基于近红外光电效应的联合收获机谷物厚度测量方法

Grain Thickness Sensor for Combine Harvester Grain Flow Measurement Based on Near-infrared Spectroscopy

摘要:

谷物在刮板升运器中的堆积状态是影响光电式流量测量精度的重要因素。为了提高联合收获机容积式谷物流量传感器的测量精度，开展了基于近红外光电效应的谷物厚度测量方法及其传感器的研究。通过激光发射器生成850～980nm的近红外光，采用硅光电池接收透射谷物的红外光线，根据光强的变化获取谷物的厚度。设计了以T型反馈网络为核心的I/V转换处理电路，根据试验测量的输出电压与谷物厚度的变化关系，拟合建立了Gaussian函数方程，分析了激光发射器功率、红外线波长对不同品种水稻厚度测量性能的影响。结果表明：当红外线波长为940nm时，回归方程的拟合精度最高，水稻厚度测量误差小于0.5mm；随着激光发射器功率的增加，水稻厚度测量量程随之增大，当功率为500mW时，谷物厚度的有效测量距离约为50mm；红外线的穿透能力随着波长的增加而增强，随着籽粒含水率的降低而减弱。提出的谷物厚度测量方法可以提高容积式谷物流量测量精度。

Abstract:

The distribution of grain in the flight elevator is an important factor affecting the grain mass flow measurement error of photoelectric sensors. To improve the grain mass flow measurement accuracy of combine harvester, a grain thickness measurement method based on infrared photoelectric effect was proposed. The sensor was mainly composed of laser emitter, silicon photocell and signal processing circuit. The nearinfrared light with wavelength of 850~980nm was generated by using the laser emitter, and the light intensity passed through the grain was received by using the silicon photocell. Then, the grain thickness can be acquired according to the variation of received light intensity. An I/V conversion circuit based on T-type feedback network was designed. The Gaussian regression equation was established to describe the relationship between the output voltage and the grain thickness. The effects of laser emitter power, infrared wavelength and rice variety on the sensor measurement performance were analyzed. The results showed that the optimal regression accuracy was received with the infrared wavelength of 940nm, and the measurement error of grain thickness was less than 0.5mm. The measurement range was increased with the increase of laser emitter power. The effective measurement range of about 50mm could be achieved when the power was 500mW. The transmission capacity of infrared ray to grain was increased with the increase of wavelength and decreased with the decrease of grain moisture content. The proposed measurement method and sensor of grain thickness can be used to measure the time interval which grain blocked the light path during the lifting process, and also can be used to analyze the grain distribution in the flight elevator. The research result provided important reference for improving the grain flow measurement accuracy.