Development of testbed for seeding performance test of drill metering device based on intermittent automatic sampling

Abstract: Aiming at the problems of manual test of performance test of drill seed metering uniformity, such as time consuming and laborious, lack of automatic test means and so on, a testbed for drill seed metering performance test was designed. With the intermittent sampling mechanism, the testbed can realize automatic sampling and sowing uniformity detection at fixed intervals. Its working principle is that the seeds falling onto the conveyor belt and moving along with the conveyor belt to form the seed zoon, when the seed zoon moving into the sampling zones, a part of seeds were pushed to the outside of seed zoon by sampling plate, which has a reciprocating motion driven by the air pump, the seeds outside the seed zoon were scattered into an arc under the thrust force of sampling plate and formed the sampled seeds. The distribution of sampled seeds were imaged by the digital camera, and then the numbers of sampled seeds were obtained by image processing technology using Matlab software, which was used to evaluate the seed metering uniformity of seed metering device. Single chip microcomputer was used to control the rotary speed of seeding shaft, start and stop of sampling plate and its movement direction and the result was displayed on upper computer. The key structure and parameters of the testbed were designed, and the seed zoon width was determined to be 30 mm, the seed guard plate length was 150 mm, and the distance between the seed guard plate and the conveyor belt was controlled to be 2-3 mm. To reduce the stacking and adhesion of seeds, ensure the uniform arrangement of sampling seed zoon, and facilitate the image processing in the later stage, three sampling plates with the shape of "一", "T" and "工" were designed. Based on the analysis of the force and motion of the seeds, it was determined that "T" shape sample plate was the optimal structure, and the sampling length was 40 mm. The wheat seed metering device with external trays was used as the research object, and the center combined rotation design test was carried out with Design-Expert software. The results showed that when the rotary speed of conveyor belts driving motor was 20, 28.79 (seed rate was 5.41 g/s) and 28.79 r/min(seed rate was 3.41 g/s), the stack rate of sample seeds was 100%、92.34% and 75.21%, separately; when the metering quantity was 6 g/s, the stack rate of sampled seed was 40.15%, and there was less stack in other treatments. Compared with the manual distance sampling, the time consuming of the intermittent automatic sampling method was about 5 s, but that of the manual distance sampling was about 1 min, and the time increased with the increase of sample seeds number, which made the time difference larger. The result illustrated that testbed for seeding performance test of drill crop based on intermittent automatic sampling was reasonable, which could improve the working efficiency.