Seeding parameter monitoring method based on laser sensors

Current parameters monitoring of corn seeding has widely used as a type of infrared photoelectric sensor, which is easily susceptible to the impact of dust and falling seeds during sowing in precision agricultural practice. The previous sensors installed in the middle and upper part of the seed guide tube cannot accurately count the double overlapping seeds in the actual sowing. There are also large monitoring deviations with low accuracy of measurement of key parameters in the system. In this study, laser-based parameter monitoring was proposed for corn seeding. The laser sensor can penetrate transparent objects, together with unique characteristics, including good directionality, high brightness, and good monochromaticity. A modulating control valve was selected to improve the anti-interference performance in the direct laser modulation. An inverter drive circuit was used to increase the driving force in the monitoring system. Taking the signal capture source, the laser sensor was easily installed on a specially designed transparent joint, which could be fully matched with the bottom end of the seed tube. The most popular microcontroller STM32 was selected as the main controller, where the timer's input capture function was used to obtain the period of pulse signals for the seeding parameters. As such, it realized the statistics on the number of seeds. The oscilloscope test results showed that the program design capture value was accurate and reliable. High-speed camera technology was utilized to analyze the falling process of seeds. It was found that the seeds were easy to collide and bounce in the lower part of the seed guide tube, particularly on the great variation in the movement route of seeds. Since the sensor installed in the upper part of the seed guide tube could not accurately monitor, the sensor position was selected at the bottom of guide tube in the installation, reducing the monitoring error and obtaining the parameters closer to the real seeding situation. Three monitoring tests were carried out for the simulated dust, seeding parameters, and double seed overlap, in order to verify the reliability of laser monitoring. In the simulated dust test, the log paper was used to simulate dust, where the size of dust was obtained via changing the thickness of the paper. Two kinds of sensors were simultaneously monitoring, where an infrared sensor was installed on the upper part of the same seed guide tube and a laser sensor on the bottom end. The experimental results show that the laser sensor achieved a higher monitoring accuracy rate under dusty working conditions, with more accurate seeding parameters, compared with the infrared sensor. Specifically, the laser sensor could still monitor normally, while the infrared sensor could not, particularly when the log paper increased to 4 layers. Nevertheless, the laser sensor could not be used when the log paper increased to 8 layers. At the speeds of 5, 6, 7, 8, 9 km/h, the average monitoring error of each parameter was below 0.5 percent points, and the average monitoring error for the number of seeds was 3. The accuracy rate reached 95.4% for the laser sensor installed at the bottom of the seed guide tube to monitor the double overlapping seeds discharged from the seeding port. In contrast, the average detection accuracy of the previous infrared sensors installed on the upper part was only below 6.6%. The experiment verified that the laser monitoring has the reliable working performance to meet the needs of actual seeding parameter monitoring.