the research objects, a bench test was carried out in Jinxiang County, Jining City, Shandong Province, China. The range of masking pulses was determined in a seed picker under the different attitudes within the normal lifting speed. In the interval of 0.09 ~ 0.15m/s seed lifting speed, the maximum and minimum pulse width of garlic seed and scoop were 440.6 and 121.6 ms, respectively, whereas, those of the empty scoop were 87.9 and 53.3 ms, respectively. As such, the critical pulse width of the seed scoop was assumed in the range of 88 to 121 ms. The critical pulse width was then defined as 100 ms, considering that the output pulse of the empty scoop was relatively fixed at the same speed, while that of the seed scoop varied significantly during operation. The distance between the installation position of the sensor and the highest point of the seed extraction chain was set at 130mm, according to the easy maintenance of small garlic seeders. A kinematics analysis was made to obtain the optimal seeding time in a rotating spoon machine for accurate seeding during replanting. At the typical lifting speed of 0.12 m/s, the angle between the radius direction of the rotating spoon-type seed replenishing machine and the gravity direction of the garlic seed to be thrown was from 58.74° to 71.99°, while the angle between the velocity and the gravity direction was from 71.17° to 71.82°, and the duration to fall into the guide cylinder was from 0.161 to 0.170 s. At the speed of 0.12 m/s, the sensor detected that the electromagnetic clutch was electrified for 625 ms after missing seeds, and then the electromagnetic clutch stopped working after 363 ms. At the same time, the garlic seeds fell into the seed tube to complete the supplemental inoculation. The results showed that the success rate of the system was 100 % for the detection of whether the spoon-chain seed collector missed or not at the different speeds of seed extraction. At the seed extraction speed of 0.12 m/s, the success rate of grade I, II, and III garlic seeds after supplemental inoculation increased from 90.13%, 93.13%, and 95.88% to 99.25%, 99.75%, and 100%, respectively. At the raising speed of 0.15 m/s, the sowing success rates of grade I, II, and III garlic increased from 90.25%, 93.13%, and 96% to 99.25%, 99.625%, and 99.88%, respectively. It infers that the missed sowing rate was significantly reduced, fully meeting the garlic sowing requirements. Furthermore, the detection and seed replenishment system can fully match the different forms of spoon and chain garlic seeders. Both the laser sensor and electromagnetic clutch can also offer strong anti-interference, simple control, stable and reliable long-term performance. The new device can also provide promising technical support to the spoon and chain garlic seeders with the seed replenishment.