A precise maize seeding parameter monitoring system at the end of seed tube: Improving monitoring accuracy using near-infrared diffusion emission-diffuse reflectance (NIRDE-DR)

In the context of precision agriculture, real-time monitoring of maize seeding parameters is of great significance for evaluating seeding situations and ensuring seeding quality. At present, seeding monitoring mainly uses the through beam photoelectric (TBP) method, which is susceptible to dust and can only be used at the upper part of the seed tube, affecting monitoring accuracy. For this purpose, this study developed a maize seeding parameter monitoring system based on near-infrared diffusion emission-diffuse reflectance (NIRDE-DR), which utilizes the diffusion emission effect of NIR rays to form a three-dimensional monitoring area for maize seeds without missed monitoring. When maize seeds with uneven surfaces enter the monitoring area, the diffuse reflectance effect of the seeds on NIR rays is utilized to change the electrical signal of the monitoring system, and the recognition of falling seeds is achieved by processing the electrical signal. NIRDE-DR takes advantage of the small size of dust particles, which are difficult to form a reflective area, effectively avoiding dust interference. Therefore, it can perform high-precision monitoring at the end of the seed tube. The NIR spectrum of coated maize seeds was measured, and the NIR wavenumber with the lowest absorbance and strongest reflection ability of maize seeds was determined as the target wavenumber of the monitoring system. The impact of the horizontal distance from the monitoring surface to the inner wall of the seed tube (HD) on seeding monitoring was clarified. The value of HD in the developed seeding parameter monitoring system was determined, so that when the NIR rays are emitted into the seed tube, they can cover the entire cross-section of the end of the seed tube without being reflected by dust, avoiding missed monitoring and false monitoring. A signal shielding filtering algorithm based on sawtooth wave shielding was proposed. In regard to the characteristic of high-frequency sawtooth wave in the signal generated by seeds passing through the monitoring area, the first rising edge of the signal is used as the seed recognition signal. By analyzing the duration of high-frequency sawtooth wave and the interval between adjacent seeds, the shielding time of the interference signal is determined to achieve effective noise reduction. Performance evaluation test in the bench results showed that NIRDE-DR has a better recognition effect on maize seeds than TBP. Performance evaluation test in the field showed that at a seeding speed of 6–14 km/h, the maximum monitoring error of the developed system for seeding quantity was 7.98 %, and the maximum monitoring error for seeding qualified rate was 7.69 %. The developed seeding parameter monitoring system has good performance, providing a reference for the advancement of seeding parameter monitoring technology at the end of the seed tube.